feat(call): add streaming voice call experience

src/app/call/voice-call-player.ts

@@ -0,0 +1,101 @@
+import type { CallAudioChunkMeta } from "@/core/net/voice-call-transport";
+
+export class VoiceCallPlayer {
+  private context: AudioContext | null = null;
+  private sources = new Set<AudioBufferSourceNode>();
+  private decodeChain: Promise<void> = Promise.resolve();
+  private scheduledUntil = 0;
+  private pendingDecodes = 0;
+  private generation = 0;
+  onPlaying: (() => void) | null = null;
+  onIdle: (() => void) | null = null;
+  onGap: ((milliseconds: number) => void) | null = null;
+  onError: ((error: Error) => void) | null = null;
+
+  get isPlaying(): boolean {
+    return this.sources.size > 0 || this.pendingDecodes > 0;
+  }
+
+  async prepare(): Promise<void> {
+    const context = this.getContext();
+    if (context.state === "suspended") await context.resume();
+  }
+
+  enqueue(_meta: CallAudioChunkMeta, bytes: ArrayBuffer): void {
+    const generation = this.generation;
+    this.pendingDecodes += 1;
+    this.decodeChain = this.decodeChain
+      .then(async () => {
+        const context = this.getContext();
+        if (context.state === "suspended") await context.resume();
+        const audioBuffer = await context.decodeAudioData(bytes.slice(0));
+        if (generation !== this.generation) return;
+        this.schedule(context, audioBuffer);
+      })
+      .catch((error: unknown) => {
+        this.onError?.(error instanceof Error ? error : new Error(String(error)));
+      })
+      .finally(() => {
+        this.pendingDecodes = Math.max(0, this.pendingDecodes - 1);
+        this.notifyIdleIfNeeded();
+      });
+  }
+
+  stop(): void {
+    this.generation += 1;
+    for (const source of this.sources) {
+      source.onended = null;
+      try {
+        source.stop();
+      } catch {
+        // 已自然结束的 source 无需重复停止。
+      }
+      source.disconnect();
+    }
+    this.sources.clear();
+    this.scheduledUntil = 0;
+    this.onIdle?.();
+  }
+
+  dispose(): void {
+    this.stop();
+    const context = this.context;
+    this.context = null;
+    if (context && context.state !== "closed") void context.close();
+  }
+
+  private getContext(): AudioContext {
+    if (!this.context || this.context.state === "closed") {
+      this.context = new AudioContext({ latencyHint: "interactive" });
+    }
+    return this.context;
+  }
+
+  private schedule(context: AudioContext, buffer: AudioBuffer): void {
+    const leadSeconds = 0.025;
+    const earliestStart = context.currentTime + leadSeconds;
+    const hadPreviousSegment = this.scheduledUntil > 0;
+    const startAt = Math.max(earliestStart, this.scheduledUntil);
+    if (hadPreviousSegment) {
+      this.onGap?.(Math.max(0, (startAt - this.scheduledUntil) * 1000));
+    }
+    const source = context.createBufferSource();
+    source.buffer = buffer;
+    source.connect(context.destination);
+    this.sources.add(source);
+    this.scheduledUntil = startAt + buffer.duration;
+    source.onended = () => {
+      source.disconnect();
+      this.sources.delete(source);
+      this.notifyIdleIfNeeded();
+    };
+    source.start(startAt);
+    this.onPlaying?.();
+  }
+
+  private notifyIdleIfNeeded(): void {
+    if (this.sources.size || this.pendingDecodes) return;
+    this.scheduledUntil = 0;
+    this.onIdle?.();
+  }
+}