fix: play completion sound in chat (#466)

packages/client/src/utils/completion-sound.ts

@@ -0,0 +1,68 @@
+type AudioContextConstructor = typeof AudioContext
+
+type WindowWithWebkitAudio = Window & typeof globalThis & {
+  webkitAudioContext?: AudioContextConstructor
+}
+
+let audioContext: AudioContext | null = null
+
+function getAudioContext(): AudioContext | null {
+  if (typeof window === 'undefined') return null
+
+  const AudioContextCtor = window.AudioContext || (window as WindowWithWebkitAudio).webkitAudioContext
+  if (!AudioContextCtor) return null
+
+  if (!audioContext) {
+    audioContext = new AudioContextCtor()
+  }
+
+  return audioContext
+}
+
+export function primeCompletionSound(): void {
+  const ctx = getAudioContext()
+  if (!ctx || ctx.state !== 'suspended') return
+
+  void ctx.resume().catch(() => {
+    // Browser autoplay policy may still reject until a user gesture. Ignore; the
+    // next send action will try again.
+  })
+}
+
+export async function playCompletionSound(): Promise<boolean> {
+  const ctx = getAudioContext()
+  if (!ctx) return false
+
+  try {
+    if (ctx.state === 'suspended') {
+      await ctx.resume()
+    }
+
+    const now = ctx.currentTime
+    const duration = 0.16
+    const oscillator = ctx.createOscillator()
+    const gain = ctx.createGain()
+
+    oscillator.type = 'sine'
+    oscillator.frequency.setValueAtTime(880, now)
+    oscillator.frequency.exponentialRampToValueAtTime(660, now + duration)
+
+    gain.gain.setValueAtTime(0.0001, now)
+    gain.gain.exponentialRampToValueAtTime(0.18, now + 0.015)
+    gain.gain.exponentialRampToValueAtTime(0.0001, now + duration)
+
+    oscillator.connect(gain)
+    gain.connect(ctx.destination)
+    oscillator.start(now)
+    oscillator.stop(now + duration)
+
+    return true
+  } catch (err) {
+    console.warn('Failed to play completion sound:', err)
+    return false
+  }
+}
+
+export function __resetCompletionSoundForTests(): void {
+  audioContext = null
+}