// --- Time Tracker Backend Server (with Time Off Requests) ---

require('dotenv').config();
const express = require('express');
const sqlite3 = require('sqlite3').verbose();
const bcrypt = require('bcryptjs');
const jwt = require('jsonwebtoken');
const cors = require('cors');
const path = require('path');

// --- Server Configuration ---
const PORT = process.env.PORT || 3000;
const JWT_SECRET = process.env.JWT_SECRET || 'default_secret_key';
const ADMIN_USERNAME = process.env.ADMIN_USERNAME || 'admin';
const ADMIN_PASSWORD = process.env.ADMIN_PASSWORD || 'adminpassword';

const app = express();
app.use(cors());
app.use(express.json());

const dbPath = path.resolve(__dirname, 'data', 'timetracker.db');
const db = new sqlite3.Database(dbPath, (err) => {
    if (err) console.error("Error opening database", err.message);
    else {
        console.log("Connected to the SQLite database.");
        initializeDatabase();
    }
});

function initializeDatabase() {
    db.serialize(() => {
        db.run(`CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, username TEXT UNIQUE NOT NULL, password TEXT NOT NULL, role TEXT NOT NULL DEFAULT 'employee')`);
        db.run(`CREATE TABLE IF NOT EXISTS time_entries (id INTEGER PRIMARY KEY AUTOINCREMENT, user_id INTEGER NOT NULL, username TEXT, punch_in_time DATETIME NOT NULL, punch_out_time DATETIME, status TEXT NOT NULL, FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE)`);
        db.run(`CREATE TABLE IF NOT EXISTS archived_time_entries (id INTEGER PRIMARY KEY, user_id INTEGER NOT NULL, username TEXT, punch_in_time DATETIME NOT NULL, punch_out_time DATETIME, status TEXT NOT NULL, archived_at DATETIME NOT NULL)`);
        // NEW: Table for time off requests
        db.run(`CREATE TABLE IF NOT EXISTS time_off_requests (id INTEGER PRIMARY KEY AUTOINCREMENT, user_id INTEGER NOT NULL, username TEXT, start_date TEXT NOT NULL, end_date TEXT NOT NULL, reason TEXT, status TEXT NOT NULL DEFAULT 'pending', FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE)`);

        db.get('SELECT * FROM users WHERE username = ?', [ADMIN_USERNAME], (err, row) => {
            if (!row) {
                bcrypt.hash(ADMIN_PASSWORD, 10, (err, hashedPassword) => {
                    db.run('INSERT INTO users (username, password, role) VALUES (?, ?, ?)', [ADMIN_USERNAME, hashedPassword, 'admin']);
                });
            }
        });
    });
}

// --- Middleware ---
const requireRole = (role) => (req, res, next) => {
    if (req.user && req.user.role === role) next();
    else res.status(403).json({ message: "Access denied." });
};

function authenticateToken(req, res, next) {
    const token = req.headers['authorization']?.split(' ')[1];
    if (token == null) return res.sendStatus(401);
    jwt.verify(token, JWT_SECRET, (err, user) => {
        if (err) return res.sendStatus(403);
        req.user = user;
        next();
    });
}

// --- API Routes ---
app.post('/api/login', (req, res) => {
    const { username, password } = req.body;
    db.get('SELECT * FROM users WHERE username = ?', [username], (err, user) => {
        if (!user) return res.status(404).json({ message: "User not found." });
        bcrypt.compare(password, user.password, (err, isMatch) => {
            if (!isMatch) return res.status(401).json({ message: "Invalid credentials." });
            const tokenPayload = { id: user.id, username: user.username, role: user.role };
            const token = jwt.sign(tokenPayload, JWT_SECRET, { expiresIn: '30d' });
            res.json({ token, user: tokenPayload });
        });
    });
});

app.post('/api/punch', authenticateToken, (req, res) => {
    const { id, username } = req.user;
    db.get(`SELECT * FROM time_entries WHERE user_id = ? ORDER BY punch_in_time DESC LIMIT 1`, [id], (err, last) => {
        if (last && last.status === 'in') {
            db.run(`UPDATE time_entries SET punch_out_time = ?, status = 'out' WHERE id = ?`, [new Date().toISOString(), last.id], () => res.json({ message: "Punched out." }));
        } else {
            db.run(`INSERT INTO time_entries (user_id, username, punch_in_time, status) VALUES (?, ?, ?, 'in')`, [id, username, new Date().toISOString()], () => res.json({ message: "Punched in." }));
        }
    });
});

app.get('/api/status', authenticateToken, (req, res) => {
    db.all(`SELECT * FROM time_entries WHERE user_id = ? ORDER BY punch_in_time DESC`, [req.user.id], (err, rows) => res.json(rows));
});

app.post('/api/user/change-password', authenticateToken, (req, res) => {
    const { currentPassword, newPassword } = req.body;
    const { id } = req.user;
    db.get('SELECT * FROM users WHERE id = ?', [id], (err, user) => {
        if (err || !user) return res.status(500).json({ message: "Could not find user." });
        bcrypt.compare(currentPassword, user.password, (err, isMatch) => {
            if (!isMatch) return res.status(401).json({ message: "Incorrect current password." });
            bcrypt.hash(newPassword, 10, (err, hashedPassword) => {
                db.run('UPDATE users SET password = ? WHERE id = ?', [hashedPassword, id], (err) => {
                    res.json({ message: "Password updated successfully." });
                });
            });
        });
    });
});

