flopobot_v2/src/game/poker.js

import pkg from "pokersolver";
const { Hand } = pkg;

// An array of all 52 standard playing cards.
export const initialCards = [
	"Ad",
	"2d",
	"3d",
	"4d",
	"5d",
	"6d",
	"7d",
	"8d",
	"9d",
	"Td",
	"Jd",
	"Qd",
	"Kd",
	"As",
	"2s",
	"3s",
	"4s",
	"5s",
	"6s",
	"7s",
	"8s",
	"9s",
	"Ts",
	"Js",
	"Qs",
	"Ks",
	"Ac",
	"2c",
	"3c",
	"4c",
	"5c",
	"6c",
	"7c",
	"8c",
	"9c",
	"Tc",
	"Jc",
	"Qc",
	"Kc",
	"Ah",
	"2h",
	"3h",
	"4h",
	"5h",
	"6h",
	"7h",
	"8h",
	"9h",
	"Th",
	"Jh",
	"Qh",
	"Kh",
];

/**
 * Creates a shuffled copy of the initial card deck.
 * @returns {Array<string>} A new array containing all 52 cards in a random order.
 */
export function initialShuffledCards() {
	// Create a copy and sort it randomly
	return [...initialCards].sort(() => 0.5 - Math.random());
}

/**
 * Finds the first active player to act after the dealer.
 * This is used to start betting rounds after the flop, turn, and river.
 * @param {object} room - The poker room object.
 * @returns {string|null} The ID of the next player, or null if none is found.
 */
export function getFirstActivePlayerAfterDealer(room) {
	const players = Object.values(room.players);
	const dealerPosition = players.findIndex((p) => p.id === room.dealer);

	// Loop through players starting from the one after the dealer
	for (let i = 1; i <= players.length; i++) {
		const nextPos = (dealerPosition + i) % players.length;
		const nextPlayer = players[nextPos];
		// Player must not be folded or all-in to be able to act
		if (nextPlayer && !nextPlayer.folded && !nextPlayer.allin) {
			return nextPlayer.id;
		}
	}
	return null; // Should not happen in a normal game
}

/**
 * Finds the next active player in turn order.
 * @param {object} room - The poker room object.
 * @returns {string|null} The ID of the next player, or null if none is found.
 */
export function getNextActivePlayer(room) {
	const players = Object.values(room.players);
	const currentPlayerPosition = players.findIndex((p) => p.id === room.current_player);

	// Loop through players starting from the one after the current player
	for (let i = 1; i <= players.length; i++) {
		const nextPos = (currentPlayerPosition + i) % players.length;
		const nextPlayer = players[nextPos];
		if (nextPlayer && !nextPlayer.folded && !nextPlayer.allin) {
			return nextPlayer.id;
		}
	}
	return null;
}

/**
 * Checks if the current betting round should end and what the next phase should be.
 * @param {object} room - The poker room object.
 * @returns {object} An object with `endRound`, `winner`, and `nextPhase` properties.
 */
export function checkEndOfBettingRound(room) {
	const activePlayers = Object.values(room.players).filter((p) => !p.folded);

	// --- Scenario 1: Only one player left (everyone else folded) ---
	if (activePlayers.length === 1) {
		return {
			endRound: true,
			winner: activePlayers[0].id,
			nextPhase: "showdown",
		};
	}

	// --- Scenario 2: All remaining players are all-in ---
	// The hand goes immediately to a "progressive showdown".
	const allInPlayers = activePlayers.filter((p) => p.allin);
	if (allInPlayers.length >= 2 && allInPlayers.length === activePlayers.length) {
		return { endRound: true, winner: null, nextPhase: "progressive-showdown" };
	}

	// --- Scenario 3: All active players have acted and bets are equal ---
	const allBetsMatched = activePlayers.every(
		(p) =>
			p.allin || // Player is all-in
			(p.bet === room.highest_bet && p.last_played_turn === room.current_turn), // Or their bet matches the highest and they've acted this turn
	);

	if (allBetsMatched) {
		let nextPhase;
		switch (room.current_turn) {
			case 0:
				nextPhase = "flop";
				break;
			case 1:
				nextPhase = "turn";
				break;
			case 2:
				nextPhase = "river";
				break;
			case 3:
				nextPhase = "showdown";
				break;
			default:
				nextPhase = null; // Should not happen
		}
		return { endRound: true, winner: null, nextPhase: nextPhase };
	}

	// --- Default: The round continues ---
	return { endRound: false, winner: null, nextPhase: null };
}

/**
 * Determines the winner(s) of the hand at showdown.
 * @param {object} room - The poker room object.
 * @returns {Array<string>} An array of winner IDs. Can contain multiple IDs in case of a split pot.
 */
export function checkRoomWinners(room) {
	const communityCards = room.tapis;
	const activePlayers = Object.values(room.players).filter((p) => !p.folded);

	// Solve each player's hand to find the best possible 5-card combination
	const playerSolutions = activePlayers.map((player) => ({
		id: player.id,
		solution: Hand.solve([...communityCards, ...player.hand]),
	}));

	if (playerSolutions.length === 0) return [];

	// Use pokersolver's `Hand.winners()` to find the best hand(s)
	const winningSolutions = Hand.winners(playerSolutions.map((ps) => ps.solution));

	// Find the player IDs that correspond to the winning hand solutions
	const winnerIds = [];
	for (const winningHand of winningSolutions) {
		for (const playerSol of playerSolutions) {
			// Compare description and card pool to uniquely identify the hand
			if (
				playerSol.solution.descr === winningHand.descr &&
				playerSol.solution.cardPool.toString() === winningHand.cardPool.toString()
			) {
				if (!winnerIds.includes(playerSol.id)) {
					winnerIds.push(playerSol.id);
				}
			}
		}
	}

	return winnerIds;
}