Minor changes to types

* Add chunk to constructor

* Add test

* Bump version

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@jogogo/mhysa",
-    "version": "0.1.0-alpha.1",
+    "version": "2.0.0-alpha.4",
     "description": "Streams and event emitter utils for Node.js",
     "keywords": [
         "promise",
@@ -35,9 +35,7 @@
         "type": "git"
     },
     "scripts": {
-        "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",
+        "test": "ava",
         "lint": "tslint -p tsconfig.json",
         "validate:tslint": "tslint-config-prettier-check ./tslint.json",
         "prepublishOnly": "yarn lint && yarn test && yarn tsc -d"
@@ -45,7 +43,7 @@
     "dependencies": {},
     "devDependencies": {
         "@types/chai": "^4.1.7",
-        "@types/node": "^12.7.2",
+        "@types/node": "^12.12.15",
         "@types/sinon": "^7.0.13",
         "ava": "^2.4.0",
         "chai": "^4.2.0",
@@ -60,7 +58,8 @@
     },
     "ava": {
         "files": [
-            "tests/*.spec.ts"
+            "tests/*.spec.ts",
+            "tests/utils/*.spec.ts"
         ],
         "sources": [
             "src/**/*.ts"

src/functions/batch.ts

@@ -12,7 +12,9 @@ export function batch(
             clearTimeout(timer);
         }
         timer = null;
+        if (buffer.length > 0) {
             self.push(buffer);
+        }
         buffer = [];
     };
     return new Transform({

src/functions/compose.ts

@@ -1,4 +1,5 @@
-import { pipeline, TransformOptions, Transform } from "stream";
+import { AllStreams, isReadable } from "../helpers";
+import { PassThrough, pipeline, TransformOptions, Transform } from "stream";
 
 export function compose(
     streams: Array<
@@ -21,18 +22,6 @@ enum EventSubscription {
     Self,
 }
 
-type AllStreams =
-    | NodeJS.ReadableStream
-    | NodeJS.ReadWriteStream
-    | NodeJS.WritableStream;
-
-function isReadable(stream: AllStreams): stream is NodeJS.WritableStream {
-    return (
-        (stream as NodeJS.ReadableStream).pipe !== undefined &&
-        (stream as any).readable === true
-    );
-}
-
 export class Compose extends Transform {
     private first: AllStreams;
     private last: AllStreams;
@@ -45,11 +34,11 @@ export class Compose extends Transform {
         options?: TransformOptions,
     ) {
         super(options);
-        this.first = streams[0];
+        this.first = new PassThrough(options);
         this.last = streams[streams.length - 1];
         this.streams = streams;
         pipeline(
-            streams,
+            [this.first, ...streams],
             errorCallback ||
                 ((error: any) => {
                     if (error) {

src/functions/demux.ts

@@ -1,99 +1,131 @@
-import { WritableOptions, Writable } from "stream";
+import { DuplexOptions, Duplex, Transform } 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,
-};
+import { isReadable } from "../helpers";
 
 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);
+export interface DemuxOptions extends DuplexOptions {
+    remultiplex?: boolean;
 }
 
-// @TODO handle pipe event ie) Multiplex
-class Demux extends Writable {
+export function demux(
+    pipelineConstructor: (
+        destKey?: string,
+        chunk?: any,
+    ) => DemuxStreams | DemuxStreams[],
+    demuxBy: string | ((chunk: any) => string),
+    options?: DemuxOptions,
+): Duplex {
+    return new Demux(pipelineConstructor, demuxBy, options);
+}
+
+class Demux extends Duplex {
     private streamsByKey: {
-        [key: string]: DemuxStreams;
+        [key: string]: DemuxStreams[];
     };
     private demuxer: (chunk: any) => string;
-    private construct: (destKey?: string) => DemuxStreams;
+    private pipelineConstructor: (
+        destKey?: string,
+        chunk?: any,
+    ) => DemuxStreams[];
+    private remultiplex: boolean;
+    private transform: Transform;
     constructor(
-        construct: (destKey?: string) => DemuxStreams,
+        pipelineConstructor: (
+            destKey?: string,
+            chunk?: any,
+        ) => DemuxStreams | DemuxStreams[],
         demuxBy: string | ((chunk: any) => string),
-        options: WritableOptions = {},
+        options: DemuxOptions = {},
     ) {
         super(options);
         this.demuxer =
             typeof demuxBy === "string" ? chunk => chunk[demuxBy] : demuxBy;
-        this.construct = construct;
+        this.pipelineConstructor = (destKey: string, chunk?: any) => {
+            const pipeline = pipelineConstructor(destKey, chunk);
+            return Array.isArray(pipeline) ? pipeline : [pipeline];
+        };
+        this.remultiplex =
+            options.remultiplex === undefined ? true : options.remultiplex;
         this.streamsByKey = {};
+        this.transform = new Transform({
+            ...options,
+            transform: (d, _, cb) => {
+                this.push(d);
+                cb(null);
+            },
+        });
+
+        this.on("unpipe", () => this._flush());
     }
 
