// --- Time Tracker Backend Server (Definitive Fix) ---

require('dotenv').config();
const express = require('express');
const sqlite3 = require('sqlite3');
const { open } = require('sqlite');
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());

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

let db;

// --- Main Server Function ---
async function startServer() {
    try {
        const dbPath = path.resolve(__dirname, 'data', 'timetracker.db');
        db = await open({
            filename: dbPath,
            driver: sqlite3.Database
        });
        console.log("Connected to the SQLite database.");
        
        await initializeDatabase();
        setupRoutes();
        app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));

    } catch (err) {
        console.error("FATAL: Could not start server.", err);
        process.exit(1);
    }
}

async function initializeDatabase() {
    console.log("Initializing database schema...");
    await db.exec(`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')`);
    await db.exec(`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)`);
    await db.exec(`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)`);
    await db.exec(`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)`);
    
    const adminUser = await db.get('SELECT * FROM users WHERE username = ?', [ADMIN_USERNAME]);
    if (!adminUser) {
        console.log("Primary admin user not found, creating one...");
        const hashedPassword = await bcrypt.hash(ADMIN_PASSWORD, 10);
        await db.run('INSERT INTO users (username, password, role) VALUES (?, ?, ?)', [ADMIN_USERNAME, hashedPassword, 'admin']);
        console.log("Primary admin user created.");
    }
    console.log("Database initialization complete.");
}

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

    const authenticateToken = (req, res, next) => {
        const token = req.headers['authorization']?.split(' ')[1];
        if (token == null) return res.status(401).json({ message: "Authentication required. No token provided." });
        jwt.verify(token, JWT_SECRET, (err, user) => {
            if (err) return res.status(403).json({ message: "Access denied. Invalid or expired token." });
            req.user = user;
            next();
        });
    };

    // --- User Routes ---
    app.post('/api/login', async (req, res) => {
        try {
            const { username, password } = req.body;
            const user = await db.get('SELECT * FROM users WHERE username = ?', [username]);
            if (!user) return res.status(404).json({ message: "User not found." });
            const isMatch = await bcrypt.compare(password, user.password);
            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: '8h' });
            res.json({ token, user: tokenPayload });
        } catch (err) { res.status(500).json({ message: "Server error during login." }); }
    });

    app.post('/api/punch', authenticateToken, async (req, res) => {
        try {
            const { id, username } = req.user;
            const last = await db.get(`SELECT * FROM time_entries WHERE user_id = ? ORDER BY punch_in_time DESC LIMIT 1`, [id]);
            if (last && last.status === 'in') {
                await db.run(`UPDATE time_entries SET punch_out_time = ?, status = 'out' WHERE id = ?`, [new Date().toISOString(), last.id]);
                res.json({ message: "Punched out." });
            } else {
                await 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." });
            }
        } catch (err) { res.status(500).json({ message: "Server error during punch." }); }
    });

    app.get('/api/status', authenticateToken, async (req, res) => {
        try {
            const rows = await db.all(`SELECT * FROM time_entries WHERE user_id = ? ORDER BY punch_in_time DESC`, [req.user.id]);
            res.json(rows);
        } catch (err) { res.status(500).json({ message: "Server error fetching status." }); }
    });

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

    app.post('/api/user/request-time-off', authenticateToken, async (req, res) => {
        try {
            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." });
            await db.run(`INSERT INTO time_off_requests (user_id, username, start_date, end_date, reason) VALUES (?, ?, ?, ?, ?)`, [id, username, startDate, endDate, reason]);
            res.status(201).json({ message: "Time off request submitted." });
        } catch (err) { res.status(500).json({ message: "Failed to submit request." }); }
    });

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

    // --- Admin Routes ---
    app.post('/api/admin/create-user', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const { username, password, role } = req.body;
            const userRole = (role === 'admin' || role === 'employee') ? role : 'employee';
            const hashedPassword = await bcrypt.hash(password, 10);
            await db.run('INSERT INTO users (username, password, role) VALUES (?, ?, ?)', [username, hashedPassword, userRole]);
            res.status(201).json({ message: `User '${username}' created as ${userRole}.` });
        } catch (err) {
            if (err.code === 'SQLITE_CONSTRAINT') return res.status(409).json({ message: "Username already exists." });
            res.status(500).json({ message: "Server error creating user." });
        }
    });
    
    app.delete('/api/admin/delete-user/:username', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            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." });
            const userToDelete = await db.get("SELECT id FROM users WHERE username = ?", [username]);
            if (!userToDelete) return res.status(404).json({ message: "User not found." });
            await db.run('DELETE FROM users WHERE id = ?', [userToDelete.id]);
            res.json({ message: `User '${username}' deleted.` });
        } catch (err) { res.status(500).json({ message: "Server error deleting user." }); }
    });

    app.post('/api/admin/reset-password', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            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." });
            const hashedPassword = await bcrypt.hash(newPassword, 10);
            const result = await db.run('UPDATE users SET password = ? WHERE username = ?', [hashedPassword, username]);
            if (result.changes === 0) return res.status(404).json({ message: "User not found." });
            res.json({ message: `Password for '${username}' has been reset.` });
        } catch (err) { res.status(500).json({ message: "Server error resetting password." }); }
    });

