xjs/animal.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
    typeof define === 'function' && define.amd ? define(factory) :
      (global.animal = factory());
}(this, (function () {
  'use strict';

  // --- Utils ---
  const isArr = (a) => Array.isArray(a);
  const isStr = (s) => typeof s === 'string';
  const isFunc = (f) => typeof f === 'function';
  const isNil = (v) => v === undefined || v === null;
  const isSVG = (el) => (typeof SVGElement !== 'undefined' && el instanceof SVGElement) || ((typeof Element !== 'undefined') && (el instanceof Element) && el.namespaceURI === 'http://www.w3.org/2000/svg');
  const isEl = (v) => (typeof Element !== 'undefined') && (v instanceof Element);
  const clamp01 = (n) => Math.max(0, Math.min(1, n));
  const toKebab = (s) => s.replace(/[A-Z]/g, (m) => '-' + m.toLowerCase());
  
  const toArray = (targets) => {
    if (isArr(targets)) return targets;
    if (isStr(targets)) {
      if (typeof document === 'undefined') return [];
      return Array.from(document.querySelectorAll(targets));
    }
    if ((typeof NodeList !== 'undefined') && (targets instanceof NodeList)) return Array.from(targets);
    if ((typeof Element !== 'undefined') && (targets instanceof Element)) return [targets];
    if ((typeof Window !== 'undefined') && (targets instanceof Window)) return [targets];
    // Plain objects (for anime.js-style object tweening)
    if (!isNil(targets) && (typeof targets === 'object' || isFunc(targets))) return [targets];
    return [];
  };

  // Selection helper (chainable, still Array-compatible)
  const _layerHandlerByEl = (typeof WeakMap !== 'undefined') ? new WeakMap() : null;
  class Selection extends Array {
    animate(params) { return animate(this, params); }
    draw(params = {}) { return svgDraw(this, params); }
    inViewAnimate(params, options = {}) { return inViewAnimate(this, params, options); }
    // Layer.js plugin-style helper:
    //   const $ = animal.$;
    //   $('.btn').layer({ title: 'Hi' });
    // Clicking the element will open Layer.
    layer(options) {
      const LayerCtor =
        (typeof window !== 'undefined' && window.Layer) ? window.Layer :
        (typeof globalThis !== 'undefined' && globalThis.Layer) ? globalThis.Layer :
        (typeof Layer !== 'undefined' ? Layer : null);
      if (!LayerCtor) return this;
      
      this.forEach((el) => {
        if (!isEl(el)) return;
        // De-dupe / replace previous binding
        if (_layerHandlerByEl) {
          const prev = _layerHandlerByEl.get(el);
          if (prev) el.removeEventListener('click', prev);
        }
        
        const handler = () => {
          let opts = options;
          if (isFunc(options)) {
            opts = options(el);
          } else if (isNil(options)) {
            opts = null;
          }
          // If no explicit options, allow data-* configuration
          if (!opts || (typeof opts === 'object' && Object.keys(opts).length === 0)) {
            const d = el.dataset || {};
            opts = {
              title: d.layerTitle || el.getAttribute('data-layer-title') || (el.textContent || '').trim(),
              text: d.layerText || el.getAttribute('data-layer-text') || '',
              icon: d.layerIcon || el.getAttribute('data-layer-icon') || null,
              showCancelButton: (d.layerCancel === 'true') || (el.getAttribute('data-layer-cancel') === 'true')
            };
          }
          
          // Prefer builder API if present, fallback to static fire.
          if (LayerCtor.$ && isFunc(LayerCtor.$)) return LayerCtor.$(opts).fire();
          if (LayerCtor.fire && isFunc(LayerCtor.fire)) return LayerCtor.fire(opts);
        };
        
        if (_layerHandlerByEl) _layerHandlerByEl.set(el, handler);
        el.addEventListener('click', handler);
      });
      
      return this;
    }
    
    // Remove click bindings added by `.layer()`
    unlayer() {
      this.forEach((el) => {
        if (!isEl(el)) return;
        if (!_layerHandlerByEl) return;
        const prev = _layerHandlerByEl.get(el);
        if (prev) el.removeEventListener('click', prev);
        _layerHandlerByEl.delete(el);
      });
      return this;
    }
  }
  
  const $ = (targets) => Selection.from(toArray(targets));

  const UNITLESS_KEYS = ['opacity', 'scale', 'scaleX', 'scaleY', 'scaleZ', 'zIndex', 'fontWeight', 'strokeDashoffset', 'strokeDasharray', 'strokeWidth'];

  const getUnit = (val, prop) => {
    if (UNITLESS_KEYS.includes(prop)) return '';
    const split = /[+-]?\d*\.?\d+(?:\.\d+)?(?:[eE][+-]?\d+)?(%|px|pt|em|rem|in|cm|mm|ex|ch|pc|vw|vh|vmin|vmax|deg|rad|turn)?$/.exec(val);
    return split ? split[1] : undefined;
  };
  
  const isCssVar = (k) => isStr(k) && k.startsWith('--');
  // Keep this intentionally broad so "unknown" config keys don't accidentally become animated props.
  // Prefer putting non-anim-prop config under `params.options`.
  const isAnimOptionKey = (k) => [
    'options',
    'duration', 'delay', 'easing', 'direction', 'fill', 'loop', 'endDelay', 'autoplay',
    'update', 'begin', 'complete',
    // WAAPI-ish common keys (ignored unless we explicitly support them)
    'iterations', 'iterationStart', 'iterationComposite', 'composite', 'playbackRate',
    // Spring helpers
    'springFrames'
  ].includes(k);
  
  const isEasingFn = (e) => typeof e === 'function';
  
