// alphabet.ts — the byte→vector mapping.
//
// 256 unit vectors, one per byte value, built by recursive refinement:
// 16 coarse directions → 64 mids → 256 fines. Same-fine neighbours
// resonate; far-apart values are quasi-orthogonal.

import { addInto, copy, normalize, randomUnit, rng, Vec } from "./vec.js";
import type { AlphabetConfig } from "./config.js";

export class Alphabet {
  readonly vecs: Vec[] = [];
  readonly config: AlphabetConfig;

  constructor(seed: number, D: number, config?: Partial<AlphabetConfig>) {
    this.config = {
      roughness: config?.roughness ?? 0.65,
      seedMask: config?.seedMask ?? 0xa1fa17,
    };
    const rand = rng((seed ^ this.config.seedMask) >>> 0);
    const refine = (parent: Vec): Vec => {
      const v = copy(parent);
      for (let i = 0; i < v.length; i++) {
        v[i] *= Math.sqrt(1 - this.config.roughness);
      }
      addInto(v, randomUnit(D, rand), Math.sqrt(this.config.roughness));
      return normalize(v);
    };
    const coarse: Vec[] = [];
    for (let i = 0; i < 16; i++) coarse.push(randomUnit(D, rand));
    const mid: Vec[] = [];
    for (let i = 0; i < 64; i++) mid.push(refine(coarse[i >> 2]));
    for (let b = 0; b < 256; b++) this.vecs.push(refine(mid[b >> 2]));
  }
}