boardgame-core/src/samples/tic-tac-toe.ts

import {createGameCommandRegistry, Part, Entity, createRegion, moveToRegion} from '@/index';

const BOARD_SIZE = 3;
const MAX_TURNS = BOARD_SIZE * BOARD_SIZE;
const WINNING_LINES: number[][][] = [
    [[0, 0], [0, 1], [0, 2]],
    [[1, 0], [1, 1], [1, 2]],
    [[2, 0], [2, 1], [2, 2]],
    [[0, 0], [1, 0], [2, 0]],
    [[0, 1], [1, 1], [2, 1]],
    [[0, 2], [1, 2], [2, 2]],
    [[0, 0], [1, 1], [2, 2]],
    [[0, 2], [1, 1], [2, 0]],
];

export type PlayerType = 'X' | 'O';
export type WinnerType = PlayerType | 'draw' | null;

type TicTacToePart = Part & { player: PlayerType };

export function createInitialState() {
    return {
        board: createRegion('board', [
            { name: 'x', min: 0, max: BOARD_SIZE - 1 },
            { name: 'y', min: 0, max: BOARD_SIZE - 1 },
        ]),
        parts: [] as TicTacToePart[],
        currentPlayer: 'X' as PlayerType,
        winner: null as WinnerType,
        turn: 0,
    };
}
export type TicTacToeState = ReturnType<typeof createInitialState>;
const registration = createGameCommandRegistry<TicTacToeState>();
export const registry = registration.registry;

registration.add('setup', async function() {
    const {context} = this;
    while (true) {
        const currentPlayer = context.value.currentPlayer;
        const turnNumber = context.value.turn + 1;
        const turnOutput = await this.run<{winner: WinnerType}>(`turn ${currentPlayer} ${turnNumber}`);
        if (!turnOutput.success) throw new Error(turnOutput.error);

        context.produce(state => {
            state.winner = turnOutput.result.winner;
            if (!state.winner) {
                state.currentPlayer = state.currentPlayer === 'X' ? 'O' : 'X';
                state.turn = turnNumber;
            }
        });
        if (context.value.winner) break;
    }

    return context.value;
});

registration.add('turn <player> <turn:number>', async function(cmd) {
    const [turnPlayer, turnNumber] = cmd.params as [PlayerType, number];

    const playCmd = await this.prompt(
        'play <player> <row:number> <col:number>',
        (command) => {
            const [player, row, col] = command.params as [PlayerType, number, number];

            if (player !== turnPlayer) {
                return `Invalid player: ${player}. Expected ${turnPlayer}.`;
            }
            if (!isValidMove(row, col)) {
                return `Invalid position: (${row}, ${col}). Must be between 0 and ${BOARD_SIZE - 1}.`;
            }
            if (isCellOccupied(this.context, row, col)) {
                return `Cell (${row}, ${col}) is already occupied.`;
            }
            return null;
        }
    );
    const [player, row, col] = playCmd.params as [PlayerType, number, number];

    placePiece(this.context, row, col, turnPlayer);

    const winner = checkWinner(this.context);
    if (winner) return { winner };
    if (turnNumber >= MAX_TURNS) return { winner: 'draw' as WinnerType };

    return { winner: null };
});

function isValidMove(row: number, col: number): boolean {
    return !isNaN(row) && !isNaN(col) && row >= 0 && row < BOARD_SIZE && col >= 0 && col < BOARD_SIZE;
}

export function isCellOccupied(host: Entity<TicTacToeState>, row: number, col: number): boolean {
    const board = host.value.board;
    return board.partMap[`${row},${col}`] !== undefined;
}

export function hasWinningLine(positions: number[][]): boolean {
    return WINNING_LINES.some(line =>
        line.every(([r, c]) =>
            positions.some(([pr, pc]) => pr === r && pc === c)
        )
    );
}

export function checkWinner(host: Entity<TicTacToeState>): WinnerType {
    const parts = host.value.parts;

    const xPositions = parts.filter((p: TicTacToePart) => p.player === 'X').map((p: TicTacToePart) => p.position);
    const oPositions = parts.filter((p: TicTacToePart) => p.player === 'O').map((p: TicTacToePart) => p.position);

    if (hasWinningLine(xPositions)) return 'X';
    if (hasWinningLine(oPositions)) return 'O';
    if (parts.length >= MAX_TURNS) return 'draw';

    return null;
}

export function placePiece(host: Entity<TicTacToeState>, row: number, col: number, player: PlayerType) {
    const board = host.value.board;
    const moveNumber = host.value.parts.length + 1;
    const piece: TicTacToePart = {
        id: `piece-${player}-${moveNumber}`,
        regionId: 'board',
        position: [row, col],
        player,
    };
    host.produce(state => {
        state.parts.push(piece);
        board.childIds.push(piece.id);
        board.partMap[`${row},${col}`] = piece.id;
    });
}