Function createRecorder

packages/world-kit/src/record.js:130–176

({ realm, niche, family, level, tier, seed, variant = 0, variants = 1 })

 * to recolour what stands in it.
 */
export function createRecorder({ realm, niche, family, level, tier, seed, variant = 0, variants = 1 }) {
  const ops = [];
  const keys = paletteKeys(realm);
  const palette = Object.freeze(Object.fromEntries(keys.map((k) => [k, k])));

  const add = (kind, args) => {
    const spec = GEOM[kind];
    const a = spec.args.map(([name, min, max, dflt], i) => {
      const raw = args[i] ?? dflt;
      if (!isNum(raw)) {
        throw new Fail(`${kind}(): argument "${name}" must be a finite number, got ${JSON.stringify(raw)}`, ops.length);
      }
      if (raw < min || raw > max) {
        throw new Fail(`${kind}(): argument "${name}" is ${raw}, outside the allowed ${min} to ${max}`, ops.length);
      }
      return spec.args[i][3] !== undefined ? Math.round(raw) : raw;
    });
    const op = { g: kind, a, m: 'stone', o: {}, p: [0, 0, 0], r: [0, 0, 0], s: [1, 1, 1] };
    ops.push(op);
    return new Shape(op);
  };

  const api = {
    P: palette,
    palette: keys,
    realm,
    niche,
    family,
    level,
    tier,
    /* Which of the recorded variants this run is, and how many there are.
       This is the ONLY spread an author can rely on. Five draws from `rnd()`
       will cluster by chance however well the generator is seeded — two of five
       landing within 0.005 of each other is ordinary luck, not a bug — and an
       archetype chosen that way silently collapses variants onto one form. An
       index divides evenly by construction: `w.variant % 3` is three forms,
       always. Branch shape on this, and spend `rnd()` on proportion. */
    variant,
    variants,
    rnd: rngOf(seed),
    lerp: (a, b, t) => a + (b - a) * t,
    TAU,
  };
  for (const kind of GEOM_KINDS) api[kind] = (...args) => add(kind, args);

  return { api, ops };
}

/** Everything the validator needs that only the recorder can know. */
export function measure(ops) {