Remove useless generic on accumulator

batch,  unbatch, rate, parallel, accumulator with rolling / sliding windows, demultiplexer

.gitignore

@@ -3,4 +3,15 @@ node_modules
 dist
 sample_output
 yarn-error.log
-TODO.md
+TODO.md
+
+
+#VIM
+## Swap
+[._]*.s[a-v][a-z]
+!*.svg  # comment out if you don't need vector files
+[._]*.sw[a-p]
+[._]s[a-rt-v][a-z]
+[._]ss[a-gi-z]
+[._]sw[a-p]
+*.orig

package.json

@@ -1,6 +1,6 @@
 {
-    "name": "mhysa",
+    "name": "@jogogo/mhysa",
-    "version": "1.0.2",
+    "version": "0.0.1-beta.4",
     "description": "Streams and event emitter utils for Node.js",
     "keywords": [
         "promise",
@@ -11,40 +11,56 @@
     "author": {
         "name": "Wenzil"
     },
+    "contributors": [
+        {
+            "name": "jerry",
+            "email": "jerry@jogogo.co"
+        },
+        {
+            "name": "lewis",
+            "email": "lewis@jogogo.co"
+        }
+    ],
     "license": "MIT",
     "main": "dist/index.js",
     "types": "dist/index.d.ts",
     "files": [
         "dist"
     ],
+    "publishConfig": {
+        "registry": "https://npm.dev.jogogo.co/"
+    },
     "repository": {
-        "url": "git@github.com:Wenzil/Mhysa.git",
+        "url": "git@github.com:Jogogoplay/mhysa.git",
         "type": "git"
     },
     "scripts": {
-        "test": "ava",
+        "test": "NODE_PATH=src node node_modules/.bin/ava 'tests/*.spec.ts' -e",
+        "test:debug": "NODE_PATH=src node inspect node_modules/ava/profile.js",
+        "test:all": "NODE_PATH=src node node_modules/.bin/ava",
         "lint": "tslint -p tsconfig.json",
         "validate:tslint": "tslint-config-prettier-check ./tslint.json",
-        "prepublishOnly": "yarn lint && yarn test && yarn tsc"
+        "prepublishOnly": "yarn lint && yarn test && yarn tsc -d"
     },
     "dependencies": {},
     "devDependencies": {
         "@types/chai": "^4.1.7",
-        "@types/node": "^10.12.10",
+        "@types/node": "^12.7.2",
-        "@types/typescript": "^2.0.0",
+        "@types/sinon": "^7.0.13",
         "ava": "^1.0.0-rc.2",
         "chai": "^4.2.0",
         "mhysa": "./",
         "prettier": "^1.14.3",
-        "ts-node": "^7.0.1",
+        "sinon": "^7.4.2",
+        "ts-node": "^8.3.0",
         "tslint": "^5.11.0",
         "tslint-config-prettier": "^1.16.0",
         "tslint-plugin-prettier": "^2.0.1",
-        "typescript": "^3.1.6"
+        "typescript": "^3.5.3"
     },
     "ava": {
         "files": [
-            "src/**/*.spec.ts"
+            "tests/*.spec.ts"
         ],
         "sources": [
             "src/**/*.ts"

src/functions/accumulator.ts

@@ -0,0 +1,180 @@
+import { Transform, TransformOptions } from "stream";
+
+export enum FlushStrategy {
+    rolling = "rolling",
+    sliding = "sliding",
+}
+
+export type AccumulatorByIteratee<T> = (event: T, bufferChunk: T) => boolean;
+
+function _accumulator<T>(
+    accumulateBy: (data: T, buffer: T[], stream: Transform) => void,
+    shouldFlush: boolean = true,
+    options: TransformOptions = {},
+) {
+    const buffer: T[] = [];
+    return new Transform({
+        ...options,
+        transform(data: T, encoding, callback) {
+            accumulateBy(data, buffer, this);
+            callback();
+        },
+        flush(callback) {
+            if (shouldFlush) {
+                this.push(buffer);
+            }
+            callback();
+        },
+    });
+}
+
+function _sliding<T>(
+    windowLength: number,
+    key?: string,
+): (event: T, buffer: T[], stream: Transform) => void {
+    return (event: T, buffer: T[], stream: Transform) => {
+        if (key) {
+            let index = 0;
+            if (event[key] === undefined) {
+                stream.emit(
+                    "error",
+                    new Error(
+                        `Key is missing in event: (${key}, ${JSON.stringify(
+                            event,
+                        )})`,
+                    ),
+                );
+                stream.resume();
+                return;
+            }
+            while (
+                index < buffer.length &&
+                buffer[index][key] + windowLength <= event[key]
+            ) {
+                index++;
+            }
+            buffer.splice(0, index);
+        } else if (buffer.length === windowLength) {
+            buffer.shift();
+        }
+        buffer.push(event);
+        stream.push([...buffer]);
+    };
+}
+
+function _slidingByFunction<T>(
+    iteratee: AccumulatorByIteratee<T>,
+): (event: T, buffer: T[], stream: Transform) => void {
+    return (event: T, buffer: T[], stream: Transform) => {
+        let index = 0;
+        while (index < buffer.length && iteratee(event, buffer[index])) {
+            index++;
+        }
+        buffer.splice(0, index);
+        buffer.push(event);
+        stream.push([...buffer]);
+    };
+}
+
+function _rollingByFunction<T>(
+    iteratee: AccumulatorByIteratee<T>,
+): (event: T, buffer: T[], stream: Transform) => void {
+    return (event: T, buffer: T[], stream: Transform) => {
+        if (iteratee) {
+            if (buffer.length > 0 && iteratee(event, buffer[0])) {
+                stream.push(buffer.slice(0));
+                buffer.length = 0;
+            }
+        }
+        buffer.push(event);
+    };
+}
+
+function _rolling<T>(
+    windowLength: number,
+    key?: string,
+): (event: T, buffer: T[], stream: Transform) => void {
+    return (event: T, buffer: T[], stream: Transform) => {
+        if (key) {
+            if (event[key] === undefined) {
+                stream.emit(
+                    "error",
+                    new Error(
+                        `Key is missing in event: (${key}, ${JSON.stringify(
+                            event,
+                        )})`,
+                    ),
+                );
+                stream.resume();
+                return;
+            } else if (
+                buffer.length > 0 &&
+                buffer[0][key] + windowLength <= event[key]
+            ) {
+                stream.push(buffer.slice(0));
+                buffer.length = 0;
+            }
+        } else if (buffer.length === windowLength) {
+            stream.push(buffer.slice(0));
+            buffer.length = 0;
+        }
+        buffer.push(event);
+    };
+}
+
+export function accumulator(
+    flushStrategy: FlushStrategy,
+    batchSize: number,
+    keyBy?: string,
+    options?: TransformOptions,
+): Transform {
+    switch (flushStrategy) {
+        case FlushStrategy.sliding:
+            return sliding(batchSize, keyBy, options);
+        case FlushStrategy.rolling:
+            return rolling(batchSize, keyBy, options);
+    }
+}
+
+export function accumulatorBy<T>(
+    flushStrategy: FlushStrategy,
+    iteratee: AccumulatorByIteratee<T>,
+    options?: TransformOptions,
+): Transform {
+    switch (flushStrategy) {
+        case FlushStrategy.sliding:
+            return slidingBy(iteratee, options);
+        case FlushStrategy.rolling:
+            return rollingBy(iteratee, options);
+    }
+}
+
+function sliding(
+    windowLength: number,
+    key?: string,
+    options?: TransformOptions,
+): Transform {
+    return _accumulator(_sliding(windowLength, key), false, options);
+}
+
+function slidingBy<T>(
+    iteratee: AccumulatorByIteratee<T>,
+    options?: TransformOptions,
+): Transform {
+    return _accumulator(_slidingByFunction(iteratee), false, options);
+}
+
+function rolling(
+    windowLength: number,
+    key?: string,
+    options?: TransformOptions,
+): Transform {
+    return _accumulator(_rolling(windowLength, key), true, options);
+}
+
+function rollingBy<T>(
+    iteratee: AccumulatorByIteratee<T>,
+    options?: TransformOptions,
+): Transform {
+    return _accumulator(_rollingByFunction(iteratee), true, options);
+}

src/functions/baseDefinitions.ts

@@ -1,12 +1,3 @@
-export interface ThroughOptions {
-    objectMode?: boolean;
-}
-
-export interface TransformOptions {
-    readableObjectMode?: boolean;
-    writableObjectMode?: boolean;
-}
-
 export interface WithEncoding {
     encoding: string;
 }
@@ -21,4 +12,3 @@ export type JsonValue = JsonPrimitive | JsonPrimitive[];
 export interface JsonParseOptions {
     pretty: boolean;
 }
-

src/functions/batch.ts

@@ -0,0 +1,38 @@
+import { Transform, TransformOptions } from "stream";
+
+export function batch(
+    batchSize: number = 1000,
+    maxBatchAge: number = 500,
+    options: TransformOptions = {},
+): Transform {
+    let buffer: any[] = [];
+    let timer: NodeJS.Timer | null = null;
+    const sendChunk = (self: Transform) => {
+        if (timer) {
+            clearTimeout(timer);
+        }
+        timer = null;
+        self.push(buffer);
+        buffer = [];
+    };
+    return new Transform({
+        ...options,
+        transform(chunk, encoding, callback) {
+            buffer.push(chunk);
+            if (buffer.length === batchSize) {
+                sendChunk(this);
+            } else {
+                if (timer === null) {
+                    timer = setInterval(() => {
+                        sendChunk(this);
+                    }, maxBatchAge);
+                }
+            }
+            callback();
+        },
+        flush(callback) {
+            sendChunk(this);
+            callback();
+        },
+    });
+}

src/functions/child.ts

@@ -0,0 +1,11 @@
+import { ChildProcess } from "child_process";
+import { duplex } from "./duplex";
+
+export function child(childProcess: ChildProcess) {
+    if (childProcess.stdin === null) {
+        throw new Error("childProcess.stdin is null");
+    } else if (childProcess.stdout === null) {
+        throw new Error("childProcess.stdout is null");
+    }
+    return duplex(childProcess.stdin, childProcess.stdout);
+}

src/functions/collect.ts

@@ -0,0 +1,18 @@
+import { Transform, TransformOptions } from "stream";
+
+export function collect(options: TransformOptions = {}): Transform {
+    const collected: any[] = [];
+    return new Transform({
+        ...options,
+        transform(data, encoding, callback) {
+            collected.push(data);
+            callback();
+        },
+        flush(callback) {
+            this.push(
+                options.objectMode ? collected : Buffer.concat(collected),
+            );
+            callback();
+        },
+    });
+}

src/functions/compose.ts

@@ -0,0 +1,106 @@
+import { pipeline, Duplex, DuplexOptions } from "stream";
+
+export function compose(
+    streams: Array<
+        NodeJS.ReadableStream | NodeJS.ReadWriteStream | NodeJS.WritableStream
+    >,
+    options?: DuplexOptions,
+): Compose {
+    if (streams.length < 2) {
+        throw new Error("At least two streams are required to compose");
+    }
+
+    return new Compose(streams, options);
+}
+
+enum EventSubscription {
+    Last = 0,
+    First,
+    All,
+    Self,
+}
+
+const eventsTarget = {
+    close: EventSubscription.Last,
+    data: EventSubscription.Last,
+    drain: EventSubscription.Self,
+    end: EventSubscription.Last,
+    error: EventSubscription.Self,
+    finish: EventSubscription.Last,
+    pause: EventSubscription.Last,
+    pipe: EventSubscription.First,
+    readable: EventSubscription.Last,
+    resume: EventSubscription.Last,
+    unpipe: EventSubscription.First,
+};
+
+type AllStreams =
+    | NodeJS.ReadableStream
+    | NodeJS.ReadWriteStream
+    | NodeJS.WritableStream;
+
+export class Compose extends Duplex {
+    private first: AllStreams;
+    private last: AllStreams;
+    private streams: AllStreams[];
+
+    constructor(streams: AllStreams[], options?: DuplexOptions) {
+        super(options);
+        this.first = streams[0];
+        this.last = streams[streams.length - 1];
+        this.streams = streams;
+        pipeline(streams, (err: any) => {
+            this.emit("error", err);
+        });
+    }
+
+    public pipe<T extends NodeJS.WritableStream>(dest: T) {
+        return (this.last as NodeJS.ReadableStream).pipe(dest);
+    }
+
+    public _write(chunk: any, encoding: string, cb: any) {
+        (this.first as NodeJS.WritableStream).write(chunk, encoding, cb);
+    }
+
+    public bubble(...events: string[]) {
+        this.streams.forEach(s => {
+            events.forEach(e => {
+                s.on(e, (...args) => super.emit(e, ...args));
+            });
+        });
+    }
+
+    public on(event: string, cb: any) {
+        switch (eventsTarget[event]) {
+            case EventSubscription.First:
+                this.first.on(event, cb);
+                break;
+            case EventSubscription.Last:
+                this.last.on(event, cb);
+                break;
+            case EventSubscription.All:
+                this.streams.forEach(s => s.on(event, cb));
+                break;
+            default:
+                super.on(event, cb);
+        }
+        return this;
+    }
+
+    public once(event: string, cb: any) {
+        switch (eventsTarget[event]) {
+            case EventSubscription.First:
+                this.first.once(event, cb);
+                break;
+            case EventSubscription.Last:
+                this.last.once(event, cb);
+                break;
+            case EventSubscription.All:
+                this.streams.forEach(s => s.once(event, cb));
+                break;
+            default:
+                super.once(event, cb);
+        }
+        return this;
+    }
+}

src/functions/concat.ts

@@ -0,0 +1,37 @@
+import { Readable } from "stream";
+
+export function concat(...streams: NodeJS.ReadableStream[]): Readable {
+    let isStarted = false;
+    let currentStreamIndex = 0;
+    const startCurrentStream = () => {
+        if (currentStreamIndex >= streams.length) {
+            wrapper.push(null);
+        } else {
+            streams[currentStreamIndex]
+                .on("data", chunk => {
+                    if (!wrapper.push(chunk)) {
+                        streams[currentStreamIndex].pause();
+                    }
+                })
+                .on("error", err => wrapper.emit("error", err))
+                .on("end", () => {
+                    currentStreamIndex++;
+                    startCurrentStream();
+                });
+        }
+    };
+
+    const wrapper = new Readable({
+        objectMode: true,
+        read() {
+            if (!isStarted) {
+                isStarted = true;
+                startCurrentStream();
+            }
+            if (currentStreamIndex < streams.length) {
+                streams[currentStreamIndex].resume();
+            }
+        },
+    });
+    return wrapper;
+}

src/functions/demux.ts

@@ -0,0 +1,99 @@
+import { WritableOptions, Writable } from "stream";
+
+enum EventSubscription {
+    Last = 0,
+    First,
+    All,
+    Self,
+    Unhandled,
+}
+
+const eventsTarget = {
+    close: EventSubscription.Self,
+    data: EventSubscription.All,
+    drain: EventSubscription.Self,
+    end: EventSubscription.Self,
+    error: EventSubscription.Self,
+    finish: EventSubscription.Self,
+    pause: EventSubscription.Self,
+    pipe: EventSubscription.Self,
+    readable: EventSubscription.Self,
+    resume: EventSubscription.Self,
+    unpipe: EventSubscription.Self,
+};
+
+type DemuxStreams = NodeJS.WritableStream | NodeJS.ReadWriteStream;
+
+export function demux(
+    construct: (destKey?: string) => DemuxStreams,
+    demuxBy: string | ((chunk: any) => string),
+    options?: WritableOptions,
+): Writable {
+    return new Demux(construct, demuxBy, options);
+}
+
+// @TODO handle pipe event ie) Multiplex
+class Demux extends Writable {
+    private streamsByKey: {
+        [key: string]: DemuxStreams;
+    };
+    private demuxer: (chunk: any) => string;
+    private construct: (destKey?: string) => DemuxStreams;
+    constructor(
+        construct: (destKey?: string) => DemuxStreams,
+        demuxBy: string | ((chunk: any) => string),
+        options: WritableOptions = {},
+    ) {
+        super(options);
+        this.demuxer =
+            typeof demuxBy === "string" ? chunk => chunk[demuxBy] : demuxBy;
+        this.construct = construct;
+        this.streamsByKey = {};
+    }
+
+    public async _write(chunk: any, encoding: any, cb: any) {
+        const destKey = this.demuxer(chunk);
+        if (this.streamsByKey[destKey] === undefined) {
+            this.streamsByKey[destKey] = await this.construct(destKey);
+        }
+        if (!this.streamsByKey[destKey].write(chunk, encoding)) {
+            this.streamsByKey[destKey].once("drain", () => {
+                cb();
+            });
+        } else {
+            cb();
+        }
+    }
+
+    public on(event: string, cb: any) {
+        switch (eventsTarget[event]) {
+            case EventSubscription.Self:
+                super.on(event, cb);
+                break;
+            case EventSubscription.All:
+                Object.keys(this.streamsByKey).forEach(key =>
+                    this.streamsByKey[key].on(event, cb),
+                );
+                break;
+            default:
+                super.on(event, cb);
+        }
+        return this;
+    }
+
+    public once(event: string, cb: any) {
+        switch (eventsTarget[event]) {
+            case EventSubscription.Self:
+                super.once(event, cb);
+                break;
+            case EventSubscription.All:
+                Object.keys(this.streamsByKey).forEach(key =>
+                    this.streamsByKey[key].once(event, cb),
+                );
+                break;
+            default:
+                super.once(event, cb);
+        }
+        return this;
+    }
+}

src/functions/duplex.ts

@@ -0,0 +1,31 @@
+import { Duplex } from "stream";
+
+export function duplex(
+    writable: NodeJS.WritableStream,
+    readable: NodeJS.ReadableStream,
+) {
+    const wrapper = new Duplex({
+        readableObjectMode: true,
+        writableObjectMode: true,
+        read() {
+            readable.resume();
+        },
+        write(chunk, encoding, callback) {
+            return writable.write(chunk, encoding, callback);
+        },
+        final(callback) {
+            writable.end(callback);
+        },
+    });
+    readable
+        .on("data", chunk => {
+            if (!wrapper.push(chunk)) {
+                readable.pause();
+            }
+        })
+        .on("error", err => wrapper.emit("error", err))
+        .on("end", () => wrapper.push(null));
+    writable.on("drain", () => wrapper.emit("drain"));
+    writable.on("error", err => wrapper.emit("error", err));
+    return wrapper;
+}

src/functions/filter.ts

@@ -0,0 +1,20 @@
+import { Transform, TransformOptions } from "stream";
+
+export function filter<T>(
+    predicate:
+        | ((chunk: T, encoding: string) => boolean)
+        | ((chunk: T, encoding: string) => Promise<boolean>),
+    options?: TransformOptions,
+) {
+    return new Transform({
+        ...options,
+        async transform(chunk: T, encoding?: any, callback?: any) {
+            const result = await predicate(chunk, encoding);
+            if (result === true) {
+                callback(null, chunk);
+            } else {
+                callback();
+            }
+        },
+    });
+}

src/functions/flatMap.ts

@@ -0,0 +1,16 @@
+import { Transform, TransformOptions } from "stream";
+
+export function flatMap<T, R>(
+    mapper:
+        | ((chunk: T, encoding: string) => R[])
+        | ((chunk: T, encoding: string) => Promise<R[]>),
+    options?: TransformOptions,
+): Transform {
+    return new Transform({
+        ...options,
+        async transform(chunk: T, encoding, callback) {
+            (await mapper(chunk, encoding)).forEach(c => this.push(c));
+            callback();
+        },
+    });
+}

src/functions/fromArray.ts

@@ -0,0 +1,16 @@
+import { Readable } from "stream";
+
+export function fromArray(array: any[]): Readable {
+    let cursor = 0;
+    return new Readable({
+        objectMode: true,
+        read() {
+            if (cursor < array.length) {
+                this.push(array[cursor]);
+                cursor++;
+            } else {
+                this.push(null);
+            }
+        },
+    });
+}