+    // tslint:disable-next-line
+    public _read(size: number) {}
+
     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);
+            const newPipelines = this.pipelineConstructor(destKey, chunk);
+            this.streamsByKey[destKey] = newPipelines;
+
+            newPipelines.forEach(newPipeline => {
+                if (this.remultiplex && isReadable(newPipeline)) {
+                    (newPipeline as NodeJS.ReadWriteStream).pipe(
+                        this.transform,
+                    );
+                } else if (this.remultiplex) {
+                    console.error(
+                        `Pipeline construct for ${destKey} does not implement readable interface`,
+                    );
                 }
-        if (!this.streamsByKey[destKey].write(chunk, encoding)) {
-            this.streamsByKey[destKey].once("drain", () => {
-                cb();
             });
-        } else {
+        }
+        const pipelines = this.streamsByKey[destKey];
+        const pendingDrains: Array<Promise<any>> = [];
+
+        pipelines.forEach(pipeline => {
+            if (!pipeline.write(chunk, encoding)) {
+                pendingDrains.push(
+                    new Promise(resolve => {
+                        pipeline.once("drain", () => {
+                            resolve();
+                        });
+                    }),
+                );
+            }
+        });
+        await Promise.all(pendingDrains);
         cb();
     }
+
+    public _flush() {
+        const pipelines: DemuxStreams[] = [].concat.apply(
+            [],
+            Object.values(this.streamsByKey),
+        );
+        const flushPromises: Array<Promise<void>> = [];
+        pipelines.forEach(pipeline => {
+            flushPromises.push(
+                new Promise(resolve => {
+                    pipeline.once("end", () => {
+                        resolve();
+                    });
+                }),
+            );
+        });
+        pipelines.forEach(pipeline => pipeline.end());
+        Promise.all(flushPromises).then(() => {
+            this.push(null);
+            this.emit("end");
+        });
     }
 
-    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),
+    public _destroy(error: any, cb: (error?: any) => void) {
+        const pipelines: DemuxStreams[] = [].concat.apply(
+            [],
+            Object.values(this.streamsByKey),
         );
-                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;
+        pipelines.forEach(p => (p as any).destroy());
+        cb(error);
     }
 }

src/helpers.ts

@@ -1,3 +1,17 @@
 export async function sleep(time: number): Promise<{} | null> {
     return time > 0 ? new Promise(resolve => setTimeout(resolve, time)) : null;
 }
+
+export type AllStreams =
+    | NodeJS.ReadableStream
+    | NodeJS.ReadWriteStream
+    | NodeJS.WritableStream;
+
+export function isReadable(
+    stream: AllStreams,
+): stream is NodeJS.WritableStream {
+    return (
+        (stream as NodeJS.ReadableStream).pipe !== undefined &&
+        (stream as any).readable === true
+    );
+}

src/index.ts

@@ -1,2 +1,6 @@
 import mhysa from "./functions";
+import * as _utils from "./utils";
 export default mhysa;
+
+// @TODO fix this with proper import export
+export const utils = { ..._utils };

src/utils/collected.ts

@@ -0,0 +1,12 @@
+import { Transform } from "stream";
+
+export function collected(stream: Transform): any {
+    return new Promise((resolve, reject) => {
+        stream.once("data", d => {
+            resolve(d);
+        });
+        stream.once("error", e => {
+            reject(e);
+        });
+    });
+}