  // Minimal cubic-bezier implementation (for JS engine easing)
  function cubicBezier(x1, y1, x2, y2) {
    // Inspired by https://github.com/gre/bezier-easing (simplified)
    const NEWTON_ITERATIONS = 4;
    const NEWTON_MIN_SLOPE = 0.001;
    const SUBDIVISION_PRECISION = 0.0000001;
    const SUBDIVISION_MAX_ITERATIONS = 10;
    
    const kSplineTableSize = 11;
    const kSampleStepSize = 1.0 / (kSplineTableSize - 1.0);
    
    const float32ArraySupported = typeof Float32Array === 'function';
    
    function A(aA1, aA2) { return 1.0 - 3.0 * aA2 + 3.0 * aA1; }
    function B(aA1, aA2) { return 3.0 * aA2 - 6.0 * aA1; }
    function C(aA1) { return 3.0 * aA1; }
    
    function calcBezier(aT, aA1, aA2) {
      return ((A(aA1, aA2) * aT + B(aA1, aA2)) * aT + C(aA1)) * aT;
    }
    
    function getSlope(aT, aA1, aA2) {
      return 3.0 * A(aA1, aA2) * aT * aT + 2.0 * B(aA1, aA2) * aT + C(aA1);
    }
    
    function binarySubdivide(aX, aA, aB) {
      let currentX, currentT, i = 0;
      do {
        currentT = aA + (aB - aA) / 2.0;
        currentX = calcBezier(currentT, x1, x2) - aX;
        if (currentX > 0.0) aB = currentT;
        else aA = currentT;
      } while (Math.abs(currentX) > SUBDIVISION_PRECISION && ++i < SUBDIVISION_MAX_ITERATIONS);
      return currentT;
    }
    
    function newtonRaphsonIterate(aX, aGuessT) {
      for (let i = 0; i < NEWTON_ITERATIONS; ++i) {
        const currentSlope = getSlope(aGuessT, x1, x2);
        if (currentSlope === 0.0) return aGuessT;
        const currentX = calcBezier(aGuessT, x1, x2) - aX;
        aGuessT -= currentX / currentSlope;
      }
      return aGuessT;
    }
    
    const sampleValues = float32ArraySupported ? new Float32Array(kSplineTableSize) : new Array(kSplineTableSize);
    for (let i = 0; i < kSplineTableSize; ++i) {
      sampleValues[i] = calcBezier(i * kSampleStepSize, x1, x2);
    }
    
    function getTForX(aX) {
      let intervalStart = 0.0;
      let currentSample = 1;
      const lastSample = kSplineTableSize - 1;
      
      for (; currentSample !== lastSample && sampleValues[currentSample] <= aX; ++currentSample) {
        intervalStart += kSampleStepSize;
      }
      --currentSample;
      
      const dist = (aX - sampleValues[currentSample]) / (sampleValues[currentSample + 1] - sampleValues[currentSample]);
      const guessForT = intervalStart + dist * kSampleStepSize;
      
      const initialSlope = getSlope(guessForT, x1, x2);
      if (initialSlope >= NEWTON_MIN_SLOPE) return newtonRaphsonIterate(aX, guessForT);
      if (initialSlope === 0.0) return guessForT;
      return binarySubdivide(aX, intervalStart, intervalStart + kSampleStepSize);
    }
    
    return (x) => {
      if (x === 0 || x === 1) return x;
      return calcBezier(getTForX(x), y1, y2);
    };
  }
  
  function resolveJsEasing(easing, springValues) {
    if (isEasingFn(easing)) return easing;
    if (typeof easing === 'object' && easing && !Array.isArray(easing)) {
      // Spring: map linear progress -> simulated spring curve (0..1)
      const values = springValues || getSpringValues(easing);
      const last = Math.max(0, values.length - 1);
      return (t) => {
        const p = clamp01(t);
        const idx = p * last;
        const i0 = Math.floor(idx);
        const i1 = Math.min(last, i0 + 1);
        const frac = idx - i0;
        const v0 = values[i0] ?? p;
        const v1 = values[i1] ?? p;
        return v0 + (v1 - v0) * frac;
      };
    }
    if (Array.isArray(easing) && easing.length === 4) {
      return cubicBezier(easing[0], easing[1], easing[2], easing[3]);
    }
    // Common named easings
    switch (easing) {
      case 'linear': return (t) => t;
      case 'ease': return cubicBezier(0.25, 0.1, 0.25, 1);
      case 'ease-in': return cubicBezier(0.42, 0, 1, 1);
      case 'ease-out': return cubicBezier(0, 0, 0.58, 1);
      case 'ease-in-out': return cubicBezier(0.42, 0, 0.58, 1);
      default: return (t) => t;
    }
  }

  // --- Spring Physics (Simplified) ---
  // Returns an array of [time, value] or just value for WAAPI linear easing
  function spring({ stiffness = 100, damping = 10, mass = 1, velocity = 0, precision = 0.01 } = {}) {
    const values = [];
    let t = 0;
    const timeStep = 1 / 60; // 60fps simulation
    let current = 0;
    let v = velocity;
    const target = 1;

    let running = true;
    while (running && t < 10) { // Safety break at 10s
      const fSpring = -stiffness * (current - target);
      const fDamper = -damping * v;
      const a = (fSpring + fDamper) / mass;
      
      v += a * timeStep;
      current += v * timeStep;
      
      values.push(current);
      t += timeStep;

      if (Math.abs(current - target) < precision && Math.abs(v) < precision) {
        running = false;
      }
    }
    if (values[values.length - 1] !== 1) values.push(1);
    
    return values;
  }
  
  // Cache spring curves by config (perf: avoid recomputing for many targets)
  // LRU-ish capped cache to avoid unbounded growth in long-lived apps.
  const SPRING_CACHE_MAX = 50;
  const springCache = new Map();
  function springCacheGet(key) {
    const v = springCache.get(key);
    if (!v) return v;
    // refresh LRU
    springCache.delete(key);
    springCache.set(key, v);
    return v;
  }
  function springCacheSet(key, values) {
    if (springCache.has(key)) springCache.delete(key);
    springCache.set(key, values);
    if (springCache.size > SPRING_CACHE_MAX) {
      const firstKey = springCache.keys().next().value;
      if (firstKey !== undefined) springCache.delete(firstKey);
    }
  }
  function getSpringValues(config = {}) {
    const {
      stiffness = 100,
      damping = 10,
      mass = 1,
      velocity = 0,
      precision = 0.01
    } = config || {};
    const key = `${stiffness}|${damping}|${mass}|${velocity}|${precision}`;
    const cached = springCacheGet(key);
    if (cached) return cached;
    const values = spring({ stiffness, damping, mass, velocity, precision });
    springCacheSet(key, values);
    return values;
  }
  
  function downsample(values, maxFrames = 120) {
    if (!values || values.length <= maxFrames) return values || [];
    const out = [];
    const lastIndex = values.length - 1;
    const step = lastIndex / (maxFrames - 1);
    for (let i = 0; i < maxFrames; i++) {
      const idx = i * step;
      const i0 = Math.floor(idx);
      const i1 = Math.min(lastIndex, i0 + 1);
      const frac = idx - i0;
      const v0 = values[i0];
      const v1 = values[i1];
      out.push(v0 + (v1 - v0) * frac);
    }
    if (out[out.length - 1] !== 1) out[out.length - 1] = 1;
    return out;
  }