src/functions/functions.ts

@@ -1,604 +0,0 @@
-import { Transform, Readable, Writable, Duplex } from "stream";
-import { performance } from "perf_hooks";
-import { ChildProcess } from "child_process";
-import { StringDecoder } from "string_decoder";
-
-import {
-    TransformOptions,
-    ThroughOptions,
-    WithEncoding,
-    SerializationFormats,
-    JsonValue,
-    JsonParseOptions,
-} from "./definitions";
-import { sleep } from "../helpers";
-
-/**
- * Convert an array into a Readable stream of its elements
- * @param array Array of elements to stream
- */
-export function fromArray(array: any[]): NodeJS.ReadableStream {
-    let cursor = 0;
-    return new Readable({
-        objectMode: true,
-        read() {
-            if (cursor < array.length) {
-                this.push(array[cursor]);
-                cursor++;
-            } else {
-                this.push(null);
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that maps streamed chunks
- * @param mapper Mapper function, mapping each (chunk, encoding) to a new chunk (or a promise of such)
- * @param options
- * @param options.readableObjectMode Whether this stream should behave as a readable stream of objects
- * @param options.writableObjectMode Whether this stream should behave as a writable stream of objects
- */
-export function map<T, R>(
-    mapper: (chunk: T, encoding: string) => R,
-    options: TransformOptions = {
-        readableObjectMode: true,
-        writableObjectMode: true,
-    },
-): NodeJS.ReadWriteStream {
-    return new Transform({
-        ...options,
-        async transform(chunk: T, encoding, callback) {
-            try {
-                const mapped = await mapper(chunk, encoding);
-                this.push(mapped);
-                callback();
-            } catch (err) {
-                callback(err);
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that flat maps streamed chunks
- * @param mapper Mapper function, mapping each (chunk, encoding) to an array of new chunks (or a promise of such)
- * @param options
- * @param options.readableObjectMode Whether this stream should behave as a readable stream of objects
- * @param options.writableObjectMode Whether this stream should behave as a writable stream of objects
- */
-export function flatMap<T, R>(
-    mapper:
-        | ((chunk: T, encoding: string) => R[])
-        | ((chunk: T, encoding: string) => Promise<R[]>),
-    options: TransformOptions = {
-        readableObjectMode: true,
-        writableObjectMode: true,
-    },
-): NodeJS.ReadWriteStream {
-    return new Transform({
-        ...options,
-        async transform(chunk: T, encoding, callback) {
-            let isPromise = false;
-            try {
-                const mapped = mapper(chunk, encoding);
-                isPromise = mapped instanceof Promise;
-                (await mapped).forEach(c => this.push(c));
-                callback();
-            } catch (err) {
-                if (isPromise) {
-                    // Calling the callback asynchronously with an error wouldn't emit the error, so emit directly
-                    this.emit("error", err);
-                    callback();
-                } else {
-                    callback(err);
-                }
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that filters out streamed chunks for which the predicate does not hold
- * @param predicate Predicate with which to filter scream chunks
- * @param options
- * @param options.objectMode Whether this stream should behave as a stream of objects
- */
-export function filter<T>(
-    predicate:
-        | ((chunk: T, encoding: string) => boolean)
-        | ((chunk: T, encoding: string) => Promise<boolean>),
-    options: ThroughOptions = {
-        objectMode: true,
-    },
-) {
-    return new Transform({
-        readableObjectMode: options.objectMode,
-        writableObjectMode: options.objectMode,
-        async transform(chunk: T, encoding, callback) {
-            let isPromise = false;
-            try {
-                const result = predicate(chunk, encoding);
-                isPromise = result instanceof Promise;
-                if (!!(await result)) {
-                    callback(undefined, chunk);
-                } else {
-                    callback();
-                }
-            } catch (err) {
-                if (isPromise) {
-                    // Calling the callback asynchronously with an error wouldn't emit the error, so emit directly
-                    this.emit("error", err);
-                    callback();
-                } else {
-                    callback(err);
-                }
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that reduces streamed chunks down to a single value and yield that
- * value
- * @param iteratee Reducer function to apply on each streamed chunk
- * @param initialValue Initial value
- * @param options
- * @param options.readableObjectMode Whether this stream should behave as a readable stream of objects
- * @param options.writableObjectMode Whether this stream should behave as a writable stream of objects
- */
-export function reduce<T, R>(
-    iteratee:
-        | ((previousValue: R, chunk: T, encoding: string) => R)
-        | ((previousValue: R, chunk: T, encoding: string) => Promise<R>),
-    initialValue: R,
-    options: TransformOptions = {
-        readableObjectMode: true,
-        writableObjectMode: true,
-    },
-) {
-    let value = initialValue;
-    return new Transform({
-        readableObjectMode: options.readableObjectMode,
-        writableObjectMode: options.writableObjectMode,
-        async transform(chunk: T, encoding, callback) {
-            let isPromise = false;
-            try {
-                const result = iteratee(value, chunk, encoding);
-                isPromise = result instanceof Promise;
-                value = await result;
-                callback();
-            } catch (err) {
-                if (isPromise) {
-                    // Calling the callback asynchronously with an error wouldn't emit the error, so emit directly
-                    this.emit("error", err);
-                    callback();
-                } else {
-                    callback(err);
-                }
-            }
-        },
-        flush(callback) {
-            // Best effort attempt at yielding the final value (will throw if e.g. yielding an object and
-            // downstream doesn't expect objects)
-            try {
-                callback(undefined, value);
-            } catch (err) {
-                try {
-                    this.emit("error", err);
-                } catch {
-                    // Best effort was made
-                }
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that splits streamed chunks using the given separator
- * @param separator Separator to split by, defaulting to "\n"
- * @param options
- * @param options.encoding Encoding written chunks are assumed to use
- */
-export function split(
-    separator: string | RegExp = "\n",
-    options: WithEncoding = { encoding: "utf8" },
-): NodeJS.ReadWriteStream {
-    let buffered = "";
-    const decoder = new StringDecoder(options.encoding);
-
-    return new Transform({
-        readableObjectMode: true,
-        transform(chunk: Buffer, encoding, callback) {
-            const asString = decoder.write(chunk);
-            const splitted = asString.split(separator);
-            if (splitted.length > 1) {
-                splitted[0] = buffered.concat(splitted[0]);
-                buffered = "";
-            }
-            buffered += splitted[splitted.length - 1];
-            splitted.slice(0, -1).forEach((part: string) => this.push(part));
-            callback();
-        },
-        flush(callback) {
-            callback(undefined, buffered + decoder.end());
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that joins streamed chunks using the given separator
- * @param separator Separator to join with
- * @param options
- * @param options.encoding Encoding written chunks are assumed to use
- */
-export function join(
-    separator: string,
-    options: WithEncoding = { encoding: "utf8" },
-): NodeJS.ReadWriteStream {
-    let isFirstChunk = true;
-    const decoder = new StringDecoder(options.encoding);
-    return new Transform({
-        readableObjectMode: true,
-        async transform(chunk: Buffer, encoding, callback) {
-            const asString = decoder.write(chunk);
-            // Take care not to break up multi-byte characters spanning multiple chunks
-            if (asString !== "" || chunk.length === 0) {
-                if (!isFirstChunk) {
-                    this.push(separator);
-                }
-                this.push(asString);
-                isFirstChunk = false;
-            }
-            callback();
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that replaces occurrences of the given string or regular expression  in
- * the streamed chunks with the specified replacement string
- * @param searchValue Search string to use
- * @param replaceValue Replacement string to use
- * @param options
- * @param options.encoding Encoding written chunks are assumed to use
- */
-export function replace(
-    searchValue: string | RegExp,
-    replaceValue: string,
-    options: WithEncoding = { encoding: "utf8" },
-): NodeJS.ReadWriteStream {
-    const decoder = new StringDecoder(options.encoding);
-    return new Transform({
-        readableObjectMode: true,
-        transform(chunk: Buffer, encoding, callback) {
-            const asString = decoder.write(chunk);
-            // Take care not to break up multi-byte characters spanning multiple chunks
-            if (asString !== "" || chunk.length === 0) {
-                callback(
-                    undefined,
-                    asString.replace(searchValue, replaceValue),
-                );
-            } else {
-                callback();
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that parses the streamed chunks as JSON. Each streamed chunk
- * must be a fully defined JSON string.
- * @param format Format of serialized data, only utf8 supported.
- */
-export function parse(
-    format: SerializationFormats = SerializationFormats.utf8,
-): NodeJS.ReadWriteStream {
-    const decoder = new StringDecoder(format);
-    return new Transform({
-        readableObjectMode: true,
-        writableObjectMode: true,
-        async transform(chunk: Buffer, encoding, callback) {
-            try {
-                const asString = decoder.write(chunk);
-                // Using await causes parsing errors to be emitted
-                callback(undefined, await JSON.parse(asString));
-            } catch (err) {
-                callback(err);
-            }
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that stringifies the streamed chunks to JSON
- */
-export function stringify(
-    options: JsonParseOptions = { pretty: false },
-): NodeJS.ReadWriteStream {
-    return new Transform({
-        readableObjectMode: true,
-        writableObjectMode: true,
-        transform(chunk: JsonValue, encoding, callback) {
-            callback(
-                undefined,
-                options.pretty
-                    ? JSON.stringify(chunk, null, 2)
-                    : JSON.stringify(chunk),
-            );
-        },
-    });
-}
-
-/**
- * Return a ReadWrite stream that collects streamed chunks into an array or buffer
- * @param options
- * @param options.objectMode Whether this stream should behave as a stream of objects
- */
-export function collect(
-    options: ThroughOptions = { objectMode: false },
-): NodeJS.ReadWriteStream {
-    const collected: any[] = [];
-    return new Transform({
-        readableObjectMode: options.objectMode,
-        writableObjectMode: options.objectMode,
-        transform(data, encoding, callback) {
-            collected.push(data);
-            callback();
-        },
-        flush(callback) {
-            this.push(
-                options.objectMode ? collected : Buffer.concat(collected),
-            );
-            callback();
-        },
-    });
-}
-
-/**
- * Return a Readable stream of readable streams concatenated together
- * @param streams Readable streams to concatenate
- */
-export function concat(
-    ...streams: NodeJS.ReadableStream[]
-): NodeJS.ReadableStream {
-    let isStarted = false;
-    let currentStreamIndex = 0;
-    const startCurrentStream = () => {
-        if (currentStreamIndex >= streams.length) {
-            wrapper.push(null);
-        } else {
-            streams[currentStreamIndex]
-                .on("data", chunk => {
-                    if (!wrapper.push(chunk)) {
-                        streams[currentStreamIndex].pause();
-                    }
-                })
-                .on("error", err => wrapper.emit("error", err))
-                .on("end", () => {
-                    currentStreamIndex++;
-                    startCurrentStream();
-                });
-        }
-    };
-
-    const wrapper = new Readable({
-        objectMode: true,
-        read() {
-            if (!isStarted) {
-                isStarted = true;
-                startCurrentStream();
-            }
-            if (currentStreamIndex < streams.length) {
-                streams[currentStreamIndex].resume();
-            }
-        },
-    });
-    return wrapper;
-}
-
-/**
- * Return a Readable stream of readable streams merged together in chunk arrival order
- * @param streams Readable streams to merge
- */
-export function merge(
-    ...streams: NodeJS.ReadableStream[]
-): NodeJS.ReadableStream {
-    let isStarted = false;
-    let streamEndedCount = 0;
-    return new Readable({
-        objectMode: true,
-        read() {
-            if (streamEndedCount >= streams.length) {
-                this.push(null);
-            } else if (!isStarted) {
-                isStarted = true;
-                streams.forEach(stream =>
-                    stream
-                        .on("data", chunk => {
-                            if (!this.push(chunk)) {
-                                streams.forEach(s => s.pause());
-                            }
-                        })
-                        .on("error", err => this.emit("error", err))
-                        .on("end", () => {
-                            streamEndedCount++;
-                            if (streamEndedCount === streams.length) {
-                                this.push(null);
-                            }
-                        }),
-                );
-            } else {
-                streams.forEach(s => s.resume());
-            }
-        },
-    });
-}
-
-/**
- * Return a Duplex stream from a writable stream that is assumed to somehow, when written to,
- * cause the given readable stream to yield chunks
- * @param writable Writable stream assumed to cause the readable stream to yield chunks when written to
- * @param readable Readable stream assumed to yield chunks when the writable stream is written to
- */
-export function duplex(writable: Writable, readable: Readable) {
-    const wrapper = new Duplex({
-        readableObjectMode: true,
-        writableObjectMode: true,
-        read() {
-            readable.resume();
-        },
-        write(chunk, encoding, callback) {
-            return writable.write(chunk, encoding, callback);
-        },
-        final(callback) {
-            writable.end(callback);
-        },
-    });
-    readable
-        .on("data", chunk => {
-            if (!wrapper.push(chunk)) {
-                readable.pause();
-            }
-        })
-        .on("error", err => wrapper.emit("error", err))
-        .on("end", () => wrapper.push(null));
-    writable.on("drain", () => wrapper.emit("drain"));
-    writable.on("error", err => wrapper.emit("error", err));
-    return wrapper;
-}
-
-/**
- * Return a Duplex stream from a child process' stdin and stdout
- * @param childProcess Child process from which to create duplex stream
- */
-export function child(childProcess: ChildProcess) {
-    return duplex(childProcess.stdin, childProcess.stdout);
-}
-
-/**
- * Return a Promise resolving to the last streamed chunk of the given readable stream, after it has
- * ended
- * @param readable Readable stream to wait on
- */
-export function last<T>(readable: Readable): Promise<T | null> {
-    let lastChunk: T | null = null;
-    return new Promise((resolve, reject) => {
-        readable
-            .on("data", chunk => (lastChunk = chunk))
-            .on("end", () => resolve(lastChunk));
-    });
-}
-
-/**
- * Stores chunks of data internally in array and batches when batchSize is reached.
- *
- * @param batchSize Size of the batches
- * @param maxBatchAge Max lifetime of a batch
- */
-export function batch(batchSize: number = 1000, maxBatchAge: number = 500) {
-    let buffer: any[] = [];
-    let timer: NodeJS.Timer | null = null;
-    let sendChunk = (self: Transform) => {
-        timer && clearTimeout(timer);
-        timer = null;
-        self.push(buffer);
-        buffer = [];
-    };
-    return new Transform({
-        objectMode: true,
-        transform(chunk, encoding, callback) {
-            buffer.push(chunk);
-            if (buffer.length === batchSize) {
-                sendChunk(this);
-            } else {
-                if (timer === null) {
-                    timer = setInterval(() => {
-                        sendChunk(this);
-                    }, maxBatchAge);
-                }
-            }
-            callback();
-        },
-        flush(callback) {
-            console.error("flushing");
-            sendChunk(this);
-            callback();
-        },
-    });
-}
-
-/**
- * Unbatches and sends individual chunks of data
- */
-export function unbatch() {
-    return new Transform({
-        objectMode: true,
-        transform(data, encoding, callback) {
-            for (const d of data) {
-                this.push(d);
-            }
-            callback();
-        },
-    });
-}
-
-/**
- * Limits date of data transferred into stream.
- * @param targetRate Desired rate in ms
- * @param period Period to sleep for when rate is above or equal to targetRate
- */
-export function rate(targetRate: number = 50, period: number = 2) {
-    const deltaMS = ((1 / targetRate) * 1000) / period; // Skip half a period
-    let total = 0;
-    const start = performance.now();
-    return new Transform({
-        objectMode: true,
-        async transform(data, encoding, callback) {
-            const currentRate = (total / (performance.now() - start)) * 1000;
-            if (targetRate && currentRate > targetRate) {
-                await sleep(deltaMS);
-            }
-            total += 1;
-            callback(undefined, data);
-        },
-    });
-}
-
-/**
- * Limits number of parallel processes in flight.
- * @param parallel Max number of parallel processes.
- * @param func Function to execute on each data chunk
- * @param pause Amount of time to pause processing when max number of parallel processes are executing.
- */
-export function parallelMap<T, R>(
-    mapper: (data: T) => R,
-    parallel: number = 10,
-    sleepTime: number = 5,
-) {
-    let inflight = 0;
-    return new Transform({
-        objectMode: true,
-        async transform(data, encoding, callback) {
-            while (parallel <= inflight) {
-                await sleep(sleepTime);
-            }
-            inflight += 1;
-            callback();
-            try {
-                const res = await mapper(data);
-                this.push(res);
-            } catch (e) {
-                this.emit(e);
-            } finally {
-                inflight -= 1;
-            }
-        },
-        async flush(callback) {
-            while (inflight > 0) {
-                await sleep(sleepTime);
-            }
-            callback();
-        },
-    });
-}

src/functions/index.ts

@@ -1,241 +1,262 @@
-import { Readable, Writable } from "stream";
-import { ChildProcess } from "child_process";
-import * as baseFunctions from "./functions";
-
 import {
-    ThroughOptions,
+    Transform,
     TransformOptions,
-    WithEncoding,
+    WritableOptions,
-    JsonParseOptions,
+    ReadableOptions,
-} from "./definitions";
+} from "stream";
+import { accumulator, accumulatorBy } from "./accumulator";
+import { batch } from "./batch";
+import { child } from "./child";
+import { collect } from "./collect";
+import { concat } from "./concat";
+import { duplex } from "./duplex";
+import { filter } from "./filter";
+import { flatMap } from "./flatMap";
+import { fromArray } from "./fromArray";
+import { join } from "./join";
+import { last } from "./last";
+import { map } from "./map";
+import { merge } from "./merge";
+import { parallelMap } from "./parallelMap";
+import { parse } from "./parse";
+import { rate } from "./rate";
+import { reduce } from "./reduce";
+import { replace } from "./replace";
+import { split } from "./split";
+import { stringify } from "./stringify";
+import { unbatch } from "./unbatch";
+import { compose } from "./compose";
+import { demux } from "./demux";
 
-/**
+export default function mhysa(defaultOptions?: TransformOptions) {
- * Convert an array into a Readable stream of its elements
+    function withDefaultOptions<T extends any[], R>(
- * @param array Array of elements to stream
+        n: number,
- */
+        fn: (...args: T) => R,
-export function fromArray(array: any[]): NodeJS.ReadableStream {
+    ): (...args: T) => R {
-    return baseFunctions.fromArray(array);
+        return (...args) => {
-}
+            const options = {
+                ...defaultOptions,
+                ...((args[n] || {}) as TransformOptions | {}),
+            };
+            const provided = args.slice(0, n);
+            const nextArgs = [
+                ...provided,
+                ...Array(n - provided.length).fill(undefined),
+                options,
+            ] as T;
+            return fn(...nextArgs) as R;
+        };
+    }
 
-/**
+    return {
- * Return a ReadWrite stream that maps streamed chunks
+        /**
- * @param mapper Mapper function, mapping each (chunk, encoding) to a new chunk (or a promise of such)
+         * Convert an array into a Readable stream of its elements
- * @param options?
+         * @param array Array of elements to stream
- * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
+         */
- * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
+        fromArray,
- */
-export function map<T, R>(
-    mapper: (chunk: T, encoding?: string) => R,
-    options?: TransformOptions,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.map(mapper, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that flat maps streamed chunks
+         * Return a ReadWrite stream that maps streamed chunks
- * @param mapper Mapper function, mapping each (chunk, encoding) to an array of new chunks (or a promise of such)
+         * @param mapper Mapper function, mapping each (chunk, encoding) to a new chunk (or a promise of such)
- * @param options?
+         * @param options?
- * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
+         * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
- * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
+         * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
- */
+         */
-export function flatMap<T, R>(
+        map: withDefaultOptions(1, map),
-    mapper:
-        | ((chunk: T, encoding: string) => R[])
-        | ((chunk: T, encoding: string) => Promise<R[]>),
-    options?: TransformOptions,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.flatMap(mapper, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that filters out streamed chunks for which the predicate does not hold
+         * Return a ReadWrite stream that flat maps streamed chunks
- * @param predicate Predicate with which to filter scream chunks
+         * @param mapper Mapper function, mapping each (chunk, encoding) to an array of new chunks (or a promise of such)
- * @param options?
+         * @param options?
- * @param options.objectMode? Whether this stream should behave as a stream of objects.
+         * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
- */
+         * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
-export function filter<T>(
+         */
-    mapper:
+        flatMap: withDefaultOptions(1, flatMap),
-        | ((chunk: T, encoding: string) => boolean)
-        | ((chunk: T, encoding: string) => Promise<boolean>),
-    options?: ThroughOptions,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.filter(mapper, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that reduces streamed chunks down to a single value and yield that
+         * Return a ReadWrite stream that filters out streamed chunks for which the predicate does not hold
- * value
+         * @param predicate Predicate with which to filter scream chunks
- * @param iteratee Reducer function to apply on each streamed chunk
+         * @param options?
- * @param initialValue Initial value
+         * @param options.objectMode? Whether this stream should behave as a stream of objects.
- * @param options?
+         */
- * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
+        filter: withDefaultOptions(1, filter),
- * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
- */
-export function reduce<T, R>(
-    iteratee:
-        | ((previousValue: R, chunk: T, encoding: string) => R)
-        | ((previousValue: R, chunk: T, encoding: string) => Promise<R>),
-    initialValue: R,
-    options?: TransformOptions,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.reduce(iteratee, initialValue, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that splits streamed chunks using the given separator
+         * Return a ReadWrite stream that reduces streamed chunks down to a single value and yield that
- * @param separator? Separator to split by, defaulting to "\n"
+         * value
- * @param options? Defaults to encoding: utf8
+         * @param iteratee Reducer function to apply on each streamed chunk
- * @param options.encoding? Encoding written chunks are assumed to use
+         * @param initialValue Initial value
- */
+         * @param options?
-export function split(
+         * @param options.readableObjectMode? Whether this stream should behave as a readable stream of objects
-    separator?: string | RegExp,
+         * @param options.writableObjectMode? Whether this stream should behave as a writable stream of objects
-    options?: WithEncoding,
+         */
-): NodeJS.ReadWriteStream {
+        reduce: withDefaultOptions(2, reduce),
-    return baseFunctions.split(separator, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that joins streamed chunks using the given separator
+         * Return a ReadWrite stream that splits streamed chunks using the given separator
- * @param separator Separator to join with
+         * @param separator? Separator to split by, defaulting to "\n"
- * @param options? Defaults to encoding: utf8
+         * @param options? Defaults to encoding: utf8
- * @param options.encoding? Encoding written chunks are assumed to use
+         * @param options.encoding? Encoding written chunks are assumed to use
- */
+         */
-export function join(
+        split,
-    separator: string,
-    options?: WithEncoding,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.join(separator, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that replaces occurrences of the given string or regular expression  in
+         * Return a ReadWrite stream that joins streamed chunks using the given separator
- * the streamed chunks with the specified replacement string
+         * @param separator Separator to join with
- * @param searchValue Search string to use
+         * @param options? Defaults to encoding: utf8
- * @param replaceValue Replacement string to use
+         * @param options.encoding? Encoding written chunks are assumed to use
- * @param options? Defaults to encoding: utf8
+         */
- * @param options.encoding Encoding written chunks are assumed to use
+        join: withDefaultOptions(1, join),
- */
-export function replace(
-    searchValue: string | RegExp,
-    replaceValue: string,
-    options?: WithEncoding,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.replace(searchValue, replaceValue, options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that parses the streamed chunks as JSON. Each streamed chunk
+         * Return a ReadWrite stream that replaces occurrences of the given string or regular expression  in
- * must be a fully defined JSON string in utf8.
+         * the streamed chunks with the specified replacement string
- */
+         * @param searchValue Search string to use
-export function parse(): NodeJS.ReadWriteStream {
+         * @param replaceValue Replacement string to use
-    return baseFunctions.parse();
+         * @param options? Defaults to encoding: utf8
-}
+         * @param options.encoding Encoding written chunks are assumed to use
+         */
+        replace,
 
-/**
+        /**
- * Return a ReadWrite stream that stringifies the streamed chunks to JSON
+         * Return a ReadWrite stream that parses the streamed chunks as JSON. Each streamed chunk
- * @param options?
+         * must be a fully defined JSON string in utf8.
- * @param options.pretty If true, whitespace is inserted into the stringified chunks.
+         */
- *
+        parse,
- */
-export function stringify(options?: JsonParseOptions): NodeJS.ReadWriteStream {
-    return baseFunctions.stringify(options);
-}
 
-/**
+        /**
- * Return a ReadWrite stream that collects streamed chunks into an array or buffer
+         * Return a ReadWrite stream that stringifies the streamed chunks to JSON
- * @param options?
+         * @param options?
- * @param options.objectMode? Whether this stream should behave as a stream of objects
+         * @param options.pretty If true, whitespace is inserted into the stringified chunks.
- */
+         *
-export function collect(options?: ThroughOptions): NodeJS.ReadWriteStream {
+         */
-    return baseFunctions.collect(options);
+        stringify,
-}
 
