const express = require('express');
const http = require('http');
const { Server } = require('socket.io');
const path = require('path');
const zlib = require('zlib');

const app = express();
const server = http.createServer(app);

// Professional Socket.IO configuration
const io = new Server(server, {
    cors: {
        origin: "*",
        methods: ["GET", "POST"]
    },
    // Optimized for slow connections
    pingTimeout: 120000,
    pingInterval: 10000,
    upgradeTimeout: 30000,
    transports: ['websocket', 'polling'],
    allowUpgrades: true,
    perMessageDeflate: {
        threshold: 256,
        zlibDeflateOptions: { level: 6 },
        zlibInflateOptions: { chunkSize: 10 * 1024 }
    },
    httpCompression: true,
    maxHttpBufferSize: 1e6
});

app.use(express.static(path.join(__dirname, 'public')));

// Game constants
const TILE_SIZE = 10;
const GRID_WIDTH = 13;
const BASE_TICK_RATE = 15; // Lower for bandwidth
const HOP_DURATION = 120;

// Game state
const players = new Map();
const gameState = {
    lanes: new Map(),
    furthestLaneIndex: 14,
    version: 0 // State version for delta sync
};

// Connection stats
const connectionStats = new Map();

// ============= LANE GENERATION =============
function generateLaneData(index, prevLane) {
    let type = 'grass';
    let runLength = 1;

    if (index <= 4) {
        type = 'grass';
    } else if (prevLane) {
        const r = Math.random();
        
        if (prevLane.type === 'grass') {
            if (r < 0.6) type = 'road';
            else if (r < 0.9) type = 'water';
            else type = 'grass';
        } else if (prevLane.type === 'road') {
            if (prevLane.runLength < 4 && r < 0.7) {
                type = 'road';
                runLength = prevLane.runLength + 1;
            } else {
                type = 'grass';
            }
        } else if (prevLane.type === 'water') {
            if (prevLane.runLength < 2 && r < 0.6) {
                type = 'water';
                runLength = prevLane.runLength + 1;
            } else {
                type = 'grass';
            }
        }
    }

    const staticObstacles = [];
    if (type === 'grass') {
        const treeCount = Math.floor(Math.random() * 3);
        for (let i = 0; i < treeCount; i++) {
            let gx = Math.floor(Math.random() * GRID_WIDTH) - Math.floor(GRID_WIDTH / 2);
            if (index < 5 && gx === 0) continue;
            if (!staticObstacles.includes(gx)) {
                staticObstacles.push(gx);
            }
        }
    }

    const lane = {
        i: index, // Short keys for bandwidth
        t: type.charAt(0), // 'g', 'r', 'w'
        rl: runLength,
        so: staticObstacles,
        sp: Math.round((Math.random() * 0.04 + 0.02) * TILE_SIZE * 100) / 100,
        d: Math.random() > 0.5 ? 1 : -1,
        obs: [],
        timer: 0,
        interval: Math.random() * 100 + 150,
        obsId: 0
    };

    // Pre-populate obstacles
    if (type === 'road' || type === 'water') {
        const count = Math.ceil(Math.random() * 2);
        for (let i = 0; i < count; i++) {
            let randX = (Math.random() * 120) - 60;
            if (Math.abs(randX) < 15) randX += (randX > 0 ? 20 : -20);
            
            const obsWidth = type === 'water' 
                ? (Math.random() > 0.5 ? 40 : 60)
                : 12;
            
            lane.obs.push({
                id: lane.obsId++,
                x: Math.round(randX * 10) / 10,
                l: type === 'water' ? 1 : 0, // isLog
                w: obsWidth
            });
        }
    }

    return lane;
}

function initializeLanes() {
    gameState.lanes.clear();
    for (let i = -4; i < 15; i++) {
        const prevLane = gameState.lanes.get(i - 1);
        gameState.lanes.set(i, generateLaneData(i, prevLane));
    }
    gameState.furthestLaneIndex = 14;
}

initializeLanes();

