minesweeper-backend/index.js

const express = require('express');
const { createServer } = require('http');
const { Server } = require('socket.io');
const cors = require('cors');
const { randomUUID } = require('crypto');


// --------------------------------------
// SERVER
// --------------------------------------

const app = express();
app.use(cors({
    origin: "*",
    methods: ["GET", "POST"],
    allowedHeaders: ["Content-Type"],
    credentials: true
}));
const server = createServer(app);
const io = new Server(server, {
    cors: {
        origin: "*",
        methods: ["GET", "POST"],
        allowedHeaders: ["Content-Type"],
        credentials: true
    }
});

io.on('connection', (socket) => {

    socket.onAny((event, ...args) => console.log(event, args));

    socket.on('disconnect', () => handleDisconnect(socket, playerRoomMap));
    socket.on('createRoom', (data) => handleCreateRoom(socket, data));
    socket.on('joinRoom', (data) => handleJoinRoom(socket, data));

    socket.on('tileClick', (data) => handleTileClick(socket, data));
    socket.on('tileSelect', (data) => handleTileSelect(socket, data));
    socket.on('tileFlag', (data) => handleTileFlag(socket, data));

});

const PORT = 5174;
server.listen(PORT, () => {
    console.log('server started at port', PORT);
});

// --------------------------------------
// ROOM HANDLING
// --------------------------------------
let rooms = new Map();
const playerRoomMap = new Map();

const handleDisconnect = (socket, playerRoomMap) => {
    const playerRoom = playerRoomMap.get(socket.id);
    if (playerRoom) {
        if (playerRoom.currentPlayer === socket.id) {
            playerRoom.currentPlayer = getNextPlayer(playerRoom.players, socket.id);
        }
        playerRoom.players = playerRoom.players.filter(user => user.socketId !== socket.id);
        if (checkLoseCondition(playerRoom.players)) {
            playerRoom.gameState = "lost";
        }
        io.to(playerRoom.id).emit('roomUserLeft', buildRoomView(playerRoom));
    }
    playerRoomMap.delete(socket.id);

    cleanupRooms();
    socket.leaveAll();
};

const handleCreateRoom = (socket, data) => {
    const { username, rows, cols, bombs, autoflag, gameMode } = data;
    const room = buildRoom(socket.id, username, parseInt(rows), parseInt(cols), parseInt(bombs), autoflag, gameMode);
    rooms.set(room.id, room);
    playerRoomMap.set(socket.id, room);
    console.log('created room', room.id);

    socket.join(room.id);
    socket.emit('youJoinedRoom', buildRoomView(room));
};

const handleJoinRoom = (socket, data) => {
    const room = rooms.get(data.room);
    if (!room) {
        console.log(`room ${data.room} does not exist`);
        socket.emit('error', `room ${data.room} does not exist`);
        return;
    }

    room.players.push(buildPlayer(socket.id, data.username));
    playerRoomMap.set(socket.id, room);

    socket.join(data.room);
    socket.broadcast.to(room.id).emit('roomUserJoined', buildRoomView(room));
    socket.emit('youJoinedRoom', buildRoomView(room));
};

// --------------------------------------
// GAME LOGIC
// --------------------------------------

const handleTileClick = (socket, data) => {
    const room = playerRoomMap.get(socket.id);
    if (!room || room.gameState !== "playing") {
        console.log("Could not find room for player", socket.id);
        socket.emit('error', "Could not find room for player");
        return;
    }

    // Find the player and make sure they are alive and have not already selected a tile
    const player = room.players.find(player => player.socketId === socket.id);
    if (!player || player.tombstone || (room.gameMode === "rounds" && player.confirmedSelection)) {
        return;
    }

    // Find the tile that was clicked and select it if it is not already selected by another player
    const tile = room.board.tiles.find(tile => tile.id === data.tileId);
    if (!isSelectableTile(tile, room.players, player.socketId)) {
        return;
    }

    if (room.gameMode === "rounds") {
        const player = room.players.find(player => player.socketId === socket.id)
        if (player) {
            player.selection = tile.id;
        }
        else {
            return;
        }
    }
    else {
        if (room.gameMode === "turns") {
            // Check that the current player is the one who has the turn
            if (room.currentPlayer !== socket.id) {
                return;
            }
        }
        else if (room.gameMode !== "realtime") {
            // Unrecognized gameMode
            return;
        }

        if (tile.bomb === true) {
            console.log('bomb clicked');
            room.players.find(user => user.socketId === socket.id).tombstone = tile.id;
        }

        revealTile(room.board, data.tileId);
        if (room.autoflag) {
            flagBombs(room.board);
        }