-/**
+        /**
- * Return a Readable stream of readable streams concatenated together
+         * Return a ReadWrite stream that collects streamed chunks into an array or buffer
- * @param streams Readable streams to concatenate
+         * @param options?
- */
+         * @param options.objectMode? Whether this stream should behave as a stream of objects
-export function concat(
+         */
-    ...streams: NodeJS.ReadableStream[]
+        collect: withDefaultOptions(0, collect),
-): NodeJS.ReadableStream {
-    return baseFunctions.concat(...streams);
-}
 
-/**
+        /**
- * Return a Readable stream of readable streams concatenated together
+         * Return a Readable stream of readable streams concatenated together
- * @param streams Readable streams to merge
+         * @param streams Readable streams to concatenate
- */
+         */
-export function merge(
+        concat,
-    ...streams: NodeJS.ReadableStream[]
-): NodeJS.ReadableStream {
-    return baseFunctions.merge(...streams);
-}
 
-/**
+        /**
- * Return a Duplex stream from a writable stream that is assumed to somehow, when written to,
+         * Return a Readable stream of readable streams concatenated together
- * cause the given readable stream to yield chunks
+         * @param streams Readable streams to merge
- * @param writable Writable stream assumed to cause the readable stream to yield chunks when written to
+         */
- * @param readable Readable stream assumed to yield chunks when the writable stream is written to
+        merge,
- */
-export function duplex(
-    writable: Writable,
-    readable: Readable,
-): NodeJS.ReadWriteStream {
-    return baseFunctions.duplex(writable, readable);
-}
 
-/**
+        /**
- * Return a Duplex stream from a child process' stdin and stdout
+         * Return a Duplex stream from a writable stream that is assumed to somehow, when written to,
- * @param childProcess Child process from which to create duplex stream
+         * cause the given readable stream to yield chunks
- */
+         * @param writable Writable stream assumed to cause the readable stream to yield chunks when written to
-export function child(childProcess: ChildProcess): NodeJS.ReadWriteStream {
+         * @param readable Readable stream assumed to yield chunks when the writable stream is written to
-    return baseFunctions.child(childProcess);
+         */
-}
+        duplex,
 
-/**
+        /**
- * Return a Promise resolving to the last streamed chunk of the given readable stream, after it has
+         * Return a Duplex stream from a child process' stdin and stdout
- * ended
+         * @param childProcess Child process from which to create duplex stream
- * @param readable Readable stream to wait on
+         */
- */
+        child,
-export function last<T>(readable: Readable): Promise<T | null> {
-    return baseFunctions.last(readable);
-}
 
-/**
+        /**
- * Stores chunks of data internally in array and batches when batchSize is reached.
+         * Return a Promise resolving to the last streamed chunk of the given readable stream, after it has
- * @param batchSize Size of the batches, defaults to 1000.
+         * ended
- * @param maxBatchAge? Max lifetime of a batch, defaults to 500
+         * @param readable Readable stream to wait on
- */
+         */
-export function batch(batchSize: number, maxBatchAge?: number): NodeJS.ReadWriteStream {
+        last,
-    return baseFunctions.batch(batchSize, maxBatchAge);
-}
 
-/**
+        /**
- * Unbatches and sends individual chunks of data
+         * Stores chunks of data internally in array and batches when batchSize is reached.
- */
+         * @param batchSize Size of the batches, defaults to 1000.
-export function unbatch(): NodeJS.ReadWriteStream {
+         * @param maxBatchAge? Max lifetime of a batch, defaults to 500
-    return baseFunctions.unbatch();
+         * @param options?
-}
+         * @param options.objectMode? Whether this stream should behave as a stream of objects
+         */
+        batch: withDefaultOptions(2, batch),
 
-/**
+        /**
- * Limits date of data transferred into stream.
+         * Unbatches and sends individual chunks of data.
- * @param options?
+         * @param options?
- * @param targetRate? Desired rate in ms
+         * @param options.objectMode? Whether this stream should behave as a stream of objects
- * @param period? Period to sleep for when rate is above or equal to targetRate
+         */
- */
+        unbatch: withDefaultOptions(0, unbatch),
-export function rate(targetRate?: number, period?: number): NodeJS.ReadWriteStream {
-    return baseFunctions.rate(targetRate, period);
-}
 
-/**
+        /**
- * Limits number of parallel processes in flight.
+         * Limits rate of data transferred into stream.
- * @param parallel Max number of parallel processes.
+         * @param targetRate? Desired rate in ms.
- * @param func Function to execute on each data chunk
+         * @param period? Period to sleep for when rate is above or equal to targetRate.
- * @param pause Amount of time to pause processing when max number of parallel processes are executing.
+         * @param options?
- */
+         */
-export function parallelMap<T, R>(
+        rate: withDefaultOptions(2, rate),
-    mapper: (chunk: T) => R,
+
-    parallel?: number,
+        /**
-    sleepTime?: number,
+         * Limits number of parallel processes in flight.
-) {
+         * @param parallel Max number of parallel processes.
-    return baseFunctions.parallelMap(mapper, parallel, sleepTime);
+         * @param func Function to execute on each data chunk.
+         * @param pause Amount of time to pause processing when max number of parallel processes are executing.
+         */
+        parallelMap: withDefaultOptions(3, parallelMap),
+
+        /**
+         * Accummulates and sends batches of data. Each chunk that flows into the stream is checked against items
+         * in the buffer. How the buffer is mutated is based on 1 of 2 possible buffering strategies:
+         * 	1. Sliding
+         * 		- If the buffer is larger than the batchSize, the front of the buffer is popped to maintain
+         * 		the batchSize. When no key is provided, the batchSize is effectively the buffer length. When
+         * 		a key is provided, the batchSize is based on the value at that key. For example, given a key
+         * 		of `timestamp` and a batchSize of 3000, each item in the buffer will be guaranteed to be
+         * 		within 3000 timestamp units from the first element. This means that with a key, multiple elements
+         * 		may be spliced off the front of the buffer. The buffer is then pushed into the stream.
+         * 	2. Rolling
+         * 		- If the buffer is larger than the batchSize, the buffer is cleared and pushed into the stream.
+         * 		When no key is provided, the batchSize is the buffer length. When a key is provided, the batchSize
+         * 		is based on the value at that key. For example, given a key of `timestamp` and a batchSize of 3000,
+         * 		each item in the buffer will be guaranteed to be within 3000 timestamp units from the first element.
+         * @param flushStrategy Buffering strategy to use.
+         * @param batchSize Size of the batch (in units of buffer length or value at key).
+         * @param keyBy Key to determine if element fits into buffer or items need to be cleared from buffer.
+         * @param options Transform stream options
+         */
+        accumulator: withDefaultOptions(3, accumulator),
+
+        /**
+         * Accummulates and sends batches of data. Each chunk that flows into the stream is checked against items
+         * in the buffer. How the buffer is mutated is based on 1 of 2 possible buffering strategies:
+         * 	1. Sliding
+         * 		- If the iteratee returns false, the front of the buffer is popped until iteratee returns true. The
+         * 		item is pushed into the buffer and buffer is pushed into stream.
+         * 	2. Rolling
+         * 		- If the iteratee returns false, the buffer is cleared and pushed into stream. The item is
+         * 		then pushed into the buffer.
+         * @param flushStrategy Buffering strategy to use.
+         * @param iteratee Function applied to buffer when a chunk of data enters stream to determine if element fits into
+         * or items need to be cleared from buffer.
+         * @param options Transform stream options
+         */
+        accumulatorBy: withDefaultOptions(2, accumulatorBy),
+
+        /**
+         * Composes multiple streams together. Writing occurs on first stream, piping occurs from last stream.
+         * @param streams Array of streams to compose. Minimum of two.
+         * @param options Transform stream options
+         */
+        compose: withDefaultOptions(1, compose),
+
+        /**
+         * Composes multiple streams together. Writing occurs on first stream, piping occurs from last stream.
+         * @param construct Constructor for new output source. Should return a Writable or ReadWrite stream.
+         * @param demuxBy
+         * @param demuxBy.key? Key to fetch value from source chunks to demultiplex source.
+         * @param demuxBy.keyBy? Function to fetch value from source chunks to demultiplex source.
+         * @param options Writable stream options
+         */
+        demux: withDefaultOptions(2, demux),
+    };
 }

src/functions/join.ts

@@ -0,0 +1,26 @@
+import { Transform, TransformOptions } from "stream";
+import { StringDecoder } from "string_decoder";
+import { WithEncoding } from "./baseDefinitions";
+
+export function join(
+    separator: string,
+    options: WithEncoding & TransformOptions = { encoding: "utf8" },
+): Transform {
+    let isFirstChunk = true;
+    const decoder = new StringDecoder(options.encoding);
+    return new Transform({
+        readableObjectMode: true,
+        async transform(chunk: Buffer, encoding, callback) {
+            const asString = decoder.write(chunk);
+            // Take care not to break up multi-byte characters spanning multiple chunks
+            if (asString !== "" || chunk.length === 0) {
+                if (!isFirstChunk) {
+                    this.push(separator);
+                }
+                this.push(asString);
+                isFirstChunk = false;
+            }
+            callback();
+        },
+    });
+}

src/functions/last.ts

@@ -0,0 +1,8 @@
+export function last<T>(readable: NodeJS.ReadableStream): Promise<T | null> {
+    let lastChunk: T | null = null;
+    return new Promise((resolve, _) => {
+        readable
+            .on("data", chunk => (lastChunk = chunk))
+            .on("end", () => resolve(lastChunk));
+    });
+}

src/functions/map.ts

@@ -0,0 +1,13 @@
+import { Transform, TransformOptions } from "stream";
+
+export function map<T, R>(
+    mapper: (chunk: T, encoding: string) => R,
+    options: TransformOptions = { objectMode: true },
+): Transform {
+    return new Transform({
+        ...options,
+        async transform(chunk: T, encoding, callback) {
+            callback(null, await mapper(chunk, encoding));
+        },
+    });
+}

src/functions/merge.ts

@@ -0,0 +1,33 @@
+import { Readable } from "stream";
+
+export function merge(...streams: Readable[]): Readable {
+    let isStarted = false;
+    let streamEndedCount = 0;
+    return new Readable({
+        objectMode: true,
+        read() {
+            if (streamEndedCount >= streams.length) {
+                this.push(null);
+            } else if (!isStarted) {
+                isStarted = true;
+                streams.forEach(stream =>
+                    stream
+                        .on("data", chunk => {
+                            if (!this.push(chunk)) {
+                                streams.forEach(s => s.pause());
+                            }
+                        })
+                        .on("error", err => this.emit("error", err))
+                        .on("end", () => {
+                            streamEndedCount++;
+                            if (streamEndedCount === streams.length) {
+                                this.push(null);
+                            }
+                        }),
+                );
+            } else {
+                streams.forEach(s => s.resume());
+            }
+        },
+    });
+}

src/functions/parallelMap.ts

@@ -0,0 +1,30 @@
+import { Transform, TransformOptions } from "stream";
+import { sleep } from "../helpers";
+
+export function parallelMap<T, R>(
+    mapper: (data: T) => R,
+    parallel: number = 10,
+    sleepTime: number = 1,
+    options?: TransformOptions,
+) {
+    let inflight = 0;
+    return new Transform({
+        ...options,
+        async transform(data, encoding, callback) {
+            while (parallel <= inflight) {
+                await sleep(sleepTime);
+            }
+            inflight += 1;
+            callback();
+            const res = await mapper(data);
+            this.push(res);
+            inflight -= 1;
+        },
+        async flush(callback) {
+            while (inflight > 0) {
+                await sleep(sleepTime);
+            }
+            callback();
+        },
+    });
+}

src/functions/parse.ts

@@ -0,0 +1,22 @@
+import { Transform } from "stream";
+import { StringDecoder } from "string_decoder";
+import { SerializationFormats } from "./baseDefinitions";
+
+export function parse(
+    format: SerializationFormats = SerializationFormats.utf8,
+): Transform {
+    const decoder = new StringDecoder(format);
+    return new Transform({
+        readableObjectMode: true,
+        writableObjectMode: true,
+        async transform(chunk: Buffer, encoding, callback) {
+            try {
+                const asString = decoder.write(chunk);
+                // Using await causes parsing errors to be emitted
+                callback(undefined, await JSON.parse(asString));
+            } catch (err) {
+                callback(err);
+            }
+        },
+    });
+}

src/functions/rate.ts

@@ -0,0 +1,24 @@
+import { Transform, TransformOptions } from "stream";
+import { performance } from "perf_hooks";
+import { sleep } from "../helpers";
+
+export function rate(
+    targetRate: number = 50,
+    period: number = 1,
+    options?: TransformOptions,
+): Transform {
+    const deltaMS = ((1 / targetRate) * 1000) / period; // Skip a full period
+    let total = 0;
+    const start = performance.now();
+    return new Transform({
+        ...options,
+        async transform(data, encoding, callback) {
+            const currentRate = (total / (performance.now() - start)) * 1000;
+            if (targetRate && currentRate > targetRate) {
+                await sleep(deltaMS);
+            }
+            total += 1;
+            callback(undefined, data);
+        },
+    });
+}

src/functions/reduce.ts

@@ -0,0 +1,31 @@
+import { Transform, TransformOptions } from "stream";
+
+export function reduce<T, R>(
+    iteratee:
+        | ((previousValue: R, chunk: T, encoding: string) => R)
+        | ((previousValue: R, chunk: T, encoding: string) => Promise<R>),
+    initialValue: R,
+    options?: TransformOptions,
+) {
+    let value = initialValue;
+    return new Transform({
+        ...options,
+        async transform(chunk: T, encoding, callback) {
+            value = await iteratee(value, chunk, encoding);
+            callback();
+        },
+        flush(callback) {
+            // Best effort attempt at yielding the final value (will throw if e.g. yielding an object and
+            // downstream doesn't expect objects)
+            try {
+                callback(undefined, value);
+            } catch (err) {
+                try {
+                    this.emit("error", err);
+                } catch {
+                    // Best effort was made
+                }
+            }
+        },
+    });
+}

src/functions/replace.ts

@@ -0,0 +1,25 @@
+import { Transform } from "stream";
+import { StringDecoder } from "string_decoder";
+import { WithEncoding } from "./baseDefinitions";
+export function replace(
+    searchValue: string | RegExp,
+    replaceValue: string,
+    options: WithEncoding = { encoding: "utf8" },
+): Transform {
+    const decoder = new StringDecoder(options.encoding);
+    return new Transform({
+        readableObjectMode: true,
+        transform(chunk: Buffer, encoding, callback) {
+            const asString = decoder.write(chunk);
+            // Take care not to break up multi-byte characters spanning multiple chunks
+            if (asString !== "" || chunk.length === 0) {
+                callback(
+                    undefined,
+                    asString.replace(searchValue, replaceValue),
+                );
+            } else {
+                callback();
+            }
+        },
+    });
+}

src/functions/split.ts

@@ -0,0 +1,29 @@
+import { Transform } from "stream";
+import { StringDecoder } from "string_decoder";
+import { WithEncoding } from "./baseDefinitions";
+
+export function split(
+    separator: string | RegExp = "\n",
+    options: WithEncoding = { encoding: "utf8" },
+): Transform {
+    let buffered = "";
+    const decoder = new StringDecoder(options.encoding);
+
+    return new Transform({
+        readableObjectMode: true,
+        transform(chunk: Buffer, encoding, callback) {
+            const asString = decoder.write(chunk);
+            const splitted = asString.split(separator);
+            if (splitted.length > 1) {
+                splitted[0] = buffered.concat(splitted[0]);
+                buffered = "";
+            }
+            buffered += splitted[splitted.length - 1];
+            splitted.slice(0, -1).forEach((part: string) => this.push(part));
+            callback();
+        },
+        flush(callback) {
+            callback(undefined, buffered + decoder.end());
+        },
+    });
+}

src/functions/stringify.ts

@@ -0,0 +1,19 @@
+import { Transform } from "stream";
+import { JsonValue, JsonParseOptions } from "./baseDefinitions";
+
+export function stringify(
+    options: JsonParseOptions = { pretty: false },
+): Transform {
+    return new Transform({
+        readableObjectMode: true,
+        writableObjectMode: true,
+        transform(chunk: JsonValue, encoding, callback) {
+            callback(
+                undefined,
+                options.pretty
+                    ? JSON.stringify(chunk, null, 2)
+                    : JSON.stringify(chunk),
+            );
+        },
+    });
+}

src/functions/unbatch.ts

@@ -0,0 +1,13 @@
+import { Transform, TransformOptions } from "stream";
+
+export function unbatch(options?: TransformOptions) {
+    return new Transform({
+        ...options,
+        transform(data, encoding, callback) {
+            for (const d of data) {
+                this.push(d);
+            }
+            callback();
+        },
+    });
+}

src/index.ts

@@ -1,22 +1,2 @@
-export {
+import mhysa from "./functions";
-    fromArray,
+export default mhysa;
-    map,
-    flatMap,
-    filter,
-    reduce,
-    split,
-    join,
-    replace,
-    parse,
-    stringify,
-    collect,
-    concat,
-    merge,
-    duplex,
-    child,
-    last,
-    batch,
-    unbatch,
-    rate,
-    parallelMap,
-} from "./functions";

