// ═══ audio.js ═══
// ============================================================
//  AUDIO.JS — Web Audio API sound effects
// ============================================================

let _audioCtx = null;
let _activeNodes = 0;
const _MAX_NODES = 12;

function getAudioCtx() {
  if (!_audioCtx) {
    try { _audioCtx = new (window.AudioContext || window.webkitAudioContext)(); }
    catch (e) { _audioCtx = null; }
  }
  // Resume if suspended (browser autoplay policy)
  if (_audioCtx && _audioCtx.state === 'suspended') _audioCtx.resume();
  return _audioCtx;
}

// ── PRIMITIVE SYNTH ───────────────────────────────────────────
// type: 'sine'|'square'|'sawtooth'|'triangle'
function playTone(freq, type, gainPeak, duration, opts = {}) {
  const ctx = getAudioCtx();
  if (!ctx) return;
  if (_activeNodes >= _MAX_NODES) return;
  _activeNodes++;
  const now = ctx.currentTime;

  const osc = ctx.createOscillator();
  const gain = ctx.createGain();

  // Optional frequency sweep
  osc.type = type;
  osc.frequency.setValueAtTime(freq, now);
  if (opts.freqEnd !== undefined) {
    osc.frequency.linearRampToValueAtTime(opts.freqEnd, now + duration);
  }

  const attack = opts.attack ?? 0.005;
  const decay  = opts.decay  ?? duration * 0.3;

  gain.gain.setValueAtTime(0, now);
  gain.gain.linearRampToValueAtTime(gainPeak, now + attack);
  gain.gain.exponentialRampToValueAtTime(0.001, now + duration);

  // Optional filter
  if (opts.filterFreq) {
    const filter = ctx.createBiquadFilter();
    filter.type = opts.filterType ?? 'lowpass';
    filter.frequency.setValueAtTime(opts.filterFreq, now);
    if (opts.filterEnd) filter.frequency.linearRampToValueAtTime(opts.filterEnd, now + duration);
    osc.connect(filter);
    filter.connect(gain);
  } else {
    osc.connect(gain);
  }

  gain.connect(ctx.destination);
  osc.onended = () => { _activeNodes--; };
  osc.start(now);
  osc.stop(now + duration + 0.01);
}

function playNoise(gainPeak, duration, opts = {}) {
  const ctx = getAudioCtx();
  if (!ctx) return;
  if (_activeNodes >= _MAX_NODES) return;
  _activeNodes++;
  const now = ctx.currentTime;
  const bufLen = Math.ceil(ctx.sampleRate * duration);
  const buf = ctx.createBuffer(1, bufLen, ctx.sampleRate);
  const data = buf.getChannelData(0);
  for (let i = 0; i < bufLen; i++) data[i] = Math.random() * 2 - 1;

  const src = ctx.createBufferSource();
  src.buffer = buf;

  const gain = ctx.createGain();
  gain.gain.setValueAtTime(gainPeak, now);
  gain.gain.exponentialRampToValueAtTime(0.001, now + duration);

  if (opts.filterFreq) {
    const filter = ctx.createBiquadFilter();
    filter.type = opts.filterType ?? 'bandpass';
    filter.frequency.setValueAtTime(opts.filterFreq, now);
    filter.Q.setValueAtTime(opts.Q ?? 1, now);
    src.connect(filter);
    filter.connect(gain);
  } else {
    src.connect(gain);
  }

  gain.connect(ctx.destination);
  src.onended = () => { _activeNodes--; };
  src.start(now);
}

// ── SOUND EFFECTS ─────────────────────────────────────────────

function sfx_cannon() {
  // Deep thud + sharp crack
  playNoise(0.4, 0.12, { filterFreq: 180, filterType: 'lowpass', Q: 0.8 });
  playTone(120, 'sawtooth', 0.3, 0.08, { freqEnd: 40 });
}

function sfx_flamethrower() {
  // Hissy noise burst
  playNoise(0.25, 0.09, { filterFreq: 2200, filterType: 'bandpass', Q: 0.5 });
}

function sfx_lightning() {
  // Sharp electric snap
  playNoise(0.5, 0.06, { filterFreq: 4000, filterType: 'highpass' });
  playTone(800, 'sawtooth', 0.2, 0.05, { freqEnd: 200 });
}

