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

import { GameContextInstance } from '../core/context';
import type { Command, CommandRunner, CommandRunnerContext } from '../utils/command';
import type { Part } from '../core/part';
import type { Region } from '../core/region';
import type { Context } from '../core/context';
import { parseCommandSchema } from '../utils/command/schema-parse';

export type TicTacToeState = Context & {
    type: 'tic-tac-toe';
    currentPlayer: 'X' | 'O';
    winner: 'X' | 'O' | 'draw' | null;
    moveCount: number;
};

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

function getBoardRegion(host: GameContextInstance) {
    return host.regions.get('board');
}

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

function checkWinner(host: GameContextInstance): '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;
}

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)
        )
    );
}

function placePiece(host: GameContextInstance, row: number, col: number, moveCount: number) {
    const board = getBoardRegion(host);
    const piece: Part = {
        id: `piece-${moveCount}`,
        sides: 1,
        side: 0,
        region: board,
        position: [row, col],
    };
    host.parts.add(piece);
    board.value.children.push(host.parts.get(piece.id));
}

export function createSetupCommand(): CommandRunner<GameContextInstance, { winner: 'X' | 'O' | 'draw' | null }> {
    return {
        schema: parseCommandSchema('start'),
        run: async function(this: CommandRunnerContext<GameContextInstance>) {
            this.context.pushContext({
                type: 'tic-tac-toe',
                currentPlayer: 'X',
                winner: null,
                moveCount: 0,
            } as TicTacToeState);

            this.context.regions.add({
                id: 'board',
                axes: [
                    { name: 'x', min: 0, max: 2 },
                    { name: 'y', min: 0, max: 2 },
                ],
                children: [],
            } as Region);

            let currentPlayer: 'X' | 'O' = 'X';
            let turnResult: TurnResult | undefined;

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

                currentPlayer = currentPlayer === 'X' ? 'O' : 'X';
                const state = this.context.latestContext<TicTacToeState>('tic-tac-toe')!;
                state.value.currentPlayer = currentPlayer;
            }

            const state = this.context.latestContext<TicTacToeState>('tic-tac-toe')!;
            state.value.winner = turnResult?.winner ?? null;
            return { winner: state.value.winner };
        },
    };
}

export function createTurnCommand(): CommandRunner<GameContextInstance, TurnResult> {
    return {
        schema: parseCommandSchema('turn <player>'),
        run: async function(this: CommandRunnerContext<GameContextInstance>, cmd: Command) {
            while (true) {
                const playCmd = await this.prompt('play <player> <row:number> <col:number>');

                const row = Number(playCmd.params[1]);
                const col = Number(playCmd.params[2]);

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

                const state = this.context.latestContext<TicTacToeState>('tic-tac-toe')!;
                if (state.value.winner) continue;

                placePiece(this.context, row, col, state.value.moveCount);
                state.value.moveCount++;

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

                if (state.value.moveCount >= 9) return { winner: 'draw' as const };
            }
        },
    };
}

export function registerTicTacToeCommands(game: GameContextInstance) {
    game.registerCommand('start', createSetupCommand());
    game.registerCommand('turn', createTurnCommand());
}

export function startTicTacToe(game: GameContextInstance) {
    game.dispatchCommand('start');
}