  // --- WAAPI Core ---
  const TRANSFORMS = ['translateX', 'translateY', 'translateZ', 'rotate', 'rotateX', 'rotateY', 'rotateZ', 'scale', 'scaleX', 'scaleY', 'scaleZ', 'skew', 'skewX', 'skewY', 'perspective', 'x', 'y'];
  
  const ALIASES = {
    x: 'translateX',
    y: 'translateY',
    z: 'translateZ'
  };

  // Basic rAF loop for non-WAAPI props or fallback
  class RafEngine {
    constructor() {
      this.animations = [];
      this.tick = this.tick.bind(this);
      this.running = false;
    }
    add(anim) {
      this.animations.push(anim);
      if (!this.running) {
        this.running = true;
        requestAnimationFrame(this.tick);
      }
    }
    remove(anim) {
      this.animations = this.animations.filter(a => a !== anim);
    }
    tick(t) {
      const now = t;
      this.animations = this.animations.filter(anim => {
        return anim.tick(now); // return true to keep
      });
      if (this.animations.length) {
        requestAnimationFrame(this.tick);
      } else {
        this.running = false;
      }
    }
  }
  const rafEngine = new RafEngine();
  
  // --- WAAPI update sampler (only used when update callback is provided) ---
  class WaapiUpdateSampler {
    constructor() {
      this.items = new Set();
      this._running = false;
      this._tick = this._tick.bind(this);
    }
    add(item) {
      this.items.add(item);
      if (!this._running) {
        this._running = true;
        requestAnimationFrame(this._tick);
      }
    }
    remove(item) {
      this.items.delete(item);
    }
    _tick(t) {
      if (!this.items.size) {
        this._running = false;
        return;
      }
      let anyActive = false;
      let anyChanged = false;
      this.items.forEach((item) => {
        const { anim, target, update } = item;
        if (!anim || !anim.effect) return;
        let dur = item._dur || 0;
        if (!dur) {
          const timing = readWaapiEffectTiming(anim.effect);
          dur = timing.duration || 0;
          item._dur = dur;
        }
        if (!dur) return;
        const p = clamp01((anim.currentTime || 0) / dur);
        if (anim.playState === 'running') anyActive = true;
        if (item._lastP !== p) {
          anyChanged = true;
          item._lastP = p;
          update({ target, progress: p, time: t });
        }
        if (anim.playState === 'finished' || anim.playState === 'idle') {
          this.items.delete(item);
        }
      });
      if (this.items.size && (anyActive || anyChanged)) {
        requestAnimationFrame(this._tick);
      } else {
        this._running = false;
      }
    }
  }
  const waapiUpdateSampler = new WaapiUpdateSampler();
  
  function readWaapiEffectTiming(effect) {
    // We compute this once per animation and cache it to avoid per-frame getComputedTiming().
    // We primarily cache `duration` to preserve existing behavior (progress maps to one iteration).
    let duration = 0;
    let endTime = 0;
    if (!effect) return { duration, endTime };
    try {
      const ct = effect.getComputedTiming ? effect.getComputedTiming() : null;
      if (ct) {
        if (typeof ct.duration === 'number' && Number.isFinite(ct.duration)) duration = ct.duration;
        if (typeof ct.endTime === 'number' && Number.isFinite(ct.endTime)) endTime = ct.endTime;
      }
    } catch (e) {
      // ignore
    }
    if (!endTime) endTime = duration || 0;
    return { duration, endTime };
  }
  
  function getDefaultUnit(prop) {
    if (!prop) return '';
    if (UNITLESS_KEYS.includes(prop)) return '';
    if (prop.startsWith('scale')) return '';
    if (prop === 'opacity') return '';
    if (prop.startsWith('rotate') || prop.startsWith('skew')) return 'deg';
    return 'px';
  }
  
  function normalizeTransformPartValue(prop, v) {
    if (typeof v !== 'number') return v;
    if (prop && prop.startsWith('scale')) return '' + v;
    if (prop && (prop.startsWith('rotate') || prop.startsWith('skew'))) return v + 'deg';
    return v + 'px';
  }

  // String number template: interpolate numeric tokens inside a string.
  // Useful for SVG path `d`, `points`, and other attributes that contain many numbers.
  const _PURE_NUMBER_RE = /^[+-]?(?:\d*\.)?\d+(?:[eE][+-]?\d+)?(?:%|px|pt|em|rem|in|cm|mm|ex|ch|pc|vw|vh|vmin|vmax|deg|rad|turn)?$/;
  function isPureNumberLike(str) {
    return _PURE_NUMBER_RE.test(String(str || '').trim());
  }
  function countDecimals(numStr) {
    const s = String(numStr || '');
    const dot = s.indexOf('.');
    if (dot < 0) return 0;
    // Strip exponent part for decimal count
    const e = s.search(/[eE]/);
    const end = e >= 0 ? e : s.length;
    const frac = s.slice(dot + 1, end);
    // Ignore trailing zeros for display
    const trimmed = frac.replace(/0+$/, '');
    return Math.min(6, trimmed.length);
  }
  function parseNumberTemplate(str) {
    const s = String(str ?? '');
    const nums = [];
    const parts = [];
    let last = 0;
    const re = /[+-]?(?:\d*\.)?\d+(?:[eE][+-]?\d+)?/g;
    let m;
    while ((m = re.exec(s))) {
      const start = m.index;
      const end = start + m[0].length;
      parts.push(s.slice(last, start));
      nums.push(parseFloat(m[0]));
      last = end;
    }
    parts.push(s.slice(last));
    return { nums, parts };
  }
  function extractNumberStrings(str) {
    // Use a fresh regex to avoid any `lastIndex` surprises.
    return String(str ?? '').match(/[+-]?(?:\d*\.)?\d+(?:[eE][+-]?\d+)?/g) || [];
  }
  function formatInterpolatedNumber(n, decimals) {
    let v = n;
    if (!Number.isFinite(v)) v = 0;
    if (Math.abs(v) < 1e-12) v = 0;
    if (!decimals) return String(Math.round(v));
    // Use fixed, then strip trailing zeros/dot to keep strings compact.
    return v.toFixed(decimals).replace(/\.?0+$/, '');
  }
  