function sfx_mortar_launch() {
  // Low thump with whistle
  playTone(80, 'sine', 0.35, 0.15, { freqEnd: 300 });
  playNoise(0.2, 0.15, { filterFreq: 300, filterType: 'lowpass' });
}

function sfx_mortar_explode() {
  // Big boom
  playNoise(0.7, 0.3, { filterFreq: 250, filterType: 'lowpass', Q: 0.5 });
  playTone(60, 'sine', 0.5, 0.25, { freqEnd: 20 });
}

function sfx_laser() {
  // High-pitched zap
  playTone(1200, 'sine', 0.15, 0.05, { freqEnd: 800 });
}

function sfx_freeze() {
  // Icy crystalline sound
  playTone(1800, 'sine', 0.2, 0.2, { freqEnd: 600, attack: 0.02 });
  playTone(2200, 'triangle', 0.1, 0.15, { freqEnd: 900 });
}

function sfx_void() {
  // Deep rumbling whoosh
  playTone(55, 'sawtooth', 0.3, 0.4, { freqEnd: 40, filterFreq: 200, filterEnd: 80 });
  playNoise(0.15, 0.4, { filterFreq: 120, filterType: 'lowpass' });
}

function sfx_missile_launch() {
  // Whoosh
  playNoise(0.3, 0.18, { filterFreq: 800, filterType: 'bandpass', Q: 0.6 });
  playTone(300, 'sawtooth', 0.2, 0.18, { freqEnd: 100 });
}

function sfx_arcane() {
  // Magical chime
  playTone(1400, 'sine', 0.15, 0.07, { freqEnd: 700 });
}

function sfx_poison_launch() {
  // Bubbly squirt
  playTone(400, 'sine', 0.2, 0.1, { freqEnd: 150 });
  playNoise(0.1, 0.1, { filterFreq: 600, filterType: 'bandpass' });
}

function sfx_enemy_die() {
  // Short crunch
  playNoise(0.3, 0.08, { filterFreq: 600, filterType: 'bandpass', Q: 1.5 });
  playTone(200, 'square', 0.15, 0.06, { freqEnd: 80 });
}

function sfx_enemy_breach() {
  // Alarm-like hit
  playTone(220, 'sawtooth', 0.5, 0.3, { freqEnd: 110 });
  playNoise(0.4, 0.2, { filterFreq: 400, filterType: 'lowpass' });
}

function sfx_buy() {
  // Satisfying purchase chime
  playTone(600, 'sine', 0.2, 0.08);
  playTone(800, 'sine', 0.15, 0.08, { attack: 0.04 });
}

function sfx_refund() {
  // Reverse chime
  playTone(800, 'sine', 0.15, 0.08);
  playTone(600, 'sine', 0.2, 0.08, { attack: 0.04 });
}

function sfx_error() {
  // Low buzzer
  playTone(180, 'square', 0.2, 0.12, { freqEnd: 160 });
}

function sfx_portal_open() {
  // Whooshy portal open
  playTone(300, 'sine', 0.15, 0.3, { freqEnd: 900, attack: 0.1 });
  playNoise(0.08, 0.3, { filterFreq: 1200, filterType: 'bandpass' });
}

function sfx_tower_damage() {
  // Heavy metallic impact
  playNoise(0.5, 0.18, { filterFreq: 350, filterType: 'lowpass' });
  playTone(100, 'sawtooth', 0.35, 0.15, { freqEnd: 50 });
}

// Map weapon def id → fire sfx
const WEAPON_SFX = {
  cannon:       sfx_cannon,
  flamethrower: sfx_flamethrower,
  chainlightning: sfx_lightning,
  mortar:       sfx_mortar_launch,
  laser:        sfx_laser,
  freezebomb:   sfx_freeze,
  voidcannon:   sfx_void,
  missilepod:   sfx_missile_launch,
  arcaneturret: sfx_arcane,
  poisoncloud:  sfx_poison_launch,
};

function sfx_weapon_fire(defId) {
  const fn = WEAPON_SFX[defId];
  if (fn) fn();
}

// Throttle repeated sounds (e.g. flamethrower fires every 8 frames)
const _sfxThrottle = {};
function sfx_weapon_fire_throttled(defId, minInterval = 100) {
  const now = Date.now();
  if (_sfxThrottle[defId] && now - _sfxThrottle[defId] < minInterval) return;
  _sfxThrottle[defId] = now;
  sfx_weapon_fire(defId);
}