/**
 * Users routes module.
 * 
 * Uses better-sqlite3 synchronous API (Punkt 6).
 * Proper authorization checks (Punkt 4).
 */
const express = require('express');
const bcrypt = require('bcryptjs');
const db = require('../db');
const { auditLog } = require('../auditLog');
const { authMiddleware, adminMiddleware, invalidateUserSessions } = require('../middleware/auth');
const { validate, validateQuery, createUserSchema, updateUserSchema, paginationSchema } = require('../middleware/validation');

const router = express.Router();

// Apply auth to all user routes
router.use(authMiddleware);

// List users (admin only) - with server-side pagination (Punkt 16: bounded limits)
router.get('/', adminMiddleware, validateQuery(paginationSchema), async (req, res) => {
  const { page, limit } = req.validatedQuery;
  const offset = (page - 1) * limit;
  const search = req.query.search;

  let whereClause = '';
  const params = [];
  if (search) {
    whereClause = ' WHERE LOWER(email) LIKE LOWER(?) OR LOWER(name) LIKE LOWER(?) OR LOWER(role) LIKE LOWER(?) OR LOWER(COALESCE(username, \'\')) LIKE LOWER(?)';
    // P10: Escape LIKE wildcards in search pattern to prevent unintended matching
    const escapedSearch = String(search).replace(/[%_\\]/g, '\\$&');
    const searchPattern = `%${escapedSearch}%`;
    params.push(searchPattern, searchPattern, searchPattern, searchPattern);
  } else {
    whereClause = ' WHERE status = \'aktiv\'';
  }

  const countSql = 'SELECT COUNT(*) as total FROM users' + whereClause;
  const dataSql = 'SELECT id, email, name, role, status, source, username FROM users' + whereClause + ' ORDER BY id ASC LIMIT ? OFFSET ?';

  const countRow = await db.prepare(countSql).get(...params);
  const rows = await db.prepare(dataSql).all(...params, limit, offset);
  const total = countRow?.total || 0;
  res.json({ users: rows || [], total, page, limit, totalPages: Math.ceil(total / limit) });
});

// Create user (admin only)
router.post('/', adminMiddleware, validate(createUserSchema), async (req, res) => {
  const { email, password, name, role, status } = req.validatedBody;
  try {
    const hash = bcrypt.hashSync(password, 12); // Punkt 10: 12 rounds per OWASP
    const info = await db.prepare('INSERT INTO users (email, password, name, role, status, source) VALUES (?, ?, ?, ?, ?, \'local\')').run(email, hash, name, role, status);
    auditLog(req.user?.id, 'create_user', 'user', info.lastInsertRowid, `Created user: ${email}`, req);
    res.status(201).json({ id: info.lastInsertRowid, email, name, role, status, source: 'local' });
  } catch (err) {
    if (err.message && err.message.includes('UNIQUE constraint')) {
      return res.status(409).json({ error: 'E-Mail bereits vergeben.' });
    }
    res.status(500).json({ error: 'Interner Serverfehler.' });
  }
});

// Update user
router.put('/:id', validate(updateUserSchema), async (req, res) => {
  const userId = parseInt(req.params.id);

  // VULN-04: Authorization check - only admin or self (with restrictions)
  const isSelf = req.user.id === userId;
  const isAdmin = req.user.role === 'admin';
  if (!isAdmin && !isSelf) {
    return res.status(403).json({ error: 'Keine Berechtigung, diesen Nutzer zu bearbeiten.' });
  }

  // K1: Strip role/status FIRST for non-admins (BEFORE reading values) to prevent
  // privilege escalation via mass assignment. Earlier code destructured first
  // and deleted afterwards, which left the local copies intact.
  if (!isAdmin) {
    delete req.validatedBody.role;
    delete req.validatedBody.status;
  }

  // Now safe to read — non-admins can never see role/status here
  const { email, name, password, role, status, current_password } = req.validatedBody;

