Z8MB1E
6968ee0abc
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
60 lines
1.9 KiB
TypeScript
60 lines
1.9 KiB
TypeScript
/**
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* Deck creation and deterministic shuffling for the poker engine.
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* Pure: randomness is always injected; no module-level state.
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*/
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import type { Card, Rank, Suit } from "./types";
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const SUITS: readonly Suit[] = ["s", "h", "d", "c"];
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const MIN_RANK: Rank = 2;
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const MAX_RANK: Rank = 14;
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/** A fresh, ordered 52-card deck (order is deterministic before shuffling). */
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export function createDeck(): Card[] {
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const deck: Card[] = [];
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for (const suit of SUITS) {
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for (let rank = MIN_RANK; rank <= MAX_RANK; rank += 1) {
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deck.push({ rank: rank as Rank, suit });
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}
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}
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return deck;
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}
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/**
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* Small, fast seeded PRNG (mulberry32). Used so a whole multi-hand game can
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* be replayed from a single integer seed stored in the table state.
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*/
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export function mulberry32(seed: number): () => number {
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let a = seed >>> 0;
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return () => {
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a = (a + 0x6d2b79f5) >>> 0;
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let t = a;
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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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/** Fisher-Yates shuffle; returns a new array, never mutates the input. */
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export function shuffleDeck(cards: readonly Card[], rng: () => number): Card[] {
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const deck = [...cards];
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for (let i = deck.length - 1; i > 0; i -= 1) {
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const j = Math.floor(rng() * (i + 1));
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const tmp = deck[i];
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deck[i] = deck[j];
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deck[j] = tmp;
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}
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return deck;
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}
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const GOLDEN_RATIO_32 = 0x9e3779b9;
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/** Per-hand seed derived from the table's base seed and the hand number. */
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export function handSeed(baseSeed: number, handNumber: number): number {
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return (baseSeed + Math.imul(handNumber, GOLDEN_RATIO_32)) >>> 0;
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}
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/** The exact shuffled deck used for a given hand of a given game seed. */
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export function createShuffledDeck(baseSeed: number, handNumber: number): Card[] {
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return shuffleDeck(createDeck(), mulberry32(handSeed(baseSeed, handNumber)));
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}
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