// Sound effects, synthesised with the Web Audio API: no audio files. Everything is soft
// (slow attacks, low levels, filtered noise) so it stays in the background of the desk.
// Browsers keep audio locked until the first click or key press; unlock() resumes it.

export function createAudio({ enabled = () => true, volume = () => 0.6 } = {}) {
  let ctx = null;
  let master = null;
  let noiseBuf = null;

  function context() {
    if (!ctx) {
      const AC = globalThis.AudioContext ?? globalThis.webkitAudioContext;
      if (!AC) return null;
      try {
        ctx = new AC();
      } catch {
        return null;
      }
      master = ctx.createGain();
      master.connect(ctx.destination);
    }
    return ctx;
  }

  function unlock() {
    const c = context();
    if (c && c.state === "suspended") c.resume?.().catch?.(() => {});
  }
  for (const ev of ["pointerdown", "keydown"]) document.addEventListener(ev, unlock, { passive: true });

  // One note: a sine (or other) wave with an attack and an exponential fade.
  function tone(c, at, { freq, to, type = "sine", dur = 0.2, gain = 0.2, attack = 0.008 }) {
    const o = c.createOscillator();
    const g = c.createGain();
    o.type = type;
    o.frequency.setValueAtTime(freq, at);
    if (to) o.frequency.exponentialRampToValueAtTime(to, at + dur);
    g.gain.setValueAtTime(0.0001, at);
    g.gain.linearRampToValueAtTime(gain, at + attack);
    g.gain.exponentialRampToValueAtTime(0.0001, at + dur);
    o.connect(g).connect(master);
    o.start(at);
    o.stop(at + dur + 0.05);
  }

  // Filtered noise: paper, pages, thumps and clicks.
  function noise(c, at, { dur = 0.15, gain = 0.1, type = "bandpass", freq = 2000, to, q = 0.8, attack = 0.02 }) {
    noiseBuf ??= (() => {
      const b = c.createBuffer(1, c.sampleRate, c.sampleRate);
      const d = b.getChannelData(0);
      for (let i = 0; i < d.length; i++) d[i] = Math.random() * 2 - 1;
      return b;
    })();
    const src = c.createBufferSource();
    src.buffer = noiseBuf;
    src.loop = true;
    const f = c.createBiquadFilter();
    f.type = type;
    f.Q.value = q;
    f.frequency.setValueAtTime(freq, at);
    if (to) f.frequency.exponentialRampToValueAtTime(to, at + dur);
    const g = c.createGain();
    g.gain.setValueAtTime(0.0001, at);
    g.gain.linearRampToValueAtTime(gain, at + attack);
    g.gain.exponentialRampToValueAtTime(0.0001, at + dur);
    src.connect(f).connect(g).connect(master);
    src.start(at);
    src.stop(at + dur + 0.05);
  }

  const SOUNDS = {
    stampYes: (c, t) => {
      tone(c, t, { freq: 150, to: 55, dur: 0.16, gain: 0.5 });
      noise(c, t, { type: "lowpass", freq: 500, dur: 0.07, gain: 0.25, attack: 0.004 });
      noise(c, t, { freq: 2200, dur: 0.04, gain: 0.07, attack: 0.004 });
    },
    stampNo: (c, t) => {
      tone(c, t, { freq: 118, to: 44, dur: 0.18, gain: 0.5 });
      noise(c, t, { type: "lowpass", freq: 420, dur: 0.08, gain: 0.28, attack: 0.004 });
      noise(c, t, { freq: 1800, dur: 0.04, gain: 0.07, attack: 0.004 });
    },
    paper: (c, t) => noise(c, t, { freq: 2600, to: 1200, dur: 0.17, gain: 0.1, attack: 0.04 }),
    page: (c, t) => {
      noise(c, t, { freq: 500, to: 3200, dur: 0.24, gain: 0.11, attack: 0.05 });
      noise(c, t + 0.2, { freq: 2400, dur: 0.06, gain: 0.05, attack: 0.01 });
    },
    sign: (c, t) => {
      noise(c, t, { freq: 3400, to: 2600, dur: 0.2, gain: 0.05, q: 2, attack: 0.05 });
      tone(c, t + 0.22, { freq: 140, to: 60, dur: 0.14, gain: 0.3 });
    },
    telegram: (c, t) => {
      for (let i = 0; i < 4; i++) noise(c, t + i * 0.07, { type: "highpass", freq: 3200, dur: 0.02, gain: 0.1, attack: 0.002 });
      tone(c, t + 0.34, { freq: 1320, dur: 0.7, gain: 0.1, attack: 0.01 });
      tone(c, t + 0.34, { freq: 1980, dur: 0.45, gain: 0.04, attack: 0.01 });
    },
    alert: (c, t) => {
      tone(c, t, { freq: 233, dur: 0.4, gain: 0.2, type: "triangle", attack: 0.03 });
      tone(c, t + 0.24, { freq: 175, dur: 0.55, gain: 0.2, type: "triangle", attack: 0.03 });
    },
    chime: (c, t) => {
      tone(c, t, { freq: 659, dur: 0.7, gain: 0.12, attack: 0.02 });
      tone(c, t + 0.16, { freq: 880, dur: 0.9, gain: 0.1, attack: 0.02 });
    },
    tick: (c, t) => tone(c, t, { freq: 1100, to: 900, dur: 0.035, gain: 0.03, attack: 0.002 }),
    tock: (c, t) => tone(c, t, { freq: 820, to: 700, dur: 0.035, gain: 0.03, attack: 0.002 }),
    click: (c, t) => {
      tone(c, t, { freq: 900, to: 600, dur: 0.04, gain: 0.06, attack: 0.002 });
      noise(c, t, { type: "highpass", freq: 3000, dur: 0.015, gain: 0.04, attack: 0.002 });
    },
    fall: (c, t) => {
      [330, 247, 196, 147].forEach((f, i) => tone(c, t + i * 0.45, { freq: f, dur: 0.9, gain: 0.14, attack: 0.04, type: "triangle" }));
    },
    fanfare: (c, t) => {
      [392, 494, 587, 784].forEach((f, i) => tone(c, t + i * 0.14, { freq: f, dur: 1.1, gain: 0.09, attack: 0.03 }));
    },
  };

  function play(name) {
    if (!enabled()) return;
    const make = SOUNDS[name];
    const c = context();
    if (!make || !c) return;
    if (c.state === "suspended") {
      c.resume?.().catch?.(() => {});
      return; // still locked: nothing to hear yet
    }
    master.gain.value = Math.max(0, Math.min(1, volume()));
    try {
      make(c, c.currentTime + 0.005);
    } catch {
      /* a failing sound never stops the game */
    }
  }

  return { play, unlock, names: Object.keys(SOUNDS) };
}