// NEW: Employee requests time off
app.post('/api/user/request-time-off', authenticateToken, (req, res) => {
    const { startDate, endDate, reason } = req.body;
    const { id, username } = req.user;
    if (!startDate || !endDate) return res.status(400).json({ message: "Start and end dates are required." });
    
    const sql = `INSERT INTO time_off_requests (user_id, username, start_date, end_date, reason) VALUES (?, ?, ?, ?, ?)`;
    db.run(sql, [id, username, startDate, endDate, reason], function(err) {
        if (err) return res.status(500).json({ message: "Failed to submit request." });
        res.status(201).json({ message: "Time off request submitted." });
    });
});

// NEW: Employee views their time off requests
app.get('/api/user/time-off-requests', authenticateToken, (req, res) => {
    const { id } = req.user;
    db.all("SELECT * FROM time_off_requests WHERE user_id = ? ORDER BY start_date DESC", [id], (err, rows) => {
        if (err) return res.status(500).json({ message: "Failed to fetch requests." });
        res.json(rows);
    });
});

// --- Admin Routes ---
app.post('/api/admin/create-user', authenticateToken, requireRole('admin'), (req, res) => {
    const { username, password, role } = req.body;
    const userRole = (role === 'admin' || role === 'employee') ? role : 'employee';
    bcrypt.hash(password, 10, (err, hashedPassword) => {
        db.run('INSERT INTO users (username, password, role) VALUES (?, ?, ?)', [username, hashedPassword, userRole], function(err) {
            if (err) return res.status(409).json({ message: "Username already exists." });
            res.status(201).json({ message: `User '${username}' created as ${userRole}.` });
        });
    });
});

app.delete('/api/admin/delete-user/:username', authenticateToken, requireRole('admin'), (req, res) => {
    const { username } = req.params;
    if (username === req.user.username) return res.status(400).json({ message: "Cannot delete your own account." });
    if (username === ADMIN_USERNAME) return res.status(403).json({ message: "The primary admin account cannot be deleted." });

    db.get("SELECT id FROM users WHERE username = ?", [username], (err, userToDelete) => {
        if (!userToDelete) return res.status(404).json({ message: "User not found." });
        db.serialize(() => {
            db.run('BEGIN TRANSACTION');
            db.run('DELETE FROM time_entries WHERE user_id = ?', [userToDelete.id]);
            db.run('DELETE FROM archived_time_entries WHERE user_id = ?', [userToDelete.id]);
            db.run('DELETE FROM users WHERE id = ?', [userToDelete.id], () => db.run('COMMIT', () => res.json({ message: `User '${username}' deleted.` })));
        });
    });
});

app.post('/api/admin/reset-password', authenticateToken, requireRole('admin'), (req, res) => {
    const { username, newPassword } = req.body;
    if (username === ADMIN_USERNAME) return res.status(403).json({ message: "The primary admin's password cannot be reset by another user." });
    bcrypt.hash(newPassword, 10, (err, hashedPassword) => {
        db.run('UPDATE users SET password = ? WHERE username = ?', [hashedPassword, username], function(err) {
            if (this.changes === 0) return res.status(404).json({ message: "User not found." });
            res.json({ message: `Password for '${username}' has been reset.` });
        });
    });
});

app.get('/api/admin/users', authenticateToken, requireRole('admin'), (req, res) => {
    db.all("SELECT id, username, role FROM users", [], (err, rows) => {
        if(err) return res.status(500).json({message: "Database error fetching users."});
        const usersWithFlags = rows.map(row => ({ ...row, isPrimary: row.username === ADMIN_USERNAME }));
        res.json(usersWithFlags);
    });
});