  // --- JS Interpolator (anime.js-ish, simplified) ---
  class JsAnimation {
    constructor(target, propValues, opts = {}, callbacks = {}) {
      this.target = target;
      this.propValues = propValues;
      this.duration = opts.duration ?? 1000;
      this.delay = opts.delay ?? 0;
      this.direction = opts.direction ?? 'normal';
      this.loop = opts.loop ?? 1;
      this.endDelay = opts.endDelay ?? 0;
      this.easing = opts.easing ?? 'linear';
      this.autoplay = opts.autoplay !== false;
      
      this.update = callbacks.update;
      this.begin = callbacks.begin;
      this.complete = callbacks.complete;
      
      this._resolve = null;
      this.finished = new Promise((res) => (this._resolve = res));
      
      this._started = false;
      this._running = false;
      this._paused = false;
      this._cancelled = false;
      this._startTime = 0;
      this._progress = 0;
      this._didBegin = false;
      
      this._ease = resolveJsEasing(this.easing, opts.springValues);
      
      this._tween = this._buildTween();
      this.tick = this.tick.bind(this);
      
      if (this.autoplay) this.play();
    }
    
    _readCurrentValue(k) {
      const t = this.target;
      // JS object
      if (!isEl(t) && !isSVG(t)) return t[k];
      
      // scroll
      if (k === 'scrollTop' || k === 'scrollLeft') return t[k];
      
      // CSS var
      if (isEl(t) && isCssVar(k)) {
        const cs = getComputedStyle(t);
        return (cs.getPropertyValue(k) || t.style.getPropertyValue(k) || '').trim();
      }
      
      // style
      if (isEl(t)) {
        const cs = getComputedStyle(t);
        // Prefer computed style (kebab) because many props aren't direct keys on cs
        const v = cs.getPropertyValue(toKebab(k));
        if (v && v.trim()) return v.trim();
        // Fallback to inline style access
        if (k in t.style) return t.style[k];
      }
      
      // SVG attribute
      if (isSVG(t)) {
        const attr = toKebab(k);
        if (t.hasAttribute(attr)) return t.getAttribute(attr);
        if (t.hasAttribute(k)) return t.getAttribute(k);
      }
      
      // Generic property
      return t[k];
    }
    
    _writeValue(k, v) {
      const t = this.target;
      // JS object
      if (!isEl(t) && !isSVG(t)) {
        t[k] = v;
        return;
      }
      
      // scroll
      if (k === 'scrollTop' || k === 'scrollLeft') {
        t[k] = v;
        return;
      }
      
      // CSS var
      if (isEl(t) && isCssVar(k)) {
        t.style.setProperty(k, v);
        return;
      }
      
      // style
      if (isEl(t) && (k in t.style)) {
        t.style[k] = v;
        return;
      }
      
      // SVG attribute
      if (isSVG(t)) {
        const attr = toKebab(k);
        t.setAttribute(attr, v);
        return;
      }
      
      // Fallback for path/d/points even if isSVG check somehow failed
      if ((k === 'd' || k === 'points') && isEl(t)) {
         t.setAttribute(k, v);
         return;
      }
      
      // Generic property
      t[k] = v;
    }
    
    _buildTween() {
      const tween = {};
      Object.keys(this.propValues).forEach((k) => {
        const raw = this.propValues[k];
        const fromRaw = isArr(raw) ? raw[0] : this._readCurrentValue(k);
        const toRaw = isArr(raw) ? raw[1] : raw;
        
        const fromStr = isNil(fromRaw) ? '0' : ('' + fromRaw).trim();
        const toStr = isNil(toRaw) ? '0' : ('' + toRaw).trim();
        
        const fromScalar = isPureNumberLike(fromStr);
        const toScalar = isPureNumberLike(toStr);

        // numeric tween (with unit preservation) — only when BOTH sides are pure scalars.
        if (fromScalar && toScalar) {
          const fromNum = parseFloat(fromStr);
          const toNum = parseFloat(toStr);
          const unit = getUnit(toStr, k) ?? getUnit(fromStr, k) ?? '';
          tween[k] = { type: 'number', from: fromNum, to: toNum, unit };
          return;
        }

        // string number-template tween (SVG path `d`, `points`, etc.)
        // Requires both strings to have the same count of numeric tokens (>= 2).
        const a = parseNumberTemplate(fromStr);
        const b = parseNumberTemplate(toStr);
        
        if (a.nums.length >= 2 && a.nums.length === b.nums.length && a.parts.length === b.parts.length) {
          const aStrs = extractNumberStrings(fromStr);
          const bStrs = extractNumberStrings(toStr);
          const decs = a.nums.map((_, i) => Math.max(countDecimals(aStrs[i]), countDecimals(bStrs[i])));
          tween[k] = { type: 'number-template', fromNums: a.nums, toNums: b.nums, parts: b.parts, decimals: decs };
          return;
        } else if ((k === 'd' || k === 'points') && (a.nums.length > 0 || b.nums.length > 0)) {
           console.warn(`[Animal.js] Morph mismatch for property "${k}".\nValues must have matching number count.`,
             { from: a.nums.length, to: b.nums.length, fromVal: fromStr, toVal: toStr }
           );
        }

        // Non-numeric: fall back to "switch" (still useful for seek endpoints)
        tween[k] = { type: 'discrete', from: fromStr, to: toStr };
      });
      return tween;
    }
    