tests/accumulator.spec.ts

@@ -0,0 +1,557 @@
+import test from "ava";
+import { expect } from "chai";
+import { Readable } from "stream";
+import mhysa from "../src";
+import { FlushStrategy } from "../src/functions/accumulator";
+import { performance } from "perf_hooks";
+const { accumulator, accumulatorBy } = mhysa({ objectMode: true });
+
+test.cb("accumulator() rolling", t => {
+    t.plan(3);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const firstFlush = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+    const secondFlush = [{ ts: 2, key: "d" }, { ts: 3, key: "e" }];
+    const thirdFlush = [{ ts: 4, key: "f" }];
+    const flushes = [firstFlush, secondFlush, thirdFlush];
+
+    source
+        .pipe(
+            accumulator(FlushStrategy.rolling, 2, undefined, {
+                objectMode: true,
+            }),
+        )
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    [...firstFlush, ...secondFlush, ...thirdFlush].forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb("accumulator() rolling with key", t => {
+    t.plan(2);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const firstFlush = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 2, key: "d" },
+    ];
+    const secondFlush = [{ ts: 3, key: "e" }];
+    const flushes = [firstFlush, secondFlush];
+
+    source
+        .pipe(accumulator(FlushStrategy.rolling, 3, "ts", { objectMode: true }))
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    [...firstFlush, ...secondFlush].forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb(
+    "accumulator() rolling should emit error and ignore chunk when its missing key",
+    t => {
+        t.plan(2);
+        let index = 0;
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const accumulatorStream = accumulator(
+            FlushStrategy.rolling,
+            3,
+            "nonExistingKey",
+            { objectMode: true },
+        );
+        const input = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+
+        source
+            .pipe(accumulatorStream)
+            .on("data", (flush: TestObject[]) => {
+                // No valid data output
+                expect(flush).to.deep.equal([]);
+            })
+            .on("error", (err: any) => {
+                source.pipe(accumulatorStream);
+                accumulatorStream.resume();
+                expect(err.message).to.equal(
+                    `Key is missing in event: (nonExistingKey, ${JSON.stringify(
+                        input[index],
+                    )})`,
+                );
+                index++;
+                t.pass();
+            })
+            .on("end", t.end);
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);
+
+test.cb(
+    "accumulator() rolling should emit error, ignore chunk when key is missing and continue processing chunks correctly",
+    t => {
+        t.plan(3);
+        let chunkIndex = 0;
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const accumulatorStream = accumulator(FlushStrategy.rolling, 3, "ts", {
+            objectMode: true,
+        });
+        const input = [
+            { ts: 0, key: "a" },
+            { ts: 1, key: "b" },
+            { ts: 2, key: "c" },
+            { key: "d" },
+            { ts: 3, key: "e" },
+        ];
+        const firstFlush = [
+            { ts: 0, key: "a" },
+            { ts: 1, key: "b" },
+            { ts: 2, key: "c" },
+        ];
+        const secondFlush = [{ ts: 3, key: "e" }];
+        const flushes = [firstFlush, secondFlush];
+
+        source
+            .pipe(accumulatorStream)
+            .on("data", (flush: TestObject[]) => {
+                t.deepEqual(flush, flushes[chunkIndex]);
+                chunkIndex++;
+            })
+            .on("error", (err: any) => {
+                source.pipe(accumulatorStream);
+                accumulatorStream.resume();
+                expect(err.message).to.equal(
+                    `Key is missing in event: (ts, ${JSON.stringify(
+                        input[3],
+                    )})`,
+                );
+                t.pass();
+            })
+            .on("end", t.end);
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);
+
+test.cb("accumulator() sliding", t => {
+    t.plan(4);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const input = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 4, key: "d" },
+    ];
+    const firstFlush = [{ ts: 0, key: "a" }];
+    const secondFlush = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+    const thirdFlush = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+    ];
+    const fourthFlush = [
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 4, key: "d" },
+    ];
+
+    const flushes = [firstFlush, secondFlush, thirdFlush, fourthFlush];
+    source
+        .pipe(
+            accumulator(FlushStrategy.sliding, 3, undefined, {
+                objectMode: true,
+            }),
+        )
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    input.forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb("accumulator() sliding with key", t => {
+    t.plan(6);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const input = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 3, key: "d" },
+        { ts: 5, key: "f" },
+        { ts: 6, key: "g" },
+    ];
+    const firstFlush = [{ ts: 0, key: "a" }];
+    const secondFlush = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+    const thirdFlush = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+    ];
+    const fourthFlush = [
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 3, key: "d" },
+    ];
+    const fifthFlush = [{ ts: 3, key: "d" }, { ts: 5, key: "f" }];
+    const sixthFlush = [{ ts: 5, key: "f" }, { ts: 6, key: "g" }];
+
+    const flushes = [
+        firstFlush,
+        secondFlush,
+        thirdFlush,
+        fourthFlush,
+        fifthFlush,
+        sixthFlush,
+    ];
+    source
+        .pipe(accumulator(FlushStrategy.sliding, 3, "ts", { objectMode: true }))
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    input.forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb(
+    "accumulator() sliding should emit error and ignore chunk when key is missing",
+    t => {
+        t.plan(2);
+        let index = 0;
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const accumulatorStream = accumulator(
+            FlushStrategy.sliding,
+            3,
+            "nonExistingKey",
+            { objectMode: true },
+        );
+        const input = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+
+        source
+            .pipe(accumulatorStream)
+            .on("data", (flush: TestObject[]) => {
+                expect(flush).to.deep.equal([]);
+            })
+            .on("error", (err: any) => {
+                source.pipe(accumulatorStream);
+                accumulatorStream.resume();
+                expect(err.message).to.equal(
+                    `Key is missing in event: (nonExistingKey, ${JSON.stringify(
+                        input[index],
+                    )})`,
+                );
+                index++;
+                t.pass();
+            })
+            .on("end", t.end);
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);
+
+test.cb(
+    "accumulator() sliding should emit error, ignore chunk when key is missing and continue processing chunks correctly",
+    t => {
+        t.plan(6);
+        let chunkIndex = 0;
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const accumulatorStream = accumulator(FlushStrategy.sliding, 3, "ts", {
+            objectMode: true,
+        });
+        const input = [
+            { ts: 0, key: "a" },
+            { key: "b" },
+            { ts: 2, key: "c" },
+            { ts: 3, key: "d" },
+            { ts: 5, key: "f" },
+            { ts: 6, key: "g" },
+        ];
+        const firstFlush = [{ ts: 0, key: "a" }];
+        const secondFlush = [{ ts: 0, key: "a" }, { ts: 2, key: "c" }];
+        const thirdFlush = [{ ts: 2, key: "c" }, { ts: 3, key: "d" }];
+        const fourthFlush = [{ ts: 3, key: "d" }, { ts: 5, key: "f" }];
+        const fifthFlush = [{ ts: 5, key: "f" }, { ts: 6, key: "g" }];
+
+        const flushes = [
+            firstFlush,
+            secondFlush,
+            thirdFlush,
+            fourthFlush,
+            fifthFlush,
+        ];
+        source
+            .pipe(accumulatorStream)
+            .on("data", (flush: TestObject[]) => {
+                t.deepEqual(flush, flushes[chunkIndex]);
+                chunkIndex++;
+            })
+            .on("error", (err: any) => {
+                source.pipe(accumulatorStream);
+                accumulatorStream.resume();
+                expect(err.message).to.equal(
+                    `Key is missing in event: (ts, ${JSON.stringify(
+                        input[1],
+                    )})`,
+                );
+                t.pass();
+            })
+            .on("end", t.end);
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);
+
+test.cb("accumulatorBy() rolling", t => {
+    t.plan(2);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const firstFlush = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 2, key: "d" },
+    ];
+    const secondFlush = [{ ts: 3, key: "e" }];
+    const flushes = [firstFlush, secondFlush];
+
+    source
+        .pipe(
+            accumulatorBy(
+                FlushStrategy.rolling,
+                (event: TestObject, bufferChunk: TestObject) => {
+                    return bufferChunk.ts + 3 <= event.ts;
+                },
+                { objectMode: true },
+            ),
+        )
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    [...firstFlush, ...secondFlush].forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb.skip(
+    "accumulatorBy() rolling should emit error when key iteratee throws",
+    t => {
+        t.plan(2);
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const input = [
+            { ts: 0, key: "a" },
+            { ts: 1, key: "b" },
+            { ts: 2, key: "c" },
+        ];
+        const accumulaterStream = accumulatorBy(
+            FlushStrategy.rolling,
+            (event: TestObject, bufferChunk: TestObject) => {
+                if (event.key !== "a") {
+                    throw new Error("Failed mapping");
+                }
+                return bufferChunk.ts + 3 <= event.ts;
+            },
+            { objectMode: true },
+        );
+        source
+            .pipe(accumulaterStream)
+            .on("error", (err: any) => {
+                source.pipe(accumulaterStream);
+                accumulaterStream.resume();
+                expect(err.message).to.equal("Failed mapping");
+                t.pass();
+            })
+            .on("end", t.end);
+
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);
+
+test.cb("accumulatorBy() sliding", t => {
+    t.plan(6);
+    let chunkIndex = 0;
+    interface TestObject {
+        ts: number;
+        key: string;
+    }
+    const source = new Readable({ objectMode: true });
+    const input = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 3, key: "d" },
+        { ts: 5, key: "f" },
+        { ts: 6, key: "g" },
+    ];
+    const firstFlush = [{ ts: 0, key: "a" }];
+    const secondFlush = [{ ts: 0, key: "a" }, { ts: 1, key: "b" }];
+    const thirdFlush = [
+        { ts: 0, key: "a" },
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+    ];
+    const fourthFlush = [
+        { ts: 1, key: "b" },
+        { ts: 2, key: "c" },
+        { ts: 3, key: "d" },
+    ];
+    const fifthFlush = [{ ts: 3, key: "d" }, { ts: 5, key: "f" }];
+    const sixthFlush = [{ ts: 5, key: "f" }, { ts: 6, key: "g" }];
+
+    const flushes = [
+        firstFlush,
+        secondFlush,
+        thirdFlush,
+        fourthFlush,
+        fifthFlush,
+        sixthFlush,
+    ];
+    source
+        .pipe(
+            accumulatorBy(
+                FlushStrategy.sliding,
+                (event: TestObject, bufferChunk: TestObject) => {
+                    return bufferChunk.ts + 3 <= event.ts ? true : false;
+                },
+                { objectMode: true },
+            ),
+        )
+        .on("data", (flush: TestObject[]) => {
+            t.deepEqual(flush, flushes[chunkIndex]);
+            chunkIndex++;
+        })
+        .on("error", (e: any) => {
+            t.end(e);
+        })
+        .on("end", t.end);
+    input.forEach(item => {
+        source.push(item);
+    });
+    source.push(null);
+});
+
+test.cb.skip(
+    "accumulatorBy() sliding should emit error when key iteratee throws",
+    t => {
+        t.plan(2);
+        interface TestObject {
+            ts: number;
+            key: string;
+        }
+        const source = new Readable({ objectMode: true });
+        const input = [
+            { ts: 0, key: "a" },
+            { ts: 1, key: "b" },
+            { ts: 2, key: "c" },
+        ];
+        const accumulaterStream = accumulatorBy(
+            FlushStrategy.sliding,
+            (event: TestObject, bufferChunk: TestObject) => {
+                if (event.key !== "a") {
+                    throw new Error("Failed mapping");
+                }
+                return bufferChunk.ts + 3 <= event.ts ? true : false;
+            },
+            { objectMode: true },
+        );
+        source
+            .pipe(accumulaterStream)
+            .on("error", (err: any) => {
+                source.pipe(accumulaterStream);
+                accumulaterStream.resume();
+                expect(err.message).to.equal("Failed mapping");
+                t.pass();
+            })
+            .on("end", t.end);
+
+        input.forEach(item => {
+            source.push(item);
+        });
+        source.push(null);
+    },
+);

tests/batch.spec.ts

@@ -0,0 +1,59 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { batch } = mhysa({ objectMode: true });
+
+test.cb("batch() batches chunks together", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = [["a", "b", "c"], ["d", "e", "f"], ["g"]];
+    let i = 0;
+    source
+        .pipe(batch(3))
+        .on("data", (element: string[]) => {
+            t.deepEqual(element, expectedElements[i]);
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push("d");
+    source.push("e");
+    source.push("f");
+    source.push("g");
+    source.push(null);
+});
+
+test.cb("batch() yields a batch after the timeout", t => {
+    t.plan(3);
+    const source = new Readable({
+        objectMode: true,
+        read(size: number) {
+            return;
+        },
+    });
+    const expectedElements = [["a", "b"], ["c"], ["d"]];
+    let i = 0;
+    source
+        .pipe(batch(3))
+        .on("data", (element: string[]) => {
+            t.deepEqual(element, expectedElements[i]);
+            i++;
+        })
+        .on("error", t.fail)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    setTimeout(() => {
+        source.push("c");
+    }, 600);
+    setTimeout(() => {
+        source.push("d");
+        source.push(null);
+    }, 600 * 2);
+});

tests/child.spec.ts

@@ -0,0 +1,29 @@
+import * as cp from "child_process";
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { child } = mhysa();
+
+test.cb(
+    "child() allows easily writing to child process stdin and reading from its stdout",
+    t => {
+        t.plan(1);
+        const source = new Readable();
+        const catProcess = cp.exec("cat");
+        let out = "";
+        source
+            .pipe(child(catProcess))
+            .on("data", chunk => (out += chunk))
+            .on("error", t.end)
+            .on("end", () => {
+                expect(out).to.equal("abcdef");
+                t.pass();
+                t.end();
+            });
+        source.push("ab");
+        source.push("cd");
+        source.push("ef");
+        source.push(null);
+    },
+);

tests/collect.spec.ts

@@ -0,0 +1,133 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { collect } = mhysa();
+
+test.cb(
+    "collect() collects streamed elements into an array (object, flowing mode)",
+    t => {
+        t.plan(1);
+        const source = new Readable({ objectMode: true });
+
+        source
+            .pipe(collect({ objectMode: true }))
+            .on("data", collected => {
+                expect(collected).to.deep.equal(["a", "b", "c"]);
+                t.pass();
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("a");
+        source.push("b");
+        source.push("c");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "collect() collects streamed elements into an array (object, paused mode)",
+    t => {
+        t.plan(1);
+        const source = new Readable({ objectMode: true });
+        const collector = source.pipe(collect({ objectMode: true }));
+
+        collector
+            .on("readable", () => {
+                let collected = collector.read();
+                while (collected !== null) {
+                    expect(collected).to.deep.equal(["a", "b", "c"]);
+                    t.pass();
+                    collected = collector.read();
+                }
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("a");
+        source.push("b");
+        source.push("c");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "collect() collects streamed bytes into a buffer (non-object, flowing mode)",
+    t => {
+        t.plan(1);
+        const source = new Readable({ objectMode: false });
+
+        source
+            .pipe(collect())
+            .on("data", collected => {
+                expect(collected).to.deep.equal(Buffer.from("abc"));
+                t.pass();
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("a");
+        source.push("b");
+        source.push("c");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "collect() collects streamed bytes into a buffer (non-object, paused mode)",
+    t => {
+        t.plan(1);
+        const source = new Readable({ objectMode: false });
+        const collector = source.pipe(collect({ objectMode: false }));
+        collector
+            .on("readable", () => {
+                let collected = collector.read();
+                while (collected !== null) {
+                    expect(collected).to.deep.equal(Buffer.from("abc"));
+                    t.pass();
+                    collected = collector.read();
+                }
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("a");
+        source.push("b");
+        source.push("c");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "collect() emits an empty array if the source was empty (object mode)",
+    t => {
+        t.plan(1);
+        const source = new Readable({ objectMode: true });
+        const collector = source.pipe(collect({ objectMode: true }));
+        collector
+            .on("data", collected => {
+                expect(collected).to.deep.equal([]);
+                t.pass();
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push(null);
+    },
+);
+
+test.cb(
+    "collect() emits nothing if the source was empty (non-object mode)",
+    t => {
+        t.plan(0);
+        const source = new Readable({ objectMode: false });
+        const collector = source.pipe(collect({ objectMode: false }));
+        collector
+            .on("data", () => t.fail())
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push(null);
+    },
+);

tests/compose.spec.ts

@@ -0,0 +1,512 @@
+const test = require("ava");
+const { expect } = require("chai");
+const { sleep } = require("../src/helpers");
+import mhysa from "../src";
+import { performance } from "perf_hooks";
+const { compose, map } = mhysa({ objectMode: true });
+
+test.cb("compose() chains two streams together in the correct order", t => {
+    t.plan(3);
+    interface Chunk {
+        visited: number[];
+        key: string;
+    }
+
+    let i = 0;
+    const first = map((chunk: Chunk) => {
+        chunk.visited.push(1);
+        return chunk;
+    });
+    const second = map((chunk: Chunk) => {
+        chunk.visited.push(2);
+        return chunk;
+    });
+
+    const composed = compose(
+        [first, second],
+        { objectMode: true },
+    );
+
+    composed.on("data", data => {
+        expect(data).to.deep.equal(result[i]);
+        t.pass();
+        i++;
+        if (i === 3) {
+            t.end();
+        }
+    });
+    composed.on("error", err => {
+        t.end(err);
+    });
+    composed.on("end", () => {
+        t.end();
+    });
+
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "c", visited: [] },
+    ];
+    const result = [
+        { key: "a", visited: [1, 2] },
+        { key: "b", visited: [1, 2] },
+        { key: "c", visited: [1, 2] },
+    ];
+
+    input.forEach(item => composed.write(item));
+});
+
+test.cb("piping compose() maintains correct order", t => {
+    t.plan(3);
+    interface Chunk {
+        visited: number[];
+        key: string;
+    }
+    let i = 0;
+    const first = map((chunk: Chunk) => {
+        chunk.visited.push(1);
+        return chunk;
+    });
+    const second = map((chunk: Chunk) => {
+        chunk.visited.push(2);
+        return chunk;
+    });
+
+    const composed = compose(
+        [first, second],
+        { objectMode: true },
+    );
+    const third = map((chunk: Chunk) => {
+        chunk.visited.push(3);
+        return chunk;
+    });
+
+    composed.pipe(third).on("data", data => {
+        expect(data).to.deep.equal(result[i]);
+        t.pass();
+        i++;
+        if (i === 3) {
+            t.end();
+        }
+    });
+
+    composed.on("error", err => {
+        t.end(err);
+    });
+
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "c", visited: [] },
+    ];
+    const result = [
+        { key: "a", visited: [1, 2, 3] },
+        { key: "b", visited: [1, 2, 3] },
+        { key: "c", visited: [1, 2, 3] },
+    ];
+
+    input.forEach(item => composed.write(item));
+});
+
+test("compose() writable length should be less than highWaterMark when handing writes", async t => {
+    t.plan(7);
+    return new Promise(async (resolve, reject) => {
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const first = map(
+            async (chunk: Chunk) => {
+                chunk.mapped.push(1);
+                return chunk;
+            },
+            {
+                objectMode: true,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                chunk.mapped.push(2);
+                return chunk;
+            },
+            { objectMode: true },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark: 2 },
+        );
+        composed.on("error", err => {
+            reject();
+        });
+
+        composed.on("drain", () => {
+            t.pass();
+            expect(composed._writableState.length).to.be.equal(0);
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            if (chunk.key === "e") {
+                resolve();
+            }
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+        ];
+
+        for (const item of input) {
+            const res = composed.write(item);
+            expect(composed._writableState.length).to.be.at.most(2);
+            t.pass();
+            if (!res) {
+                await sleep(10);
+            }
+        }
+    });
+});
+
+test("compose() should emit drain event ~rate * highWaterMark ms for every write that causes backpressure", async t => {
+    t.plan(7);
+    const _rate = 100;
+    const highWaterMark = 2;
+    return new Promise(async (resolve, reject) => {
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const first = map(
+            async (chunk: Chunk) => {
+                await sleep(_rate);
+                chunk.mapped.push(1);
+                return chunk;
+            },
+            {
+                objectMode: true,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                chunk.mapped.push(2);
+                return chunk;
+            },
+            { objectMode: true },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark },
+        );
+        composed.on("error", err => {
+            reject();
+        });
+
+        composed.on("drain", () => {
+            t.pass();
+            expect(composed._writableState.length).to.be.equal(0);
+            expect(performance.now() - start).to.be.closeTo(
+                _rate * highWaterMark,
+                40,
+            );
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            pendingReads--;
+            if (pendingReads === 0) {
+                resolve();
+            }
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+        ];
+
+        let start = performance.now();
+        let pendingReads = input.length;
+        start = performance.now();
+        for (const item of input) {
+            const res = composed.write(item);
+            expect(composed._writableState.length).to.be.at.most(highWaterMark);
+            t.pass();
+            if (!res) {
+                await sleep(_rate * highWaterMark * 2);
+                start = performance.now();
+            }
+        }
+    });
+});
+
+test.cb(
+    "compose() should emit drain event after 500 ms when writing 5 items that take 100ms to process with a highWaterMark of 5 ",
+    t => {
+        t.plan(6);
+        const _rate = 100;
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const first = map(
+            async (chunk: Chunk) => {
+                await sleep(_rate);
+                chunk.mapped.push(1);
+                return chunk;
+            },
+            {
+                objectMode: true,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                chunk.mapped.push(2);
+                return chunk;
+            },
+            { objectMode: true },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark: 5 },
+        );
+
+        composed.on("error", err => {
+            t.end(err);
+        });
+
+        composed.on("drain", () => {
+            expect(composed._writableState.length).to.be.equal(0);
+            expect(performance.now() - start).to.be.closeTo(
+                _rate * input.length,
+                50,
+            );
+            t.pass();
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            t.pass();
+            if (chunk.key === "e") {
+                t.end();
+            }
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+        ];
+        input.forEach(item => {
+            composed.write(item);
+        });
+        const start = performance.now();
+    },
+);
+
+test.cb(
+    "compose() should emit drain event immediately when second stream is bottleneck",
+    t => {
+        t.plan(6);
+        const _rate = 200;
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const first = map(
+            (chunk: Chunk) => {
+                chunk.mapped.push(1);
+                return chunk;
+            },
+            {
+                objectMode: true,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                pendingReads--;
+                await sleep(_rate);
+                expect(second._writableState.length).to.be.equal(1);
+                expect(first._readableState.length).to.equal(pendingReads);
+                chunk.mapped.push(2);
+                return chunk;
+            },
+            { objectMode: true, highWaterMark: 1 },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark: 5 },
+        );
+        composed.on("error", err => {
+            t.end(err);
+        });
+
+        composed.on("drain", () => {
+            expect(composed._writableState.length).to.be.equal(0);
+            expect(performance.now() - start).to.be.lessThan(_rate);
+            t.pass();
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            expect(composed._writableState.length).to.be.equal(0);
+            t.pass();
+            if (chunk.key === "e") {
+                t.end();
+            }
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+        ];
+        let pendingReads = input.length;
+
+        input.forEach(item => {
+            composed.write(item);
+        });
+
+        const start = performance.now();
+    },
+);
+
+test.cb(
+    "compose() should emit drain event and first should contain up to highWaterMark items in readable state when second is bottleneck",
+    t => {
+        t.plan(6);
+        interface Chunk {
+            index: number;
+            mapped: string[];
+        }
+        const first = map(
+            async (chunk: Chunk) => {
+                expect(first._readableState.length).to.be.at.most(2);
+                chunk.mapped.push("first");
+                return chunk;
+            },
+            {
+                objectMode: true,
+                highWaterMark: 2,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                expect(second._writableState.length).to.be.equal(1);
+                await sleep(100);
+                chunk.mapped.push("second");
+                return chunk;
+            },
+            { objectMode: true, highWaterMark: 2 },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark: 5 },
+        );
+        composed.on("error", err => {
+            t.end(err);
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            expect(chunk.mapped.length).to.equal(2);
+            expect(chunk.mapped).to.deep.equal(["first", "second"]);
+            t.pass();
+            if (chunk.index === 5) {
+                t.end();
+            }
+        });
+
+        composed.on("drain", () => {
+            expect(composed._writableState.length).to.be.equal(0);
+            t.pass();
+        });
+
+        const input = [
+            { index: 1, mapped: [] },
+            { index: 2, mapped: [] },
+            { index: 3, mapped: [] },
+            { index: 4, mapped: [] },
+            { index: 5, mapped: [] },
+        ];
+
+        input.forEach(item => {
+            composed.write(item);
+        });
+    },
+);
+
+test.cb(
+    "compose() should not emit drain event writing 5 items to compose with a highWaterMark of 6",
+    t => {
+        t.plan(5);
+        const _rate = 100;
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const first = map(
+            async (chunk: Chunk) => {
+                await sleep(_rate);
+                chunk.mapped.push(1);
+                return chunk;
+            },
+            {
+                objectMode: true,
+            },
+        );
+
+        const second = map(
+            async (chunk: Chunk) => {
+                chunk.mapped.push(2);
+                return chunk;
+            },
+            { objectMode: true },
+        );
+
+        const composed = compose(
+            [first, second],
+            { objectMode: true, highWaterMark: 6 },
+        );
+
+        composed.on("error", err => {
+            t.end(err);
+        });
+
+        composed.on("drain", () => {
+            t.end(new Error("Drain should not be emitted"));
+        });
+
+        composed.on("data", (chunk: Chunk) => {
+            t.pass();
+            if (chunk.key === "e") {
+                t.end();
+            }
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+        ];
+
+        input.forEach(item => {
+            composed.write(item);
+        });
+    },
+);

