InnerOS/src/lib/audio.ts

// Audio playback using pre-generated files + server-side TTS API.
// All functions silently no-op when audio playback fails.

function playFile(path: string) {
  try {
    const audio = new Audio(path);
    audio.play().catch(() => {});
  } catch {}
}

export function playStartChime() {
  playFile("/audio/start-chime.wav");
}

export function playTick() {
  playFile("/audio/tick.wav");
}

export function playEndChime() {
  playFile("/audio/end-chime.wav");
}

export function playMidGuidance(lang: string) {
  const file = lang === "zh" ? "mid-guidance-zh.mp3" : "mid-guidance-en.mp3";
  playFile(`/audio/${file}`);
}

export function playEndGuidance(lang: string) {
  const file = lang === "zh" ? "end-guidance-zh.mp3" : "end-guidance-en.mp3";
  playFile(`/audio/${file}`);
}

// Dynamic TTS via server-side Edge TTS (neural voices) API.
// Falls back silently on error (network issue, edge-tts not installed, etc.).
export async function speakText(text: string, lang: string = "zh"): Promise<void> {
  try {
    const url = `/api/audio/tts?text=${encodeURIComponent(text)}&lang=${lang}&rate=-40%25`;
    const response = await fetch(url);
    if (!response.ok) return;
    const blob = await response.blob();
    const blobUrl = URL.createObjectURL(blob);

    await new Promise<void>((resolve) => {
      const audio = new Audio(blobUrl);
      audio.onended = () => { URL.revokeObjectURL(blobUrl); resolve(); };
      audio.onerror = () => { URL.revokeObjectURL(blobUrl); resolve(); };
      audio.play().catch(() => { URL.revokeObjectURL(blobUrl); resolve(); });
    });
  } catch {}
}