const express = require('express');
const mysql = require('mysql2/promise');
const bcrypt = require('bcryptjs');
const session = require('express-session');
const path = require('path');
require('dotenv').config({ path: path.join(__dirname, '../.env') });

const app = express();

const FRONTEND_DIR = path.join(__dirname, '../frontend');

const pool = mysql.createPool({
    host: process.env.DB_HOST,
    port: Number(process.env.DB_PORT),
    user: process.env.DB_USER,
    password: process.env.DB_PASSWORD,
    database: process.env.DB_NAME,
    waitForConnections: true,
    connectionLimit: 10,
    queueLimit: 0
});

app.use(express.urlencoded({ extended: true }));
app.use(express.json());

app.use(session({
    secret: process.env.SESSION_SECRET,
    resave: false,
    saveUninitialized: false
}));

app.get('/', (req, res) => {
    if (req.session.user) {
        return res.redirect('/index.html');
    }
    res.sendFile(path.join(FRONTEND_DIR, 'login.html'));
});

app.get('/register', (req, res) => {
    res.sendFile(path.join(FRONTEND_DIR, 'register.html'));
});

app.get('/index.html', (req, res) => {
    if (!req.session.user) {
        return res.redirect('/');
    }
    res.sendFile(path.join(FRONTEND_DIR, 'index.html'));
});

app.post('/register', async (req, res) => {
    const { username, password, password2 } = req.body;

    if (!username || !password || !password2) {
        return res.redirect('/register.html?error=' + encodeURIComponent('Vyplň všetky polia'));
    }

    if (password !== password2) {
        return res.redirect('/register.html?error=' + encodeURIComponent('Heslá sa nezhodujú'));
    }

    try {
        const hashedPassword = await bcrypt.hash(password, 10);

        await pool.execute(
            'INSERT INTO users (username, password) VALUES (?, ?)',
            [username, hashedPassword]
        );

        return res.redirect('/');
    } catch (err) {
        console.error(err);
        return res.redirect('/register.html?error=' + encodeURIComponent('Používateľ už existuje'));
    }
});

app.post('/login', async (req, res) => {
    const { username, password } = req.body;

    if (!username || !password) {
        return res.redirect('/?error=Vyplň%20všetky%20polia');
    }

    try {
        const [rows] = await pool.execute(
            'SELECT * FROM users WHERE username = ?',
            [username]
        );

        const row = rows[0];

        if (!row) {
            return res.redirect('/?error=Zlé%20meno%20alebo%20heslo');
        }

        const result = await bcrypt.compare(password, row.password);

        if (!result) {
            return res.redirect('/?error=Zlé%20meno%20alebo%20heslo');
        }

        req.session.user = {
            id: row.id,
            username: row.username
        };

        return res.redirect('/index.html');
    } catch (err) {
        console.error(err);
        return res.redirect('/?error=Chyba%20databázy');
    }
});

app.post('/logout', (req, res) => {
    req.session.destroy(() => {
        res.redirect('/');
    });
});

app.get('/api/me', (req, res) => {
    if (!req.session.user) {
        return res.status(401).json({ error: 'Neprihlásený používateľ' });
    }

    res.json(req.session.user);
});

app.get('/api/tasks', async (req, res) => {
    if (!req.session.user) {
        return res.status(401).json({ error: 'Neprihlásený používateľ' });
    }

    try {
        const [rows] = await pool.execute(
            'SELECT * FROM tasks WHERE user_id = ? ORDER BY deadline ASC',
            [req.session.user.id]
        );

        res.json(rows);
    } catch (err) {
        console.error(err);
        return res.status(500).json({ error: 'Chyba pri načítaní úloh' });
    }
});

app.post('/api/tasks', async (req, res) => {
    if (!req.session.user) {
        return res.status(401).json({ error: 'Neprihlásený používateľ' });
    }

    const { title, description, deadline } = req.body;

    if (!title || !description || !deadline) {
        return res.status(400).json({ error: 'Vyplň všetky polia' });
    }

    try {
        const [result] = await pool.execute(
            'INSERT INTO tasks (user_id, title, description, deadline) VALUES (?, ?, ?, ?)',
            [req.session.user.id, title, description, deadline]
        );

        const [rows] = await pool.execute(
            'SELECT * FROM tasks WHERE id = ?',
            [result.insertId]
        );

        res.json(rows[0]);
    } catch (err) {
        console.error(err);
        return res.status(500).json({ error: 'Chyba pri ukladaní úlohy' });
    }
});

app.delete('/api/tasks/:id', async (req, res) => {
    if (!req.session.user) {
        return res.status(401).json({ error: 'Neprihlásený používateľ' });
    }

    try {
        await pool.execute(
            'DELETE FROM tasks WHERE id = ? AND user_id = ?',
            [req.params.id, req.session.user.id]
        );

        res.json({ success: true });
    } catch (err) {
        console.error(err);
        return res.status(500).json({ error: 'Chyba pri mazaní úlohy' });
    }
});

app.patch('/api/tasks/:id/toggle', async (req, res) => {
    if (!req.session.user) {
        return res.status(401).json({ error: 'Neprihlásený používateľ' });
    }

    const { status } = req.body;

    try {
        await pool.execute(
            'UPDATE tasks SET status = ? WHERE id = ? AND user_id = ?',
            [status ? 1 : 0, req.params.id, req.session.user.id]
        );

        res.json({ success: true });
    } catch (err) {
        console.error(err);
        return res.status(500).json({ error: 'Chyba pri zmene stavu úlohy' });
    }
});

app.use(express.static(FRONTEND_DIR));

const PORT = process.env.PORT || 3000;

app.listen(PORT, async () => {
    try {
        const connection = await pool.getConnection();
        console.log('Pripojenie na MySQL úspešné.');
        connection.release();
    } catch (err) {
        console.error('Nepodarilo sa pripojiť na MySQL:', err.message);
    }

    console.log(`Server beží na http://localhost:${PORT}`);
});