fix(frontend): track playback completion and meaningful inactivity

vocero-frontend/src/audio/audio-playback.test.ts

@@ -0,0 +1,56 @@
+import { afterEach, beforeEach, expect, it, vi } from "vitest";
+
+let processor: AudioWorkletProcessor;
+const port = { onmessage: undefined as ((event: MessageEvent) => void) | undefined, postMessage: vi.fn() };
+beforeEach(async () => {
+  vi.resetModules();
+  port.postMessage.mockClear();
+  vi.stubGlobal("sampleRate", 48000);
+  vi.stubGlobal(
+    "AudioWorkletProcessor",
+    class {
+      port = port;
+    },
+  );
+  vi.stubGlobal("registerProcessor", (_name: string, Processor: new () => AudioWorkletProcessor) => {
+    processor = new Processor();
+  });
+  await import("./audio-playback.worklet");
+});
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+function send(data: unknown) {
+  port.onmessage?.(new MessageEvent("message", { data }));
+}
+function render(blocks: number) {
+  let audible = false;
+  for (let index = 0; index < blocks; index++) {
+    const output = new Float32Array(128);
+    processor.process([], [[output]]);
+    audible ||= output.some((value) => value !== 0);
+  }
+  return audible;
+}
+it("flushes a final chunk shorter than the prebuffer and signals after playback finishes", () => {
+  send({ kind: "audio", samples: new Float32Array(160).fill(0.5), sequence: 1 });
+  expect(render(1)).toBe(false);
+  expect(port.postMessage).not.toHaveBeenCalled();
+  send({ kind: "finish", sequence: 1 });
+  expect(render(1)).toBe(true);
+  expect(port.postMessage).not.toHaveBeenCalled();
+  render(12);
+  expect(port.postMessage).toHaveBeenCalledExactlyOnceWith({ kind: "drained", sequence: 1 });
+});
+it("discards cleared samples and identifies the latest playback generation", () => {
+  send({ kind: "audio", samples: new Float32Array(16000).fill(0.5), sequence: 1 });
+  expect(render(1)).toBe(true);
+  send({ kind: "clear", sequence: 2 });
+  render(2);
+  expect(port.postMessage).toHaveBeenLastCalledWith({ kind: "drained", sequence: 2 });
+  expect(render(10)).toBe(false);
+  send({ kind: "audio", samples: new Float32Array(160).fill(0.25), sequence: 3 });
+  send({ kind: "finish", sequence: 3 });
+  expect(render(12)).toBe(true);
+  expect(port.postMessage).toHaveBeenLastCalledWith({ kind: "drained", sequence: 3 });
+});