const express = require('express');
const bcrypt = require('bcryptjs');
const { randomUUID } = require('crypto');
const rateLimit = require('express-rate-limit');
const db = require('../db');
const asyncHandler = require('../middleware/asyncHandler');
const { requireLogin } = require('../middleware/auth');

const router = express.Router();

const loginLimiter = rateLimit({
    windowMs: 15 * 60 * 1000,
    max: 20,
    message: { error: 'Zu viele Anmeldeversuche, bitte später erneut versuchen.' },
    standardHeaders: true,
    legacyHeaders: false,
});

// Whether the system needs initial setup (no users yet).
router.get('/setup-required', asyncHandler(async (req, res) => {
    const row = await db.get('SELECT COUNT(*) AS n FROM users');
    res.json({ setupRequired: row.n === 0 });
}));

// One-shot setup: create the first admin user. Only works when users table is empty.
router.post('/setup', asyncHandler(async (req, res) => {
    const existing = await db.get('SELECT COUNT(*) AS n FROM users');
    if (existing.n > 0) {
        return res.status(403).json({ error: 'Setup bereits abgeschlossen' });
    }
    const { username, password, displayName } = req.body || {};
    if (!username || !password) {
        return res.status(400).json({ error: 'Username und Passwort erforderlich' });
    }
    if (password.length < 8) {
        return res.status(400).json({ error: 'Passwort muss mindestens 8 Zeichen lang sein' });
    }
    const hash = await bcrypt.hash(password, 10);
    const uuid = randomUUID();
    const result = await db.run(
        'INSERT INTO users (uuid, username, password_hash, display_name, is_admin) VALUES (?, ?, ?, ?, 1)',
        [uuid, username, hash, displayName || username]
    );
    req.session.userId = result.lastID;
    req.session.username = username;
    req.session.isAdmin = true;
    res.json({ id: result.lastID, username, isAdmin: true });
}));

router.post('/login', loginLimiter, asyncHandler(async (req, res) => {
    const { username, password } = req.body || {};
    if (!username || !password) {
        return res.status(400).json({ error: 'Username und Passwort erforderlich' });
    }
    const user = await db.get(
        'SELECT id, username, password_hash, display_name, is_admin FROM users WHERE username = ?',
        [username]
    );
    if (!user) {
        return res.status(401).json({ error: 'Ungültige Anmeldedaten' });
    }
    const ok = await bcrypt.compare(password, user.password_hash);
    if (!ok) {
        return res.status(401).json({ error: 'Ungültige Anmeldedaten' });
    }
    req.session.regenerate((err) => {
        if (err) return res.status(500).json({ error: 'Session-Fehler' });
        req.session.userId = user.id;
        req.session.username = user.username;
        req.session.isAdmin = !!user.is_admin;
        res.json({
            id: user.id,
            username: user.username,
            displayName: user.display_name,
            isAdmin: !!user.is_admin,
        });
    });
}));

router.post('/logout', (req, res) => {
    if (!req.session) return res.json({ ok: true });
    req.session.destroy(() => {
        res.clearCookie('connect.sid');
        res.json({ ok: true });
    });
});

router.get('/me', requireLogin, asyncHandler(async (req, res) => {
    const user = await db.get(
        'SELECT id, username, display_name, is_admin FROM users WHERE id = ?',
        [req.session.userId]
    );
    if (!user) {
        req.session.destroy(() => {});
        return res.status(401).json({ error: 'Benutzer nicht gefunden' });
    }
    res.json({
        id: user.id,
        username: user.username,
        displayName: user.display_name,
        isAdmin: !!user.is_admin,
    });
}));

router.post('/change-password', requireLogin, asyncHandler(async (req, res) => {
    const { oldPassword, newPassword } = req.body || {};
    if (!oldPassword || !newPassword) {
        return res.status(400).json({ error: 'Altes und neues Passwort erforderlich' });
    }
    if (newPassword.length < 8) {
        return res.status(400).json({ error: 'Neues Passwort muss mindestens 8 Zeichen lang sein' });
    }
    const user = await db.get('SELECT password_hash FROM users WHERE id = ?', [req.session.userId]);
    if (!user) return res.status(401).json({ error: 'Benutzer nicht gefunden' });
    const ok = await bcrypt.compare(oldPassword, user.password_hash);
    if (!ok) return res.status(401).json({ error: 'Altes Passwort falsch' });
    const newHash = await bcrypt.hash(newPassword, 10);
    await db.run('UPDATE users SET password_hash = ? WHERE id = ?', [newHash, req.session.userId]);
    res.json({ ok: true });
}));

module.exports = router;