    _apply(progress, time) {
      this._progress = clamp01(progress);
      Object.keys(this._tween).forEach((k) => {
        const t = this._tween[k];
        if (t.type === 'number') {
          const eased = this._ease ? this._ease(this._progress) : this._progress;
          const val = t.from + (t.to - t.from) * eased;
          if (!isEl(this.target) && !isSVG(this.target) && t.unit === '') {
            this._writeValue(k, val);
          } else {
            this._writeValue(k, (val + t.unit));
          }
        } else if (t.type === 'number-template') {
          const eased = this._ease ? this._ease(this._progress) : this._progress;
          const { fromNums, toNums, parts, decimals } = t;
          let out = parts[0] || '';
          for (let i = 0; i < fromNums.length; i++) {
            const v = fromNums[i] + (toNums[i] - fromNums[i]) * eased;
            out += formatInterpolatedNumber(v, decimals ? decimals[i] : 0);
            out += parts[i + 1] || '';
          }
          this._writeValue(k, out);
        } else {
          const val = this._progress >= 1 ? t.to : t.from;
          this._writeValue(k, val);
        }
      });
      
      if (this.update) this.update({ target: this.target, progress: this._progress, time });
    }
    
    seek(progress) {
      // Seek does not auto-play; it's intended for scroll-linked or manual control.
      const t = (typeof performance !== 'undefined' ? performance.now() : 0);
      this._apply(progress, t);
    }
    
    play() {
      if (this._cancelled) return;
      if (!this._started) {
        this._started = true;
        this._startTime = performance.now() + this.delay - (this._progress * this.duration);
        // begin fired on first active tick to avoid firing during delay.
      }
      this._paused = false;
      if (!this._running) {
        this._running = true;
        rafEngine.add(this);
      }
    }
    
    pause() {
      this._paused = true;
    }
    
    cancel() {
      this._cancelled = true;
      this._running = false;
      rafEngine.remove(this);
      // Resolve to avoid hanging awaits
      if (this._resolve) this._resolve();
    }
    
    finish() {
      this.seek(1);
      this._running = false;
      rafEngine.remove(this);
      if (this.complete) this.complete(this.target);
      if (this._resolve) this._resolve();
    }
    
    tick(now) {
      if (this._cancelled) return false;
      if (this._paused) return true;
      
      if (!this._started) {
        this._started = true;
        this._startTime = now + this.delay;
      }
      
      if (now < this._startTime) return true;
      if (!this._didBegin) {
        this._didBegin = true;
        if (this.begin) this.begin(this.target);
      }
      
      const totalDur = this.duration + (this.endDelay || 0);
      const elapsed = now - this._startTime;
      const iter = totalDur > 0 ? Math.floor(elapsed / totalDur) : 0;
      const inIter = totalDur > 0 ? (elapsed - iter * totalDur) : elapsed;
      
      const iterations = this.loop === true ? Infinity : this.loop;
      if (iterations !== Infinity && iter >= iterations) {
        this._apply(this._mapDirection(1, iterations - 1));
        this._running = false;
        if (this.complete) this.complete(this.target);
        if (this._resolve) this._resolve();
        return false;
      }
      
      // if we're in endDelay portion, hold the end state
      let p = clamp01(inIter / this.duration);
      if (this.duration <= 0) p = 1;
      if (this.endDelay && inIter > this.duration) p = 1;
      
      this._apply(this._mapDirection(p, iter), now);
      
      // Keep running until loops exhausted
      return true;
    }
    
    _mapDirection(p, iterIndex) {
      const dir = this.direction;
      const flip = (dir === 'reverse') || (dir === 'alternate-reverse');
      const isAlt = (dir === 'alternate') || (dir === 'alternate-reverse');
      let t = flip ? (1 - p) : p;
      if (isAlt && (iterIndex % 2 === 1)) t = 1 - t;
      return t;
    }
  }
  
  // --- Controls (Motion One-ish, chainable / thenable) ---
  class Controls {
    constructor({ waapi = [], js = [], finished }) {
      this.animations = waapi; // backward compat with old `.animations` usage
      this.jsAnimations = js;
      this.finished = finished || Promise.resolve();
    }
    then(onFulfilled, onRejected) { return this.finished.then(onFulfilled, onRejected); }
    catch(onRejected) { return this.finished.catch(onRejected); }
    finally(onFinally) { return this.finished.finally(onFinally); }
    
    play() {
      if (this._onPlay) this._onPlay.forEach((fn) => fn && fn());
      if (this._ensureWaapiUpdate) this._ensureWaapiUpdate();
      this.animations.forEach((a) => a && a.play && a.play());
      this.jsAnimations.forEach((a) => a && a.play && a.play());
      return this;
    }
    pause() {
      this.animations.forEach((a) => a && a.pause && a.pause());
      this.jsAnimations.forEach((a) => a && a.pause && a.pause());
      return this;
    }
    cancel() {
      this.animations.forEach((a) => a && a.cancel && a.cancel());
      this.jsAnimations.forEach((a) => a && a.cancel && a.cancel());
      return this;
    }
    finish() {
      this.animations.forEach((a) => a && a.finish && a.finish());
      this.jsAnimations.forEach((a) => a && a.finish && a.finish());
      return this;
    }
    seek(progress) {
      const p = clamp01(progress);
      const t = (typeof performance !== 'undefined' ? performance.now() : 0);
      this.animations.forEach((anim) => {
        if (anim && anim.effect) {
          let timing = this._waapiTimingByAnim && this._waapiTimingByAnim.get(anim);
          if (!timing) {
            timing = readWaapiEffectTiming(anim.effect);
            if (this._waapiTimingByAnim) this._waapiTimingByAnim.set(anim, timing);
          }
          const dur = timing.duration || 0;
          if (!dur) return;
          anim.currentTime = dur * p;
          const target = this._waapiTargetByAnim && this._waapiTargetByAnim.get(anim);
          if (this._fireUpdate && target) this._fireUpdate({ target, progress: p, time: t });
        }
      });
      this.jsAnimations.forEach((a) => a && a.seek && a.seek(p));
      return this;
    }
  }

