mirror of
https://github.com/Sendouc/sendou.ink.git
synced 2026-03-21 18:04:39 -05:00
79 lines
2.4 KiB
TypeScript
79 lines
2.4 KiB
TypeScript
function cyrb128(str: string) {
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let h1 = 1779033703;
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let h2 = 3144134277;
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let h3 = 1013904242;
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let h4 = 2773480762;
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// biome-ignore lint/suspicious/noImplicitAnyLet: biome migration
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for (let i = 0, k; i < str.length; i++) {
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k = str.charCodeAt(i);
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h1 = h2 ^ Math.imul(h1 ^ k, 597399067);
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h2 = h3 ^ Math.imul(h2 ^ k, 2869860233);
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h3 = h4 ^ Math.imul(h3 ^ k, 951274213);
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h4 = h1 ^ Math.imul(h4 ^ k, 2716044179);
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}
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h1 = Math.imul(h3 ^ (h1 >>> 18), 597399067);
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h2 = Math.imul(h4 ^ (h2 >>> 22), 2869860233);
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h3 = Math.imul(h1 ^ (h3 >>> 17), 951274213);
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h4 = Math.imul(h2 ^ (h4 >>> 19), 2716044179);
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return [
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(h1 ^ h2 ^ h3 ^ h4) >>> 0,
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(h2 ^ h1) >>> 0,
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(h3 ^ h1) >>> 0,
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(h4 ^ h1) >>> 0,
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];
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}
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function mulberry32(a: number) {
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return () => {
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// biome-ignore lint/suspicious/noAssignInExpressions: biome migration
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// biome-ignore lint/style/noParameterAssign: biome migration
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let t = (a += 0x6d2b79f5);
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t = Math.imul(t ^ (t >>> 15), t | 1);
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t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
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return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
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};
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}
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/**
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* Creates a seeded pseudo-random number generator that produces consistent results for the same seed.
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* Uses mulberry32 algorithm with cyrb128 hash function for string-to-number conversion.
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*
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* @param seed - String seed value (e.g., "2025-1-8" for daily rotation)
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* @returns Object with random number generation methods:
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* - `random(lo?, hi?)` - Returns random float between lo (inclusive) and hi (exclusive)
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* - `randomInteger(lo, hi?)` - Returns random integer between lo (inclusive) and hi (exclusive)
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* - `seededShuffle(array)` - Returns shuffled copy of array using seeded Fisher-Yates algorithm
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*
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* @example
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* const { seededShuffle } = seededRandom("2025-1-8");
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* const shuffled = seededShuffle([1, 2, 3, 4, 5]);
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*/
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export const seededRandom = (seed: string) => {
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const rng = mulberry32(cyrb128(seed)[0]);
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const random = (lo?: number, hi?: number, defaultHi = 1) => {
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const actualLo = hi === undefined ? 0 : (lo ?? 0);
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const actualHi = hi === undefined ? (lo ?? defaultHi) : hi;
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return rng() * (actualHi - actualLo) + actualLo;
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};
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const randomInteger = (lo: number, hi?: number) =>
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Math.floor(random(lo, hi, 2));
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const seededShuffle = <T>(o: T[]) => {
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const a = o.slice();
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for (let i = a.length - 1; i > 0; i--) {
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const j = randomInteger(i + 1);
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const x = a[i];
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a[i] = a[j]!;
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a[j] = x!;
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}
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return a;
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};
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return { random, randomInteger, seededShuffle };
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};
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