// ============= COLLISION DETECTION =============
function checkCollisionAtPosition(gridX, gridZ, worldX = null) {
    const lane = gameState.lanes.get(gridZ);
    if (!lane) return { hit: false };

    const px = worldX !== null ? worldX : gridX * TILE_SIZE;

    if (Math.abs(px) > (GRID_WIDTH * TILE_SIZE / 2 + 10)) {
        return { hit: true, type: 'bounds' };
    }

    if (lane.t === 'g') {
        if (lane.so.includes(gridX)) {
            return { hit: true, type: 'tree', blocked: true };
        }
        return { hit: false };
    }

    if (lane.t === 'r') {
        for (const obs of lane.obs) {
            const left = obs.x - obs.w / 2;
            const right = obs.x + obs.w / 2;
            if (px + 3 > left && px - 3 < right) {
                return { hit: true, type: 'car' };
            }
        }
        return { hit: false };
    }

    if (lane.t === 'w') {
        for (const obs of lane.obs) {
            if (Math.abs(px - obs.x) < (obs.w / 2) + 4) {
                return { hit: false, onLog: true, logId: obs.id };
            }
        }
        return { hit: true, type: 'water' };
    }

    return { hit: false };
}

function validateMove(player, dx, dz) {
    if (!player.alive) return { valid: false, reason: 'dead' };
    if (dz < 0) return { valid: false, reason: 'backward' };

    const targetX = player.gx + dx;
    const targetZ = player.gz + dz;

    if (Math.abs(targetX) > Math.floor(GRID_WIDTH / 2)) {
        return { valid: false, reason: 'bounds' };
    }

    const lane = gameState.lanes.get(targetZ);
    if (lane && lane.t === 'g' && lane.so.includes(targetX)) {
        return { valid: false, reason: 'tree' };
    }

    return { valid: true, tx: targetX, tz: targetZ };
}

// ============= LEADERBOARD =============
function getLeaderboard() {
    return Array.from(players.values())
        .filter(p => p.alive || p.score > 0)
        .sort((a, b) => b.score - a.score)
        .slice(0, 3)
        .map((p, i) => ({
            r: i + 1,
            n: p.name,
            s: p.score
        }));
}

// Compact player data for network
function compactPlayer(p) {
    return {
        id: p.id,
        n: p.name,
        gx: p.gx,
        gz: p.gz,
        wx: Math.round(p.wx * 10) / 10,
        wz: Math.round(p.wz * 10) / 10,
        r: Math.round(p.rot * 100) / 100,
        s: p.score,
        a: p.alive ? 1 : 0,
        h: p.hopping ? 1 : 0,
        ht: p.hopTime
    };
}

// Compact lane data
function compactLane(lane) {
    return {
        i: lane.i,
        t: lane.t,
        rl: lane.rl,
        so: lane.so,
        sp: lane.sp,
        d: lane.d,
        obs: lane.obs.map(o => ({
            id: o.id,
            x: Math.round(o.x * 10) / 10,
            l: o.l,
            w: o.w
        }))
    };
}

// ============= SOCKET HANDLING =============
io.on('connection', (socket) => {
    console.log(`[${new Date().toISOString()}] Connection: ${socket.id}`);
    
    // Initialize connection stats
    connectionStats.set(socket.id, {
        connected: Date.now(),
        lastPing: Date.now(),
        ping: 0,
        quality: 'good'
    });

    // Send immediate acknowledgment
    socket.emit('ack', { 
        id: socket.id, 
        t: Date.now(),
        v: gameState.version 
    });

    socket.on('join', (data) => {
        try {
            const name = (data.name || 'Anon').substring(0, 12).replace(/[<>\"\'&]/g, '');
            
            const player = {
                id: socket.id,
                name: name,
                gx: 0, gz: 0,
                wx: 0, wz: 0,
                score: 0,
                alive: true,
                hopping: false,
                hopTime: 0,
                hopStart: { x: 0, z: 0 },
                hopTarget: { x: 0, z: 0 },
                rot: 0,
                logId: null,
                lastMove: 0,
                moveSeq: 0
            };
            
            players.set(socket.id, player);

            // Send minimal initial state
            const lanesArr = [];
            gameState.lanes.forEach((lane) => {
                lanesArr.push(compactLane(lane));
            });

            const otherPlayers = [];
            players.forEach((p, id) => {
                if (id !== socket.id) {
                    otherPlayers.push(compactPlayer(p));
                }
            });

            socket.emit('init', {
                p: compactPlayer(player),
                ps: otherPlayers,
                ls: lanesArr,
                t: Date.now(),
                lb: getLeaderboard()
            });

