repterra-web/js/audio.js

/* =========================================================
 * REPRTERRA WEB — audio.js
 * Tiny WebAudio synth for SFX. No assets needed.
 * ========================================================= */
'use strict';
window.RTS = window.RTS || {};

RTS.audio = (function () {
  let ctx = null;
  let master = null;
  let muted = false;
  let lastPlay = {}; // throttle

  function ensure() {
    if (ctx) return true;
    try {
      const AC = window.AudioContext || window.webkitAudioContext;
      if (!AC) return false;
      ctx = new AC();
      master = ctx.createGain();
      master.gain.value = 0.32;
      master.connect(ctx.destination);
    } catch (e) { return false; }
    return true;
  }

  function resume() {
    if (!ensure()) return;
    if (ctx.state === 'suspended') ctx.resume();
  }

  function throttled(name, minGap) {
    const t = performance.now();
    if (lastPlay[name] && t - lastPlay[name] < minGap) return true;
    lastPlay[name] = t;
    return false;
  }

  // basic tone
  function tone(freq, dur, type, vol, slideTo, delay) {
    if (muted || !ensure()) return;
    const t0 = ctx.currentTime + (delay || 0);
    const o = ctx.createOscillator();
    const g = ctx.createGain();
    o.type = type || 'square';
    o.frequency.setValueAtTime(freq, t0);
    if (slideTo) o.frequency.exponentialRampToValueAtTime(Math.max(20, slideTo), t0 + dur);
    g.gain.setValueAtTime(vol || 0.2, t0);
    g.gain.exponentialRampToValueAtTime(0.001, t0 + dur);
    o.connect(g); g.connect(master);
    o.start(t0); o.stop(t0 + dur + 0.02);
  }

  // noise burst
  function noise(dur, vol, filterFreq, delay) {
    if (muted || !ensure()) return;
    const t0 = ctx.currentTime + (delay || 0);
    const len = Math.max(1, Math.floor(ctx.sampleRate * dur));
    const buf = ctx.createBuffer(1, len, ctx.sampleRate);
    const d = buf.getChannelData(0);
    for (let i = 0; i < len; i++) d[i] = Math.random() * 2 - 1;
    const src = ctx.createBufferSource();
    src.buffer = buf;
    const f = ctx.createBiquadFilter();
    f.type = 'lowpass';
    f.frequency.value = filterFreq || 1200;
    const g = ctx.createGain();
    g.gain.setValueAtTime(vol || 0.2, t0);
    g.gain.exponentialRampToValueAtTime(0.001, t0 + dur);
    src.connect(f); f.connect(g); g.connect(master);
    src.start(t0); src.stop(t0 + dur + 0.02);
  }

  const S = {};
  S.click     = () => { tone(700, 0.05, 'square', 0.10); };
  S.build     = () => { noise(0.15, 0.3, 500); tone(140, 0.12, 'triangle', 0.25, 90); };
  S.deny      = () => { tone(180, 0.12, 'sawtooth', 0.14, 120); };
  S.shoot     = () => { if (!throttled('shoot', 60)) noise(0.06, 0.14, 3200); };
  S.arrow     = () => { if (!throttled('arrow', 70)) tone(900, 0.07, 'triangle', 0.08, 300); };
  S.cannon    = () => { noise(0.35, 0.5, 350); tone(70, 0.3, 'sine', 0.4, 40); };
  S.spit      = () => { if (!throttled('spit', 120)) tone(300, 0.1, 'sawtooth', 0.09, 160); };
  S.die       = () => { if (!throttled('die', 80)) tone(220, 0.18, 'sawtooth', 0.16, 60); };
  S.thud      = () => { if (!throttled('thud', 120)) { noise(0.08, 0.22, 240); tone(90, 0.09, 'sine', 0.2, 55); } };
  S.roar      = () => { tone(110, 0.7, 'sawtooth', 0.34, 55); noise(0.5, 0.22, 300); };
  S.alarm     = () => { tone(520, 0.28, 'square', 0.16); tone(380, 0.28, 'square', 0.16, null, 0.3); tone(520, 0.28, 'square', 0.16, null, 0.6); };
  S.coin      = () => { tone(880, 0.05, 'sine', 0.08); tone(1320, 0.08, 'sine', 0.08, null, 0.05); };
  S.train     = () => { tone(440, 0.08, 'square', 0.1); tone(660, 0.1, 'square', 0.1, null, 0.08); };
  S.win       = () => { [523, 659, 784, 1046].forEach((f, i) => tone(f, 0.22, 'triangle', 0.22, null, i * 0.16)); };
  S.lose      = () => { [392, 330, 262, 196].forEach((f, i) => tone(f, 0.3, 'sawtooth', 0.2, null, i * 0.22)); };
  S.explode   = () => { noise(0.6, 0.55, 260); tone(55, 0.5, 'sine', 0.45, 30); };

  S.toggleMute = function () { muted = !muted; return muted; };
  S.isMuted = () => muted;
  S.resume = resume;

  return S;
})();