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

import {createGameCommandRegistry} from '../';
import type { Part } from '../';
import {Entity, entity} from "../";
import {Region} from "../";

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: entity<Region>('board', {
            id: 'board',
            axes: [
                { name: 'x', min: 0, max: BOARD_SIZE - 1 },
                { name: 'y', min: 0, max: BOARD_SIZE - 1 },
            ],
            children: [],
        }),
        parts: [] as Entity<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 maxRetries = MAX_TURNS * 2;
    let retries = 0;

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

        if (player !== turnPlayer) continue;
        if (!isValidMove(row, col)) continue;
        if (isCellOccupied(this.context, row, col)) continue;

        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 };
    }

    throw new Error('Too many invalid attempts');
});

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

export function getBoardRegion(host: Entity<TicTacToeState>) {
    return host.value.board;
}

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

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.map((e: Entity<TicTacToePart>) => e.value);

    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 = getBoardRegion(host);
    const moveNumber = host.value.parts.length + 1;
    const piece: TicTacToePart = {
        id: `piece-${player}-${moveNumber}`,
        region: board,
        position: [row, col],
        player,
    };
    host.produce(state => {
        const e = entity(piece.id, piece)
        state.parts.push(e);
        board.produce(draft => {
            draft.children.push(e);
        });
    });
}