tests/concat.spec.ts

@@ -0,0 +1,181 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { concat, collect } = mhysa();
+
+test.cb(
+    "concat() concatenates multiple readable streams (object, flowing mode)",
+    t => {
+        t.plan(6);
+        const source1 = new Readable({ objectMode: true });
+        const source2 = new Readable({ objectMode: true });
+        const expectedElements = ["a", "b", "c", "d", "e", "f"];
+        let i = 0;
+        concat(source1, source2)
+            .on("data", (element: string) => {
+                expect(element).to.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source1.push("a");
+        source2.push("d");
+        source1.push("b");
+        source2.push("e");
+        source1.push("c");
+        source2.push("f");
+        source2.push(null);
+        source1.push(null);
+    },
+);
+
+test.cb(
+    "concat() concatenates multiple readable streams (object, paused mode)",
+    t => {
+        t.plan(6);
+        const source1 = new Readable({ objectMode: true });
+        const source2 = new Readable({ objectMode: true });
+        const expectedElements = ["a", "b", "c", "d", "e", "f"];
+        let i = 0;
+        const concatenation = concat(source1, source2)
+            .on("readable", () => {
+                let element = concatenation.read();
+                while (element !== null) {
+                    expect(element).to.equal(expectedElements[i]);
+                    t.pass();
+                    i++;
+                    element = concatenation.read();
+                }
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source1.push("a");
+        source2.push("d");
+        source1.push("b");
+        source2.push("e");
+        source1.push("c");
+        source2.push("f");
+        source2.push(null);
+        source1.push(null);
+    },
+);
+
+test.cb(
+    "concat() concatenates multiple readable streams (non-object, flowing mode)",
+    t => {
+        t.plan(6);
+        const source1 = new Readable({ objectMode: false });
+        const source2 = new Readable({ objectMode: false });
+        const expectedElements = ["a", "b", "c", "d", "e", "f"];
+        let i = 0;
+        concat(source1, source2)
+            .on("data", (element: string) => {
+                expect(element).to.deep.equal(Buffer.from(expectedElements[i]));
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source1.push("a");
+        source2.push("d");
+        source1.push("b");
+        source2.push("e");
+        source1.push("c");
+        source2.push("f");
+        source2.push(null);
+        source1.push(null);
+    },
+);
+
+test.cb(
+    "concat() concatenates multiple readable streams (non-object, paused mode)",
+    t => {
+        t.plan(6);
+        const source1 = new Readable({ objectMode: false, read: () => ({}) });
+        const source2 = new Readable({ objectMode: false, read: () => ({}) });
+        const expectedElements = ["a", "b", "c", "d", "e", "f"];
+        let i = 0;
+        const concatenation = concat(source1, source2)
+            .on("readable", () => {
+                let element = concatenation.read();
+                while (element !== null) {
+                    expect(element).to.deep.equal(
+                        Buffer.from(expectedElements[i]),
+                    );
+                    t.pass();
+                    i++;
+                    element = concatenation.read();
+                }
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source1.push("a");
+        setTimeout(() => source2.push("d"), 10);
+        setTimeout(() => source1.push("b"), 20);
+        setTimeout(() => source2.push("e"), 30);
+        setTimeout(() => source1.push("c"), 40);
+        setTimeout(() => source2.push("f"), 50);
+        setTimeout(() => source2.push(null), 60);
+        setTimeout(() => source1.push(null), 70);
+    },
+);
+
+test.cb("concat() concatenates a single readable stream (object mode)", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "b", "c", "d", "e", "f"];
+    let i = 0;
+    concat(source)
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb(
+    "concat() concatenates a single readable stream (non-object mode)",
+    t => {
+        t.plan(3);
+        const source = new Readable({ objectMode: false });
+        const expectedElements = ["a", "b", "c", "d", "e", "f"];
+        let i = 0;
+        concat(source)
+            .on("data", (element: string) => {
+                expect(element).to.deep.equal(Buffer.from(expectedElements[i]));
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("a");
+        source.push("b");
+        source.push("c");
+        source.push(null);
+    },
+);
+
+test.cb("concat() concatenates empty list of readable streams", t => {
+    t.plan(0);
+    concat()
+        .pipe(collect())
+        .on("data", _ => {
+            t.fail();
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+});

tests/defaultOptions.spec.ts

@@ -0,0 +1,21 @@
+import { Readable } from "stream";
+import test from "ava";
+import mhysa from "../src";
+
+const withDefaultOptions = mhysa({ objectMode: true });
+const withoutOptions = mhysa();
+
+test("Mhysa instances can have default options", t => {
+    let batch = withDefaultOptions.batch();
+    t.true(batch._readableState.objectMode);
+    t.true(batch._writableState.objectMode);
+    batch = withDefaultOptions.batch(3);
+    t.true(batch._readableState.objectMode);
+    t.true(batch._writableState.objectMode);
+    batch = withDefaultOptions.batch(3, 1);
+    t.true(batch._readableState.objectMode);
+    t.true(batch._writableState.objectMode);
+    batch = withDefaultOptions.batch(3, 1, { objectMode: false });
+    t.false(batch._readableState.objectMode);
+    t.false(batch._writableState.objectMode);
+});

tests/demux.spec.ts

@@ -0,0 +1,657 @@
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+import { Writable } from "stream";
+const sinon = require("sinon");
+const { sleep } = require("../src/helpers");
+import { performance } from "perf_hooks";
+const { demux, map } = mhysa();
+
+interface Test {
+    key: string;
+    visited: number[];
+}
+
+test.cb("demux() constructor should be called once per key", t => {
+    t.plan(1);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+    const construct = sinon.spy((destKey: string) => {
+        const dest = map((chunk: Test) => {
+            chunk.visited.push(1);
+            return chunk;
+        });
+
+        return dest;
+    });
+
+    const demuxed = demux(construct, "key", { objectMode: true });
+
+    demuxed.on("finish", () => {
+        expect(construct.withArgs("a").callCount).to.equal(1);
+        expect(construct.withArgs("b").callCount).to.equal(1);
+        expect(construct.withArgs("c").callCount).to.equal(1);
+        t.pass();
+        t.end();
+    });
+
+    input.forEach(event => demuxed.write(event));
+    demuxed.end();
+});
+
+test.cb("demux() should send input through correct pipeline", t => {
+    t.plan(6);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+    const pipelineSpies = {};
+    const construct = (destKey: string) => {
+        const mapper = sinon.spy((chunk: Test) => {
+            return { ...chunk, visited: [1] };
+        });
+        const dest = map(mapper);
+        pipelineSpies[destKey] = mapper;
+
+        return dest;
+    };
+
+    const demuxed = demux(construct, "key", { objectMode: true });
+
+    demuxed.on("finish", () => {
+        pipelineSpies["a"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("a");
+            t.pass();
+        });
+        pipelineSpies["b"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("b");
+            t.pass();
+        });
+        pipelineSpies["c"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("c");
+            t.pass();
+        });
+        t.end();
+    });
+
+    input.forEach(event => demuxed.write(event));
+    demuxed.end();
+});
+
+test.cb("demux() constructor should be called once per key using keyBy", t => {
+    t.plan(1);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+
+    const construct = sinon.spy((destKey: string) => {
+        const dest = map((chunk: Test) => {
+            chunk.visited.push(1);
+            return chunk;
+        });
+
+        return dest;
+    });
+
+    const demuxed = demux(construct, item => item.key, { objectMode: true });
+
+    demuxed.on("finish", () => {
+        expect(construct.withArgs("a").callCount).to.equal(1);
+        expect(construct.withArgs("b").callCount).to.equal(1);
+        expect(construct.withArgs("c").callCount).to.equal(1);
+        t.pass();
+        t.end();
+    });
+
+    input.forEach(event => demuxed.write(event));
+    demuxed.end();
+});
+
+test.cb("demux() should send input through correct pipeline using keyBy", t => {
+    t.plan(6);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+    const pipelineSpies = {};
+    const construct = (destKey: string) => {
+        const mapper = sinon.spy((chunk: Test) => {
+            return { ...chunk, visited: [1] };
+        });
+        const dest = map(mapper);
+        pipelineSpies[destKey] = mapper;
+
+        return dest;
+    };
+
+    const demuxed = demux(construct, item => item.key, { objectMode: true });
+
+    demuxed.on("finish", () => {
+        pipelineSpies["a"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("a");
+            t.pass();
+        });
+        pipelineSpies["b"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("b");
+            t.pass();
+        });
+        pipelineSpies["c"].getCalls().forEach(call => {
+            expect(call.args[0].key).to.equal("c");
+            t.pass();
+        });
+        t.end();
+    });
+
+    input.forEach(event => demuxed.write(event));
+    demuxed.end();
+});
+
+test("demux() write should return false after if it has >= highWaterMark items buffered and drain should be emitted", t => {
+    return new Promise(async (resolve, reject) => {
+        t.plan(7);
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const input: Chunk[] = [
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+        ];
+        let pendingReads = input.length;
+        const highWaterMark = 5;
+        const slowProcessorSpeed = 25;
+        const construct = (destKey: string) => {
+            const first = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    return { ...chunk, mapped: [1] };
+                },
+                { highWaterMark: 1, objectMode: true },
+            );
+
+            first.on("data", chunk => {
+                expect(chunk.mapped).to.deep.equal([1]);
+                pendingReads--;
+                if (pendingReads === 0) {
+                    resolve();
+                }
+                t.pass();
+            });
+
+            return first;
+        };
+
+        const _demux = demux(construct, "key", {
+            objectMode: true,
+            highWaterMark,
+        });
+
+        _demux.on("error", err => {
+            reject();
+        });
+
+        for (const item of input) {
+            const res = _demux.write(item);
+            expect(_demux._writableState.length).to.be.at.most(highWaterMark);
+            if (!res) {
+                await new Promise((resolv, rej) => {
+                    _demux.once("drain", () => {
+                        expect(_demux._writableState.length).to.be.equal(0);
+                        t.pass();
+                        resolv();
+                    });
+                });
+            }
+        }
+    });
+});
+
+test("demux() should emit one drain event after slowProcessorSpeed * highWaterMark ms", t => {
+    return new Promise(async (resolve, reject) => {
+        t.plan(7);
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const input: Chunk[] = [
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+        ];
+        let pendingReads = input.length;
+        const highWaterMark = 5;
+        const slowProcessorSpeed = 25;
+
+        const construct = (destKey: string) => {
+            const first = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { highWaterMark: 1, objectMode: true },
+            );
+
+            first.on("data", () => {
+                t.pass();
+                pendingReads--;
+                if (pendingReads === 0) {
+                    resolve();
+                }
+            });
+            return first;
+        };
+        const _demux = demux(construct, "key", {
+            objectMode: true,
+            highWaterMark,
+        });
+        _demux.on("error", err => {
+            reject();
+        });
+
+        const start = performance.now();
+        for (const item of input) {
+            const res = _demux.write(item);
+            if (!res) {
+                await new Promise((resolv, rej) => {
+                    // This event should be received after all items in demux are processed
+                    _demux.once("drain", () => {
+                        expect(performance.now() - start).to.be.greaterThan(
+                            slowProcessorSpeed * highWaterMark,
+                        );
+                        t.pass();
+                        resolv();
+                    });
+                });
+            }
+        }
+    });
+});
+
+test("demux() should emit one drain event when writing 6 items with highWaterMark of 5", t => {
+    return new Promise(async (resolve, reject) => {
+        t.plan(7);
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const highWaterMark = 5;
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+        ];
+        let pendingReads = input.length;
+        const construct = (destKey: string) => {
+            const first = map(
+                async (chunk: Chunk) => {
+                    await sleep(50);
+                    chunk.mapped.push(2);
+                    return chunk;
+                },
+                { highWaterMark: 1, objectMode: true },
+            );
+
+            first.on("data", () => {
+                pendingReads--;
+                t.pass();
+                if (pendingReads === 0) {
+                    resolve();
+                }
+            });
+            return first;
+        };
+        const _demux = demux(construct, "key", {
+            objectMode: true,
+            highWaterMark: 5,
+        });
+
+        _demux.on("error", err => {
+            reject();
+        });
+
+        for (const item of input) {
+            const res = _demux.write(item);
+            expect(_demux._writableState.length).to.be.at.most(highWaterMark);
+            if (!res) {
+                await new Promise(_resolve => {
+                    _demux.once("drain", () => {
+                        _resolve();
+                        expect(_demux._writableState.length).to.be.equal(0);
+                        t.pass();
+                    });
+                });
+            }
+        }
+    });
+});
+
+test.cb.only(
+    "demux() should emit drain event when third stream is bottleneck",
+    t => {
+        t.plan(8);
+        const slowProcessorSpeed = 100;
+        const highWaterMark = 5;
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const sink = new Writable({
+            objectMode: true,
+            write(chunk, encoding, cb) {
+                expect(chunk.mapped).to.deep.equal([1, 2]);
+                t.pass();
+                pendingReads--;
+                if (pendingReads === 0) {
+                    t.end();
+                }
+                cb();
+            },
+        });
+        const construct = (destKey: string) => {
+            const first = map(
+                (chunk: Chunk) => {
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            const second = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    chunk.mapped.push(2);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            first.pipe(second).pipe(sink);
+            return first;
+        };
+        const _demux = demux(construct, () => "a", {
+            objectMode: true,
+            highWaterMark,
+        });
+        _demux.on("error", err => {
+            t.end(err);
+        });
+
+        // This event should be received after at least 5 * slowProcessorSpeed (two are read immediately by first and second, 5 remaining in demux before drain event)
+        _demux.on("drain", () => {
+            expect(_demux._writableState.length).to.be.equal(0);
+            expect(performance.now() - start).to.be.greaterThan(
+                slowProcessorSpeed * (input.length - 2),
+            );
+            t.pass();
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+            { key: "f", mapped: [] },
+            { key: "g", mapped: [] },
+        ];
+        let pendingReads = input.length;
+
+        const start = performance.now();
+        input.forEach(item => {
+            _demux.write(item);
+        });
+    },
+);
+
+test.cb(
+    "demux() should emit drain event when second stream is bottleneck",
+    t => {
+        t.plan(8);
+        const slowProcessorSpeed = 100;
+        const highWaterMark = 5;
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const sink = new Writable({
+            objectMode: true,
+            write(chunk, encoding, cb) {
+                expect(chunk.mapped).to.deep.equal([1, 2]);
+                t.pass();
+                pendingReads--;
+                if (pendingReads === 0) {
+                    t.end();
+                }
+                cb();
+            },
+        });
+        const construct = (destKey: string) => {
+            const first = map(
+                (chunk: Chunk) => {
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+            const second = map(
+                (chunk: Chunk) => {
+                    chunk.mapped.push(2);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            const third = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    chunk.mapped.push(3);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            first
+                .pipe(second)
+                .pipe(third)
+                .pipe(sink);
+            return first;
+        };
+        const _demux = demux(construct, () => "a", {
+            objectMode: true,
+            highWaterMark,
+        });
+        _demux.on("error", err => {
+            t.end(err);
+        });
+
+        // This event should be received after at least 3 * slowProcessorSpeed (two are read immediately by first and second, 3 remaining in demux before drain event)
+        _demux.on("drain", () => {
+            expect(_demux._writableState.length).to.be.equal(0);
+            expect(performance.now() - start).to.be.greaterThan(
+                slowProcessorSpeed * (input.length - 4),
+            );
+            t.pass();
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "b", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "d", mapped: [] },
+            { key: "e", mapped: [] },
+            { key: "f", mapped: [] },
+            { key: "g", mapped: [] },
+        ];
+        let pendingReads = input.length;
+
+        const start = performance.now();
+        input.forEach(item => {
+            _demux.write(item);
+        });
+    },
+);
+
+test("demux() should be blocked by slowest pipeline", t => {
+    t.plan(1);
+    const slowProcessorSpeed = 100;
+    interface Chunk {
+        key: string;
+        mapped: number[];
+    }
+    return new Promise(async (resolve, reject) => {
+        const construct = (destKey: string) => {
+            const first = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            first.on("data", chunk => {
+                pendingReads--;
+                if (chunk.key === "b") {
+                    expect(performance.now() - start).to.be.greaterThan(
+                        slowProcessorSpeed * totalItems,
+                    );
+                    t.pass();
+                    expect(pendingReads).to.equal(0);
+                    resolve();
+                }
+            });
+            return first;
+        };
+        const _demux = demux(construct, "key", {
+            objectMode: true,
+            highWaterMark: 1,
+        });
+        _demux.on("error", err => {
+            reject(err);
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "c", mapped: [] },
+            { key: "b", mapped: [] },
+        ];
+
+        let pendingReads = input.length;
+        const totalItems = input.length;
+        const start = performance.now();
+        for (const item of input) {
+            if (!_demux.write(item)) {
+                await new Promise(_resolve => {
+                    _demux.once("drain", () => {
+                        _resolve();
+                    });
+                });
+            }
+        }
+    });
+});
+
+test("demux() should emit drain event when second stream in pipeline is bottleneck", t => {
+    t.plan(5);
+    const highWaterMark = 3;
+    return new Promise(async (resolve, reject) => {
+        interface Chunk {
+            key: string;
+            mapped: number[];
+        }
+        const sink = new Writable({
+            objectMode: true,
+            write(chunk, encoding, cb) {
+                expect(chunk.mapped).to.deep.equal([1, 2]);
+                t.pass();
+                cb();
+                if (pendingReads === 0) {
+                    resolve();
+                }
+            },
+        });
+
+        const construct = (destKey: string) => {
+            const first = map(
+                (chunk: Chunk) => {
+                    expect(first._readableState.length).to.be.at.most(2);
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 2 },
+            );
+
+            const second = map(
+                async (chunk: Chunk) => {
+                    await sleep(100);
+                    chunk.mapped.push(2);
+                    expect(second._writableState.length).to.be.equal(1);
+                    pendingReads--;
+                    return chunk;
+                },
+                { objectMode: true, highWaterMark: 1 },
+            );
+
+            first.pipe(second).pipe(sink);
+            return first;
+        };
+
+        const _demux = demux(construct, "key", {
+            objectMode: true,
+            highWaterMark,
+        });
+        _demux.on("error", err => {
+            reject();
+        });
+
+        _demux.on("drain", () => {
+            expect(_demux._writableState.length).to.be.equal(0);
+            t.pass();
+        });
+
+        const input = [
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+            { key: "a", mapped: [] },
+        ];
+        let pendingReads = input.length;
+
+        input.forEach(item => {
+            _demux.write(item);
+        });
+    });
+});

tests/duplex.spec.ts

@@ -0,0 +1,29 @@
+import * as cp from "child_process";
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { duplex } = mhysa();
+
+test.cb(
+    "duplex() combines a writable and readable stream into a ReadWrite stream",
+    t => {
+        t.plan(1);
+        const source = new Readable();
+        const catProcess = cp.exec("cat");
+        let out = "";
+        source
+            .pipe(duplex(catProcess.stdin!, catProcess.stdout!))
+            .on("data", chunk => (out += chunk))
+            .on("error", t.end)
+            .on("end", () => {
+                expect(out).to.equal("abcdef");
+                t.pass();
+                t.end();
+            });
+        source.push("ab");
+        source.push("cd");
+        source.push("ef");
+        source.push(null);
+    },
+);

tests/filter.spec.ts

@@ -0,0 +1,117 @@
+import test from "ava";
+import { expect } from "chai";
+import { Readable } from "stream";
+import mhysa from "../src";
+const { filter } = mhysa();
+
+test.cb("filter() filters elements synchronously", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "c"];
+    let i = 0;
+    source
+        .pipe(
+            filter((element: string) => element !== "b", {
+                readableObjectMode: true,
+                writableObjectMode: true,
+            }),
+        )
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb("filter() filters elements asynchronously", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "c"];
+    let i = 0;
+    source
+        .pipe(
+            filter(
+                async (element: string) => {
+                    await Promise.resolve();
+                    return element !== "b";
+                },
+                { readableObjectMode: true, writableObjectMode: true },
+            ),
+        )
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb.skip("filter() emits errors during synchronous filtering", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            filter(
+                (element: string) => {
+                    if (element !== "a") {
+                        throw new Error("Failed filtering");
+                    }
+                    return true;
+                },
+                { readableObjectMode: true, writableObjectMode: true },
+            ),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed filtering");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb.skip("filter() emits errors during asynchronous filtering", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            filter(
+                async (element: string) => {
+                    await Promise.resolve();
+                    if (element !== "a") {
+                        throw new Error("Failed filtering");
+                    }
+                    return true;
+                },
+                { readableObjectMode: true, writableObjectMode: true },
+            ),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed filtering");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});

tests/flatMap.spec.ts

@@ -0,0 +1,101 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { flatMap } = mhysa({ objectMode: true });
+
+test.cb("flatMap() maps elements synchronously", t => {
+    t.plan(6);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "A", "b", "B", "c", "C"];
+    let i = 0;
+    source
+        .pipe(flatMap((element: string) => [element, element.toUpperCase()]))
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb("flatMap() maps elements asynchronously", t => {
+    t.plan(6);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "A", "b", "B", "c", "C"];
+    let i = 0;
+    source
+        .pipe(
+            flatMap(async (element: string) => {
+                await Promise.resolve();
+                return [element, element.toUpperCase()];
+            }),
+        )
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb.skip("flatMap() emits errors during synchronous mapping", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            flatMap((element: string) => {
+                if (element !== "a") {
+                    throw new Error("Failed mapping");
+                }
+                return [element, element.toUpperCase()];
+            }),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed mapping");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb.skip("flatMap() emits errors during asynchronous mapping", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            flatMap(async (element: string) => {
+                await Promise.resolve();
+                if (element !== "a") {
+                    throw new Error("Failed mapping");
+                }
+                return [element, element.toUpperCase()];
+            }),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed mapping");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});

tests/fromArray.spec.ts

@@ -0,0 +1,46 @@
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { fromArray } = mhysa();
+
+test.cb("fromArray() streams array elements in flowing mode", t => {
+    t.plan(3);
+    const elements = ["a", "b", "c"];
+    const stream = fromArray(elements);
+    let i = 0;
+    stream
+        .on("data", (element: string) => {
+            expect(element).to.equal(elements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+});
+
+test.cb("fromArray() ends immediately if there are no array elements", t => {
+    t.plan(0);
+    fromArray([])
+        .on("data", () => t.fail())
+        .on("error", t.end)
+        .on("end", t.end);
+});
+
+test.cb("fromArray() streams array elements in paused mode", t => {
+    t.plan(3);
+    const elements = ["a", "b", "c"];
+    const stream = fromArray(elements);
+    let i = 0;
+    stream
+        .on("readable", () => {
+            let element = stream.read();
+            while (element !== null) {
+                expect(element).to.equal(elements[i]);
+                t.pass();
+                i++;
+                element = stream.read();
+            }
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+});

tests/join.spec.ts

@@ -0,0 +1,57 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { join } = mhysa();
+
+test.cb("join() joins chunks using the specified separator", t => {
+    t.plan(9);
+    const source = new Readable({ objectMode: true });
+    const expectedParts = ["ab|", "|", "c|d", "|", "|", "|", "e", "|", "|f|"];
+    let i = 0;
+    source
+        .pipe(join("|"))
+        .on("data", part => {
+            expect(part).to.equal(expectedParts[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("ab|");
+    source.push("c|d");
+    source.push("|");
+    source.push("e");
+    source.push("|f|");
+    source.push(null);
+});
+
+test.cb(
+    "join() joins chunks using the specified separator without breaking up multi-byte characters " +
+        "spanning multiple chunks",
+    t => {
+        t.plan(5);
+        const source = new Readable({ objectMode: true });
+        const expectedParts = ["ø", "|", "ö", "|", "一"];
+        let i = 0;
+        source
+            .pipe(join("|"))
+            .on("data", part => {
+                expect(part).to.equal(expectedParts[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push(Buffer.from("ø").slice(0, 1)); // 2-byte character spanning two chunks
+        source.push(Buffer.from("ø").slice(1, 2));
+        source.push(Buffer.from("ö").slice(0, 1)); // 2-byte character spanning two chunks
+        source.push(Buffer.from("ö").slice(1, 2));
+        source.push(Buffer.from("一").slice(0, 1)); // 3-byte character spanning three chunks
+        source.push(Buffer.from("一").slice(1, 2));
+        source.push(Buffer.from("一").slice(2, 3));
+        source.push(null);
+    },
+);