  // --- Main Animation Logic ---
  function animate(targets, params) {
    const elements = toArray(targets);
    const safeParams = params || {};
    const optionsNamespace = (safeParams.options && typeof safeParams.options === 'object') ? safeParams.options : {};
    // `params.options` provides a safe namespace for config keys without risking them being treated as animated props.
    // Top-level keys still win for backward compatibility.
    const merged = { ...optionsNamespace, ...safeParams };
    const { 
      duration = 1000, 
      delay = 0, 
      easing = 'ease-out', 
      direction = 'normal', 
      fill = 'forwards',
      loop = 1,
      endDelay = 0,
      autoplay = true,
      springFrames = 120,
      update, // callback
      begin, // callback
      complete // callback
    } = merged;

    let isSpring = false;
    let springValuesRaw = null;
    let springValuesSampled = null;
    let springDurationMs = null;

    if (typeof easing === 'object' && !Array.isArray(easing)) {
        isSpring = true;
        springValuesRaw = getSpringValues(easing);
        const frames = (typeof springFrames === 'number' && springFrames > 1) ? Math.floor(springFrames) : 120;
        springValuesSampled = downsample(springValuesRaw, frames);
        springDurationMs = springValuesRaw.length * 1000 / 60;
    }
    
    // Callback aggregation (avoid double-calling when WAAPI+JS both run)
    const cbState = typeof WeakMap !== 'undefined' ? new WeakMap() : null;
    const getState = (t) => {
      if (!cbState) return { begun: false, completed: false, lastUpdateBucket: -1 };
      let s = cbState.get(t);
      if (!s) {
        s = { begun: false, completed: false, lastUpdateBucket: -1 };
        cbState.set(t, s);
      }
      return s;
    };
    const fireBegin = (t) => {
      if (!begin) return;
      const s = getState(t);
      if (s.begun) return;
      s.begun = true;
      begin(t);
    };
    const fireComplete = (t) => {
      if (!complete) return;
      const s = getState(t);
      if (s.completed) return;
      s.completed = true;
      complete(t);
    };
    const fireUpdate = (payload) => {
      if (!update) return;
      const t = payload && payload.target;
      const time = payload && payload.time;
      if (!t) return update(payload);
      const s = getState(t);
      const bucket = Math.floor(((typeof time === 'number' ? time : (typeof performance !== 'undefined' ? performance.now() : 0))) / 16);
      if (bucket === s.lastUpdateBucket) return;
      s.lastUpdateBucket = bucket;
      update(payload);
    };

    const propEntries = [];
    Object.keys(safeParams).forEach((key) => {
      if (key === 'options') return;
      if (isAnimOptionKey(key)) return;
      propEntries.push({ key, canonical: ALIASES[key] || key, val: safeParams[key] });
    });

    // Create animations but don't play if autoplay is false
    const waapiAnimations = [];
    const jsAnimations = [];
    const engineInfo = {
      isSpring,
      waapiKeys: [],
      jsKeys: []
    };
    const waapiKeySet = new Set();
    const jsKeySet = new Set();
    
    const onPlayHooks = [];
    const waapiUpdateItems = [];
    const waapiTargetByAnim = (typeof WeakMap !== 'undefined') ? new WeakMap() : null;
    const waapiTimingByAnim = (typeof WeakMap !== 'undefined') ? new WeakMap() : null;
    let waapiUpdateStarted = false;
    const ensureWaapiUpdate = () => {
      if (waapiUpdateStarted) return;
      waapiUpdateStarted = true;
      waapiUpdateItems.forEach((item) => waapiUpdateSampler.add(item));
    };

    const promises = elements.map((el) => {
      // Route props per target (fix mixed HTML/SVG/object target arrays).
      const waapiProps = {};
      const jsProps = {};
      propEntries.forEach(({ key, canonical, val }) => {
        const isTransform = TRANSFORMS.includes(canonical) || TRANSFORMS.includes(key);
        if (!el || (!isEl(el) && !isSVG(el))) {
          jsProps[key] = val;
          jsKeySet.add(key);
          return;
        }
        const isSvgTarget = isSVG(el);
        if (isSvgTarget) {
          if (isTransform || key === 'opacity' || key === 'filter') {
            waapiProps[canonical] = val;
            waapiKeySet.add(canonical);
          } else {
            jsProps[key] = val;
            jsKeySet.add(key);
          }
          return;
        }
        // HTML element
        if (isCssVar(key)) {
          jsProps[key] = val;
          jsKeySet.add(key);
          return;
        }
        const isCssLike = isTransform || key === 'opacity' || key === 'filter' || (isEl(el) && (key in el.style));
        if (isCssLike) {
          waapiProps[canonical] = val;
          waapiKeySet.add(canonical);
        } else {
          jsProps[key] = val;
          jsKeySet.add(key);
        }
      });

      // 1. WAAPI Animation
      let waapiAnim = null;
      let waapiPromise = Promise.resolve();
      
      if (Object.keys(waapiProps).length > 0) {
        const buildFrames = (propValues) => {
          // Spring: share sampled progress; per-target we only compute start/end once per prop.
          if (isSpring && springValuesSampled && springValuesSampled.length) {
            const cs = (isEl(el) && typeof getComputedStyle !== 'undefined') ? getComputedStyle(el) : null;
            const metas = Object.keys(propValues).map((k) => {
              const raw = propValues[k];
              const rawFrom = Array.isArray(raw) ? raw[0] : undefined;
              const rawTo = Array.isArray(raw) ? raw[1] : raw;
              const toNum = parseFloat(('' + rawTo).trim());
              const fromNumExplicit = Array.isArray(raw) ? parseFloat(('' + rawFrom).trim()) : NaN;
              const isT = TRANSFORMS.includes(ALIASES[k] || k) || TRANSFORMS.includes(k);
              const unit = getUnit(('' + rawTo), k) ?? getUnit(('' + rawFrom), k) ?? getDefaultUnit(k);
              
              let fromNum = 0;
              if (Number.isFinite(fromNumExplicit)) {
                fromNum = fromNumExplicit;
              } else if (k.startsWith('scale')) {
                fromNum = 1;
              } else if (k === 'opacity' && cs) {
                const n = parseFloat(cs.opacity);
                if (!Number.isNaN(n)) fromNum = n;
              } else if (!isT && cs) {
                const cssVal = cs.getPropertyValue(toKebab(k));
                const n = parseFloat(cssVal);
                if (!Number.isNaN(n)) fromNum = n;
              }
              
