/* Newbury Exhibit — AR marker proof of concept
 *
 * Goal of this module: prove the full chain works on a real phone —
 *   camera frame -> ArUco 4x4 detection -> a ghost sprite locked onto the marker.
 * No server/sync yet; this is the localisation primitive everything else builds on.
 *
 * Detector: js-aruco2 (global `AR`), dictionary ARUCO_4X4_1000.
 */
(function () {
  'use strict';

  const video = document.getElementById('video');
  const overlay = document.getElementById('overlay');
  const ctx = overlay.getContext('2d');
  const startScreen = document.getElementById('start');
  const goBtn = document.getElementById('go');
  const errEl = document.getElementById('err');
  const hud = document.getElementById('hud');
  const seenTag = document.getElementById('seen');
  const midEl = document.getElementById('mid');
  const fpsEl = document.getElementById('fps');

  // Offscreen canvas we actually read pixels from (matches video native size).
  const grab = document.createElement('canvas');
  const gctx = grab.getContext('2d', { willReadFrequently: true });

  let detector = null;
  let running = false;
  let lastSeen = 0;          // timestamp of last successful detection
  const HOLD_MS = 250;       // keep ghost visible briefly through dropped frames

  // Ghost sprite (animated WebP if present, else procedural wisp fallback).
  const ghostImg = new Image();
  let ghostReady = false;
  ghostImg.onload = () => { ghostReady = true; };
  ghostImg.onerror = () => { ghostReady = false; }; // fall back to procedural
  // Optional: drop a sprite at this path to use it. Safe if 404 -> procedural wisp.
  ghostImg.src = 'assets/ghost_blue.webp';

  function sizeToVideo() {
    const vw = video.videoWidth, vh = video.videoHeight;
    if (!vw || !vh) return;
    grab.width = vw; grab.height = vh;

    // Cover-fit the viewport while keeping native pixels for detection.
    const scale = Math.max(window.innerWidth / vw, window.innerHeight / vh);
    const dw = vw * scale, dh = vh * scale;
    for (const el of [video, overlay]) {
      el.style.width = dw + 'px';
      el.style.height = dh + 'px';
    }
    overlay.width = dw; overlay.height = dh;
    overlay._scale = scale; // px-per-native-pixel for drawing in display space
  }

  async function start() {
    errEl.textContent = '';
    try {
      const stream = await navigator.mediaDevices.getUserMedia({
        video: { facingMode: { ideal: 'environment' }, width: { ideal: 1280 }, height: { ideal: 720 } },
        audio: false,
      });
      video.srcObject = stream;
      await video.play();
    } catch (e) {
      errEl.textContent = 'Camera unavailable: ' + (e.message || e.name) +
        '. On iPhone this page must be served over HTTPS and you must allow camera access.';
      return;
    }

    detector = new AR.Detector({ dictionaryName: 'ARUCO_4X4_1000' });

    await new Promise((res) => {
      if (video.readyState >= 2) return res();
      video.onloadeddata = () => res();
    });
    sizeToVideo();
    window.addEventListener('resize', sizeToVideo);

    startScreen.classList.add('hidden');
    hud.classList.remove('hidden');
    running = true;
    requestAnimationFrame(loop);
  }

  // ---- detection + render loop ----
  let frames = 0, fpsStamp = performance.now();

  function loop(now) {
    if (!running) return;
    requestAnimationFrame(loop);
    if (video.readyState < 2 || !grab.width) return;

    gctx.drawImage(video, 0, 0, grab.width, grab.height);
    const img = gctx.getImageData(0, 0, grab.width, grab.height);

    let markers = [];
    try { markers = detector.detect(img); } catch (_) { markers = []; }

    const s = overlay._scale || 1;
    ctx.clearRect(0, 0, overlay.width, overlay.height);

    if (markers.length) {
      lastSeen = now;
      const m = markers[0];
      drawMarkerOutline(m, s);
      drawGhostOnMarker(m, s, now);
      seenTag.textContent = 'locked';
      seenTag.className = 'tag on';
      midEl.textContent = m.id;
    } else if (now - lastSeen < HOLD_MS) {
      // brief hold-over: keep last ghost roughly; (cheap version: skip)
      seenTag.textContent = 'holding…';
      seenTag.className = 'tag on';
    } else {
      seenTag.textContent = 'searching…';
      seenTag.className = 'tag off';
      midEl.textContent = '—';
    }