app.post('/api/admin/update-role', authenticateToken, requireRole('admin'), (req, res) => {
    const { username, newRole } = req.body;
    if (username === ADMIN_USERNAME) return res.status(403).json({ message: "The primary admin's role cannot be changed." });
    if (!['admin', 'employee'].includes(newRole)) return res.status(400).json({ message: "Invalid role." });
    db.get("SELECT role FROM users WHERE username = ?", [username], (err, userToUpdate) => {
        if (!userToUpdate) return res.status(404).json({ message: "User not found." });
        if (userToUpdate.role === 'admin' && newRole === 'employee') {
            db.get("SELECT COUNT(*) as adminCount FROM users WHERE role = 'admin'", (err, row) => {
                if (row.adminCount <= 1) return res.status(400).json({ message: "Cannot remove the last administrator." });
                db.run('UPDATE users SET role = ? WHERE username = ?', [newRole, username], () => res.json({ message: `Role for '${username}' updated.` }));
            });
        } else {
            db.run('UPDATE users SET role = ? WHERE username = ?', [newRole, username], () => res.json({ message: `Role for '${username}' updated.` }));
        }
    });
});

app.post('/api/admin/add-punch', authenticateToken, requireRole('admin'), (req, res) => {
    const { userId, username, punchInTime, punchOutTime } = req.body;
    db.run(`INSERT INTO time_entries (user_id, username, punch_in_time, punch_out_time, status) VALUES (?, ?, ?, ?, 'out')`, [userId, username, punchInTime, punchOutTime], () => res.status(201).json({message: "Time punch added."}));
});

app.post('/api/admin/force-clock-out', authenticateToken, requireRole('admin'), (req, res) => {
    const { userId } = req.body;
    db.run(`UPDATE time_entries SET punch_out_time = ?, status = 'out' WHERE user_id = ? AND status = 'in'`, [new Date().toISOString(), userId], function(err) {
        if(this.changes === 0) return res.status(404).json({message: "No active punch-in found."});
        res.json({message: "User has been clocked out."});
    });
});

// NEW: Get all time off requests
app.get('/api/admin/time-off-requests', authenticateToken, requireRole('admin'), (req, res) => {
    db.all("SELECT * FROM time_off_requests ORDER BY start_date DESC", [], (err, rows) => {
        if (err) return res.status(500).json({ message: "Failed to fetch requests." });
        res.json(rows);
    });
});

// NEW: Update status of a time off request
app.post('/api/admin/update-time-off-status', authenticateToken, requireRole('admin'), (req, res) => {
    const { requestId, status } = req.body;
    if (!requestId || !['approved', 'denied'].includes(status)) {
        return res.status(400).json({ message: "Request ID and a valid status are required." });
    }
    db.run("UPDATE time_off_requests SET status = ? WHERE id = ?", [status, requestId], function(err) {
        if (err) return res.status(500).json({ message: "Failed to update status." });
        if (this.changes === 0) return res.status(404).json({ message: "Request not found." });
        res.json({ message: `Request has been ${status}.` });
    });
});


app.get('/api/admin/logs', authenticateToken, requireRole('admin'), (req, res) => {
    db.all(`SELECT * FROM time_entries ORDER BY punch_in_time DESC`, (err, rows) => res.json(rows));
});

app.delete('/api/admin/logs/:id', authenticateToken, requireRole('admin'), (req, res) => {
    db.run('DELETE FROM time_entries WHERE id = ?', [req.params.id], () => res.json({ message: 'Entry deleted.' }));
});

app.put('/api/admin/logs/:id', authenticateToken, requireRole('admin'), (req, res) => {
    const { punch_in_time, punch_out_time } = req.body;
    const status = punch_out_time ? 'out' : 'in';
    db.run(`UPDATE time_entries SET punch_in_time = ?, punch_out_time = ?, status = ? WHERE id = ?`, [punch_in_time, punch_out_time, status, req.params.id], () => res.json({ message: 'Entry updated.' }));
});

app.post('/api/admin/archive', authenticateToken, requireRole('admin'), (req, res) => {
    db.all(`SELECT * FROM time_entries WHERE status = 'out'`, (err, rows) => {
        if (rows.length === 0) return res.json({ message: "No entries to archive." });
        const archiveTime = new Date().toISOString();
        db.serialize(() => {
            db.run('BEGIN TRANSACTION');
            const insert = db.prepare('INSERT INTO archived_time_entries VALUES (?, ?, ?, ?, ?, ?, ?)');
            rows.forEach(r => insert.run(r.id, r.user_id, r.username, r.punch_in_time, r.punch_out_time, r.status, archiveTime));
            insert.finalize();
            const idsToDelete = rows.map(r => r.id);
            db.run(`DELETE FROM time_entries WHERE id IN (${idsToDelete.map(() => '?').join(',')})`, idsToDelete);
            db.run('COMMIT', () => res.json({ message: `Archived ${rows.length} entries.` }));
        });
    });
});

app.get('/api/admin/archives', authenticateToken, requireRole('admin'), (req, res) => {
    db.all(`SELECT * FROM archived_time_entries ORDER BY archived_at DESC, id DESC`, (err, rows) => res.json(rows));
});

app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));