  // P7: Non-admins changing their own password must verify the current password
  if (!isAdmin && isSelf && password && password.trim()) {
    if (!current_password) {
      return res.status(400).json({ error: 'Aktuelles Passwort ist erforderlich, um das Passwort zu ändern.' });
    }
    const userRow = await db.prepare('SELECT password FROM users WHERE id = ?').get(userId);
    if (!userRow) return res.status(404).json({ error: 'Nutzer nicht gefunden.' });
    let currentMatch = false;
    if (userRow.password.startsWith('$2a$') || userRow.password.startsWith('$2b$')) {
      currentMatch = bcrypt.compareSync(current_password, userRow.password);
    } else {
      currentMatch = userRow.password === current_password;
    }
    if (!currentMatch) {
      return res.status(403).json({ error: 'Aktuelles Passwort ist falsch.' });
    }
  }

  const user = await db.prepare('SELECT * FROM users WHERE id = ?').get(userId);
  if (!user) return res.status(404).json({ error: 'Nutzer nicht gefunden.' });

  // AD users: only role and status can be changed
  if (user.source === 'ad') {
    const finalRole = role || user.role;
    const finalStatus = status || user.status;
    if (role && !['admin', 'user'].includes(role)) {
      return res.status(400).json({ error: 'Rolle muss "admin" oder "user" sein.' });
    }
    if (status && !['aktiv', 'inaktiv'].includes(status)) {
      return res.status(400).json({ error: 'Status muss "aktiv" oder "inaktiv" sein.' });
    }
    await db.prepare('UPDATE users SET role = ?, status = ? WHERE id = ?').run(finalRole, finalStatus, userId);
    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated AD user role/status`, req);
    return res.json({ id: userId, email: user.email, name: user.name, role: finalRole, status: finalStatus, source: user.source, username: user.username });
  }

  // Local users: full edit
  if (!email) {
    return res.status(400).json({ error: 'E-Mail ist erforderlich.' });
  }
  if (role && !['admin', 'user'].includes(role)) {
    return res.status(400).json({ error: 'Rolle muss "admin" oder "user" sein.' });
  }
  if (status && !['aktiv', 'inaktiv'].includes(status)) {
    return res.status(400).json({ error: 'Status muss "aktiv" oder "inaktiv" sein.' });
  }

  const finalName = name !== undefined ? name : (user.name || '');
  const finalRole = role || user.role;
  const finalStatus = status || user.status;

  if (password && password.trim()) {
    const hash = bcrypt.hashSync(password, 12); // Punkt 10: 12 rounds per OWASP
    try {
      await db.prepare('UPDATE users SET email = ?, name = ?, password = ?, role = ?, status = ? WHERE id = ?').run(email, finalName, hash, finalRole, finalStatus, userId);
    } catch (err) {
      if (err.message && err.message.includes('UNIQUE constraint')) {
        return res.status(409).json({ error: 'E-Mail bereits vergeben.' });
      }
      throw err;
    }
    // VULN-13: Invalidate all sessions for this user after password change
    await invalidateUserSessions(userId);
    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user with new password (sessions invalidated)`, req);
    res.json({ id: userId, email, name: finalName, role: finalRole, status: finalStatus, source: user.source, username: user.username });
  } else {
    try {
      await db.prepare('UPDATE users SET email = ?, name = ?, role = ?, status = ? WHERE id = ?').run(email, finalName, finalRole, finalStatus, userId);
    } catch (err) {
      if (err.message && err.message.includes('UNIQUE constraint')) {
        return res.status(409).json({ error: 'E-Mail bereits vergeben.' });
      }
      throw err;
    }
    auditLog(req.user?.id, 'update_user', 'user', userId, `Updated local user`, req);
    res.json({ id: userId, email, name: finalName, role: finalRole, status: finalStatus, source: user.source, username: user.username });
  }
});

// Delete user (admin only)
router.delete('/:id', adminMiddleware, async (req, res) => {
  const userId = parseInt(req.params.id);
  const user = await db.prepare('SELECT * FROM users WHERE id = ?').get(userId);
  if (!user) return res.status(404).json({ error: 'Nutzer nicht gefunden.' });
  if (user.source === 'ad') {
    return res.status(403).json({ error: 'AD-Nutzer koennen nicht geloescht werden. Bitte im Active Directory entfernen.' });
  }
  const info = await db.prepare('DELETE FROM users WHERE id = ?').run(userId);
  if (info.changes === 0) return res.status(404).json({ error: 'Nutzer nicht gefunden.' });
  auditLog(req.user?.id, 'delete_user', 'user', userId, `Deleted user: ${user.email}`, req);
  res.json({ message: 'Nutzer geloescht.' });
});

module.exports = router;