/* Subliminal image flasher.
 *
 * Reads /subliminals.json (a live listing of the drop folder served at
 * /audio/subliminals/), preloads the images, and briefly flashes a random one over the
 * whole viewport at randomized intervals. Used during the antechamber wait AND while the
 * main session audio plays -- so the subject is fed images they never consciously read.
 *
 * The flash is deliberately faint and brief (true subliminal): ~90ms at low opacity,
 * every 4-8s. The layer is position:fixed with pointer-events:none, so it floats over the
 * page without ever intercepting clicks. It sits below the trance overlay (z-50).
 *
 * start()/stop() are idempotent. If the folder is empty or the manifest fails to load it
 * stays silent and invisible -- a no-op, like the antechamber bed when its bank is empty.
 *
 * Mirrors the persistence trick in loop.js: state lives on `window`, the layer is created
 * once on <body>, so the 1.5s HTMX progress-poll swaps of #audio-area never disturb it.
 */
(function () {
  "use strict";

  var MANIFEST = "/subliminals.json";
  var FLASH_MS = 90;        // how long a single image is visible (true subliminal)
  var GAP_MIN = 4000;       // min ms between flashes
  var GAP_MAX = 8000;       // max ms between flashes (randomized for an organic cadence)
  var FIRST_MAX = 2500;     // cap on the very first delay so something shows soon
  var OPACITY = 0.22;       // peak opacity -- faint, hard to consciously catch

  var imgs = [];            // image urls
  var queue = [];           // upcoming urls (reshuffled when drained)
  var state = "idle";       // idle | loading | running | stopped
  var timer = null;         // pending "flash next" timer
  var layer = null;         // the fixed full-viewport overlay
  var hideTimer = null;     // pending "hide current flash" timer

  function shuffle(a) {
    a = a.slice();
    for (var i = a.length - 1; i > 0; i--) {
      var j = Math.floor(Math.random() * (i + 1));
      var t = a[i]; a[i] = a[j]; a[j] = t;
    }
    return a;
  }

  function nextUrl() {
    if (!queue.length) queue = shuffle(imgs);
    return queue.shift();
  }

  function ensureLayer() {
    if (layer) return;
    layer = document.createElement("div");
    layer.id = "subliminal-layer";
    layer.setAttribute("aria-hidden", "true");
    layer.style.cssText =
      "position:fixed;inset:0;z-index:40;pointer-events:none;display:flex;" +
      "align-items:center;justify-content:center;opacity:0;" +
      "transition:opacity 60ms ease-out;";
    var img = document.createElement("img");
    img.id = "subliminal-img";
    img.alt = "";
    img.style.cssText = "max-width:78vw;max-height:78vh;object-fit:contain;";
    layer.appendChild(img);
    document.body.appendChild(layer);
  }

  function scheduleNext(maxFirst) {
    var gap = GAP_MIN + Math.floor(Math.random() * (GAP_MAX - GAP_MIN));
    if (maxFirst) gap = Math.min(gap, maxFirst);
    timer = setTimeout(flash, gap);
  }

  function flash() {
    if (state !== "running" || !imgs.length) return;
    var img = document.getElementById("subliminal-img");
    if (img) {
      img.src = nextUrl();
      layer.style.opacity = String(OPACITY);
      hideTimer = setTimeout(function () {
        if (layer) layer.style.opacity = "0";
      }, FLASH_MS);
    }
    scheduleNext();
  }

  window.Subliminal = {
    start: function () {
      // Dom-controlled, per-subject, default OFF. The experience template sets
      // window.SUBLIMINALS_ON from the subject's dossier; until it's true this is a
      // no-op no matter who calls start() (voice click, audio onplay, handoff).
      if (!window.SUBLIMINALS_ON) return;
      if (state === "running" || state === "loading") return;
      state = "loading";
      fetch(MANIFEST, { cache: "no-store" })
        .then(function (r) { return r.json(); })
        .then(function (data) {
          if (!Array.isArray(data) || !data.length) { state = "idle"; return; }
          imgs = data.map(function (d) { return d.url || d; });
          imgs.forEach(function (u) { var p = new Image(); p.src = u; }); // preload
          queue = shuffle(imgs);
          ensureLayer();
          state = "running";
          scheduleNext(FIRST_MAX);
        })
        .catch(function () { state = "idle"; });
    },

    stop: function () {
      state = "stopped";
      if (timer) { clearTimeout(timer); timer = null; }
      if (hideTimer) { clearTimeout(hideTimer); hideTimer = null; }
      if (layer) layer.style.opacity = "0";
    }
  };
})();