        if (checkLoseCondition(room.players)) {
            room.gameState = "lost";
        }
        else if (checkWinCondition(room.players, room.board)) {
            room.gameState = "won";
        }
        room.currentPlayer = getNextPlayer(room.players, room.currentPlayer);
    }

    io.to(room.id).emit('updateRoom', buildRoomView(room));
};

const handleTileSelect = (socket, data) => {
    const room = playerRoomMap.get(socket.id);
    if (!room || room.gameState !== "playing") {
        console.log("Could not find room for player", socket.id);
        socket.emit('error', "Could not find room for player");
        return;
    }

    if (room.gameMode !== "rounds") {
        console.log('game mode is not rounds');
        return;
    }

    if (room.players.find(user => user.socketId === socket.id).tombstone) {
        console.log('player is dead');
        return;
    }

    const player = room.players.find(player => player.socketId === socket.id);
    if (!player || player.tombstone || !player.selection || player.confirmedSelection) {
        return;
    }

    // Find the tile that was clicked and select it if it is not already selected by another player
    const tile = room.board.tiles.find(tile => tile.id === data.tileId);
    if (!isSelectableTile(tile, room.players, player.socketId)) {
        console.log('tile is not selectable');
        return;
    }

    player.confirmedSelection = true;
    const playersSelected = room.players.filter(player => !player.tombstone && player.selection && player.confirmedSelection === true);

    const shouldPlayRound = playersSelected.length === room.players.filter(player => !player.tombstone).length ||
        room.players.filter(player => player.tombstone).length === room.board.tiles.filter(tile => !tile.revealed).length;
    if (shouldPlayRound) {
        room.players.filter(player => !player.tombstone).forEach(player => {
            if (room.board.tiles.find(tile => tile.id === player.selection).bomb === true) {
                player.tombstone = player.selection;
            }
            revealTile(room.board, player.selection);
        });

        if (room.autoflag) {
            flagBombs(room.board);
        }

        room.players.forEach(player => {
            player.selection = null;
            player.confirmedSelection = false;
        });

        if (checkLoseCondition(room.players)) {
            room.gameState = "lost";
        }
        else if (checkWinCondition(room.players, room.board)) {
            room.gameState = "won";
        }
    }

    io.to(room.id).emit('updateRoom', buildRoomView(room));
};

const handleTileFlag = (socket, data) => {
    const room = playerRoomMap.get(socket.id);
    if (!room) {
        console.log("Could not find room for player", socket.id);
        socket.emit('error', "Could not find room for player");
        return;
    }

    if (room.players.find(user => user.socketId === socket.id).tombstone) {
        console.log('player is dead');
        return;
    }

    if (room.gameMode === "turns" && room.currentPlayer !== socket.id) {
        return;
    }

    // Find the tile that was clicked and select it if it is not already selected by another player
    const tile = room.board.tiles.find(tile => tile.id === data.tileId);
    if (!tile || tile.revealed || room.players.some(player => player.selection === data.tileId)) {
        return;
    }

    tile.flagged = !tile.flagged;
    if (checkWinCondition(room.players, room.board)) {
        room.gameState = "won";
    }

    io.to(room.id).emit('updateRoom', buildRoomView(room));
};

// --------------------------------------
// HELPER FUNCTIONS
// --------------------------------------

const cleanupRooms = () => {
    for (let room of rooms.values()) {
        if (room.players.length === 0) {
            rooms.delete(room.id);
        }
    }
};

const buildRoom = (userId, username, rows, cols, bombs, autoflag, gameMode) => {
    const roomId = randomUUID().slice(0, 5); // TODO: avoid collisions
    const board = buildBoard(rows, cols, bombs);
    const user = buildPlayer(userId, username);
    return {
        id: roomId,
        autoflag: autoflag,
        players: [user],
        gameMode: gameMode,
        gameState: "playing",
        currentPlayer: user.socketId,
        board: board
    };
};

const buildBoard = (rows, cols, bombs) => {
    // Generate empty board
    const board = {
        rows: rows,
        cols: cols,
        bombs: bombs,
        tiles: Array(rows * cols).fill().map((_, idx) => {
            return {
                id: idx,
                value: null,
                bomb: false,
                revealed: false,
                flagged: false,
                playerSelect: null
            }
        })
    };

    // Place bombs
    for (let i = 0; i < bombs; i++) {
        const bombIdx = Math.floor(Math.random() * board.tiles.length);
        board.tiles[bombIdx].bomb = true;
    }