              const to = Number.isFinite(toNum) ? toNum : 0;
              return { k, isT, unit: unit ?? '', from: fromNum, to };
            });
            
            const frames = new Array(springValuesSampled.length);
            for (let i = 0; i < springValuesSampled.length; i++) {
              const v = springValuesSampled[i];
              const frame = {};
              let transformStr = '';
              for (let j = 0; j < metas.length; j++) {
                const m = metas[j];
                const current = m.from + (m.to - m.from) * v;
                const outVal = (m.unit === '' ? ('' + current) : (current + m.unit));
                if (m.isT) transformStr += `${m.k}(${outVal}) `;
                else frame[m.k] = outVal;
              }
              if (transformStr) frame.transform = transformStr.trim();
              frames[i] = frame;
            }
            if (frames[0] && Object.keys(frames[0]).length === 0) frames.shift();
            return frames;
          }
          
          // Non-spring: 2-keyframe path
          const frame0 = {};
          const frame1 = {};
          let transform0 = '';
          let transform1 = '';
          Object.keys(propValues).forEach((k) => {
            const val = propValues[k];
            const isT = TRANSFORMS.includes(ALIASES[k] || k) || TRANSFORMS.includes(k);
            if (Array.isArray(val)) {
              const from = isT ? normalizeTransformPartValue(k, val[0]) : val[0];
              const to = isT ? normalizeTransformPartValue(k, val[1]) : val[1];
              if (isT) {
                transform0 += `${k}(${from}) `;
                transform1 += `${k}(${to}) `;
              } else {
                frame0[k] = from;
                frame1[k] = to;
              }
            } else {
              if (isT) transform1 += `${k}(${normalizeTransformPartValue(k, val)}) `;
              else frame1[k] = val;
            }
          });
          if (transform0) frame0.transform = transform0.trim();
          if (transform1) frame1.transform = transform1.trim();
          const out = [frame0, frame1];
          if (Object.keys(out[0]).length === 0) out.shift();
          return out;
        };

        const finalFrames = buildFrames(waapiProps);

        const opts = {
            duration: isSpring ? springDurationMs : duration,
            delay,
            fill,
            iterations: loop,
            easing: isSpring ? 'linear' : easing,
            direction,
            endDelay
        };

        const animation = el.animate(finalFrames, opts);
        if (!autoplay) animation.pause();
        waapiAnim = animation;
        waapiPromise = animation.finished;
        waapiAnimations.push(waapiAnim);
        if (waapiTargetByAnim) waapiTargetByAnim.set(waapiAnim, el);
        if (waapiTimingByAnim) waapiTimingByAnim.set(waapiAnim, readWaapiEffectTiming(waapiAnim.effect));
        
        if (begin) {
          // Fire begin when play starts (and also for autoplay on next frame)
          onPlayHooks.push(() => fireBegin(el));
          if (autoplay && typeof requestAnimationFrame !== 'undefined') requestAnimationFrame(() => fireBegin(el));
        }
        if (complete) {
          waapiAnim.addEventListener?.('finish', () => fireComplete(el));
        }
        if (update) {
          const timing = (waapiTimingByAnim && waapiTimingByAnim.get(waapiAnim)) || readWaapiEffectTiming(waapiAnim.effect);
          const item = { anim: waapiAnim, target: el, update: fireUpdate, _lastP: null, _dur: timing.duration || 0 };
          waapiUpdateItems.push(item);
          // Ensure removal on finish/cancel
          waapiAnim.addEventListener?.('finish', () => waapiUpdateSampler.remove(item));
          waapiAnim.addEventListener?.('cancel', () => waapiUpdateSampler.remove(item));
          // Start sampler only when needed (autoplay or explicit play)
          if (autoplay) ensureWaapiUpdate();
        }
      }

      // 2. JS Animation (Fallback / Attributes)
      let jsPromise = Promise.resolve();
      if (Object.keys(jsProps).length > 0) {
        const jsAnim = new JsAnimation(
          el,
          jsProps,
          { duration, delay, easing, autoplay, direction, loop, endDelay, springValues: isSpring ? springValuesRaw : null },
          { update: fireUpdate, begin: fireBegin, complete: fireComplete }
        );
        jsAnimations.push(jsAnim);
        jsPromise = jsAnim.finished;
      }

      return Promise.all([waapiPromise, jsPromise]);
    });

    const finished = Promise.all(promises);
    const controls = new Controls({ waapi: waapiAnimations, js: jsAnimations, finished });
    controls.engine = engineInfo;
    controls._onPlay = onPlayHooks;
    controls._fireUpdate = fireUpdate;
    controls._waapiTargetByAnim = waapiTargetByAnim;
    controls._waapiTimingByAnim = waapiTimingByAnim;
    controls._ensureWaapiUpdate = update ? ensureWaapiUpdate : null;
    if (!autoplay) controls.pause();
    engineInfo.waapiKeys = Array.from(waapiKeySet);
    engineInfo.jsKeys = Array.from(jsKeySet);
    return controls;
  }

  // --- SVG Draw ---
  function svgDraw(targets, params = {}) {
     const elements = toArray(targets);
     elements.forEach(el => {
         if (!isSVG(el)) return;
         const len = el.getTotalLength ? el.getTotalLength() : 0;
         el.style.strokeDasharray = len;
         el.style.strokeDashoffset = len; 
         
         animate(el, {
             strokeDashoffset: [len, 0],
             ...params
         });
     });
  }

  // --- In View ---
  function inViewAnimate(targets, params, options = {}) {
      const elements = toArray(targets);
      const observer = new IntersectionObserver((entries) => {
          entries.forEach(entry => {
              if (entry.isIntersecting) {
                  animate(entry.target, params);
                  if (options.once !== false) observer.unobserve(entry.target);
              }
          });
      }, { threshold: options.threshold || 0.1 });
      
      elements.forEach(el => observer.observe(el));
      // Return cleanup so callers can disconnect observers in long-lived pages (esp. once:false).
      return () => {
        try {
          elements.forEach((el) => observer.unobserve(el));
          observer.disconnect();
        } catch (e) {
          // ignore
        }
      };
  }
  
