// Trim a GLB's baked animation down to a [0, tEnd] window (seconds) — for the angelfish
// pack that's the Idle clip (GLB frames 0–109 ≈ 3.633s), which drops ~95% of the animation
// data (the full Take is 75.67s). Geometry/skin/textures are untouched. Shared input
// accessors are sliced once; outputs per-sampler. Usage: node trim-idle.mjs in.glb out.glb 3.633
import { NodeIO } from '@gltf-transform/core';
import { ALL_EXTENSIONS } from '@gltf-transform/extensions';
import { prune } from '@gltf-transform/functions';

const [, , inPath, outPath, tEndStr] = process.argv;
const tEnd = parseFloat(tEndStr);
const io = new NodeIO().registerExtensions(ALL_EXTENSIONS);
const doc = await io.read(inPath);
const root = doc.getRoot();

// Pass 1: per UNIQUE input time-track, compute how many keyframes fall in [0, tEnd]
// (BEFORE mutating — all channels share one input), then slice the input once.
const keepByInput = new Map();
for (const anim of root.listAnimations())
  for (const s of anim.listSamplers()) {
    const input = s.getInput();
    if (keepByInput.has(input)) continue;
    const times = input.getArray();
    let last = 0;
    for (let i = 0; i < times.length; i++) { if (times[i] <= tEnd + 1e-6) last = i; else break; }
    const keep = last + 1;
    keepByInput.set(input, keep);
    if (keep >= 2 && keep < times.length) input.setArray(times.slice(0, keep));
  }
// Pass 2: slice every sampler's OUTPUT to its input's keep count.
for (const anim of root.listAnimations())
  for (const s of anim.listSamplers()) {
    const keep = keepByInput.get(s.getInput());
    const output = s.getOutput();
    const comps = output.getElementSize();
    if (keep * comps < output.getArray().length) output.setArray(output.getArray().slice(0, keep * comps));
  }
await doc.transform(prune());   // repack buffers + drop the orphaned (trimmed-away) data
await io.write(outPath, doc);
console.log('wrote', outPath);