    // Calculate values
    board.tiles.forEach((tile, idx) => {
        if (tile.bomb === true) {
            return;
        }

        const bombCount = getSurroundingTiles(board, idx)
            .filter(tile => tile && tile.bomb)
            .length;
        tile.value = bombCount;
    });

    return board;
};

const buildPlayer = (socketId, name) => {
    const getRandomColorHex = () => {
        const colorValue = Math.floor(0x888888 + (Math.random() * 0xffffff - 0x888888));
        return '#' + colorValue.toString(16).padStart(6, '0');
    };

    return {
        socketId,
        name,
        color: getRandomColorHex()
    };
};

const buildRoomView = (room) => {
    const buildBoardView = (board, gameState) => {
        return {
            rows: board.rows,
            cols: board.cols,
            bombs: board.bombs,
            tiles: board.tiles.map(tile => tile.revealed || gameState === "lost" || gameState === "won"
                ? { id: tile.id, value: tile.value, bomb: tile.bomb }
                : { id: tile.id, flagged: tile.flagged }
            )
        };
    }

    return {
        id: room.id,
        players: room.players,
        gameMode: room.gameMode,
        gameState: room.gameState,
        currentPlayer: room.currentPlayer,
        board: buildBoardView(room.board, room.gameState)
    };
};

const revealTile = (board, idx) => {
    const tile = board.tiles.find(tile => tile.id === idx);
    if (!tile || tile.revealed || tile.flagged) {
        return;
    }

    tile.revealed = true;
    if (tile.value === 0) {
        const neighbors = getSurroundingTiles(board, idx);
        neighbors.forEach(neighbor => revealTile(board, neighbor.id));
    }
};

const flagBombs = (board) => {
    board.tiles.forEach(tile => {
        if (!tile.bomb && !tile.flagged) {
            const neighbors = getSurroundingTiles(board, tile.id);
            if (tile.revealed && neighbors.filter(neighbor => !neighbor.revealed || neighbor.bomb).length == tile.value) {
                neighbors.forEach(neighbor => {
                    if (!neighbor.revealed && !neighbor.flagged) {
                        neighbor.flagged = true;
                    }
                });
            }
        }
    });
};

const getSurroundingTiles = (board, idx) => {
    const { rows, cols } = board;

    const neighbors = [];

    const isTopBorder = idx < cols;
    const isBottomBorder = idx >= (rows - 1) * cols;
    const isLeftBorder = idx % cols === 0;
    const isRightBorder = (idx + 1) % cols === 0;

    // Top left
    neighbors.push(!isTopBorder && !isLeftBorder ? board.tiles[idx - cols - 1] : undefined);

    // Top
    neighbors.push(!isTopBorder ? board.tiles[idx - cols] : undefined);
    
    // Top right
    neighbors.push(!isTopBorder && !isRightBorder ? board.tiles[idx - cols + 1] : undefined);

    // Left
    neighbors.push(!isLeftBorder ? board.tiles[idx - 1] : undefined);

    // Right
    neighbors.push(!isRightBorder ? board.tiles[idx + 1] : undefined);

    // Bottom left
    neighbors.push(!isBottomBorder && !isLeftBorder ? board.tiles[idx + cols - 1] : undefined);

    // Bottom
    neighbors.push(!isBottomBorder ? board.tiles[idx + cols] : undefined);

    // Bottom right
    neighbors.push(!isBottomBorder && !isRightBorder ? board.tiles[idx + cols + 1] : undefined);

    return neighbors.filter(tile => tile != undefined);
};

const checkWinCondition = (players, board) => {
    return board.tiles.every(tile =>
        tile.revealed
        || (tile.bomb && tile.flagged)
        || players.some(player => player.tombstone === tile.id))
        && players.filter(player => !player.tombstone).length > 0;
};

const checkLoseCondition = (players) => {
    return players.every(player => player.tombstone);
}

const isSelectableTile = (tile, players, currentPlayerId) => {
    return tile
        && !tile.revealed
        && !tile.flagged
        && players.filter(player => player.socketId != currentPlayerId).every(player => player.selection !== tile.id)
        && players.every(player => player.tombstone !== tile.id);
}

const getNextPlayer = (players, currentPlayerId) => {
    if (players.every(player => player.tombstone)) {
        return null;
    }

    let currentPlayerIdx = players.findIndex(player => player.socketId === currentPlayerId);
    let nextPlayerIdx;
    do {
        nextPlayerIdx = (currentPlayerIdx + 1) % players.length;
        currentPlayerIdx = nextPlayerIdx;
    } while (players[nextPlayerIdx].tombstone);
    return players[nextPlayerIdx].socketId;
}