Add experimental 2-way audio support.

src/utils/microphone.ts

@@ -0,0 +1,84 @@
+export class MicrophoneController {
+  protected _stream?: MediaStream | null;
+  protected _timerID: number | null = null;
+
+  // We keep mute state separate from the stream state so that mute/unmute can
+  // be expressed before the stream is created -- and when it's create it will
+  // have the right mute status.
+  protected _mute = true;
+
+  protected _disconnectSeconds: number;
+
+  constructor(disconnectSeconds?: number) {
+    this._disconnectSeconds = disconnectSeconds ?? 0;
+  }
+
+  public async connect(): Promise<void> {
+    try {
+      this._stream = await navigator.mediaDevices.getUserMedia({
+        audio: true,
+        video: false,
+      });
+    } catch (e) {
+      this._stream = null;
+    }
+    this._setMute();
+  }
+
+  public async disconnect(): Promise<void> {
+    this._stream?.getTracks().forEach((track) => track.stop());
+    this._stream = undefined;
+  }
+
+  public getStream(): MediaStream | undefined {
+    return this._stream ?? undefined;
+  }
+
+  protected _setMute(): void {
+    this._stream?.getTracks().forEach((track) => {
+      track.enabled = !this._mute;
+    });
+    this._startTimer();
+  }
+
+  public mute(): void {
+    this._mute = true;
+    this._setMute();
+  }
+
+  public unmute(): void {
+    this._mute = false;
+    this._setMute();
+  }
+
+  public isConnected(): boolean {
+    return !!this._stream;
+  }
+
+  public isForbidden(): boolean {
+    return this._stream === null;
+  }
+
+  public isMuted(): boolean {
+    // For safety, this function always returns the stream mute status directly
+    // (rather the internal state).
+    return !this._stream || this._stream.getTracks().every((track) => !track.enabled);
+  }
+
+  protected _clearTimer(): void {
+    if (this._timerID) {
+      window.clearTimeout(this._timerID);
+      this._timerID = null;
+    }
+  }
+
+  protected _startTimer(): void {
+    if (this._disconnectSeconds) {
+      this._clearTimer();
+      this._timerID = window.setTimeout(() => {
+        this._clearTimer();
+        this.disconnect();
+      }, this._disconnectSeconds * 1000);
+    }
+  }
+}