tests/last.spec.ts

@@ -0,0 +1,16 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { last } = mhysa();
+
+test("last() resolves to the last chunk streamed by the given readable stream", async t => {
+    const source = new Readable({ objectMode: true });
+    const lastPromise = last(source);
+    source.push("ab");
+    source.push("cd");
+    source.push("ef");
+    source.push(null);
+    const lastChunk = await lastPromise;
+    expect(lastChunk).to.equal("ef");
+});

tests/map.spec.ts

@@ -0,0 +1,57 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { map } = mhysa();
+
+test.cb("map() maps elements synchronously", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const mapStream = map((element: string) => element.toUpperCase(), {
+        objectMode: true,
+    });
+    const expectedElements = ["A", "B", "C"];
+    let i = 0;
+    source
+        .pipe(mapStream)
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb("map() maps elements asynchronously", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const mapStream = map(
+        async (element: string) => {
+            await Promise.resolve();
+            return element.toUpperCase();
+        },
+        { objectMode: true },
+    );
+    const expectedElements = ["A", "B", "C"];
+    let i = 0;
+    source
+        .pipe(mapStream)
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});

tests/merge.spec.ts

@@ -0,0 +1,61 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { merge } = mhysa();
+
+test.cb(
+    "merge() merges multiple readable streams in chunk arrival order",
+    t => {
+        t.plan(6);
+        const source1 = new Readable({ objectMode: true, read: () => ({}) });
+        const source2 = new Readable({ objectMode: true, read: () => ({}) });
+        const expectedElements = ["a", "d", "b", "e", "c", "f"];
+        let i = 0;
+        merge(source1, source2)
+            .on("data", (element: string) => {
+                expect(element).to.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source1.push("a");
+        setTimeout(() => source2.push("d"), 10);
+        setTimeout(() => source1.push("b"), 20);
+        setTimeout(() => source2.push("e"), 30);
+        setTimeout(() => source1.push("c"), 40);
+        setTimeout(() => source2.push("f"), 50);
+        setTimeout(() => source2.push(null), 60);
+        setTimeout(() => source1.push(null), 70);
+    },
+);
+
+test.cb("merge() merges a readable stream", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true, read: () => ({}) });
+    const expectedElements = ["a", "b", "c"];
+    let i = 0;
+    merge(source)
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});
+
+test.cb("merge() merges an empty list of readable streams", t => {
+    t.plan(0);
+    merge()
+        .on("data", () => t.pass())
+        .on("error", t.end)
+        .on("end", t.end);
+});

tests/parallelMap.spec.ts

@@ -0,0 +1,78 @@
+import { Readable } from "stream";
+import { performance } from "perf_hooks";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+import { sleep } from "../src/helpers";
+const { parallelMap } = mhysa({ objectMode: true });
+
+test.cb("parallelMap() parallel mapping", t => {
+    t.plan(6);
+    const offset = 50;
+    const source = new Readable({ objectMode: true });
+    const expectedElements = [
+        "a_processed",
+        "b_processed",
+        "c_processed",
+        "d_processed",
+        "e_processed",
+        "f_processed",
+    ];
+    interface IPerfData {
+        start: number;
+        output?: string;
+        finish?: number;
+    }
+    const orderedResults: IPerfData[] = [];
+    source
+        .pipe(
+            parallelMap(async (data: any) => {
+                const perfData: IPerfData = { start: performance.now() };
+                const c = data + "_processed";
+                perfData.output = c;
+                await sleep(offset);
+                perfData.finish = performance.now();
+                orderedResults.push(perfData);
+                return c;
+            }, 2),
+        )
+        .on("data", (element: string) => {
+            t.true(expectedElements.includes(element));
+        })
+        .on("error", t.end)
+        .on("end", async () => {
+            expect(orderedResults[0].finish).to.be.lessThan(
+                orderedResults[2].start,
+            );
+            expect(orderedResults[1].finish).to.be.lessThan(
+                orderedResults[3].start,
+            );
+            expect(orderedResults[2].finish).to.be.lessThan(
+                orderedResults[4].start,
+            );
+            expect(orderedResults[3].finish).to.be.lessThan(
+                orderedResults[5].start,
+            );
+            expect(orderedResults[0].start).to.be.lessThan(
+                orderedResults[2].start + offset,
+            );
+            expect(orderedResults[1].start).to.be.lessThan(
+                orderedResults[3].start + offset,
+            );
+            expect(orderedResults[2].start).to.be.lessThan(
+                orderedResults[4].start + offset,
+            );
+            expect(orderedResults[3].start).to.be.lessThan(
+                orderedResults[5].start + offset,
+            );
+            t.end();
+        });
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push("d");
+    source.push("e");
+    source.push("f");
+    source.push(null);
+});

tests/parse.spec.ts

@@ -0,0 +1,41 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { parse } = mhysa();
+
+test.cb("parse() parses the streamed elements as JSON", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["abc", {}, []];
+    let i = 0;
+    source
+        .pipe(parse())
+        .on("data", part => {
+            expect(part).to.deep.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push('"abc"');
+    source.push("{}");
+    source.push("[]");
+    source.push(null);
+});
+
+test.cb("parse() emits errors on invalid JSON", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(parse())
+        .resume()
+        .on("error", () => t.pass())
+        .on("end", t.end);
+
+    source.push("{}");
+    source.push({});
+    source.push([]);
+    source.push(null);
+});

tests/rate.spec.ts

@@ -0,0 +1,90 @@
+import { Readable } from "stream";
+import { performance } from "perf_hooks";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { rate } = mhysa({ objectMode: true });
+
+test.cb("rate() sends data at a rate of 150", t => {
+    t.plan(5);
+    const targetRate = 150;
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "b", "c", "d", "e"];
+    const start = performance.now();
+    let i = 0;
+
+    source
+        .pipe(rate(targetRate))
+        .on("data", (element: string[]) => {
+            const currentRate = (i / (performance.now() - start)) * 1000;
+            expect(element).to.deep.equal(expectedElements[i]);
+            expect(currentRate).lessThan(targetRate);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push("d");
+    source.push("e");
+    source.push(null);
+});
+
+test.cb("rate() sends data at a rate of 50", t => {
+    t.plan(5);
+    const targetRate = 50;
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "b", "c", "d", "e"];
+    const start = performance.now();
+    let i = 0;
+
+    source
+        .pipe(rate(targetRate))
+        .on("data", (element: string[]) => {
+            const currentRate = (i / (performance.now() - start)) * 1000;
+            expect(element).to.deep.equal(expectedElements[i]);
+            expect(currentRate).lessThan(targetRate);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push("d");
+    source.push("e");
+    source.push(null);
+});
+
+test.cb("rate() sends data at a rate of 1", t => {
+    t.plan(5);
+    const targetRate = 1;
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "b", "c", "d", "e"];
+    const start = performance.now();
+    let i = 0;
+
+    source
+        .pipe(rate(targetRate))
+        .on("data", (element: string[]) => {
+            const currentRate = (i / (performance.now() - start)) * 1000;
+            expect(element).to.deep.equal(expectedElements[i]);
+            expect(currentRate).lessThan(targetRate);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push("d");
+    source.push("e");
+    source.push(null);
+});

tests/reduce.spec.ts

@@ -0,0 +1,99 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { reduce } = mhysa({ objectMode: true });
+
+test.cb("reduce() reduces elements synchronously", t => {
+    t.plan(1);
+    const source = new Readable({ objectMode: true });
+    const expectedValue = 6;
+    source
+        .pipe(reduce((acc: number, element: string) => acc + element.length, 0))
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedValue);
+            t.pass();
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("ab");
+    source.push("cd");
+    source.push("ef");
+    source.push(null);
+});
+
+test.cb("reduce() reduces elements asynchronously", t => {
+    t.plan(1);
+    const source = new Readable({ objectMode: true });
+    const expectedValue = 6;
+    source
+        .pipe(
+            reduce(async (acc: number, element: string) => {
+                await Promise.resolve();
+                return acc + element.length;
+            }, 0),
+        )
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedValue);
+            t.pass();
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("ab");
+    source.push("cd");
+    source.push("ef");
+    source.push(null);
+});
+
+test.cb.skip("reduce() emits errors during synchronous reduce", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            reduce((acc: number, element: string) => {
+                if (element !== "ab") {
+                    throw new Error("Failed reduce");
+                }
+                return acc + element.length;
+            }, 0),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed reduce");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("ab");
+    source.push("cd");
+    source.push("ef");
+    source.push(null);
+});
+
+test.cb.skip("reduce() emits errors during asynchronous reduce", t => {
+    t.plan(2);
+    const source = new Readable({ objectMode: true });
+    source
+        .pipe(
+            reduce(async (acc: number, element: string) => {
+                await Promise.resolve();
+                if (element !== "ab") {
+                    throw new Error("Failed mapping");
+                }
+                return acc + element.length;
+            }, 0),
+        )
+        .resume()
+        .on("error", err => {
+            expect(err.message).to.equal("Failed mapping");
+            t.pass();
+        })
+        .on("end", t.end);
+
+    source.push("ab");
+    source.push("cd");
+    source.push("ef");
+    source.push(null);
+});

tests/replace.spec.ts

@@ -0,0 +1,81 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { replace } = mhysa();
+
+test.cb(
+    "replace() replaces occurrences of the given string in the streamed elements with the specified " +
+        "replacement string",
+    t => {
+        t.plan(3);
+        const source = new Readable({ objectMode: true });
+        const expectedElements = ["abc", "xyf", "ghi"];
+        let i = 0;
+        source
+            .pipe(replace("de", "xy"))
+            .on("data", part => {
+                expect(part).to.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("abc");
+        source.push("def");
+        source.push("ghi");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "replace() replaces occurrences of the given regular expression in the streamed elements with " +
+        "the specified replacement string",
+    t => {
+        t.plan(3);
+        const source = new Readable({ objectMode: true });
+        const expectedElements = ["abc", "xyz", "ghi"];
+        let i = 0;
+        source
+            .pipe(replace(/^def$/, "xyz"))
+            .on("data", part => {
+                expect(part).to.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("abc");
+        source.push("def");
+        source.push("ghi");
+        source.push(null);
+    },
+);
+
+test.cb(
+    "replace() replaces occurrences of the given multi-byte character even if it spans multiple chunks",
+    t => {
+        t.plan(3);
+        const source = new Readable({ objectMode: true });
+        const expectedElements = ["ø", "O", "a"];
+        let i = 0;
+        source
+            .pipe(replace("ö", "O"))
+            .on("data", part => {
+                expect(part).to.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push(Buffer.from("ø").slice(0, 1)); // 2-byte character spanning two chunks
+        source.push(Buffer.from("ø").slice(1, 2));
+        source.push(Buffer.from("ö").slice(0, 1)); // 2-byte character spanning two chunks
+        source.push(Buffer.from("ö").slice(1, 2));
+        source.push("a");
+        source.push(null);
+    },
+);

tests/split.spec.ts

@@ -0,0 +1,99 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { split } = mhysa();
+
+test.cb("split() splits chunks using the default separator (\\n)", t => {
+    t.plan(5);
+    const source = new Readable({ objectMode: true });
+    const expectedParts = ["ab", "c", "d", "ef", ""];
+    let i = 0;
+    source
+        .pipe(split())
+        .on("data", part => {
+            expect(part).to.equal(expectedParts[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("ab\n");
+    source.push("c");
+    source.push("\n");
+    source.push("d");
+    source.push("\nef\n");
+    source.push(null);
+});
+
+test.cb("split() splits chunks using the specified separator", t => {
+    t.plan(6);
+    const source = new Readable({ objectMode: true });
+    const expectedParts = ["ab", "c", "d", "e", "f", ""];
+    let i = 0;
+    source
+        .pipe(split("|"))
+        .on("data", (part: string) => {
+            expect(part).to.equal(expectedParts[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("ab|");
+    source.push("c|d");
+    source.push("|");
+    source.push("e");
+    source.push("|f|");
+    source.push(null);
+});
+
+test.cb(
+    "split() splits utf8 encoded buffers using the specified separator",
+    t => {
+        t.plan(3);
+        const expectedElements = ["a", "b", "c"];
+        let i = 0;
+        const through = split(",");
+        const buf = Buffer.from("a,b,c");
+        through
+            .on("data", element => {
+                expect(element).to.equal(expectedElements[i]);
+                i++;
+                t.pass();
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        for (let j = 0; j < buf.length; ++j) {
+            through.write(buf.slice(j, j + 1));
+        }
+        through.end();
+    },
+);
+
+test.cb(
+    "split() splits utf8 encoded buffers with multi-byte characters using the specified separator",
+    t => {
+        t.plan(3);
+        const expectedElements = ["一", "一", "一"];
+        let i = 0;
+        const through = split(",");
+        const buf = Buffer.from("一,一,一"); // Those spaces are multi-byte utf8 characters (code: 4E00)
+        through
+            .on("data", element => {
+                expect(element).to.equal(expectedElements[i]);
+                i++;
+                t.pass();
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        for (let j = 0; j < buf.length; ++j) {
+            through.write(buf.slice(j, j + 1));
+        }
+        through.end();
+    },
+);

tests/stringify.spec.ts

@@ -0,0 +1,62 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { stringify } = mhysa();
+
+test.cb("stringify() stringifies the streamed elements as JSON", t => {
+    t.plan(4);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = [
+        '"abc"',
+        "0",
+        '{"a":"a","b":"b","c":"c"}',
+        '["a","b","c"]',
+    ];
+    let i = 0;
+    source
+        .pipe(stringify())
+        .on("data", part => {
+            expect(part).to.deep.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("abc");
+    source.push(0);
+    source.push({ a: "a", b: "b", c: "c" });
+    source.push(["a", "b", "c"]);
+    source.push(null);
+});
+
+test.cb(
+    "stringify() stringifies the streamed elements as pretty-printed JSON",
+    t => {
+        t.plan(4);
+        const source = new Readable({ objectMode: true });
+        const expectedElements = [
+            '"abc"',
+            "0",
+            '{\n  "a": "a",\n  "b": "b",\n  "c": "c"\n}',
+            '[\n  "a",\n  "b",\n  "c"\n]',
+        ];
+        let i = 0;
+        source
+            .pipe(stringify({ pretty: true }))
+            .on("data", part => {
+                expect(part).to.deep.equal(expectedElements[i]);
+                t.pass();
+                i++;
+            })
+            .on("error", t.end)
+            .on("end", t.end);
+
+        source.push("abc");
+        source.push(0);
+        source.push({ a: "a", b: "b", c: "c" });
+        source.push(["a", "b", "c"]);
+        source.push(null);
+    },
+);

tests/unbatch.spec.ts

@@ -0,0 +1,27 @@
+import { Readable } from "stream";
+import test from "ava";
+import { expect } from "chai";
+import mhysa from "../src";
+const { unbatch, batch } = mhysa({ objectMode: true });
+
+test.cb("unbatch() unbatches", t => {
+    t.plan(3);
+    const source = new Readable({ objectMode: true });
+    const expectedElements = ["a", "b", "c"];
+    let i = 0;
+    source
+        .pipe(batch(3))
+        .pipe(unbatch())
+        .on("data", (element: string) => {
+            expect(element).to.equal(expectedElements[i]);
+            t.pass();
+            i++;
+        })
+        .on("error", t.end)
+        .on("end", t.end);
+
+    source.push("a");
+    source.push("b");
+    source.push("c");
+    source.push(null);
+});

tsconfig.json

@@ -1,18 +1,21 @@
 {
-    "compilerOptions": {
+  "compilerOptions": {
-        "noImplicitAny": true,
+    "noImplicitAny": true,
-        "strictNullChecks": true,
+    "strictNullChecks": true,
-        "noImplicitReturns": true,
+    "noImplicitReturns": true,
-        "noUnusedLocals": true,
+    "noUnusedLocals": false,
-        "noImplicitThis": true,
+    "noImplicitThis": true,
-        "forceConsistentCasingInFileNames": true,
+    "forceConsistentCasingInFileNames": true,
-        "suppressImplicitAnyIndexErrors": true,
+    "suppressImplicitAnyIndexErrors": true,
-        "outDir": "./dist",
+    "outDir": "./dist",
-        "module": "commonjs",
+    "module": "commonjs"
-        "target": "es5",
+  },
-        "lib": ["es2016"],
+  "target": "es5",
-        "sourceMap": true,
+  "lib": [
-        "declaration": true
+    "es2016"
-    },
+  ],
-    "include": ["src/**/*.ts"]
+  "sourceMap": true,
+  "declaration": true,
+  "include": ["src/**/*"],
+  "exclude": ["tests", "node_modules"]
 }

tslint.json

@@ -9,6 +9,7 @@
         "no-implicit-dependencies": [true, "dev"],
         "prettier": [true, ".prettierrc"],
         "ordered-imports": false,
-        "interface-name": false
+        "interface-name": false,
+	"object-literal-sort-keys": false
     }
 }

yarn.lock

@@ -37,41 +37,41 @@
     imurmurhash "^0.1.4"
     slide "^1.1.5"
 
-"@babel/code-frame@^7.0.0":
+"@babel/code-frame@^7.0.0", "@babel/code-frame@^7.5.5":
-  version "7.0.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/code-frame/-/code-frame-7.0.0.tgz#06e2ab19bdb535385559aabb5ba59729482800f8"
+  resolved "https://registry.yarnpkg.com/@babel/code-frame/-/code-frame-7.5.5.tgz#bc0782f6d69f7b7d49531219699b988f669a8f9d"
-  integrity sha512-OfC2uemaknXr87bdLUkWog7nYuliM9Ij5HUcajsVcMCpQrcLmtxRbVFTIqmcSkSeYRBFBRxs2FiUqFJDLdiebA==
+  integrity sha512-27d4lZoomVyo51VegxI20xZPuSHusqbQag/ztrBC7wegWoQ1nLREPVSKSW8byhTlzTKyNE4ifaTA6lCp7JjpFw==
   dependencies:
     "@babel/highlight" "^7.0.0"
 
 "@babel/core@^7.4.0":
-  version "7.5.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.5.0.tgz#6ed6a2881ad48a732c5433096d96d1b0ee5eb734"
+  resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.5.5.tgz#17b2686ef0d6bc58f963dddd68ab669755582c30"
-  integrity sha512-6Isr4X98pwXqHvtigw71CKgmhL1etZjPs5A67jL/w0TkLM9eqmFR40YrnJvEc1WnMZFsskjsmid8bHZyxKEAnw==
+  integrity sha512-i4qoSr2KTtce0DmkuuQBV4AuQgGPUcPXMr9L5MyYAtk06z068lQ10a4O009fe5OB/DfNV+h+qqT7ddNV8UnRjg==
   dependencies:
-    "@babel/code-frame" "^7.0.0"
+    "@babel/code-frame" "^7.5.5"
-    "@babel/generator" "^7.5.0"
+    "@babel/generator" "^7.5.5"
-    "@babel/helpers" "^7.5.0"
+    "@babel/helpers" "^7.5.5"
-    "@babel/parser" "^7.5.0"
+    "@babel/parser" "^7.5.5"
     "@babel/template" "^7.4.4"
-    "@babel/traverse" "^7.5.0"
+    "@babel/traverse" "^7.5.5"
-    "@babel/types" "^7.5.0"
+    "@babel/types" "^7.5.5"
     convert-source-map "^1.1.0"
     debug "^4.1.0"
     json5 "^2.1.0"
-    lodash "^4.17.11"
+    lodash "^4.17.13"
     resolve "^1.3.2"
     semver "^5.4.1"
     source-map "^0.5.0"
 
-"@babel/generator@^7.0.0", "@babel/generator@^7.4.0", "@babel/generator@^7.5.0":
+"@babel/generator@^7.0.0", "@babel/generator@^7.4.0", "@babel/generator@^7.5.5":
-  version "7.5.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/generator/-/generator-7.5.0.tgz#f20e4b7a91750ee8b63656073d843d2a736dca4a"
+  resolved "https://registry.yarnpkg.com/@babel/generator/-/generator-7.5.5.tgz#873a7f936a3c89491b43536d12245b626664e3cf"
-  integrity sha512-1TTVrt7J9rcG5PMjvO7VEG3FrEoEJNHxumRq66GemPmzboLWtIjjcJgk8rokuAS7IiRSpgVSu5Vb9lc99iJkOA==
+  integrity sha512-ETI/4vyTSxTzGnU2c49XHv2zhExkv9JHLTwDAFz85kmcwuShvYG2H08FwgIguQf4JC75CBnXAUM5PqeF4fj0nQ==
   dependencies:
-    "@babel/types" "^7.5.0"
+    "@babel/types" "^7.5.5"
     jsesc "^2.5.1"
-    lodash "^4.17.11"
+    lodash "^4.17.13"
     source-map "^0.5.0"
     trim-right "^1.0.1"
 
@@ -122,16 +122,16 @@
     "@babel/types" "^7.0.0"
 
 "@babel/helper-module-transforms@^7.4.4":
-  version "7.4.4"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/helper-module-transforms/-/helper-module-transforms-7.4.4.tgz#96115ea42a2f139e619e98ed46df6019b94414b8"
+  resolved "https://registry.yarnpkg.com/@babel/helper-module-transforms/-/helper-module-transforms-7.5.5.tgz#f84ff8a09038dcbca1fd4355661a500937165b4a"
-  integrity sha512-3Z1yp8TVQf+B4ynN7WoHPKS8EkdTbgAEy0nU0rs/1Kw4pDgmvYH3rz3aI11KgxKCba2cn7N+tqzV1mY2HMN96w==
+  integrity sha512-jBeCvETKuJqeiaCdyaheF40aXnnU1+wkSiUs/IQg3tB85up1LyL8x77ClY8qJpuRJUcXQo+ZtdNESmZl4j56Pw==
   dependencies:
     "@babel/helper-module-imports" "^7.0.0"
     "@babel/helper-simple-access" "^7.1.0"
     "@babel/helper-split-export-declaration" "^7.4.4"
     "@babel/template" "^7.4.4"
-    "@babel/types" "^7.4.4"
+    "@babel/types" "^7.5.5"
-    lodash "^4.17.11"
+    lodash "^4.17.13"
 
