// engine/anim/root-motion.js - written by Muse Glimmer (Phase 32, part A, 27 Sep 2026; raw output in game/muse-authored/phase32/raw/),
// reviewed by Grok Bot (coach) with game/muse-authored/phase32/harness/. Coach fixes are marked [coach fix P32-n], see FIXES-P32.md.
(function () {
  function dot(a, b) {
    return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
  }
  function sub(a, b) {
    return [a[0] - b[0], a[1] - b[1], a[2] - b[2]];
  }
  function add(a, b) {
    return [a[0] + b[0], a[1] + b[1], a[2] + b[2]];
  }
  function scale(a, s) {
    return [a[0] * s, a[1] * s, a[2] * s];
  }
  function len(v) {
    return Math.sqrt(dot(v, v));
  }
  function hVec(v, up) {
    var d = dot(v, up);
    return [v[0] - d * up[0], v[1] - d * up[1], v[2] - d * up[2]];
  }
  function measure(clip, node, up) {
    var tracks = clip.tracks || [];
    var tr = null;
    for (var i = 0; i < tracks.length; i++) {
      var t = tracks[i];
      if (t.node === node && t.path === 'translation') {
        tr = t;
        break;
      }
    }
    if (!tr) return null;
    var times = tr.times;
    var values = tr.values;
    var n = times.length;
    if (n === 0) return null;
    var first = [values[0], values[1], values[2]];
    var lastIdx = (n - 1) * 3;
    var last = [values[lastIdx], values[lastIdx + 1], values[lastIdx + 2]];
    var net = sub(last, first);
    var hnet = hVec(net, up);
    var horiz = len(hnet);
    var vert = Math.abs(dot(net, up));
    var maxHoriz = 0;
    for (var i = 0; i < n; i++) {
      var idx = i * 3;
      var key = [values[idx], values[idx + 1], values[idx + 2]];
      var diff = sub(key, first);
      var hd = hVec(diff, up);
      var l = len(hd);
      if (l > maxHoriz) maxHoriz = l;
    }
    var duration = clip.duration || 0;
    var speed = duration > 0 ? horiz / duration : 0;
    return { keys: n, first: first, last: last, net: net, horiz: horiz, vert: vert, maxHoriz: maxHoriz, speed: speed };
  }
  function strip(clip, node, up, opts) {
    opts = opts || {};
    var mode = opts.mode === 'lock' ? 'lock' : 'drift';
    var tracks = clip.tracks || [];
    var found = false;
    var newTracks = [];
    var removed = [0, 0, 0];
    for (var i = 0; i < tracks.length; i++) {
      var t = tracks[i];
      if (t.node === node && t.path === 'translation' && t.times.length > 0) { // [coach fix P32-3] an empty track made NaN keys; now treated as no track
        found = true;
        var times = t.times;
        var values = t.values;
        var n = times.length;
        var first = [values[0], values[1], values[2]];
        var lastIdx = (n - 1) * 3;
        var last = [values[lastIdx], values[lastIdx + 1], values[lastIdx + 2]];
        var net = sub(last, first);
        var hnet = hVec(net, up);
        removed = hnet;
        var newValues = new Float32Array(values.length);
        newValues.set(values);
        var t0 = times[0];
        var tLast = times[n - 1];
        var denom = tLast - t0;
        for (var k = 0; k < n; k++) {
          var idx = k * 3;
          var key = [values[idx], values[idx + 1], values[idx + 2]];
          var newKey;
          if (mode === 'drift') {
            var u = denom !== 0 ? (times[k] - t0) / denom : 0;
            var subVec = scale(hnet, u);
            newKey = sub(key, subVec);
          } else {
            var diff = sub(key, first);
            var hdiff = hVec(diff, up);
            newKey = sub(key, hdiff);
          }
          newValues[idx] = newKey[0];
          newValues[idx + 1] = newKey[1];
          newValues[idx + 2] = newKey[2];
        }
        var newTrack = Object.assign({}, t, { times: times, values: newValues }); // [coach fix P32-3] keep any other track fields (was a fixed field list)
        newTracks.push(newTrack);
      } else {
        newTracks.push(t);
      }
    }
    if (!found) {
      return { clip: clip, removed: [0, 0, 0], mode: mode };
    }
    var newClip = { name: clip.name, duration: clip.duration, tracks: newTracks };
    return { clip: newClip, removed: removed, mode: mode };
  }
  function pickRoot(skeleton, clips, hipsNode) {
    var nodes = (skeleton && skeleton.nodes) || [];
    var candidates = new Set();
    for (var i = 0; i < clips.length; i++) {
      var trs = clips[i].tracks || [];
      for (var j = 0; j < trs.length; j++) {
        var t = trs[j];
        if (t.path === 'translation') {
          candidates.add(t.node);
        }
      }
    }
    function moves(nodeIdx) {
      for (var i = 0; i < clips.length; i++) {
        var trs = clips[i].tracks || [];
        for (var j = 0; j < trs.length; j++) {
          var t = trs[j];
          if (t.node === nodeIdx && t.path === 'translation') {
            var times = t.times;
            var values = t.values;
            var n = times.length;
            if (n < 2) continue;
            var first = [values[0], values[1], values[2]];
            var maxd = 0;
            for (var k = 1; k < n; k++) {
              var idx = k * 3;
              var key = [values[idx], values[idx + 1], values[idx + 2]];
              var d = Math.sqrt(
                (key[0] - first[0]) * (key[0] - first[0]) + (key[1] - first[1]) * (key[1] - first[1]) + (key[2] - first[2]) * (key[2] - first[2]),
              );
              if (d > maxd) maxd = d;
            }
            if (maxd > 1e-6) return true;
          }
        }
      }
      return false;
    }
    if (hipsNode >= 0 && hipsNode < nodes.length) {
      var chain = [];
      var cur = hipsNode;
      while (cur >= 0 && cur < nodes.length && chain.length <= nodes.length) { // [coach fix P32-3] stop on bad / cyclic parent indices (was an endless loop or a TypeError)
        chain.push(cur);
        var p = nodes[cur].parent;
        if (p == null || p < 0) break;
        cur = p;
      }
      for (var i = 0; i < chain.length; i++) {
        var nIdx = chain[i];
        if (candidates.has(nIdx) && moves(nIdx)) {
          return nIdx;
        }
      }
    }
    var bestIdx = -1;
    var bestDepth = Infinity;
    function depth(idx) {
      var d = 0;
      var cur = idx;
      while (cur >= 0 && cur < nodes.length && d <= nodes.length) { // [coach fix P32-3] cycle guard
        var p = nodes[cur].parent;
        if (p == null || p < 0) break;
        d++;
        cur = p;
      }
      return d;
    }
    candidates.forEach(function (nIdx) {
      if (!moves(nIdx)) return;
      var d = depth(nIdx);
      if (d < bestDepth || (d === bestDepth && nIdx < bestIdx)) {
        bestDepth = d;
        bestIdx = nIdx;
      }
    });
    return bestIdx;
  }
  var MuseRootMotion = { measure: measure, strip: strip, pickRoot: pickRoot };
  if (typeof window !== 'undefined') window.MuseRootMotion = MuseRootMotion;
  if (typeof module !== 'undefined') module.exports = MuseRootMotion;
})();