import {
    createGameCommandRegistry, Part, createRegion,
    IGameContext
} 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 Record<string, TicTacToePart>,
        currentPlayer: 'X' as PlayerType,
        winner: null as WinnerType,
        turn: 0,
    };
}
export type TicTacToeState = ReturnType<typeof createInitialState>;
export type TicTacToeGame = IGameContext<TicTacToeState>;
export const registry = createGameCommandRegistry<TicTacToeState>();

export async function start(game: TicTacToeGame) {
    while (true) {
        const currentPlayer = game.value.currentPlayer;
        const turnNumber = game.value.turn + 1;
        const turnOutput = await turn(game, currentPlayer, turnNumber);

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

    return game.value;
}

const turn = registry.register({
    schema: 'turn <player> <turnNumber:number>',
    async run(game: TicTacToeGame, turnPlayer: PlayerType, turnNumber: number) {
        const {player, row, col} = await game.prompt(
            'play <player> <row:number> <col:number>',
            (player: string, row: number, col: number) => {
                if (player !== turnPlayer) {
                    throw `Invalid player: ${player}. Expected ${turnPlayer}.`;
                } else if (!isValidMove(row, col)) {
                    throw `Invalid position: (${row}, ${col}). Must be between 0 and ${BOARD_SIZE - 1}.`;
                } else if (isCellOccupied(game, row, col)) {
                    throw `Cell (${row}, ${col}) is already occupied.`;
                } else {
                    return { player, row, col };
                }
            },
            game.value.currentPlayer
        );

        placePiece(game, row, col, turnPlayer);

        const winner = checkWinner(game);
        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: TicTacToeGame, row: number, col: number): boolean {
    return !!host.value.board.partMap[`${row},${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: TicTacToeGame): WinnerType {
    const parts = host.value.parts;
    const partsArray = Object.values(parts);

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

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

    return null;
}

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