            // Notify others
            socket.broadcast.emit('pj', compactPlayer(player));
            
            console.log(`[${new Date().toISOString()}] Joined: ${name} (${socket.id})`);
        } catch (err) {
            console.error('Join error:', err);
            socket.emit('err', { m: 'Join failed' });
        }
    });

    socket.on('m', (data) => { // Move
        const player = players.get(socket.id);
        if (!player) return;

        const now = Date.now();
        
        // Rate limit: 70ms minimum
        if (now - player.lastMove < 70) {
            socket.emit('mr', { s: data.s, r: 'fast' });
            return;
        }

        if (player.hopping) {
            socket.emit('mr', { s: data.s, r: 'hop' });
            return;
        }

        if (!player.alive) {
            socket.emit('mr', { s: data.s, r: 'dead' });
            return;
        }

        const { dx, dz, s } = data;
        const v = validateMove(player, dx, dz);

        if (!v.valid) {
            socket.emit('mr', { s, r: v.reason });
            return;
        }

        // Execute move
        player.lastMove = now;
        player.hopping = true;
        player.hopTime = now;
        player.hopStart = { x: player.wx, z: player.wz };
        player.hopTarget = { x: v.tx * TILE_SIZE, z: v.tz * TILE_SIZE };
        player.gx = v.tx;
        player.gz = v.tz;
        player.wx = v.tx * TILE_SIZE;
        player.wz = v.tz * TILE_SIZE;
        player.logId = null;
        player.moveSeq = s;

        // Rotation
        if (dx === 1) player.rot = -Math.PI / 2;
        else if (dx === -1) player.rot = Math.PI / 2;
        else if (dz === 1) player.rot = 0;
        else if (dz === -1) player.rot = Math.PI;

        // Score
        if (v.tz > player.score) {
            player.score = v.tz;
            io.emit('lb', getLeaderboard());
        }

        // Generate new lanes
        const spawnZ = player.score + 12;
        while (spawnZ > gameState.furthestLaneIndex) {
            gameState.furthestLaneIndex++;
            const prevLane = gameState.lanes.get(gameState.furthestLaneIndex - 1);
            const newLane = generateLaneData(gameState.furthestLaneIndex, prevLane);
            gameState.lanes.set(gameState.furthestLaneIndex, newLane);
            io.emit('nl', compactLane(newLane));
        }

        // Confirm
        socket.emit('mc', {
            s,
            gx: player.gx,
            gz: player.gz,
            sc: player.score,
            t: now
        });

        // Broadcast
        socket.broadcast.emit('pm', {
            id: player.id,
            gx: player.gx,
            gz: player.gz,
            wx: player.wx,
            wz: player.wz,
            r: player.rot,
            t: now,
            hs: player.hopStart,
            ht: player.hopTarget
        });
    });

    socket.on('p', (ct) => { // Ping
        const stats = connectionStats.get(socket.id);
        if (stats) {
            stats.lastPing = Date.now();
        }
        socket.emit('po', { c: ct, s: Date.now() });
    });

    socket.on('rs', () => { // Respawn
        const player = players.get(socket.id);
        if (!player) return;

        player.gx = 0;
        player.gz = 0;
        player.wx = 0;
        player.wz = 0;
        player.score = 0;
        player.alive = true;
        player.hopping = false;
        player.logId = null;
        player.rot = 0;

        socket.emit('rsd', compactPlayer(player));
        socket.broadcast.emit('prs', { id: player.id });
        io.emit('lb', getLeaderboard());
    });

    socket.on('hb', () => { // Heartbeat
        socket.emit('hba');
    });

    socket.on('disconnect', (reason) => {
        console.log(`[${new Date().toISOString()}] Disconnect: ${socket.id} (${reason})`);
        players.delete(socket.id);
        connectionStats.delete(socket.id);
        io.emit('pl', socket.id);
        io.emit('lb', getLeaderboard());
    });

    socket.on('error', (err) => {
        console.error(`Socket error ${socket.id}:`, err);
    });
});

// ============= GAME LOOP =============
let lastTick = Date.now();

function gameTick() {
    const now = Date.now();
    const dt = now - lastTick;
    lastTick = now;

