/**
 * The spike, out loud.
 *
 * One oscillator per beep, scheduled by how much fuse is left: a slow tick
 * when it is planted, a stutter when it is about to go. No audio files, and
 * nothing is created until the person has clicked the page — a browser will
 * not start an audio context before that, and should not.
 */

/** Seconds between beeps for this much fuse left. */
export function beepInterval(fuse) {
  if (fuse <= 0) return 0;
  return Math.max(0.12, Math.min(1, fuse / 30));
}

/** The pitch rises as the fuse burns, so it is audible without watching. */
export const beepPitch = (fuse) => 760 + 620 * (1 - Math.min(1, fuse / 45));

export function makeBeeper() {
  let audio = null;
  let next = 0;

  const context = () => {
    if (audio) return audio;
    const Ctor = globalThis.AudioContext || globalThis.webkitAudioContext;
    if (!Ctor) return null;
    audio = new Ctor();
    return audio;
  };

  return {
    /** Called on a click: browsers only allow audio to start from a gesture. */
    wake() {
      const ctx = context();
      if (ctx && ctx.state === "suspended") ctx.resume();
    },
    /** Called every frame with the fuse the server last sent. */
    update(planted, fuse, now) {
      if (!planted || fuse <= 0) {
        next = 0;
        return;
      }
      if (!audio) return; // no gesture yet; nothing to play into
      if (now < next) return;
      next = now + beepInterval(fuse);
      beep(audio, beepPitch(fuse));
    },
  };
}

function beep(audio, hz) {
  const osc = audio.createOscillator();
  const gain = audio.createGain();
  osc.type = "square";
  osc.frequency.value = hz;
  gain.gain.setValueAtTime(0.0001, audio.currentTime);
  gain.gain.exponentialRampToValueAtTime(0.09, audio.currentTime + 0.01);
  gain.gain.exponentialRampToValueAtTime(0.0001, audio.currentTime + 0.09);
  osc.connect(gain).connect(audio.destination);
  osc.start();
  osc.stop(audio.currentTime + 0.1);
}