/** Детерминированный 512-d L2-нормализованный псевдо-эмбеддинг. */
import { createHash } from 'node:crypto';

function seededRandom(seed: number): () => number {
  let s = seed >>> 0;
  return () => {
    s = (s * 1664525 + 1013904223) >>> 0;
    return s / 0xffffffff;
  };
}

export function makeEmbedding(seed: number, jitter = 0): number[] {
  // Гауссово приближение через 12-tap uniform.
  const rng = seededRandom(seed);
  const jitterRng = seededRandom(seed + Math.floor(jitter * 1000) + 7);
  const vec = new Array<number>(512);
  let norm = 0;
  for (let i = 0; i < 512; i++) {
    let s = 0;
    for (let k = 0; k < 12; k++) s += rng();
    const base = s - 6;
    let noise = 0;
    if (jitter > 0) {
      let s2 = 0;
      for (let k = 0; k < 12; k++) s2 += jitterRng();
      noise = (s2 - 6) * jitter;
    }
    const v = base + noise;
    vec[i] = v;
    norm += v * v;
  }
  norm = Math.sqrt(norm) || 1;
  for (let i = 0; i < 512; i++) vec[i] /= norm;
  return vec;
}

/** Хеш для логов. */
export function embeddingFingerprint(embedding: number[]): string {
  return createHash('sha1').update(embedding.slice(0, 32).join(',')).digest('hex').slice(0, 12);
}