/**
 * Video Editor Timeline Animator
 * Animates playhead scrubbing across the timeline and video preview crossfades.
 * Mirrors the structure and conventions of dashboard-animator.js.
 */
(function () {
  'use strict';

  var DURATION = 10000; // ms for one full playhead sweep (left → right, then loop)
  var X_MIN    = 104;   // leftmost playhead centre (SVG units)
  var X_MAX    = 504;   // rightmost playhead centre (end of clip area)

  function makeState(svg) {
    return {
      svg:          svg,
      playheadLine: svg.querySelector('#ve-playhead-line'),
      playheadHead: svg.querySelector('#ve-playhead-head'),
      scene1:       svg.querySelector('#ve-scene-1'),
      scene2:       svg.querySelector('#ve-scene-2'),
      scene3:       svg.querySelector('#ve-scene-3'),
      innerScreen:  svg.querySelector('#ve-inner-screen'),
      timecode:     svg.querySelector('#ve-timecode'),
      scrubPct:     0,
      lastTime:     performance.now(),
      paused:       false
    };
  }

  function lerp(a, b, t) { return a + (b - a) * t; }

  function updatePlayhead(st) {
    var xC = lerp(X_MIN, X_MAX, st.scrubPct);
    if (st.playheadLine) st.playheadLine.setAttribute('x', (xC - 1).toFixed(1));
    if (st.playheadHead) st.playheadHead.setAttribute('transform', 'translate(' + xC.toFixed(1) + ',234)');
    if (st.timecode) {
      var s = Math.floor(st.scrubPct * 10);
      st.timecode.textContent = '0:' + (s < 10 ? '0' + s : s);
    }
  }

  function updateScenes(st) {
    var p = st.scrubPct;
    var o1, o2, o3, fade;
    if (p < 0.30) {
      o1 = 1; o2 = 0; o3 = 0;
    } else if (p < 0.40) {
      fade = (p - 0.30) / 0.10; o1 = 1 - fade; o2 = fade; o3 = 0;
    } else if (p < 0.65) {
      o1 = 0; o2 = 1; o3 = 0;
    } else if (p < 0.75) {
      fade = (p - 0.65) / 0.10; o1 = 0; o2 = 1 - fade; o3 = fade;
    } else {
      o1 = 0; o2 = 0; o3 = 1;
    }
    if (st.scene1) st.scene1.setAttribute('opacity', o1.toFixed(3));
    if (st.scene2) st.scene2.setAttribute('opacity', o2.toFixed(3));
    if (st.scene3) st.scene3.setAttribute('opacity', o3.toFixed(3));
    if (st.innerScreen) {
      st.innerScreen.setAttribute('fill',
        p < 0.38 ? 'url(#ve-scr-warm)' :
        p < 0.72 ? 'url(#ve-scr-cold)' :
                   'url(#ve-scr-go)'
      );
    }
  }

  function loop(st, now) {
    if (!st.paused) {
      var delta = now - st.lastTime;
      st.lastTime = now;
      st.scrubPct += delta / DURATION;
      if (st.scrubPct >= 1) st.scrubPct -= 1;
      updatePlayhead(st);
      updateScenes(st);
    } else {
      st.lastTime = now; // keep fresh so there is no jump on resume
    }
    requestAnimationFrame(function (t) { loop(st, t); });
  }

  function observe(st) {
    if (!('IntersectionObserver' in window)) return;
    new IntersectionObserver(function (entries) {
      for (var i = 0; i < entries.length; i++) {
        st.paused = !entries[i].isIntersecting;
      }
    }, { rootMargin: '200px', threshold: 0.05 }).observe(st.svg);
  }

  function boot() {
    var svgs = document.querySelectorAll('.ve-svg');
    if (!svgs.length) return;
    if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) return;
    for (var i = 0; i < svgs.length; i++) {
      (function (svg) {
        if (svg._veAnim) return;
        var st = makeState(svg);
        svg._veAnim = st;
        observe(st);
        requestAnimationFrame(function (t) { loop(st, t); });
      })(svgs[i]);
    }
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', boot);
  } else {
    boot();
  }
})();