 "@babel/helper-plugin-utils@^7.0.0":
   version "7.0.0"
@@ -139,11 +139,11 @@
   integrity sha512-CYAOUCARwExnEixLdB6sDm2dIJ/YgEAKDM1MOeMeZu9Ld/bDgVo8aiWrXwcY7OBh+1Ea2uUcVRcxKk0GJvW7QA==
 
 "@babel/helper-regex@^7.4.4":
-  version "7.4.4"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/helper-regex/-/helper-regex-7.4.4.tgz#a47e02bc91fb259d2e6727c2a30013e3ac13c4a2"
+  resolved "https://registry.yarnpkg.com/@babel/helper-regex/-/helper-regex-7.5.5.tgz#0aa6824f7100a2e0e89c1527c23936c152cab351"
-  integrity sha512-Y5nuB/kESmR3tKjU8Nkn1wMGEx1tjJX076HBMeL3XLQCu6vA/YRzuTW0bbb+qRnXvQGn+d6Rx953yffl8vEy7Q==
+  integrity sha512-CkCYQLkfkiugbRDO8eZn6lRuR8kzZoGXCg3149iTk5se7g6qykSpy3+hELSwquhu+TgHn8nkLiBwHvNX8Hofcw==
   dependencies:
-    lodash "^4.17.11"
+    lodash "^4.17.13"
 
 "@babel/helper-remap-async-to-generator@^7.1.0":
   version "7.1.0"
@@ -181,14 +181,14 @@
     "@babel/traverse" "^7.1.0"
     "@babel/types" "^7.2.0"
 
-"@babel/helpers@^7.5.0":
+"@babel/helpers@^7.5.5":
-  version "7.5.1"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/helpers/-/helpers-7.5.1.tgz#65407c741a56ddd59dd86346cd112da3de912db3"
+  resolved "https://registry.yarnpkg.com/@babel/helpers/-/helpers-7.5.5.tgz#63908d2a73942229d1e6685bc2a0e730dde3b75e"
-  integrity sha512-rVOTDv8sH8kNI72Unenusxw6u+1vEepZgLxeV+jHkhsQlYhzVhzL1EpfoWT7Ub3zpWSv2WV03V853dqsnyoQzA==
+  integrity sha512-nRq2BUhxZFnfEn/ciJuhklHvFOqjJUD5wpx+1bxUF2axL9C+v4DE/dmp5sT2dKnpOs4orZWzpAZqlCy8QqE/7g==
   dependencies:
     "@babel/template" "^7.4.4"
-    "@babel/traverse" "^7.5.0"
+    "@babel/traverse" "^7.5.5"
-    "@babel/types" "^7.5.0"
+    "@babel/types" "^7.5.5"
 
 "@babel/highlight@^7.0.0":
   version "7.5.0"
@@ -199,10 +199,10 @@
     esutils "^2.0.2"
     js-tokens "^4.0.0"
 
-"@babel/parser@^7.0.0", "@babel/parser@^7.4.4", "@babel/parser@^7.5.0":
+"@babel/parser@^7.0.0", "@babel/parser@^7.4.4", "@babel/parser@^7.5.5":
-  version "7.5.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/parser/-/parser-7.5.0.tgz#3e0713dff89ad6ae37faec3b29dcfc5c979770b7"
+  resolved "https://registry.yarnpkg.com/@babel/parser/-/parser-7.5.5.tgz#02f077ac8817d3df4a832ef59de67565e71cca4b"
-  integrity sha512-I5nW8AhGpOXGCCNYGc+p7ExQIBxRFnS2fd/d862bNOKvmoEPjYPcfIjsfdy0ujagYOIYPczKgD9l3FsgTkAzKA==
+  integrity sha512-E5BN68cqR7dhKan1SfqgPGhQ178bkVKpXTPEXnFJBrEt8/DKRZlybmy+IgYLTeN7tp1R5Ccmbm2rBk17sHYU3g==
 
 "@babel/plugin-proposal-async-generator-functions@^7.0.0":
   version "7.2.0"
@@ -214,9 +214,9 @@
     "@babel/plugin-syntax-async-generators" "^7.2.0"
 
 "@babel/plugin-proposal-object-rest-spread@^7.0.0":
-  version "7.5.1"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-object-rest-spread/-/plugin-proposal-object-rest-spread-7.5.1.tgz#5788ab097c63135e4236548b4f112bfce09dd394"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-object-rest-spread/-/plugin-proposal-object-rest-spread-7.5.5.tgz#61939744f71ba76a3ae46b5eea18a54c16d22e58"
-  integrity sha512-PVGXx5LYHcT7L4MdoE+rM5uq68IKlvU9lljVQ4OXY6aUEnGvezcGbM4VNY57Ug+3R2Zg/nYHlEdiWoIBoRA0mw==
+  integrity sha512-F2DxJJSQ7f64FyTVl5cw/9MWn6naXGdk3Q3UhDbFEEHv+EilCPoeRD3Zh/Utx1CJz4uyKlQ4uH+bJPbEhMV7Zw==
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-object-rest-spread" "^7.2.0"
@@ -295,28 +295,28 @@
     "@babel/parser" "^7.4.4"
     "@babel/types" "^7.4.4"
 
-"@babel/traverse@^7.1.0", "@babel/traverse@^7.5.0":
+"@babel/traverse@^7.1.0", "@babel/traverse@^7.5.5":
-  version "7.5.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/traverse/-/traverse-7.5.0.tgz#4216d6586854ef5c3c4592dab56ec7eb78485485"
+  resolved "https://registry.yarnpkg.com/@babel/traverse/-/traverse-7.5.5.tgz#f664f8f368ed32988cd648da9f72d5ca70f165bb"
-  integrity sha512-SnA9aLbyOCcnnbQEGwdfBggnc142h/rbqqsXcaATj2hZcegCl903pUD/lfpsNBlBSuWow/YDfRyJuWi2EPR5cg==
+  integrity sha512-MqB0782whsfffYfSjH4TM+LMjrJnhCNEDMDIjeTpl+ASaUvxcjoiVCo/sM1GhS1pHOXYfWVCYneLjMckuUxDaQ==
   dependencies:
-    "@babel/code-frame" "^7.0.0"
+    "@babel/code-frame" "^7.5.5"
-    "@babel/generator" "^7.5.0"
+    "@babel/generator" "^7.5.5"
     "@babel/helper-function-name" "^7.1.0"
     "@babel/helper-split-export-declaration" "^7.4.4"
-    "@babel/parser" "^7.5.0"
+    "@babel/parser" "^7.5.5"
-    "@babel/types" "^7.5.0"
+    "@babel/types" "^7.5.5"
     debug "^4.1.0"
     globals "^11.1.0"
-    lodash "^4.17.11"
+    lodash "^4.17.13"
 
-"@babel/types@^7.0.0", "@babel/types@^7.2.0", "@babel/types@^7.4.4", "@babel/types@^7.5.0":
+"@babel/types@^7.0.0", "@babel/types@^7.2.0", "@babel/types@^7.4.4", "@babel/types@^7.5.5":
-  version "7.5.0"
+  version "7.5.5"
-  resolved "https://registry.yarnpkg.com/@babel/types/-/types-7.5.0.tgz#e47d43840c2e7f9105bc4d3a2c371b4d0c7832ab"
+  resolved "https://registry.yarnpkg.com/@babel/types/-/types-7.5.5.tgz#97b9f728e182785909aa4ab56264f090a028d18a"
-  integrity sha512-UFpDVqRABKsW01bvw7/wSUe56uy6RXM5+VJibVVAybDGxEW25jdwiFJEf7ASvSaC7sN7rbE/l3cLp2izav+CtQ==
+  integrity sha512-s63F9nJioLqOlW3UkyMd+BYhXt44YuaFm/VV0VwuteqjYwRrObkU7ra9pY4wAJR3oXi8hJrMcrcJdO/HH33vtw==
   dependencies:
     esutils "^2.0.2"
-    lodash "^4.17.11"
+    lodash "^4.17.13"
     to-fast-properties "^2.0.0"
 
 "@concordance/react@^2.0.0":
@@ -326,10 +326,39 @@
   dependencies:
     arrify "^1.0.1"
 
+"@sinonjs/commons@^1", "@sinonjs/commons@^1.3.0", "@sinonjs/commons@^1.4.0":
+  version "1.6.0"
+  resolved "https://registry.yarnpkg.com/@sinonjs/commons/-/commons-1.6.0.tgz#ec7670432ae9c8eb710400d112c201a362d83393"
+  integrity sha512-w4/WHG7C4WWFyE5geCieFJF6MZkbW4VAriol5KlmQXpAQdxvV0p26sqNZOW6Qyw6Y0l9K4g+cHvvczR2sEEpqg==
+  dependencies:
+    type-detect "4.0.8"
+
+"@sinonjs/formatio@^3.2.1":
+  version "3.2.1"
+  resolved "https://registry.yarnpkg.com/@sinonjs/formatio/-/formatio-3.2.1.tgz#52310f2f9bcbc67bdac18c94ad4901b95fde267e"
+  integrity sha512-tsHvOB24rvyvV2+zKMmPkZ7dXX6LSLKZ7aOtXY6Edklp0uRcgGpOsQTTGTcWViFyx4uhWc6GV8QdnALbIbIdeQ==
+  dependencies:
+    "@sinonjs/commons" "^1"
+    "@sinonjs/samsam" "^3.1.0"
+
+"@sinonjs/samsam@^3.1.0", "@sinonjs/samsam@^3.3.3":
+  version "3.3.3"
+  resolved "https://registry.yarnpkg.com/@sinonjs/samsam/-/samsam-3.3.3.tgz#46682efd9967b259b81136b9f120fd54585feb4a"
+  integrity sha512-bKCMKZvWIjYD0BLGnNrxVuw4dkWCYsLqFOUWw8VgKF/+5Y+mE7LfHWPIYoDXowH+3a9LsWDMo0uAP8YDosPvHQ==
+  dependencies:
+    "@sinonjs/commons" "^1.3.0"
+    array-from "^2.1.1"
+    lodash "^4.17.15"
+
+"@sinonjs/text-encoding@^0.7.1":
+  version "0.7.1"
+  resolved "https://registry.yarnpkg.com/@sinonjs/text-encoding/-/text-encoding-0.7.1.tgz#8da5c6530915653f3a1f38fd5f101d8c3f8079c5"
+  integrity sha512-+iTbntw2IZPb/anVDbypzfQa+ay64MW0Zo8aJ8gZPWMMK6/OubMVb6lUPMagqjOPnmtauXnFCACVl3O7ogjeqQ==
+
 "@types/chai@^4.1.7":
-  version "4.1.7"
+  version "4.2.0"
-  resolved "https://registry.yarnpkg.com/@types/chai/-/chai-4.1.7.tgz#1b8e33b61a8c09cbe1f85133071baa0dbf9fa71a"
+  resolved "https://registry.yarnpkg.com/@types/chai/-/chai-4.2.0.tgz#2478260021408dec32c123a7cad3414beb811a07"
-  integrity sha512-2Y8uPt0/jwjhQ6EiluT0XCri1Dbplr0ZxfFXUz+ye13gaqE8u5gL5ppao1JrUYr9cIip5S6MvQzBS7Kke7U9VA==
+  integrity sha512-zw8UvoBEImn392tLjxoavuonblX/4Yb9ha4KBU10FirCfwgzhKO0dvyJSF9ByxV1xK1r2AgnAi/tvQaLgxQqxA==
 
 "@types/events@*":
   version "3.0.0"
@@ -350,22 +379,15 @@
   resolved "https://registry.yarnpkg.com/@types/minimatch/-/minimatch-3.0.3.tgz#3dca0e3f33b200fc7d1139c0cd96c1268cadfd9d"
   integrity sha512-tHq6qdbT9U1IRSGf14CL0pUlULksvY9OZ+5eEgl1N7t+OA3tGvNpxJCzuKQlsNgCVwbAs670L1vcVQi8j9HjnA==
 
-"@types/node@*":
+"@types/node@*", "@types/node@^12.7.2":
-  version "12.0.12"
+  version "12.7.2"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.0.12.tgz#cc791b402360db1eaf7176479072f91ee6c6c7ca"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.7.2.tgz#c4e63af5e8823ce9cc3f0b34f7b998c2171f0c44"
-  integrity sha512-Uy0PN4R5vgBUXFoJrKryf5aTk3kJ8Rv3PdlHjl6UaX+Cqp1QE0yPQ68MPXGrZOfG7gZVNDIJZYyot0B9ubXUrQ==
+  integrity sha512-dyYO+f6ihZEtNPDcWNR1fkoTDf3zAK3lAABDze3mz6POyIercH0lEUawUFXlG8xaQZmm1yEBON/4TsYv/laDYg==
 
-"@types/node@^10.12.10":
+"@types/sinon@^7.0.13":
-  version "10.14.12"
+  version "7.0.13"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-10.14.12.tgz#0eec3155a46e6c4db1f27c3e588a205f767d622f"
+  resolved "https://registry.yarnpkg.com/@types/sinon/-/sinon-7.0.13.tgz#ca039c23a9e27ebea53e0901ef928ea2a1a6d313"
-  integrity sha512-QcAKpaO6nhHLlxWBvpc4WeLrTvPqlHOvaj0s5GriKkA1zq+bsFBPpfYCvQhLqLgYlIko8A9YrPdaMHCo5mBcpg==
+  integrity sha512-d7c/C/+H/knZ3L8/cxhicHUiTDxdgap0b/aNJfsmLwFu/iOP17mdgbQsbHA3SJmrzsjD0l3UEE5SN4xxuz5ung==
-
-"@types/typescript@^2.0.0":
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/@types/typescript/-/typescript-2.0.0.tgz#c433539c98bae28682b307eaa7a0fd2115b83c28"
-  integrity sha1-xDNTnJi64oaCswfqp6D9IRW4PCg=
-  dependencies:
-    typescript "*"
 
 abbrev@1:
   version "1.1.1"
@@ -427,6 +449,11 @@ are-we-there-yet@~1.1.2:
     delegates "^1.0.0"
     readable-stream "^2.0.6"
 
+arg@^4.1.0:
+  version "4.1.1"
+  resolved "https://registry.yarnpkg.com/arg/-/arg-4.1.1.tgz#485f8e7c390ce4c5f78257dbea80d4be11feda4c"
+  integrity sha512-SlmP3fEA88MBv0PypnXZ8ZfJhwmDeIE3SP71j37AiXQBXYosPV0x6uISAaHYSlSVhmHOVkomen0tbGk6Anlebw==
+
 argparse@^1.0.7:
   version "1.0.10"
   resolved "https://registry.yarnpkg.com/argparse/-/argparse-1.0.10.tgz#bcd6791ea5ae09725e17e5ad988134cd40b3d911"
@@ -459,6 +486,11 @@ array-find-index@^1.0.1:
   resolved "https://registry.yarnpkg.com/array-find-index/-/array-find-index-1.0.2.tgz#df010aa1287e164bbda6f9723b0a96a1ec4187a1"
   integrity sha1-3wEKoSh+Fku9pvlyOwqWoexBh6E=
 
+array-from@^2.1.1:
+  version "2.1.1"
+  resolved "https://registry.yarnpkg.com/array-from/-/array-from-2.1.1.tgz#cfe9d8c26628b9dc5aecc62a9f5d8f1f352c1195"
+  integrity sha1-z+nYwmYoudxa7MYqn12PHzUsEZU=
+
 array-union@^1.0.1, array-union@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/array-union/-/array-union-1.0.2.tgz#9a34410e4f4e3da23dea375be5be70f24778ec39"
@@ -678,7 +710,7 @@ braces@^2.3.1, braces@^2.3.2:
     split-string "^3.0.2"
     to-regex "^3.0.1"
 
-buffer-from@^1.0.0, buffer-from@^1.1.0:
+buffer-from@^1.0.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.1.tgz#32713bc028f75c02fdb710d7c7bcec1f2c6070ef"
   integrity sha512-MQcXEUbCKtEo7bhqEs6560Hyd4XaovZlO/k9V3hjVUF/zwW7KBVdSK4gIt/bzwS9MbR5qob+F5jusZsb0YQK2A==
@@ -818,9 +850,9 @@ class-utils@^0.3.5:
     static-extend "^0.1.1"
 
 clean-stack@^2.0.0:
-  version "2.1.0"
+  version "2.2.0"
-  resolved "https://registry.yarnpkg.com/clean-stack/-/clean-stack-2.1.0.tgz#9e7fec7f3f8340a2ab4f127c80273085e8fbbdd0"
+  resolved "https://registry.yarnpkg.com/clean-stack/-/clean-stack-2.2.0.tgz#ee8472dbb129e727b31e8a10a427dee9dfe4008b"
-  integrity sha512-uQWrpRm+iZZUCAp7ZZJQbd4Za9I3AjR/3YTjmcnAtkauaIm/T5CT6U8zVI6e60T6OANqBFAzuR9/HB3NzuZCRA==
+  integrity sha512-4diC9HaTE+KRAMWhDhrGOECgWZxoevMc5TlkObMqNSsVU62PYzXZ/SMTjzyGAFF1YusgxGcSWTEXBhp0CPwQ1A==
 
 clean-yaml-object@^0.1.0:
   version "0.1.0"
@@ -1120,11 +1152,16 @@ detect-libc@^1.0.2:
   resolved "https://registry.yarnpkg.com/detect-libc/-/detect-libc-1.0.3.tgz#fa137c4bd698edf55cd5cd02ac559f91a4c4ba9b"
   integrity sha1-+hN8S9aY7fVc1c0CrFWfkaTEups=
 
-diff@^3.1.0, diff@^3.2.0:
+diff@^3.2.0, diff@^3.5.0:
   version "3.5.0"
   resolved "https://registry.yarnpkg.com/diff/-/diff-3.5.0.tgz#800c0dd1e0a8bfbc95835c202ad220fe317e5a12"
   integrity sha512-A46qtFgd+g7pDZinpnwiRJtxbC1hpgf0uzP3iG89scHk0AUC7A1TGxf5OiiOUv/JMZR8GOt8hL900hV0bOy5xA==
 
+diff@^4.0.1:
+  version "4.0.1"
+  resolved "https://registry.yarnpkg.com/diff/-/diff-4.0.1.tgz#0c667cb467ebbb5cea7f14f135cc2dba7780a8ff"
+  integrity sha512-s2+XdvhPCOF01LRQBC8hf4vhbVmI2CGS5aZnxLJlT5FtdhPCDFq80q++zK2KlrVorVDdL5BOGZ/VfLrVtYNF+Q==
+
 dir-glob@^2.0.0:
   version "2.2.2"
   resolved "https://registry.yarnpkg.com/dir-glob/-/dir-glob-2.2.2.tgz#fa09f0694153c8918b18ba0deafae94769fc50c4"
@@ -1215,14 +1252,14 @@ espurify@^1.6.0:
     core-js "^2.0.0"
 
 estraverse@^4.0.0, estraverse@^4.1.1:
-  version "4.2.0"
+  version "4.3.0"
-  resolved "https://registry.yarnpkg.com/estraverse/-/estraverse-4.2.0.tgz#0dee3fed31fcd469618ce7342099fc1afa0bdb13"
+  resolved "https://registry.yarnpkg.com/estraverse/-/estraverse-4.3.0.tgz#398ad3f3c5a24948be7725e83d11a7de28cdbd1d"
-  integrity sha1-De4/7TH81GlhjOc0IJn8GvoL2xM=
+  integrity sha512-39nnKffWz8xN1BU/2c79n9nB9HDzo0niYUqx6xyqUnyoAnQyyWpOTdZEeiCch8BBu515t4wp9ZmgVfVhn9EBpw==
 
 esutils@^2.0.2:
-  version "2.0.2"
+  version "2.0.3"
-  resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.2.tgz#0abf4f1caa5bcb1f7a9d8acc6dea4faaa04bac9b"
+  resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.3.tgz#74d2eb4de0b8da1293711910d50775b9b710ef64"
-  integrity sha1-Cr9PHKpbyx96nYrMbepPqqBLrJs=
+  integrity sha512-kVscqXk4OCp68SZ0dkgEKVi6/8ij300KBWTJq32P/dYeWTSwK41WyTxalN1eRmA5Z9UU/LX9D7FWSmV9SAYx6g==
 
 execa@^0.7.0:
   version "0.7.0"
@@ -1459,9 +1496,9 @@ got@^6.7.1:
     url-parse-lax "^1.0.0"
 
 graceful-fs@^4.1.11, graceful-fs@^4.1.15, graceful-fs@^4.1.2:
-  version "4.2.0"
+  version "4.2.2"
-  resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.2.0.tgz#8d8fdc73977cb04104721cb53666c1ca64cd328b"
+  resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.2.2.tgz#6f0952605d0140c1cfdb138ed005775b92d67b02"
-  integrity sha512-jpSvDPV4Cq/bgtpndIWbI5hmYxhQGHPC4d4cqBPb4DLniCfhJokdXhwhaDuLBGLQdvvRum/UiX6ECVIPvDXqdg==
+  integrity sha512-IItsdsea19BoLC7ELy13q1iJFNmd7ofZH5+X/pJr90/nRoPEX0DJo1dHDbgtYWOhJhcCgMDTOw84RZ72q6lB+Q==
 
 has-flag@^3.0.0:
   version "3.0.0"
@@ -1517,9 +1554,9 @@ hasha@^3.0.0:
     is-stream "^1.0.1"
 
 hosted-git-info@^2.1.4:
-  version "2.7.1"
+  version "2.8.4"
-  resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.7.1.tgz#97f236977bd6e125408930ff6de3eec6281ec047"
+  resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.8.4.tgz#44119abaf4bc64692a16ace34700fed9c03e2546"
-  integrity sha512-7T/BxH19zbcCTa8XkMlbK5lTo1WtgkFi3GvdWEyNuc4Vex7/9Dqbnpsf4JMydcfj9HCg4zUWFTL3Za6lapg5/w==
+  integrity sha512-pzXIvANXEFrc5oFFXRMkbLPQ2rXRoDERwDLyrcUxGhaZhgP54BBSl9Oheh7Vv0T090cszWBxPjkQQ5Sq1PbBRQ==
 
 iconv-lite@^0.4.4:
   version "0.4.24"
@@ -1828,6 +1865,11 @@ is-windows@^1.0.2:
   resolved "https://registry.yarnpkg.com/is-windows/-/is-windows-1.0.2.tgz#d1850eb9791ecd18e6182ce12a30f396634bb19d"
   integrity sha512-eXK1UInq2bPmjyX6e3VHIzMLobc4J94i4AWn+Hpq3OU5KkrRC96OAcR3PRJ/pGu6m8TRnBHP9dkXQVsT/COVIA==
 