src/utils/index.ts

@@ -0,0 +1 @@
+export { collected } from "./collected";

tests/batch.spec.ts

@@ -2,7 +2,7 @@ import { Readable } from "stream";
 import test from "ava";
 import { expect } from "chai";
 import mhysa from "../src";
-const { batch } = mhysa({ objectMode: true });
+const { batch, map, fromArray } = mhysa({ objectMode: true });
 
 test.cb("batch() batches chunks together", t => {
     t.plan(3);
@@ -57,3 +57,28 @@ test.cb("batch() yields a batch after the timeout", t => {
         source.push(null);
     }, 600 * 2);
 });
+
+test.cb(
+    "batch() yields all input data even when the last element(s) dont make a full batch",
+    t => {
+        const data = [1, 2, 3, 4, 5, 6, 7];
+
+        fromArray([...data])
+            .pipe(batch(3))
+            .pipe(
+                map(d => {
+                    t.deepEqual(
+                        d,
+                        [data.shift(), data.shift(), data.shift()].filter(
+                            x => !!x,
+                        ),
+                    );
+                }),
+            )
+            .on("error", t.fail)
+            .on("finish", () => {
+                t.is(data.length, 0);
+                t.end();
+            });
+    },
+);

tests/compose.spec.ts

@@ -4,7 +4,7 @@ import { sleep } from "../src/helpers";
 import { Readable, Writable } from "stream";
 import mhysa from "../src";
 import { performance } from "perf_hooks";
-const { compose, map } = mhysa({ objectMode: true });
+const { compose, map, fromArray } = mhysa({ objectMode: true });
 
 test.cb("compose() chains two streams together in the correct order", t => {
     t.plan(3);
@@ -98,7 +98,7 @@ test.cb("piping compose() maintains correct order", t => {
 });
 
 test("compose() writable length should be less than highWaterMark when handing writes", async t => {
-    t.plan(7);
+    t.plan(2);
     return new Promise(async (resolve, reject) => {
         interface Chunk {
             key: string;
@@ -114,9 +114,13 @@ test("compose() writable length should be less than highWaterMark when handing w
             return chunk;
         });
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark: 2,
-        });
+            },
+        );
         composed.on("error", err => {
             reject();
         });
@@ -140,19 +144,12 @@ test("compose() writable length should be less than highWaterMark when handing w
             { 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);
-            }
-        }
+        fromArray(input).pipe(composed);
     });
 });
 
 test("compose() should emit drain event ~rate * highWaterMark ms for every write that causes backpressure", async t => {
-    t.plan(7);
+    t.plan(2);
     const _rate = 100;
     const highWaterMark = 2;
     return new Promise(async (resolve, reject) => {
@@ -171,9 +168,13 @@ test("compose() should emit drain event ~rate * highWaterMark ms for every write
             return chunk;
         });
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark,
-        });
+            },
+        );
         composed.on("error", err => {
             reject();
         });
@@ -181,19 +182,14 @@ test("compose() should emit drain event ~rate * highWaterMark ms for every write
         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();
-            }
+            t.deepEqual(chunk.mapped, [1, 2]);
         });
 
+        composed.on("finish", () => resolve());
+
         const input = [
             { key: "a", mapped: [] },
             { key: "b", mapped: [] },
@@ -201,19 +197,7 @@ test("compose() should emit drain event ~rate * highWaterMark ms for every write
             { 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();
-            }
-        }
+        fromArray(input).pipe(composed);
     });
 });
 
@@ -237,9 +221,13 @@ test.cb(
             return chunk;
         });
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark: 5,
-        });
+            },
+        );
 
         composed.on("error", err => {
             t.end(err);
@@ -247,10 +235,6 @@ test.cb(
 
         composed.on("drain", () => {
             expect(composed._writableState.length).to.be.equal(0);
-            expect(performance.now() - start).to.be.closeTo(
-                _rate * input.length,
-                50,
-            );
             t.pass();
         });
 
