const express = require('express');
const router = express.Router();
const db = require('../db');
const crypto = require('crypto');
const { isAuthenticated, hasRole } = require('../middleware/authMiddleware');
const { generateToken } = require('../middleware/csrfMiddleware');

const cryptoUtil = require('../utils/cryptoUtil');

async function encrypt(text) {
    return await cryptoUtil.encrypt(text);
}

async function decrypt(text) {
    return await cryptoUtil.decrypt(text);
}

function hashPassword(password) {
    return crypto.createHash('sha256').update(password).digest('hex');
}

// --- Routes ---

// 1. Login
router.post('/login', async (req, res) => {
    const { id, password } = req.body;
    try {
        const hashedPassword = hashPassword(password);
        const [rows] = await db.query('SELECT * FROM users WHERE id = ? AND password = ?', [id, hashedPassword]);

        if (rows.length > 0) {
            const user = rows[0];
            // Update last_login
            await db.query('UPDATE users SET last_login = NOW() WHERE id = ?', [user.id]);

            // Remove sensitive data
            delete user.password;

            // Should we decrypt phone? Maybe not needed for session, but let's decrypt just in case UI needs it
            if (user.phone) user.phone = await decrypt(user.phone);

            // Save user to session
            req.session.user = user;

            // Generate CSRF Token
            const csrfToken = generateToken();
            req.session.csrfToken = csrfToken;

            // Explicitly save session before response (optional but safer for race conditions)
            req.session.save(err => {
                if (err) {
                    console.error('Session save error:', err);
                    return res.status(500).json({ success: false, message: 'Session error' });
                }
                res.json({ success: true, user, csrfToken });
            });
        } else {
            res.status(401).json({ success: false, message: 'Invalid credentials' });
        }
    } catch (err) {
        console.error('Login error:', err);
        res.status(500).json({ success: false, message: 'Server error' });
    }
});

// 1.5. Check Session (New)
router.get('/check', async (req, res) => {
    try {
        if (req.session.user) {
            // Ensure CSRF token exists, if not generate one (edge case)
            if (!req.session.csrfToken) {
                req.session.csrfToken = generateToken();
            }

            // Fetch session timeout from settings
            const [rows] = await db.query("SELECT setting_value FROM system_settings WHERE setting_key = 'session_timeout'");
            const timeoutMinutes = rows.length > 0 ? parseInt(rows[0].setting_value) : 60;

            res.json({
                isAuthenticated: true,
                user: req.session.user,
                csrfToken: req.session.csrfToken,
                sessionTimeout: timeoutMinutes * 60 * 1000 // Convert to ms
            });
        } else {
            res.json({ isAuthenticated: false });
        }
    } catch (err) {
        console.error('Check session error:', err);
        res.status(500).json({ success: false, message: 'Server error' });
    }
});

// 1.6. Logout (New)
router.post('/logout', (req, res) => {
    req.session.destroy(err => {
        if (err) {
            console.error('Logout error:', err);
            return res.status(500).json({ success: false, message: 'Logout failed' });
        }
        res.clearCookie('smartims_sid'); // matching key in index.js
        res.json({ success: true, message: 'Logged out' });
    });
});

// 1.7 Verify Supervisor (For sensitive settings)
router.post('/verify-supervisor', isAuthenticated, async (req, res) => {
    const { password } = req.body;
    if (!password) return res.status(400).json({ error: 'Password required' });

    try {
        if (req.session.user.role !== 'supervisor') {
            return res.status(403).json({ error: '권한이 없습니다. 최고관리자만 접근 가능합니다.' });
        }

        const hashedPassword = hashPassword(password);
        const [rows] = await db.query('SELECT 1 FROM users WHERE id = ? AND password = ?', [req.session.user.id, hashedPassword]);

        if (rows.length > 0) {
            res.json({ success: true, message: 'Verification successful' });
        } else {
            res.status(401).json({ success: false, message: '비밀번호가 일치하지 않습니다.' });
        }
    } catch (err) {
        console.error('Verify supervisor error:', err);
        res.status(500).json({ error: '인증 처리 중 오류가 발생했습니다.' });
    }
});

// 2. List Users (Admin Only)
router.get('/users', isAuthenticated, hasRole('admin'), async (req, res) => {
    try {
        const [rows] = await db.query('SELECT id, name, department, position, phone, role, last_login, created_at, updated_at FROM users ORDER BY created_at DESC');

        if (!rows || rows.length === 0) {
            return res.json([]);
        }

        // Use Promise.all for safe async decryption
        const users = await Promise.all(rows.map(async (u) => {
            const decryptedPhone = await decrypt(u.phone);
            return {
                ...u,
                phone: decryptedPhone
            };
        }));

        res.json(users);
    } catch (err) {
        console.error('Failed to list users:', err);
        res.status(500).json({ error: '데이터를 불러오는 중 오류가 발생했습니다.' });
    }
});

// 3. Create User
router.post('/users', isAuthenticated, hasRole('admin'), async (req, res) => {
    const { id, password, name, department, position, phone, role } = req.body;

    if (!id || !password || !name) {
        return res.status(400).json({ error: 'Missing required fields' });
    }

    try {
        // Check if ID exists
        const [existing] = await db.query('SELECT id FROM users WHERE id = ?', [id]);
        if (existing.length > 0) {
            return res.status(409).json({ error: 'User ID already exists' });
        }

        const hashedPassword = hashPassword(password);
        const encryptedPhone = await encrypt(phone);

        const sql = `
            INSERT INTO users (id, password, name, department, position, phone, role)
            VALUES (?, ?, ?, ?, ?, ?, ?)
        `;

        await db.query(sql, [id, hashedPassword, name, department, position, encryptedPhone, role || 'user']);

        res.status(201).json({ message: 'User created' });
    } catch (err) {
        console.error(err);
        res.status(500).json({ error: 'Database error' });
    }
});

// 4. Update User
router.put('/users/:id', isAuthenticated, hasRole('admin'), async (req, res) => {
    const { password, name, department, position, phone, role } = req.body;
    const userId = req.params.id;

    try {
        // Fetch current to keep old values if not provided? Frontend usually sends all.
        // We update everything provided.

        // Build query dynamically or just assume full update
        let updates = [];
        let params = [];

        if (password) {
            updates.push('password = ?');
            params.push(hashPassword(password));
        }
        if (name) {
            updates.push('name = ?');
            params.push(name);
        }
        if (department !== undefined) {
            updates.push('department = ?');
            params.push(department);
        }
        if (position !== undefined) {
            updates.push('position = ?');
            params.push(position);
        }
        if (phone !== undefined) {
            updates.push('phone = ?');
            params.push(await encrypt(phone));
        }
        if (role) {
            updates.push('role = ?');
            params.push(role);
        }

        if (updates.length === 0) return res.json({ message: 'No changes' });

        const sql = `UPDATE users SET ${updates.join(', ')} WHERE id = ?`;
        params.push(userId);

        await db.query(sql, params);
        res.json({ message: 'User updated' });

    } catch (err) {
        console.error(err);
        res.status(500).json({ error: 'Database error' });
    }
});

// 5. Delete User
router.delete('/users/:id', isAuthenticated, hasRole('admin'), async (req, res) => {
    try {
        // Prevent deleting last admin? Optional.
        // Prevent deleting self?

        await db.query('DELETE FROM users WHERE id = ?', [req.params.id]);
        res.json({ message: 'User deleted' });
    } catch (err) {
        console.error(err);
        res.status(500).json({ error: 'Database error' });
    }
});

module.exports = router;