Refactoring

src/functions/duplex.ts

@@ -0,0 +1,36 @@
+import { Duplex } from "stream";
+/**
+ * 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: 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;
+}