@@ -271,7 +255,6 @@ test.cb(
         input.forEach(item => {
             composed.write(item);
         });
-        const start = performance.now();
     },
 );
 
@@ -301,9 +284,13 @@ test.cb(
             { highWaterMark: 1 },
         );
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark: 5,
-        });
+            },
+        );
         composed.on("error", err => {
             t.end(err);
         });
@@ -368,9 +355,13 @@ test.cb(
             { highWaterMark: 2 },
         );
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark: 5,
-        });
+            },
+        );
         composed.on("error", err => {
             t.end(err);
         });
@@ -423,9 +414,13 @@ test.cb(
             return chunk;
         });
 
-        const composed = compose([first, second], undefined, {
+        const composed = compose(
+            [first, second],
+            undefined,
+            {
                 highWaterMark: 6,
-        });
+            },
+        );
 
         composed.on("error", err => {
             t.end(err);
@@ -475,9 +470,12 @@ test.cb("compose() should be 'destroyable'", t => {
         return chunk;
     });
 
-    const composed = compose([first, second], (err: any) => {
+    const composed = compose(
+        [first, second],
+        (err: any) => {
             t.pass();
-    });
+        },
+    );
 
     const fakeSource = new Readable({
         objectMode: true,
@@ -533,9 +531,13 @@ test.cb("compose() `finish` and `end` propagates", t => {
         return chunk;
     });
 
-    const composed = compose([first, second], undefined, {
+    const composed = compose(
+        [first, second],
+        undefined,
+        {
             highWaterMark: 3,
-    });
+        },
+    );
 
     const fakeSource = new Readable({
         objectMode: true,

tests/demux.spec.ts

@@ -1,11 +1,11 @@
 import test from "ava";
 import { expect } from "chai";
 import mhysa from "../src";
-import { Writable } from "stream";
+import { Writable, Readable } from "stream";
 const sinon = require("sinon");
 const { sleep } = require("../src/helpers");
 import { performance } from "perf_hooks";
-const { demux, map } = mhysa();
+const { demux, map, fromArray } = mhysa({ objectMode: true });
 
 interface Test {
     key: string;
@@ -31,7 +31,7 @@ test.cb("demux() constructor should be called once per key", t => {
         return dest;
     });
 
-    const demuxed = demux(construct, "key", { objectMode: true });
+    const demuxed = demux(construct, "key", {});
 
     demuxed.on("finish", () => {
         expect(construct.withArgs("a").callCount).to.equal(1);
@@ -41,8 +41,35 @@ test.cb("demux() constructor should be called once per key", t => {
         t.end();
     });
 
-    input.forEach(event => demuxed.write(event));
-    demuxed.end();
+    fromArray(input).pipe(demuxed);
+});
+
+test.cb("demux() item written passed in constructor", t => {
+    t.plan(4);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "c", visited: [] },
+    ];
+    const construct = sinon.spy((destKey: string, item: any) => {
+        expect(item).to.deep.equal({ key: destKey, visited: [] });
+        t.pass();
+        const dest = map((chunk: Test) => {
+            chunk.visited.push(1);
+            return chunk;
+        });
+
+        return dest;
+    });
+
+    const demuxed = demux(construct, "key", {});
+
+    demuxed.on("finish", () => {
+        t.pass();
+        t.end();
+    });
+
+    fromArray(input).pipe(demuxed);
 });
 
 test.cb("demux() should send input through correct pipeline", t => {
@@ -66,7 +93,7 @@ test.cb("demux() should send input through correct pipeline", t => {
         return dest;
     };
 
-    const demuxed = demux(construct, "key", { objectMode: true });
+    const demuxed = demux(construct, "key", {});
 
     demuxed.on("finish", () => {
         pipelineSpies["a"].getCalls().forEach(call => {
@@ -84,8 +111,7 @@ test.cb("demux() should send input through correct pipeline", t => {
         t.end();
     });
 
-    input.forEach(event => demuxed.write(event));
-    demuxed.end();
+    fromArray(input).pipe(demuxed);
 });
 
 test.cb("demux() constructor should be called once per key using keyBy", t => {
@@ -108,7 +134,7 @@ test.cb("demux() constructor should be called once per key using keyBy", t => {
         return dest;
     });
 
