// modules/utils/perlin.js — Classic Perlin noise for procedural generation

export function createPerlinNoise() {
  const p = new Uint8Array(256);
  for (let i = 0; i < 256; i++) p[i] = i;
  let seed = 42;
  function seededRand() {
    seed = (seed * 1664525 + 1013904223) & 0xffffffff;
    return (seed >>> 0) / 0xffffffff;
  }
  for (let i = 255; i > 0; i--) {
    const j = Math.floor(seededRand() * (i + 1));
    const tmp = p[i]; p[i] = p[j]; p[j] = tmp;
  }
  const perm = new Uint8Array(512);
  for (let i = 0; i < 512; i++) perm[i] = p[i & 255];

  function fade(t) { return t * t * t * (t * (t * 6 - 15) + 10); }
  function lerp(a, b, t) { return a + t * (b - a); }
  function grad(hash, x, y, z) {
    const h = hash & 15;
    const u = h < 8 ? x : y;
    const v = h < 4 ? y : (h === 12 || h === 14) ? x : z;
    return ((h & 1) ? -u : u) + ((h & 2) ? -v : v);
  }

  return function noise(x, y, z) {
    z = z || 0;
    const X = Math.floor(x) & 255, Y = Math.floor(y) & 255, Z = Math.floor(z) & 255;
    x -= Math.floor(x); y -= Math.floor(y); z -= Math.floor(z);
    const u = fade(x), v = fade(y), w = fade(z);
    const A = perm[X] + Y, AA = perm[A] + Z, AB = perm[A + 1] + Z;
    const B = perm[X + 1] + Y, BA = perm[B] + Z, BB = perm[B + 1] + Z;
    return lerp(
      lerp(lerp(grad(perm[AA],     x,   y,   z  ), grad(perm[BA],     x-1, y,   z  ), u),
           lerp(grad(perm[AB],     x,   y-1, z  ), grad(perm[BB],     x-1, y-1, z  ), u), v),
      lerp(lerp(grad(perm[AA + 1], x,   y,   z-1), grad(perm[BA + 1], x-1, y,   z-1), u),
           lerp(grad(perm[AB + 1], x,   y-1, z-1), grad(perm[BB + 1], x-1, y-1, z-1), u), v),
      w
    );
  };
}

export const perlin = createPerlinNoise();