function cyrb128(str: string) { let h1 = 1779033703; let h2 = 3144134277; let h3 = 1013904242; let h4 = 2773480762; // biome-ignore lint/suspicious/noImplicitAnyLet: biome migration for (let i = 0, k; i < str.length; i++) { k = str.charCodeAt(i); h1 = h2 ^ Math.imul(h1 ^ k, 597399067); h2 = h3 ^ Math.imul(h2 ^ k, 2869860233); h3 = h4 ^ Math.imul(h3 ^ k, 951274213); h4 = h1 ^ Math.imul(h4 ^ k, 2716044179); } h1 = Math.imul(h3 ^ (h1 >>> 18), 597399067); h2 = Math.imul(h4 ^ (h2 >>> 22), 2869860233); h3 = Math.imul(h1 ^ (h3 >>> 17), 951274213); h4 = Math.imul(h2 ^ (h4 >>> 19), 2716044179); return [ (h1 ^ h2 ^ h3 ^ h4) >>> 0, (h2 ^ h1) >>> 0, (h3 ^ h1) >>> 0, (h4 ^ h1) >>> 0, ]; } function mulberry32(a: number) { return () => { // biome-ignore lint/suspicious/noAssignInExpressions: biome migration // biome-ignore lint/style/noParameterAssign: biome migration let t = (a += 0x6d2b79f5); t = Math.imul(t ^ (t >>> 15), t | 1); t ^= t + Math.imul(t ^ (t >>> 7), t | 61); return ((t ^ (t >>> 14)) >>> 0) / 4294967296; }; } /** * Creates a seeded pseudo-random number generator that produces consistent results for the same seed. * Uses mulberry32 algorithm with cyrb128 hash function for string-to-number conversion. * * @param seed - String seed value (e.g., "2025-1-8" for daily rotation) * @returns Object with random number generation methods: * - `random(lo?, hi?)` - Returns random float between lo (inclusive) and hi (exclusive) * - `randomInteger(lo, hi?)` - Returns random integer between lo (inclusive) and hi (exclusive) * - `seededShuffle(array)` - Returns shuffled copy of array using seeded Fisher-Yates algorithm * * @example * const { seededShuffle } = seededRandom("2025-1-8"); * const shuffled = seededShuffle([1, 2, 3, 4, 5]); */ export const seededRandom = (seed: string) => { const rng = mulberry32(cyrb128(seed)[0]); const random = (lo?: number, hi?: number, defaultHi = 1) => { const actualLo = hi === undefined ? 0 : (lo ?? 0); const actualHi = hi === undefined ? (lo ?? defaultHi) : hi; return rng() * (actualHi - actualLo) + actualLo; }; const randomInteger = (lo: number, hi?: number) => Math.floor(random(lo, hi, 2)); const seededShuffle = (o: T[]) => { const a = o.slice(); for (let i = a.length - 1; i > 0; i--) { const j = randomInteger(i + 1); const x = a[i]; a[i] = a[j]!; a[j] = x!; } return a; }; return { random, randomInteger, seededShuffle }; };