let audioCtx: AudioContext | null = null;

function getAudioContext(): AudioContext {
  if (!audioCtx) {
    audioCtx = new AudioContext();
  }
  if (audioCtx.state === 'suspended') {
    audioCtx.resume();
  }
  return audioCtx;
}

function playTone(
  ctx: AudioContext,
  frequency: number,
  startTime: number,
  duration: number,
  type: OscillatorType = 'sine',
  volume = 0.3,
) {
  const osc = ctx.createOscillator();
  const gain = ctx.createGain();

  osc.type = type;
  osc.frequency.value = frequency;
  gain.gain.setValueAtTime(volume, startTime);
  gain.gain.exponentialRampToValueAtTime(0.001, startTime + duration);

  osc.connect(gain);
  gain.connect(ctx.destination);
  osc.start(startTime);
  osc.stop(startTime + duration);
}

export function playCorrectSound() {
  try {
    const ctx = getAudioContext();
    const now = ctx.currentTime;
    // Cheerful ascending two-note ding
    playTone(ctx, 523.25, now, 0.15, 'sine', 0.25); // C5
    playTone(ctx, 659.25, now + 0.12, 0.2, 'sine', 0.25); // E5
  } catch { /* audio unavailable */ }
}

export function playIncorrectSound() {
  try {
    const ctx = getAudioContext();
    const now = ctx.currentTime;
    // Gentle descending two-note
    playTone(ctx, 330, now, 0.15, 'triangle', 0.2); // E4
    playTone(ctx, 262, now + 0.12, 0.25, 'triangle', 0.2); // C4
  } catch { /* audio unavailable */ }
}

export function playCompletionSound() {
  try {
    const ctx = getAudioContext();
    const now = ctx.currentTime;
    // Ascending fanfare
    playTone(ctx, 523.25, now, 0.15, 'sine', 0.2); // C5
    playTone(ctx, 659.25, now + 0.1, 0.15, 'sine', 0.2); // E5
    playTone(ctx, 783.99, now + 0.2, 0.15, 'sine', 0.2); // G5
    playTone(ctx, 1046.5, now + 0.3, 0.35, 'sine', 0.25); // C6
  } catch { /* audio unavailable */ }
}