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

import {createGameCommand, createGameCommandRegistry, IGameContext} from '../core/game';
import { registerCommand } from '../utils/command';
import type { Part } from '../core/part';

type TurnResult = {
    winner: 'X' | 'O' | 'draw' | null;
};

export function createInitialState() {
    return {
        currentPlayer: 'X' as 'X' | 'O',
        winner: null as 'X' | 'O' | 'draw' | null,
        moveCount: 0,
    };
}
export type TicTacToeState = ReturnType<typeof createInitialState>;

export function getBoardRegion(host: IGameContext<TicTacToeState>) {
    return host.regions.get('board');
}

export function isCellOccupied(host: IGameContext<TicTacToeState>, row: number, col: number): boolean {
    const board = getBoardRegion(host);
    return board.value.children.some(
        part => {
            return part.value.position[0] === row && part.value.position[1] === col;
        }
    );
}

export function hasWinningLine(positions: number[][]): boolean {
    const lines = [
        [[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]],
    ];

    return lines.some(line =>
        line.every(([r, c]) =>
            positions.some(([pr, pc]) => pr === r && pc === c)
        )
    );
}

export function checkWinner(host: IGameContext<TicTacToeState>): 'X' | 'O' | 'draw' | null {
    const parts = Object.values(host.parts.collection.value).map((s: { value: Part }) => s.value);

    const xPositions = parts.filter((_: Part, i: number) => i % 2 === 0).map((p: Part) => p.position);
    const oPositions = parts.filter((_: Part, i: number) => i % 2 === 1).map((p: Part) => p.position);

    if (hasWinningLine(xPositions)) return 'X';
    if (hasWinningLine(oPositions)) return 'O';

    return null;
}

export function placePiece(host: IGameContext<TicTacToeState>, row: number, col: number, moveCount: number) {
    const board = getBoardRegion(host);
    const piece: Part = {
        id: `piece-${moveCount}`,
        region: board,
        position: [row, col],
    };
    host.parts.add(piece);
    board.produce(draft => {
        draft.children.push(host.parts.get(piece.id));
    });
}

const setup = createGameCommand<TicTacToeState, { winner: 'X' | 'O' | 'draw' | null }>(
    'setup',
    async function() {
        this.context.regions.add({
            id: 'board',
            axes: [
                { name: 'x', min: 0, max: 2 },
                { name: 'y', min: 0, max: 2 },
            ],
            children: [],
        });

        let currentPlayer: 'X' | 'O' = 'X';
        let winner: 'X' | 'O' | 'draw' | null = null;
        let turn = 1;

        while (true) {
            const turnOutput = await this.run<TurnResult>(`turn ${currentPlayer} ${turn++}`);
            if (!turnOutput.success) throw new Error(turnOutput.error);
            winner = turnOutput.result.winner;
            if (winner) break;

            currentPlayer = currentPlayer === 'X' ? 'O' : 'X';
        }

        return { winner };
    }
)

const turn = createGameCommand<TicTacToeState, TurnResult>(
    'turn <player> <turn:number>',
    async function(cmd) {
        const [turnPlayer, turnNumber] = cmd.params as [string, number];
        while (true) {
            const playCmd = await this.prompt('play <player> <row:number> <col:number>');
            const [player, row, col] = playCmd.params as [string, number, number];
            if(turnPlayer !== player) continue;

            if (isNaN(row) || isNaN(col) || row < 0 || row > 2 || col < 0 || col > 2) continue;
            if (isCellOccupied(this.context, row, col)) continue;

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

            const winner = checkWinner(this.context);
            if (winner) return { winner };

            if (turnNumber >= 9) return { winner: 'draw' as const };
        }
    }
);

export const registry = createGameCommandRegistry<TicTacToeState>();
registerCommand(registry, setup);
registerCommand(registry, turn);