-    const demuxed = demux(construct, item => item.key, { objectMode: true });
+    const demuxed = demux(construct, item => item.key, {});
 
     demuxed.on("finish", () => {
         expect(construct.withArgs("a").callCount).to.equal(1);
@@ -118,8 +144,7 @@ test.cb("demux() constructor should be called once per key using keyBy", t => {
         t.end();
     });
 
-    input.forEach(event => demuxed.write(event));
-    demuxed.end();
+    fromArray(input).pipe(demuxed);
 });
 
 test.cb("demux() should send input through correct pipeline using keyBy", t => {
@@ -143,7 +168,7 @@ test.cb("demux() should send input through correct pipeline using keyBy", t => {
         return dest;
     };
 
-    const demuxed = demux(construct, item => item.key, { objectMode: true });
+    const demuxed = demux(construct, item => item.key, {});
 
     demuxed.on("finish", () => {
         pipelineSpies["a"].getCalls().forEach(call => {
@@ -161,11 +186,10 @@ test.cb("demux() should send input through correct pipeline using keyBy", t => {
         t.end();
     });
 
-    input.forEach(event => demuxed.write(event));
-    demuxed.end();
+    fromArray(input).pipe(demuxed);
 });
 
-test("demux() write should return false after if it has >= highWaterMark items buffered and drain should be emitted", t => {
+test("demux() write should return false and emit drain if more than highWaterMark items are buffered", t => {
     return new Promise(async (resolve, reject) => {
         t.plan(7);
         interface Chunk {
@@ -189,7 +213,7 @@ test("demux() write should return false after if it has >= highWaterMark items b
                     await sleep(slowProcessorSpeed);
                     return { ...chunk, mapped: [1] };
                 },
-                { highWaterMark: 1, objectMode: true },
+                { highWaterMark: 1 },
             );
 
             first.on("data", chunk => {
@@ -205,7 +229,6 @@ test("demux() write should return false after if it has >= highWaterMark items b
         };
 
         const _demux = demux(construct, "key", {
-            objectMode: true,
             highWaterMark,
         });
 
@@ -229,7 +252,7 @@ test("demux() write should return false after if it has >= highWaterMark items b
     });
 });
 
-test("demux() should emit one drain event after slowProcessorSpeed * highWaterMark ms", t => {
+test("demux() should emit one drain event after slowProcessorSpeed * highWaterMark ms when first stream is bottleneck", t => {
     return new Promise(async (resolve, reject) => {
         t.plan(7);
         interface Chunk {
@@ -255,7 +278,7 @@ test("demux() should emit one drain event after slowProcessorSpeed * highWaterMa
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { highWaterMark: 1, objectMode: true },
+                { highWaterMark: 1 },
             );
 
             first.on("data", () => {
@@ -268,7 +291,6 @@ test("demux() should emit one drain event after slowProcessorSpeed * highWaterMa
             return first;
         };
         const _demux = demux(construct, "key", {
-            objectMode: true,
             highWaterMark,
         });
         _demux.on("error", err => {
@@ -296,7 +318,7 @@ test("demux() should emit one drain event after slowProcessorSpeed * highWaterMa
 
 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);
+        t.plan(1);
         interface Chunk {
             key: string;
             mapped: number[];
@@ -318,12 +340,11 @@ test("demux() should emit one drain event when writing 6 items with highWaterMar
                     chunk.mapped.push(2);
                     return chunk;
                 },
-                { highWaterMark: 1, objectMode: true },
+                { highWaterMark: 1 },
             );
 
             first.on("data", () => {
                 pendingReads--;
-                t.pass();
                 if (pendingReads === 0) {
                     resolve();
                 }
@@ -331,7 +352,6 @@ test("demux() should emit one drain event when writing 6 items with highWaterMar
             return first;
         };
         const _demux = demux(construct, "key", {
-            objectMode: true,
             highWaterMark: 5,
         });
 
@@ -355,9 +375,10 @@ test("demux() should emit one drain event when writing 6 items with highWaterMar
     });
 });
 
