@xpressit/winning-poker-hand-rank/src/card.ts

Determine winning poker hand rank

import { PlayingCard } from './types';

// primes are the first 13 prime numbers (one per card rank).
const PRIMES = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41];

export type Card = number;

type Rank = number;
type Suit = number;

export const RANK_TWO = 0;
export const RANK_THREE = 1;
export const RANK_FOUR = 2;
export const RANK_FIVE = 3;
export const RANK_SIX = 4;
export const RANK_SEVEN = 5;
export const RANK_EIGHT = 6;
export const RANK_NINE = 7;
export const RANK_TEN = 8;
export const RANK_JACK = 9;
export const RANK_QUEEN = 10;
export const RANK_KING = 11;
export const RANK_ACE = 12;

const runeToRank: { [key: string]: Rank | undefined } = {
    '2': RANK_TWO,
    '3': RANK_THREE,
    '4': RANK_FOUR,
    '5': RANK_FIVE,
    '6': RANK_SIX,
    '7': RANK_SEVEN,
    '8': RANK_EIGHT,
    '9': RANK_NINE,
    T: RANK_TEN,
    J: RANK_JACK,
    Q: RANK_QUEEN,
    K: RANK_KING,
    A: RANK_ACE,
};
const runeToSuit: { [key: string]: Suit | undefined } = {
    S: 1,
    H: 2,
    D: 4,
    C: 8,
};

const toRankAndSuit = (playingCard: PlayingCard) => {
    const rank = runeToRank[playingCard[0]];
    const suit = runeToSuit[playingCard[1]];
    if (!suit || rank === undefined) {
        throw new Error(`Invalid playing card: ${playingCard}`);
    }
    return [rank, suit];
};

export const toCard = (playingCard: PlayingCard): Card => {
    const [rank, suit] = toRankAndSuit(playingCard);
    return ((1 << rank) << 16) | (suit << 12) | (rank << 8) | PRIMES[rank];
};

const rankToRune: { [key: string]: string | undefined } = {
    '12': 'A',
    '11': 'K',
    '10': 'Q',
    '9': 'J',
    '8': 'T',
    '7': '9',
    '6': '8',
    '5': '7',
    '4': '6',
    '3': '5',
    '2': '4',
    '1': '3',
    '0': '2',
};

const suitToRune: { [key: string]: string | undefined } = {
    '8': 'C',
    '4': 'D',
    '2': 'H',
    '1': 'S',
};

const getCardRank = (card: Card) => {
    return (card >> 8) & 0xf;
};

const getCardSuit = (card: Card) => {
    return (card >> 12) & 0xf;
};

export const toPlayingCard = (card: Card): PlayingCard => {
    const rankRune = rankToRune['' + getCardRank(card)];
    const suitRune = suitToRune['' + getCardSuit(card)];
    if (!rankRune || !suitRune) {
        throw new Error(`Cannot convert Card ${card} to PlayingCard`);
    }
    return (rankRune + suitRune) as PlayingCard;
};

export const cardCompareDescFn = (c1: Card, c2: Card) => {
    const r1 = getCardRank(c1);
    const r2 = getCardRank(c2);
    if (r1 === r2) {
        const s1 = getCardSuit(c1);
        const s2 = getCardSuit(c2);
        return s2 - s1;
    }
    return r2 - r1;
};