    // Update obstacles
    gameState.lanes.forEach((lane) => {
        if (lane.t === 'r' || lane.t === 'w') {
            lane.timer += dt;
            
            if (lane.timer > lane.interval) {
                const startX = -lane.d * (GRID_WIDTH * TILE_SIZE / 2 + 60);
                const obsWidth = lane.t === 'w' ? (Math.random() > 0.5 ? 40 : 60) : 12;
                
                lane.obs.push({
                    id: lane.obsId++,
                    x: startX,
                    l: lane.t === 'w' ? 1 : 0,
                    w: obsWidth
                });
                
                lane.timer = 0;
                lane.interval = Math.random() * 100 + 200;
            }

            // Move obstacles
            for (let i = lane.obs.length - 1; i >= 0; i--) {
                const obs = lane.obs[i];
                obs.x += lane.sp * lane.d * (dt / 16.67);
                if (Math.abs(obs.x) > 400) {
                    lane.obs.splice(i, 1);
                }
            }
        }
    });

    // Update players
    players.forEach((player) => {
        if (!player.alive) return;

        // Complete hop
        if (player.hopping && now - player.hopTime >= HOP_DURATION) {
            player.hopping = false;
            
            const col = checkCollisionAtPosition(player.gx, player.gz, player.wx);
            
            if (col.hit) {
                player.alive = false;
                io.emit('pd', { id: player.id, type: col.type });
                io.emit('lb', getLeaderboard());
            } else if (col.onLog) {
                player.logId = col.logId;
            }
        }

        // Check collision during hop
        if (player.hopping) {
            const progress = (now - player.hopTime) / HOP_DURATION;
            const cx = player.hopStart.x + (player.hopTarget.x - player.hopStart.x) * progress;
            const cz = player.hopStart.z + (player.hopTarget.z - player.hopStart.z) * progress;
            const cgz = Math.round(cz / TILE_SIZE);
            
            const lane = gameState.lanes.get(cgz);
            if (lane && lane.t === 'r') {
                for (const obs of lane.obs) {
                    if (Math.abs(cx - obs.x) < (obs.w / 2 + 3)) {
                        player.alive = false;
                        player.hopping = false;
                        io.emit('pd', { id: player.id, type: 'car' });
                        io.emit('lb', getLeaderboard());
                        break;
                    }
                }
            }
        }

        // Log riding
        if (!player.hopping && player.logId !== null) {
            const lane = gameState.lanes.get(player.gz);
            if (lane) {
                const log = lane.obs.find(o => o.id === player.logId);
                if (log) {
                    player.wx = log.x;
                    player.gx = Math.round(player.wx / TILE_SIZE);
                    
                    if (Math.abs(player.wx) > (GRID_WIDTH * TILE_SIZE / 2 + 10)) {
                        player.alive = false;
                        io.emit('pd', { id: player.id, type: 'bounds' });
                        io.emit('lb', getLeaderboard());
                    }
                } else {
                    player.logId = null;
                    if (lane.t === 'w') {
                        player.alive = false;
                        io.emit('pd', { id: player.id, type: 'water' });
                        io.emit('lb', getLeaderboard());
                    }
                }
            }
        }
    });

    // Broadcast state (minimal)
    const playersData = [];
    players.forEach(p => playersData.push(compactPlayer(p)));

    const obsData = {};
    gameState.lanes.forEach((lane, key) => {
        if (lane.t !== 'g' && lane.obs.length > 0) {
            obsData[key] = lane.obs.map(o => ({
                id: o.id,
                x: Math.round(o.x * 10) / 10
            }));
        }
    });

    io.emit('gs', {
        ps: playersData,
        obs: obsData,
        t: now
    });
}

setInterval(gameTick, 1000 / BASE_TICK_RATE);

// Cleanup old lanes
setInterval(() => {
    let minZ = Infinity;
    players.forEach(p => {
        if (p.gz < minZ) minZ = p.gz;
    });
    if (minZ === Infinity) minZ = 0;

    gameState.lanes.forEach((lane, key) => {
        if (key < minZ - 15) {
            gameState.lanes.delete(key);
        }
    });
}, 10000);

// Health check endpoint
app.get('/health', (req, res) => {
    res.json({ 
        status: 'ok', 
        players: players.size,
        uptime: process.uptime()
    });
});

const PORT = process.env.PORT || 7860;
server.listen(PORT, '0.0.0.0', () => {
    console.log(`Server running on port ${PORT}`);
});