+isarray@0.0.1:
+  version "0.0.1"
+  resolved "https://registry.yarnpkg.com/isarray/-/isarray-0.0.1.tgz#8a18acfca9a8f4177e09abfc6038939b05d1eedf"
+  integrity sha1-ihis/Kmo9Bd+Cav8YDiTmwXR7t8=
+
 isarray@1.0.0, isarray@~1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/isarray/-/isarray-1.0.0.tgz#bb935d48582cba168c06834957a54a3e07124f11"
@@ -1895,6 +1937,11 @@ json5@^2.1.0:
   dependencies:
     minimist "^1.2.0"
 
+just-extend@^4.0.2:
+  version "4.0.2"
+  resolved "https://registry.yarnpkg.com/just-extend/-/just-extend-4.0.2.tgz#f3f47f7dfca0f989c55410a7ebc8854b07108afc"
+  integrity sha512-FrLwOgm+iXrPV+5zDU6Jqu4gCRXbWEQg2O3SKONsWE4w7AXFRkryS53bpWdaL9cNol+AmR3AEYz6kn+o0fCPnw==
+
 kind-of@^3.0.2, kind-of@^3.0.3, kind-of@^3.2.0:
   version "3.2.2"
   resolved "https://registry.yarnpkg.com/kind-of/-/kind-of-3.2.2.tgz#31ea21a734bab9bbb0f32466d893aea51e4a3c64"
@@ -2009,14 +2056,14 @@ lodash.islength@^4.0.1:
   integrity sha1-Tpho1FJXXXUK/9NYyXlUPcIO1Xc=
 
 lodash.merge@^4.6.1:
-  version "4.6.1"
+  version "4.6.2"
-  resolved "https://registry.yarnpkg.com/lodash.merge/-/lodash.merge-4.6.1.tgz#adc25d9cb99b9391c59624f379fbba60d7111d54"
+  resolved "https://registry.yarnpkg.com/lodash.merge/-/lodash.merge-4.6.2.tgz#558aa53b43b661e1925a0afdfa36a9a1085fe57a"
-  integrity sha512-AOYza4+Hf5z1/0Hztxpm2/xiPZgi/cjMqdnKTUWTBSKchJlxXXuUSxCCl8rJlf4g6yww/j6mA8nC8Hw/EZWxKQ==
+  integrity sha512-0KpjqXRVvrYyCsX1swR/XTK0va6VQkQM6MNo7PqW77ByjAhoARA8EfrP1N4+KlKj8YS0ZUCtRT/YUuhyYDujIQ==
 
-lodash@^4.17.11:
+lodash@^4.17.13, lodash@^4.17.15:
-  version "4.17.11"
+  version "4.17.15"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.11.tgz#b39ea6229ef607ecd89e2c8df12536891cac9b8d"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
-  integrity sha512-cQKh8igo5QUhZ7lg38DYWAxMvjSAKG0A8wGSVimP07SIUEK2UO+arSRKbRZWtelMtN5V0Hkwh5ryOto/SshYIg==
+  integrity sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A==
 
 log-symbols@^2.2.0:
   version "2.2.0"
@@ -2025,6 +2072,11 @@ log-symbols@^2.2.0:
   dependencies:
     chalk "^2.0.1"
 
+lolex@^4.1.0, lolex@^4.2.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/lolex/-/lolex-4.2.0.tgz#ddbd7f6213ca1ea5826901ab1222b65d714b3cd7"
+  integrity sha512-gKO5uExCXvSm6zbF562EvM+rd1kQDnB9AZBbiQVzf1ZmdDpxUSvpnAaVOP83N/31mRK8Ml8/VE8DMvsAZQ+7wg==
+
 loud-rejection@^1.0.0, loud-rejection@^1.2.0:
   version "1.6.0"
   resolved "https://registry.yarnpkg.com/loud-rejection/-/loud-rejection-1.6.0.tgz#5b46f80147edee578870f086d04821cf998e551f"
@@ -2255,6 +2307,17 @@ needle@^2.2.1:
     iconv-lite "^0.4.4"
     sax "^1.2.4"
 
+nise@^1.5.2:
+  version "1.5.2"
+  resolved "https://registry.yarnpkg.com/nise/-/nise-1.5.2.tgz#b6d29af10e48b321b307e10e065199338eeb2652"
+  integrity sha512-/6RhOUlicRCbE9s+94qCUsyE+pKlVJ5AhIv+jEE7ESKwnbXqulKZ1FYU+XAtHHWE9TinYvAxDUJAb912PwPoWA==
+  dependencies:
+    "@sinonjs/formatio" "^3.2.1"
+    "@sinonjs/text-encoding" "^0.7.1"
+    just-extend "^4.0.2"
+    lolex "^4.1.0"
+    path-to-regexp "^1.7.0"
+
 node-pre-gyp@^0.12.0:
   version "0.12.0"
   resolved "https://registry.yarnpkg.com/node-pre-gyp/-/node-pre-gyp-0.12.0.tgz#39ba4bb1439da030295f899e3b520b7785766149"
@@ -2547,6 +2610,13 @@ path-parse@^1.0.6:
   resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.6.tgz#d62dbb5679405d72c4737ec58600e9ddcf06d24c"
   integrity sha512-GSmOT2EbHrINBf9SR7CDELwlJ8AENk3Qn7OikK4nFYAu3Ote2+JYNVvkpAEQm3/TLNEJFD/xZJjzyxg3KBWOzw==
 
+path-to-regexp@^1.7.0:
+  version "1.7.0"
+  resolved "https://registry.yarnpkg.com/path-to-regexp/-/path-to-regexp-1.7.0.tgz#59fde0f435badacba103a84e9d3bc64e96b9937d"
+  integrity sha1-Wf3g9DW62suhA6hOnTvGTpa5k30=
+  dependencies:
+    isarray "0.0.1"
+
 path-type@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/path-type/-/path-type-3.0.0.tgz#cef31dc8e0a1a3bb0d105c0cd97cf3bf47f4e36f"
@@ -2702,7 +2772,7 @@ redent@^2.0.0:
     indent-string "^3.0.0"
     strip-indent "^2.0.0"
 
-regenerate-unicode-properties@^8.0.2:
+regenerate-unicode-properties@^8.1.0:
   version "8.1.0"
   resolved "https://registry.yarnpkg.com/regenerate-unicode-properties/-/regenerate-unicode-properties-8.1.0.tgz#ef51e0f0ea4ad424b77bf7cb41f3e015c70a3f0e"
   integrity sha512-LGZzkgtLY79GeXLm8Dp0BVLdQlWICzBnJz/ipWUgo59qBaZ+BHtq51P2q1uVZlppMuUAT37SDk39qUbjTWB7bA==
@@ -2723,12 +2793,12 @@ regex-not@^1.0.0, regex-not@^1.0.2:
     safe-regex "^1.1.0"
 
 regexpu-core@^4.5.4:
-  version "4.5.4"
+  version "4.5.5"
-  resolved "https://registry.yarnpkg.com/regexpu-core/-/regexpu-core-4.5.4.tgz#080d9d02289aa87fe1667a4f5136bc98a6aebaae"
+  resolved "https://registry.yarnpkg.com/regexpu-core/-/regexpu-core-4.5.5.tgz#aaffe61c2af58269b3e516b61a73790376326411"
-  integrity sha512-BtizvGtFQKGPUcTy56o3nk1bGRp4SZOTYrDtGNlqCQufptV5IkkLN6Emw+yunAJjzf+C9FQFtvq7IoA3+oMYHQ==
+  integrity sha512-FpI67+ky9J+cDizQUJlIlNZFKual/lUkFr1AG6zOCpwZ9cLrg8UUVakyUQJD7fCDIe9Z2nwTQJNPyonatNmDFQ==
   dependencies:
     regenerate "^1.4.0"
-    regenerate-unicode-properties "^8.0.2"
+    regenerate-unicode-properties "^8.1.0"
     regjsgen "^0.5.0"
     regjsparser "^0.6.0"
     unicode-match-property-ecmascript "^1.0.4"
@@ -2806,9 +2876,9 @@ resolve-url@^0.2.1:
   integrity sha1-LGN/53yJOv0qZj/iGqkIAGjiBSo=
 
 resolve@^1.10.0, resolve@^1.3.2:
-  version "1.11.1"
+  version "1.12.0"
-  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.11.1.tgz#ea10d8110376982fef578df8fc30b9ac30a07a3e"
+  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.12.0.tgz#3fc644a35c84a48554609ff26ec52b66fa577df6"
-  integrity sha512-vIpgF6wfuJOZI7KKKSP+HmiKggadPQAdsp5HiC1mvqnfp0gF1vdwgBWZIdrVft9pgqoMFQN+R7BSWZiBxx+BBw==
+  integrity sha512-B/dOmuoAik5bKcD6s6nXDCjzUKnaDvdkRyAk6rsmsKLipWj4797iothd7jmmUhWTfinVMU+wc56rYKsit2Qy4w==
   dependencies:
     path-parse "^1.0.6"
 
@@ -2826,9 +2896,9 @@ ret@~0.1.10:
   integrity sha512-TTlYpa+OL+vMMNG24xSlQGEJ3B/RzEfUlLct7b5G/ytav+wPrplCpVMFuwzXbkecJrb6IYo1iFb0S9v37754mg==
 
 rimraf@^2.6.1, rimraf@^2.6.3:
-  version "2.6.3"
+  version "2.7.1"
-  resolved "https://registry.yarnpkg.com/rimraf/-/rimraf-2.6.3.tgz#b2d104fe0d8fb27cf9e0a1cda8262dd3833c6cab"
+  resolved "https://registry.yarnpkg.com/rimraf/-/rimraf-2.7.1.tgz#35797f13a7fdadc566142c29d4f07ccad483e3ec"
-  integrity sha512-mwqeW5XsA2qAejG46gYdENaxXjx9onRNCfn7L0duuP4hCuTIi/QO7PDK07KJfp1d+izWPrzEJDcSqBa0OZQriA==
+  integrity sha512-uWjbaKIK3T1OSVptzX7Nl6PvQ3qAGtKEtVRjRuazjfL3Bx5eI409VZSqgND+4UNnmzLVdPj9FqFJNPqBZFve4w==
   dependencies:
     glob "^7.1.3"
 
@@ -2867,9 +2937,9 @@ semver-diff@^2.0.0:
     semver "^5.0.3"
 
 "semver@2 || 3 || 4 || 5", semver@^5.0.3, semver@^5.1.0, semver@^5.3.0, semver@^5.4.1, semver@^5.5.1, semver@^5.6.0:
-  version "5.7.0"
+  version "5.7.1"
-  resolved "https://registry.yarnpkg.com/semver/-/semver-5.7.0.tgz#790a7cf6fea5459bac96110b29b60412dc8ff96b"
+  resolved "https://registry.yarnpkg.com/semver/-/semver-5.7.1.tgz#a954f931aeba508d307bbf069eff0c01c96116f7"
-  integrity sha512-Ya52jSX2u7QKghxeoFGpLwCtGlt7j0oY9DYb5apt9nPlJ42ID+ulTXESnt/qAQcoSERyZ5sl3LDIOw0nAn/5DA==
+  integrity sha512-sauaDf/PZdVgrLTNYHRtpXa1iRiKcaebiKQ1BJdpQlWH2lCvexQdX55snPFyK7QzpudqbCI0qXFfOasHdyNDGQ==
 
 serialize-error@^2.1.0:
   version "2.1.0"
@@ -2908,6 +2978,19 @@ signal-exit@^3.0.0, signal-exit@^3.0.2:
   resolved "https://registry.yarnpkg.com/signal-exit/-/signal-exit-3.0.2.tgz#b5fdc08f1287ea1178628e415e25132b73646c6d"
   integrity sha1-tf3AjxKH6hF4Yo5BXiUTK3NkbG0=
 
+sinon@^7.4.2:
+  version "7.4.2"
+  resolved "https://registry.yarnpkg.com/sinon/-/sinon-7.4.2.tgz#ecd54158fef2fcfbdb231a3fa55140e8cb02ad6c"
+  integrity sha512-pY5RY99DKelU3pjNxcWo6XqeB1S118GBcVIIdDi6V+h6hevn1izcg2xv1hTHW/sViRXU7sUOxt4wTUJ3gsW2CQ==
+  dependencies:
+    "@sinonjs/commons" "^1.4.0"
+    "@sinonjs/formatio" "^3.2.1"
+    "@sinonjs/samsam" "^3.3.3"
+    diff "^3.5.0"
+    lolex "^4.2.0"
+    nise "^1.5.2"
+    supports-color "^5.5.0"
+
 slash@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/slash/-/slash-1.0.0.tgz#c41f2f6c39fc16d1cd17ad4b5d896114ae470d55"
@@ -2971,18 +3054,10 @@ source-map-resolve@^0.5.0:
     source-map-url "^0.4.0"
     urix "^0.1.0"
 
-source-map-support@^0.5.11:
+source-map-support@^0.5.11, source-map-support@^0.5.6:
-  version "0.5.12"
+  version "0.5.13"
-  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.12.tgz#b4f3b10d51857a5af0138d3ce8003b201613d599"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.13.tgz#31b24a9c2e73c2de85066c0feb7d44767ed52932"
-  integrity sha512-4h2Pbvyy15EE02G+JOZpUCmqWJuqrs+sEkzewTm++BPi7Hvn/HwcqLAcNxYAyI0x13CpPPn+kMjl+hplXMHITQ==
+  integrity sha512-SHSKFHadjVA5oR4PPqhtAVdcBWwRYVd6g6cAXnIbRiIwc2EhPrTuKUBdSLvlEKyIP3GCf89fltvcZiP9MMFA1w==
-  dependencies:
-    buffer-from "^1.0.0"
-    source-map "^0.6.0"
-
-source-map-support@^0.5.6:
-  version "0.5.9"
-  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.9.tgz#41bc953b2534267ea2d605bccfa7bfa3111ced5f"
-  integrity sha512-gR6Rw4MvUlYy83vP0vxoVNzM6t8MUXqNuRsuBmBHQDu1Fh6X015FrLdgoDKcNdkwGubozq0P4N0Q37UyFVr1EA==
   dependencies:
     buffer-from "^1.0.0"
     source-map "^0.6.0"
@@ -3024,9 +3099,9 @@ spdx-expression-parse@^3.0.0:
     spdx-license-ids "^3.0.0"
 
 spdx-license-ids@^3.0.0:
-  version "3.0.4"
+  version "3.0.5"
-  resolved "https://registry.yarnpkg.com/spdx-license-ids/-/spdx-license-ids-3.0.4.tgz#75ecd1a88de8c184ef015eafb51b5b48bfd11bb1"
+  resolved "https://registry.yarnpkg.com/spdx-license-ids/-/spdx-license-ids-3.0.5.tgz#3694b5804567a458d3c8045842a6358632f62654"
-  integrity sha512-7j8LYJLeY/Yb6ACbQ7F76qy5jHkp0U6jgBfJsk97bwWlVUnUWsAgpyaCvo17h0/RQGnQ036tVDomiwoI4pDkQA==
+  integrity sha512-J+FWzZoynJEXGphVIS+XEh3kFSjZX/1i9gFBaWQcB+/tmpe2qUsSBABpcxqxnAxFdiUFEgAX1bjYGQvIZmoz9Q==
 
 split-string@^3.0.1, split-string@^3.0.2:
   version "3.1.0"
@@ -3136,7 +3211,7 @@ supertap@^1.0.0:
     serialize-error "^2.1.0"
     strip-ansi "^4.0.0"
 
-supports-color@^5.3.0:
+supports-color@^5.3.0, supports-color@^5.5.0:
   version "5.5.0"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-5.5.0.tgz#e2e69a44ac8772f78a1ec0b35b689df6530efc8f"
   integrity sha512-QjVjwdXIt408MIiAqCX4oUKsgU2EqAGzs2Ppkm4aQYbjm+ZEWEcW4SfFNTr4uMNZma0ey4f5lgLrkB0aX0QMow==
@@ -3235,26 +3310,18 @@ trim-right@^1.0.1:
   resolved "https://registry.yarnpkg.com/trim-right/-/trim-right-1.0.1.tgz#cb2e1203067e0c8de1f614094b9fe45704ea6003"
   integrity sha1-yy4SAwZ+DI3h9hQJS5/kVwTqYAM=
 
-ts-node@^7.0.1:
+ts-node@^8.3.0:
-  version "7.0.1"
+  version "8.3.0"
-  resolved "https://registry.yarnpkg.com/ts-node/-/ts-node-7.0.1.tgz#9562dc2d1e6d248d24bc55f773e3f614337d9baf"
+  resolved "https://registry.yarnpkg.com/ts-node/-/ts-node-8.3.0.tgz#e4059618411371924a1fb5f3b125915f324efb57"
-  integrity sha512-BVwVbPJRspzNh2yfslyT1PSbl5uIk03EZlb493RKHN4qej/D06n1cEhjlOJG69oFsE7OT8XjpTUcYf6pKTLMhw==
+  integrity sha512-dyNS/RqyVTDcmNM4NIBAeDMpsAdaQ+ojdf0GOLqE6nwJOgzEkdRNzJywhDfwnuvB10oa6NLVG1rUJQCpRN7qoQ==
   dependencies:
-    arrify "^1.0.0"
+    arg "^4.1.0"
-    buffer-from "^1.1.0"
+    diff "^4.0.1"
-    diff "^3.1.0"
     make-error "^1.1.1"
-    minimist "^1.2.0"
-    mkdirp "^0.5.1"
     source-map-support "^0.5.6"
-    yn "^2.0.0"
+    yn "^3.0.0"
 
-tslib@^1.7.1:
+tslib@^1.7.1, tslib@^1.8.0, tslib@^1.8.1:
-  version "1.9.3"
-  resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.9.3.tgz#d7e4dd79245d85428c4d7e4822a79917954ca286"
-  integrity sha512-4krF8scpejhaOgqzBEcGM7yDIEfi0/8+8zDRZhNZZ2kjmHJ4hv3zCbQWxoJGz1iw5U0Jl0nma13xzHXcncMavQ==
-
-tslib@^1.8.0, tslib@^1.8.1:
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.10.0.tgz#c3c19f95973fb0a62973fb09d90d961ee43e5c8a"
   integrity sha512-qOebF53frne81cf0S9B41ByenJ3/IuH8yJKngAX35CmiZySA0khhkovshKK+jGCaMnVomla7gVlIcc3EvKPbTQ==
@@ -3299,7 +3366,7 @@ tsutils@^2.29.0:
   dependencies:
     tslib "^1.8.1"
 
-type-detect@^4.0.0, type-detect@^4.0.5:
+type-detect@4.0.8, type-detect@^4.0.0, type-detect@^4.0.5:
   version "4.0.8"
   resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-4.0.8.tgz#7646fb5f18871cfbb7749e69bd39a6388eb7450c"
   integrity sha512-0fr/mIH1dlO+x7TlcMy+bIDqKPsw/70tVyeHW787goQjhmqaZe10uwLujubK9q9Lg6Fiho1KUKDYz0Z7k7g5/g==
@@ -3309,10 +3376,10 @@ type-fest@^0.3.0:
   resolved "https://registry.yarnpkg.com/type-fest/-/type-fest-0.3.1.tgz#63d00d204e059474fe5e1b7c011112bbd1dc29e1"
   integrity sha512-cUGJnCdr4STbePCgqNFbpVNCepa+kAVohJs1sLhxzdH+gnEoOd8VhbYa7pD3zZYGiURWM2xzEII3fQcRizDkYQ==
 
-typescript@*, typescript@^3.1.6:
+typescript@^3.5.3:
-  version "3.5.2"
+  version "3.5.3"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.5.2.tgz#a09e1dc69bc9551cadf17dba10ee42cf55e5d56c"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.5.3.tgz#c830f657f93f1ea846819e929092f5fe5983e977"
-  integrity sha512-7KxJovlYhTX5RaRbUdkAXN1KUZ8PwWlTzQdHV6xNqvuFOs7+WBo10TQUqT19Q/Jz2hk5v9TQDIhyLhhJY4p5AA==
+  integrity sha512-ACzBtm/PhXBDId6a6sDJfroT2pOWt/oOnk4/dElG5G33ZL776N3Y6/6bKZJBFpd+b05F3Ct9qDjMeJmRWtE2/g==
 
 uid2@0.0.3:
   version "0.0.3"
@@ -3485,9 +3552,9 @@ xdg-basedir@^3.0.0:
   integrity sha1-SWsswQnsqNus/i3HK2A8F8WHCtQ=
 
 xtend@^4.0.0:
-  version "4.0.1"
+  version "4.0.2"
-  resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.1.tgz#a5c6d532be656e23db820efb943a1f04998d63af"
+  resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.2.tgz#bb72779f5fa465186b1f438f674fa347fdb5db54"
-  integrity sha1-pcbVMr5lbiPbgg77lDofBJmNY68=
+  integrity sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==
 
 yallist@^2.1.2:
   version "2.1.2"
@@ -3506,7 +3573,7 @@ yargs-parser@^10.0.0:
   dependencies:
     camelcase "^4.1.0"
 
-yn@^2.0.0:
+yn@^3.0.0:
-  version "2.0.0"
+  version "3.1.1"
-  resolved "https://registry.yarnpkg.com/yn/-/yn-2.0.0.tgz#e5adabc8acf408f6385fc76495684c88e6af689a"
+  resolved "https://registry.yarnpkg.com/yn/-/yn-3.1.1.tgz#1e87401a09d767c1d5eab26a6e4c185182d2eb50"
-  integrity sha1-5a2ryKz0CPY4X8dklWhMiOavaJo=
+  integrity sha512-Ux4ygGWsu2c7isFWe8Yu1YluJmqVhxqK2cLXNQA5AcC3QfbGNpM7fu0Y8b/z16pXLnFxZYvWhd3fhBY9DLmC6Q==