    frames++;
    if (now - fpsStamp > 500) {
      fpsEl.textContent = Math.round((frames * 1000) / (now - fpsStamp));
      frames = 0; fpsStamp = now;
    }
  }

  function corners(m, s) {
    // js-aruco corners are in native pixel space (origin top-left).
    return m.corners.map((c) => ({ x: c.x * s, y: c.y * s }));
  }

  function drawMarkerOutline(m, s) {
    const c = corners(m, s);
    ctx.lineWidth = 3;
    ctx.strokeStyle = 'rgba(82,158,255,0.9)';
    ctx.beginPath();
    ctx.moveTo(c[0].x, c[0].y);
    for (let i = 1; i < c.length; i++) ctx.lineTo(c[i].x, c[i].y);
    ctx.closePath();
    ctx.stroke();
    // corner dot to show orientation lock (first corner)
    ctx.fillStyle = 'var(--yellow)';
    ctx.fillStyle = '#fff35d';
    ctx.beginPath(); ctx.arc(c[0].x, c[0].y, 5, 0, Math.PI * 2); ctx.fill();
  }

  function centroid(c) {
    let x = 0, y = 0;
    for (const p of c) { x += p.x; y += p.y; }
    return { x: x / c.length, y: y / c.length };
  }

  function markerSpan(c) {
    // average side length in display px -> sprite scale reference
    let sum = 0;
    for (let i = 0; i < c.length; i++) {
      const a = c[i], b = c[(i + 1) % c.length];
      sum += Math.hypot(b.x - a.x, b.y - a.y);
    }
    return sum / c.length;
  }

  function drawGhostOnMarker(m, s, now) {
    const c = corners(m, s);
    const mid = centroid(c);
    const span = markerSpan(c);

    // Ghost hovers above the marker, gently bobbing — a tiny taste of the
    // motion solver the sync server will eventually drive.
    const t = now / 1000;
    const bob = Math.sin(t * 2.2) * span * 0.10;
    const sway = Math.cos(t * 1.3) * span * 0.06;
    const cx = mid.x + sway;
    const cy = mid.y - span * 0.95 + bob; // float above the plaque
    const size = span * 1.4;

    if (ghostReady) {
      ctx.save();
      ctx.globalAlpha = 0.92;
      ctx.drawImage(ghostImg, cx - size / 2, cy - size / 2, size, size);
      ctx.restore();
    } else {
      drawWisp(cx, cy, size * 0.5, t);
    }

    // tether line so it reads as "bound to this marker"
    ctx.strokeStyle = 'rgba(81,234,241,0.35)';
    ctx.lineWidth = 2;
    ctx.setLineDash([4, 6]);
    ctx.beginPath(); ctx.moveTo(mid.x, mid.y); ctx.lineTo(cx, cy + size * 0.25); ctx.stroke();
    ctx.setLineDash([]);
  }

  // Procedural fallback wisp in Hidden Side "Sad/Blue" gradient.
  function drawWisp(cx, cy, r, t) {
    const grad = ctx.createRadialGradient(cx, cy - r * 0.3, r * 0.2, cx, cy, r);
    grad.addColorStop(0, 'rgba(81,234,241,0.95)');
    grad.addColorStop(0.5, 'rgba(82,158,255,0.65)');
    grad.addColorStop(1, 'rgba(82,158,255,0)');
    ctx.fillStyle = grad;
    ctx.beginPath();
    // teardrop-ish body
    const wob = Math.sin(t * 3) * r * 0.08;
    ctx.ellipse(cx, cy, r * 0.8 + wob, r, 0, 0, Math.PI * 2);
    ctx.fill();
    // eyes
    ctx.fillStyle = 'rgba(8,12,30,0.85)';
    ctx.beginPath(); ctx.ellipse(cx - r * 0.28, cy - r * 0.1, r * 0.10, r * 0.16, 0, 0, Math.PI * 2); ctx.fill();
    ctx.beginPath(); ctx.ellipse(cx + r * 0.28, cy - r * 0.1, r * 0.10, r * 0.16, 0, 0, Math.PI * 2); ctx.fill();
  }

  goBtn.addEventListener('click', start);
})();