-test.cb.only(
-    "demux() should emit drain event when third stream is bottleneck",
+test.cb(
+    "demux() should emit drain event when second stream is bottleneck after (highWaterMark - 2) * slowProcessorSpeed ms",
     t => {
+        // ie) first two items are pushed directly into first and second streams (highWaterMark - 2 remain in demux)
         t.plan(8);
         const slowProcessorSpeed = 100;
         const highWaterMark = 5;
@@ -383,7 +404,7 @@ test.cb.only(
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { highWaterMark: 1 },
             );
 
             const second = map(
@@ -392,25 +413,23 @@ test.cb.only(
                     chunk.mapped.push(2);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { 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),
+                slowProcessorSpeed * 3,
             );
             t.pass();
         });
@@ -427,15 +446,14 @@ test.cb.only(
         let pendingReads = input.length;
 
         const start = performance.now();
-        input.forEach(item => {
-            _demux.write(item);
-        });
+        fromArray(input).pipe(_demux);
     },
 );
 
 test.cb(
-    "demux() should emit drain event when second stream is bottleneck",
+    "demux() should emit drain event when third stream is bottleneck",
     t => {
+        // @TODO investigate why drain is emitted after slowProcessorSpeed
         t.plan(8);
         const slowProcessorSpeed = 100;
         const highWaterMark = 5;
@@ -446,7 +464,7 @@ test.cb(
         const sink = new Writable({
             objectMode: true,
             write(chunk, encoding, cb) {
-                expect(chunk.mapped).to.deep.equal([1, 2]);
+                expect(chunk.mapped).to.deep.equal([1, 2, 3]);
                 t.pass();
                 pendingReads--;
                 if (pendingReads === 0) {
@@ -461,14 +479,14 @@ test.cb(
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { highWaterMark: 1 },
             );
             const second = map(
                 (chunk: Chunk) => {
                     chunk.mapped.push(2);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { highWaterMark: 1 },
             );
 
             const third = map(
@@ -477,7 +495,7 @@ test.cb(
                     chunk.mapped.push(3);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { highWaterMark: 1 },
             );
 
             first
@@ -487,18 +505,16 @@ test.cb(
             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),
+                slowProcessorSpeed,
             );
             t.pass();
         });
@@ -515,9 +531,7 @@ test.cb(
         let pendingReads = input.length;
 
         const start = performance.now();
-        input.forEach(item => {
-            _demux.write(item);
-        });
+        fromArray(input).pipe(_demux);
     },
 );
 
@@ -536,10 +550,21 @@ test("demux() should be blocked by slowest pipeline", t => {
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { objectMode: true, highWaterMark: 1 },
+                { highWaterMark: 1 },
             );
 
-            first.on("data", chunk => {
+            return first;
+        };
+
+        const _demux = demux(construct, "key", {
+            highWaterMark: 1,
+        });
+
+        _demux.on("error", err => {
+            reject(err);
+        });
+
+        _demux.on("data", async chunk => {
             pendingReads--;
             if (chunk.key === "b") {
                 expect(performance.now() - start).to.be.greaterThan(
@@ -550,22 +575,12 @@ test("demux() should be blocked by slowest pipeline", t => {
                 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: [] },
         ];
 
@@ -584,74 +599,266 @@ test("demux() should be blocked by slowest pipeline", t => {
     });
 });
 
