let audioCtx: AudioContext | null = null;

function getAudioCtx(): AudioContext | null {
  if (audioCtx) return audioCtx;
  try {
    const Ctx = window.AudioContext || (window as unknown as { webkitAudioContext: typeof AudioContext }).webkitAudioContext;
    audioCtx = new Ctx();
    return audioCtx;
  } catch {
    return null;
  }
}

/** Short two-tone ping for chat notifications */
export function playChatSound() {
  const ctx = getAudioCtx();
  if (!ctx) return;
  if (ctx.state === 'suspended') {
    void ctx.resume();
  }
  const playTone = (freq: number, start: number, duration: number) => {
    const osc = ctx.createOscillator();
    const gain = ctx.createGain();
    osc.type = 'sine';
    osc.frequency.value = freq;
    gain.gain.setValueAtTime(0.0001, start);
    gain.gain.exponentialRampToValueAtTime(0.12, start + 0.02);
    gain.gain.exponentialRampToValueAtTime(0.0001, start + duration);
    osc.connect(gain);
    gain.connect(ctx.destination);
    osc.start(start);
    osc.stop(start + duration + 0.02);
  };
  const t = ctx.currentTime;
  playTone(880, t, 0.12);
  playTone(1174, t + 0.14, 0.14);
}

/** Louder alert for student violations (quit / kill app) */
export function playAlertSound() {
  const ctx = getAudioCtx();
  if (!ctx) return;
  if (ctx.state === 'suspended') {
    void ctx.resume();
  }
  const playTone = (freq: number, start: number, duration: number) => {
    const osc = ctx.createOscillator();
    const gain = ctx.createGain();
    osc.type = 'square';
    osc.frequency.value = freq;
    gain.gain.setValueAtTime(0.0001, start);
    gain.gain.exponentialRampToValueAtTime(0.1, start + 0.02);
    gain.gain.exponentialRampToValueAtTime(0.0001, start + duration);
    osc.connect(gain);
    gain.connect(ctx.destination);
    osc.start(start);
    osc.stop(start + duration + 0.02);
  };
  const t = ctx.currentTime;
  playTone(520, t, 0.16);
  playTone(390, t + 0.18, 0.2);
  playTone(520, t + 0.4, 0.18);
}