// Lantern sound: dungeon ambience plus effects tied to game events. Silent until the
// visitor turns it on. Assets are CC0 (see /static/assets/audio/CREDITS.txt).
"use strict";

(() => {
  const DIR = "/static/assets/audio/";
  const SFX = {
    step: ["footstep00", "footstep01", "footstep02", "footstep03", "footstep04"],
    pickup: ["metalClick"],
    unlock: ["metalLatch"],
    door: ["doorOpen_1"],
    write: ["bookFlip1"],
    win: ["handleCoins"],
    fail: ["creak1"],
  };
  const STEP_MS = 222; // matches the 3D hero's walking speed (4.5 cells per second)
  const MUSIC_VOLUME = 0.55;

  let enabled = false;
  let ctx = null;
  const buffers = {};
  const music = new Audio(DIR + "dungeon-ambience.mp3");
  music.loop = true;
  music.preload = "none";
  music.volume = 0;

  function storedPreference() {
    try { return localStorage.getItem("lantern-sound") === "on"; } catch { return false; }
  }
  function storePreference(on) {
    try { localStorage.setItem("lantern-sound", on ? "on" : "off"); } catch { /* private mode */ }
  }

  async function loadBuffers() {
    const names = [...new Set(Object.values(SFX).flat())];
    await Promise.all(names.map(async (n) => {
      try {
        const res = await fetch(`${DIR}${n}.mp3`);
        buffers[n] = await ctx.decodeAudioData(await res.arrayBuffer());
      } catch { /* a missing effect should never break the page */ }
    }));
  }

  function fadeMusic(target, ms = 1200) {
    const start = music.volume, t0 = performance.now();
    const step = (now) => {
      const k = Math.min(1, (now - t0) / ms);
      music.volume = start + (target - start) * k;
      if (k < 1) requestAnimationFrame(step);
      else if (target === 0) music.pause();
    };
    requestAnimationFrame(step);
  }

  // Announce each sound so a screen recorder can rebuild the soundtrack in sync
  // (browser video capture has no audio). Harmless when nobody listens.
  function announce(kind, delayMs = 0, gain = 1) {
    window.dispatchEvent(new CustomEvent("lantern-sound", { detail: { kind, delayMs, gain } }));
  }

  function play(kind, delayMs = 0, gain = 0.6) {
    if (!enabled || !ctx) return;
    announce(kind, delayMs, gain);
    const names = SFX[kind];
    const buf = buffers[names[Math.floor(Math.random() * names.length)]];
    if (!buf) return;
    const src = ctx.createBufferSource();
    const g = ctx.createGain();
    g.gain.value = gain;
    src.buffer = buf;
    src.playbackRate.value = 0.94 + Math.random() * 0.12; // keep repeated steps from sounding mechanical
    src.connect(g).connect(ctx.destination);
    src.start(ctx.currentTime + delayMs / 1000);
  }

  async function setEnabled(on) {
    enabled = on;
    storePreference(on);
    const btn = document.getElementById("sound");
    if (btn) {
      btn.setAttribute("aria-pressed", String(on));
      btn.textContent = on ? "Sound on" : "Sound off";
    }
    if (on) {
      if (!ctx) {
        ctx = new (window.AudioContext || window.webkitAudioContext)();
        loadBuffers();
      }
      if (ctx.state === "suspended") await ctx.resume();
      music.play().then(() => { fadeMusic(MUSIC_VOLUME); announce("music", 0, MUSIC_VOLUME); }).catch(() => {});
    } else {
      fadeMusic(0, 400);
    }
  }

  /** Sounds for one Beam call, played as the hero walks its route. */
  function turn(turnEvent) {
    if (!enabled) return;
    let steps = 0;
    for (const e of turnEvent.executed) {
      if (e.tool === "write_notes") play("write", 0, 0.5);
      if (e.tool === "act") steps += (e.path || []).length;
    }
    for (let i = 0; i < steps; i++) play("step", i * STEP_MS, 0.35);
    const msg = (turnEvent.frame.message || "").toLowerCase();
    const after = steps * STEP_MS;
    if (msg.includes("unlock")) { play("unlock", after, 0.7); play("door", after + 350, 0.6); }
    else if (/^[a-z] - /.test(msg)) play("pickup", after, 0.7); // inventory line: "g - a key ..."
  }

  function end(endEvent) {
    if (endEvent.outcome === "success") play("win", 300, 0.7);
    else if (endEvent.outcome !== "stopped") play("fail", 300, 0.6);
  }

  function lessons() { play("write", 0, 0.5); }

  document.addEventListener("DOMContentLoaded", () => {
    const btn = document.getElementById("sound");
    if (!btn) return;
    btn.addEventListener("click", () => setEnabled(!enabled));
    // Browsers only allow audio after a user gesture, so a remembered "on" waits for one.
    if (storedPreference()) {
      btn.textContent = "Sound on (click to start)";
      const resume = (e) => {
        window.removeEventListener("pointerdown", resume);
        if (e.target.closest("#sound")) return; // the button's own click handler turns sound on
        setEnabled(true);
      };
      window.addEventListener("pointerdown", resume);
    }
  });

  window.LanternAudio = { turn, end, lessons, get enabled() { return enabled; } };
})();