-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) => {
+test.cb("Demux should remux to sink", t => {
+    t.plan(6);
+    let i = 0;
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+    const result = [
+        { key: "a", visited: ["a"] },
+        { key: "b", visited: ["b"] },
+        { key: "a", visited: ["a"] },
+        { key: "c", visited: ["c"] },
+        { key: "a", visited: ["a"] },
+        { key: "b", visited: ["b"] },
+    ];
+    const construct = (destKey: string) => {
+        const dest = map((chunk: any) => {
+            chunk.visited.push(destKey);
+            return chunk;
+        });
+
+        return dest;
+    };
+
+    const sink = map(d => {
+        t.deepEqual(d, result[i]);
+        i++;
+        if (i === input.length) {
+            t.end();
+        }
+    });
+
+    const demuxed = demux(construct, "key", {});
+
+    fromArray(input)
+        .pipe(demuxed)
+        .pipe(sink);
+});
+
+test.cb("Demux should send data events", t => {
+    t.plan(6);
+    let i = 0;
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+    ];
+    const result = [
+        { key: "a", visited: ["a"] },
+        { key: "b", visited: ["b"] },
+        { key: "a", visited: ["a"] },
+        { key: "c", visited: ["c"] },
+        { key: "a", visited: ["a"] },
+        { key: "b", visited: ["b"] },
+    ];
+    const construct = (destKey: string) => {
+        const dest = map((chunk: any) => {
+            chunk.visited.push(destKey);
+            return chunk;
+        });
+
+        return dest;
+    };
+
+    const demuxed = demux(construct, "key", {});
+
+    fromArray(input).pipe(demuxed);
+
+    demuxed.on("data", d => {
+        t.deepEqual(d, result[i]);
+        i++;
+        if (i === input.length) {
+            t.end();
+        }
+    });
+});
+
+test.cb("demux() `finish` and `end` propagates", t => {
     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();
-                }
-            },
-        });
+
+    t.plan(9);
 
     const construct = (destKey: string) => {
-            const first = map(
-                (chunk: Chunk) => {
-                    expect(first._readableState.length).to.be.at.most(2);
-                    chunk.mapped.push(1);
+        const dest = map((chunk: any) => {
+            chunk.mapped.push(destKey);
             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;
+        });
+        return dest;
     };
 
     const _demux = demux(construct, "key", {
-            objectMode: true,
-            highWaterMark,
-        });
-        _demux.on("error", err => {
-            reject();
+        highWaterMark: 3,
     });
 
-        _demux.on("drain", () => {
-            expect(_demux._writableState.length).to.be.equal(0);
+    const fakeSource = new Readable({
+        objectMode: true,
+        read() {
+            return;
+        },
+    });
+
+    const sink = map((d: any) => {
+        const curr = input.shift();
+        t.is(curr.key, d.key);
+        t.deepEqual(d.mapped, [d.key]);
+    });
+
+    fakeSource.pipe(_demux).pipe(sink);
+
+    fakeSource.on("end", () => {
+        t.pass();
+    });
+    _demux.on("finish", () => {
+        t.pass();
+    });
+    _demux.on("unpipe", () => {
+        t.pass();
+    });
+    _demux.on("end", () => {
+        t.pass();
+        t.end();
+    });
+    sink.on("finish", () => {
         t.pass();
     });
 