  // --- Scroll Linked ---
  function scroll(animationPromise, options = {}) {
      // options: container (default window), range [start, end] (default viewport logic)
      const container = options.container || window;
      const target = options.target || document.body; // Element to track for progress
      // If passing an animation promise, we control its WAAPI animations
      
      const controls = animationPromise;
      // Back-compat: old return value was a Promise with `.animations`
      const hasSeek = controls && isFunc(controls.seek);
      const anims = (controls && controls.animations) || (animationPromise && animationPromise.animations) || [];
      const jsAnims = (controls && controls.jsAnimations) || [];
      if (!hasSeek && !anims.length && !jsAnims.length) return;
      
      // Cache WAAPI timing per animation to avoid repeated getComputedTiming() during scroll.
      const timingCache = (typeof WeakMap !== 'undefined') ? new WeakMap() : null;
      const getEndTime = (anim) => {
        if (!anim || !anim.effect) return 0;
        if (timingCache) {
          const cached = timingCache.get(anim);
          if (cached) return cached;
        }
        const timing = readWaapiEffectTiming(anim.effect);
        const end = timing.duration || 0;
        if (timingCache && end) timingCache.set(anim, end);
        return end;
      };

      const updateScroll = () => {
          let progress = 0;
          
          if (container === window) {
              const scrollY = window.scrollY;
              const winH = window.innerHeight;
              const docH = document.body.scrollHeight;
              
              // Simple progress: how far down the page (0 to 1)
              // Or element based?
              // Motion One defaults to element entering view.
              
              if (options.target) {
                  const rect = options.target.getBoundingClientRect();
                  const start = winH; 
                  const end = -rect.height;
                  // progress 0 when rect.top == start (just entering)
                  // progress 1 when rect.top == end (just left)
                  
                  const totalDistance = start - end;
                  const currentDistance = start - rect.top;
                  progress = currentDistance / totalDistance;
              } else {
                  // Whole page scroll
                  progress = scrollY / (docH - winH);
              }
          } else if (container && (typeof Element !== 'undefined') && (container instanceof Element)) {
              // Scroll container progress
              const el = container;
              const scrollTop = el.scrollTop;
              const max = (el.scrollHeight - el.clientHeight) || 1;
              if (options.target) {
                const containerRect = el.getBoundingClientRect();
                const rect = options.target.getBoundingClientRect();
                const start = containerRect.height;
                const end = -rect.height;
                const totalDistance = start - end;
                const currentDistance = start - (rect.top - containerRect.top);
                progress = currentDistance / totalDistance;
              } else {
                progress = scrollTop / max;
              }
          }
          
          // Clamp
          progress = clamp01(progress);
          
          if (hasSeek) {
            controls.seek(progress);
            return;
          }
          
          anims.forEach((anim) => {
            if (anim.effect) {
              const end = getEndTime(anim);
              if (!end) return;
              anim.currentTime = end * progress;
            }
          });
      };

      let rafId = 0;
      const onScroll = () => {
        if (rafId) return;
        rafId = requestAnimationFrame(() => {
          rafId = 0;
          updateScroll();
        });
      };
      
      const eventTarget = (container && container.addEventListener) ? container : window;
      eventTarget.addEventListener('scroll', onScroll, { passive: true });
      updateScroll(); // Initial
      
      return () => {
        if (rafId) cancelAnimationFrame(rafId);
        eventTarget.removeEventListener('scroll', onScroll);
      };
  }

  // --- Timeline ---
  function timeline(defaults = {}) {
      const steps = [];
      const api = {
        currentTime: 0,
        add: (targets, params, offset) => {
          const animParams = { ...defaults, ...params };
          let start = api.currentTime;
          
          if (offset !== undefined) {
            if (isStr(offset) && offset.startsWith('-=')) start -= parseFloat(offset.slice(2));
            else if (isStr(offset) && offset.startsWith('+=')) start += parseFloat(offset.slice(2));
            else if (typeof offset === 'number') start = offset;
          }
          
          const dur = animParams.duration || 1000;
          const step = { targets, animParams, start, _scheduled: false };
          steps.push(step);
          
          // Backward compatible: schedule immediately (existing docs rely on this)
          if (start <= 0) {
            animate(targets, animParams);
            step._scheduled = true;
          } else {
            setTimeout(() => {
              animate(targets, animParams);
            }, start);
            step._scheduled = true;
          }
          
          api.currentTime = Math.max(api.currentTime, start + dur);
          return api;
        },
        // Optional: if you create a timeline and want to defer scheduling yourself
        play: () => {
          steps.forEach((s) => {
            if (s._scheduled) return;
            if (s.start <= 0) animate(s.targets, s.animParams);
            else setTimeout(() => animate(s.targets, s.animParams), s.start);
            s._scheduled = true;
          });
          return api;
        }
      };
      return api;
  }

  // --- Export ---
  // transform `$` to be the main export `animal`, with statics attached
  const animal = $;
  
  // Extend $ behavior to act as a global selector and property accessor
  Object.assign(animal, {
    animate,
    timeline,
    draw: svgDraw,
    svgDraw,
    inViewAnimate,
    spring,
    scroll,
    $: animal // Self-reference for backward compatibility
  });

  // Expose Layer if available or allow lazy loading
  Object.defineProperty(animal, 'Layer', {
    get: () => {
      return (typeof window !== 'undefined' && window.Layer) ? window.Layer :
             (typeof globalThis !== 'undefined' && globalThis.Layer) ? globalThis.Layer :
             (typeof Layer !== 'undefined' ? Layer : null);
    }
  });

  // Shortcut for Layer.fire or new Layer()
  // Allows $.fire({ title: 'Hi' }) or $.layer({ title: 'Hi' })
  animal.fire = (options) => {
    const L = animal.Layer;
    if (L) return (L.fire ? L.fire(options) : new L(options).fire());
    console.warn('Layer module not loaded.');
    return Promise.reject('Layer module not loaded');
  };
  // 'layer' alias for static usage
  animal.layer = animal.fire;

  return animal;

})));