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

    app.post('/api/admin/update-role', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            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." });
            const userToUpdate = await db.get("SELECT role FROM users WHERE username = ?", [username]);
            if (!userToUpdate) return res.status(404).json({ message: "User not found." });
            if (userToUpdate.role === 'admin' && newRole === 'employee') {
                const { adminCount } = await db.get("SELECT COUNT(*) as adminCount FROM users WHERE role = 'admin'");
                if (adminCount <= 1) return res.status(400).json({ message: "Cannot remove the last administrator." });
            }
            await db.run('UPDATE users SET role = ? WHERE username = ?', [newRole, username]);
            res.json({ message: `Role for '${username}' updated.` });
        } catch (err) { res.status(500).json({ message: "Server error updating role." }); }
    });

    app.post('/api/admin/add-punch', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const { userId, username, punchInTime, punchOutTime } = req.body;
            await 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."});
        } catch (err) { res.status(500).json({ message: "Server error adding punch." }); }
    });

    app.post('/api/admin/force-clock-out', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const { userId } = req.body;
            const result = await db.run(`UPDATE time_entries SET punch_out_time = ?, status = 'out' WHERE user_id = ? AND status = 'in'`, [new Date().toISOString(), userId]);
            if(result.changes === 0) return res.status(404).json({message: "No active punch-in found."});
            res.json({message: "User has been clocked out."});
        } catch (err) { res.status(500).json({ message: "Server error forcing clock out." }); }
    });

    app.get('/api/admin/logs', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const rows = await db.all(`SELECT * FROM time_entries ORDER BY punch_in_time DESC`);
            res.json(rows);
        } catch (err) { res.status(500).json({ message: "Server error fetching logs." }); }
    });

    app.delete('/api/admin/logs/:id', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            await db.run('DELETE FROM time_entries WHERE id = ?', [req.params.id]);
            res.json({ message: 'Entry deleted.' });
        } catch (err) { res.status(500).json({ message: "Server error deleting log." }); }
    });

    app.put('/api/admin/logs/:id', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const { punch_in_time, punch_out_time } = req.body;
            const status = punch_out_time ? 'out' : 'in';
            await 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.' });
        } catch (err) { res.status(500).json({ message: "Server error updating log." }); }
    });

    app.post('/api/admin/archive', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const rows = await db.all(`SELECT * FROM time_entries WHERE status = 'out'`);
            if (rows.length === 0) return res.json({ message: "No entries to archive." });
            const archiveTime = new Date().toISOString();
            await db.run('BEGIN TRANSACTION');
            const insert = await db.prepare('INSERT INTO archived_time_entries VALUES (?, ?, ?, ?, ?, ?, ?)');
            for (const r of rows) {
                await insert.run(r.id, r.user_id, r.username, r.punch_in_time, r.punch_out_time, r.status, archiveTime);
            }
            await insert.finalize();
            const idsToDelete = rows.map(r => r.id);
            await db.run(`DELETE FROM time_entries WHERE id IN (${idsToDelete.map(() => '?').join(',')})`, idsToDelete);
            await db.run('COMMIT');
            res.json({ message: `Archived ${rows.length} entries.` });
        } catch (err) {
            await db.run('ROLLBACK');
            res.status(500).json({ message: "Server error archiving entries." });
        }
    });

    app.get('/api/admin/archives', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const rows = await db.all(`SELECT * FROM archived_time_entries ORDER BY archived_at DESC, id DESC`);
            res.json(rows);
        } catch (err) { res.status(500).json({ message: "Server error fetching archives." }); }
    });

    app.get('/api/admin/time-off-requests/pending', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const rows = await db.all("SELECT * FROM time_off_requests WHERE status = 'pending' ORDER BY start_date ASC");
            res.json(rows);
        } catch (err) { res.status(500).json({ message: "Failed to fetch pending requests." }); }
    });

    app.get('/api/admin/time-off-requests/history', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            const rows = await db.all("SELECT * FROM time_off_requests WHERE status != 'pending' ORDER BY start_date DESC");
            res.json(rows);
        } catch (err) { res.status(500).json({ message: "Failed to fetch request history." }); }
    });

    app.post('/api/admin/update-time-off-status', authenticateToken, requireRole('admin'), async (req, res) => {
        try {
            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." });
            }
            const result = await db.run("UPDATE time_off_requests SET status = ? WHERE id = ?", [status, requestId]);
            if (result.changes === 0) return res.status(404).json({ message: "Request not found." });
            res.json({ message: `Request has been ${status}.` });
        } catch (err) { res.status(500).json({ message: "Failed to update status." }); }
    });
}

startServer();