     const input = [
         { key: "a", mapped: [] },
+        { key: "b", mapped: [] },
         { key: "a", mapped: [] },
         { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
+        { key: "b", mapped: [] },
     ];
-        let pendingReads = input.length;
-
-        input.forEach(item => {
-            _demux.write(item);
-        });
-    });
+    fakeSource.push(input[0]);
+    fakeSource.push(input[1]);
+    fakeSource.push(null);
+});
+
+test.cb("demux() `unpipe` propagates", t => {
+    interface Chunk {
+        key: string;
+        mapped: number[];
+    }
+
+    t.plan(7);
+
+    const construct = (destKey: string) => {
+        const dest = map((chunk: any) => {
+            chunk.mapped.push(destKey);
+            return chunk;
+        });
+        return dest;
+    };
+
+    const _demux = demux(construct, "key", {
+        highWaterMark: 3,
+    });
+
+    const fakeSource = new Readable({
+        objectMode: true,
+        read() {
+            return;
+        },
+    });
+
+    const sink = map((d: any) => {
+        const curr = input.shift();
+        t.is(curr.key, d.key);
+        t.deepEqual(d.mapped, [d.key]);
+    });
+
+    fakeSource.pipe(_demux).pipe(sink);
+
+    _demux.on("unpipe", () => {
+        t.pass();
+    });
+
+    sink.on("unpipe", () => {
+        t.pass();
+    });
+
+    sink.on("finish", () => {
+        t.pass();
+        t.end();
+    });
+
+    const input = [
+        { key: "a", mapped: [] },
+        { key: "b", mapped: [] },
+        { key: "a", mapped: [] },
+        { key: "a", mapped: [] },
+        { key: "b", mapped: [] },
+    ];
+    fakeSource.push(input[0]);
+    fakeSource.push(input[1]);
+    fakeSource.push(null);
+});
+
+test.cb("demux() should be 'destroyable'", t => {
+    t.plan(2);
+    const _sleep = 100;
+    interface Chunk {
+        key: string;
+        mapped: string[];
+    }
+
+    const construct = (destKey: string) => {
+        const first = map(async (chunk: Chunk) => {
+            await sleep(_sleep);
+            chunk.mapped.push(destKey);
+            return chunk;
+        });
+        return first;
+    };
+
+    const _demux = demux(construct, "key");
+
+    const fakeSource = new Readable({
+        objectMode: true,
+        read() {
+            return;
+        },
+    });
+
+    const fakeSink = new Writable({
+        objectMode: true,
+        write(data, enc, cb) {
+            const cur = input.shift();
+            t.is(cur.key, data.key);
+            t.deepEqual(cur.mapped, ["a"]);
+            if (cur.key === "a") {
+                _demux.destroy();
+            }
+            cb();
+        },
+    });
+
+    _demux.on("close", t.end);
+    fakeSource.pipe(_demux).pipe(fakeSink);
+
+    const input = [
+        { key: "a", mapped: [] },
+        { key: "b", mapped: [] },
+        { key: "c", mapped: [] },
+        { key: "d", mapped: [] },
+        { key: "e", mapped: [] },
+    ];
+    fakeSource.push(input[0]);
+    fakeSource.push(input[1]);
+    fakeSource.push(input[2]);
+    fakeSource.push(input[3]);
+    fakeSource.push(input[4]);
 });

tests/utils/collected.spec.ts

@@ -0,0 +1,9 @@
+import test from "ava";
+import { collected } from "../../src/utils";
+import mhysa from "../../src";
+const { fromArray, collect } = mhysa({ objectMode: true });
+
+test("collected returns a promise for the first data point", async t => {
+    const data = collected(fromArray([1, 2, 3, 4]).pipe(collect()));
+    t.deepEqual(await data, [1, 2, 3, 4]);
+});

yarn.lock

@@ -409,10 +409,10 @@
   resolved "https://registry.yarnpkg.com/@types/node/-/node-12.7.2.tgz#c4e63af5e8823ce9cc3f0b34f7b998c2171f0c44"
   integrity sha512-dyYO+f6ihZEtNPDcWNR1fkoTDf3zAK3lAABDze3mz6POyIercH0lEUawUFXlG8xaQZmm1yEBON/4TsYv/laDYg==
 
-"@types/node@^12.7.2":
-  version "12.12.14"
-  resolved "https://npm.dev.jogogo.co/@types%2fnode/-/node-12.12.14.tgz#1c1d6e3c75dba466e0326948d56e8bd72a1903d2"
-  integrity sha512-u/SJDyXwuihpwjXy7hOOghagLEV1KdAST6syfnOk6QZAMzZuWZqXy5aYYZbh8Jdpd4escVFP0MvftHNDb9pruA==
+"@types/node@^12.12.15":
+  version "12.12.15"
+  resolved "https://npm.dev.jogogo.co/@types%2fnode/-/node-12.12.15.tgz#8dfb6ce22fedd469128137640a3aa8f17415422f"
+  integrity sha512-Pv+vWicyFd07Hw/SmNnTUguqrHgDfMtjabvD9sQyxeqbpCEg8CmViLBaVPHtNsoBgZECrRf5/pgV6FJIBrGSjw==
 
 "@types/sinon@^7.0.13":
   version "7.5.1"
@@ -1935,7 +1935,7 @@ merge2@^1.2.3, merge2@^1.3.0:
   integrity sha512-2j4DAdlBOkiSZIsaXk4mTE3sRS02yBHAtfy127xRV3bQUFqXkjHCHLW6Scv7DwNRbIWNHH8zpnz9zMaKXIdvYw==
 
 mhysa@./:
-  version "0.0.1-beta.4"
+  version "2.0.0-alpha.1"
 
 micromatch@^4.0.2:
   version "4.0.2"