const jwt = require('jsonwebtoken');
const bcrypt = require('bcrypt');
const crypto = require('crypto');
const mongoose = require('mongoose');
const { asyncController } = require('../utils/asyncController');
const { recordAuditTrail } = require('../services/auditTrailService');
const AdminUser = require('../models/AdminUser');
const { ensureAdminInitialized } = require('../services/adminAuthService');
const { isValidPersonName } = require('../validation/commonValidation');
const { env } = require('../configs/env');

const JWT_SECRET = env.jwtSecret;
const BCRYPT_SALT_ROUNDS = 12;

const USERNAME_PATTERN = /^[a-z0-9._-]{3,30}$/;

const buildAuthUser = (admin) => ({
  id: String(admin._id),
  username: admin.username,
  name: admin.name,
  role: 'admin',
  isActive: admin.isActive !== false,
});

const generateToken = (user, sessionToken) => {
  if (!JWT_SECRET) {
    throw new Error('JWT_SECRET is not configured');
  }

  const payload = { id: user.id };
  if (sessionToken) payload.st = sessionToken;

  return jwt.sign(payload, JWT_SECRET, {
    expiresIn: env.jwtExpire,
  });
};

const normalizeUsername = (value) => String(value || '').trim().toLowerCase();

const buildManagedUser = (admin) => ({
  id: String(admin._id),
  username: admin.username,
  name: admin.name,
  role: admin.role || 'admin',
  isActive: admin.isActive !== false,
  createdAt: admin.createdAt,
  updatedAt: admin.updatedAt,
});

const login = asyncController(async (req, res) => {
  await ensureAdminInitialized();

  const identifier = String(req.body?.email || req.body?.username || '').trim();
  const password = String(req.body?.password || '');

  if (!identifier || !password) {
    return res.status(400).json({ message: 'Username and password are required' });
  }

  const admin = await AdminUser.findOne({
    username: identifier.toLowerCase(),
  }).select('+passwordHash');

  if (!admin) {
    return res.status(401).json({ message: 'Incorrect username or password.' });
  }

  if (admin.isActive === false) {
    return res.status(403).json({ message: 'This account is inactive' });
  }

  const isValidPass = await bcrypt.compare(password, admin.passwordHash || '');
  if (!isValidPass) {
    return res.status(401).json({ message: 'Incorrect username or password.' });
  }

  const sessionToken = crypto.randomBytes(32).toString('hex');
  await AdminUser.findByIdAndUpdate(admin._id, { sessionToken });

  const user = buildAuthUser(admin);
  const token = generateToken(user, sessionToken);

  void recordAuditTrail({
    req,
    actor: { id: user.id, name: user.name },
    action: 'login',
    moduleName: 'auth',
    summary: 'Admin logged in',
    endpoint: 'POST /api/auth/login',
    method: 'POST',
    statusCode: 200,
  });

  res.cookie('token', token, {
    httpOnly: true,
    secure: env.isProduction,
    sameSite: 'strict',
  });

  return res.json({ token, user });
});

const register = async (req, res) => {
  return res.status(501).json({ message: 'Registration is disabled for this project' });
};

const getMe = (req, res) => {
  return res.json(req.user || null);
};

const updateProfile = asyncController(async (req, res) => {
  await ensureAdminInitialized();

  const { currentPassword, newName, newUsername, newPassword } = req.body || {};

  if (!currentPassword) {
    return res.status(400).json({ message: 'Current password is required' });
  }

  const adminId = req.user?.id || req.user?._id;
  if (!adminId) {
    return res.status(401).json({ message: 'Not authorized, invalid token' });
  }

  const admin = await AdminUser.findById(adminId).select('+passwordHash');
  if (!admin) {
    return res.status(404).json({ message: 'Account not found' });
  }

  const isCurrentPasswordValid = await bcrypt.compare(currentPassword, admin.passwordHash || '');
  if (!isCurrentPasswordValid) {
    return res.status(401).json({ message: 'Current password is incorrect' });
  }

  if (newUsername !== undefined) {
    const normalizedUsername = normalizeUsername(newUsername);

    if (!USERNAME_PATTERN.test(normalizedUsername)) {
      return res.status(400).json({
        message: 'Username must be 3-30 characters using letters, numbers, dots, dashes, or underscores',
      });
    }

    if (normalizedUsername !== admin.username) {
      const usernameInUse = await AdminUser.findOne({
        username: normalizedUsername,
        _id: { $ne: admin._id },
      })
        .select('_id')
        .lean();

      if (usernameInUse) {
        return res.status(409).json({ message: 'Username is already taken' });
      }

      admin.username = normalizedUsername;
    }
  }

  if (newName && newName.trim()) {
    if (!isValidPersonName(newName)) {
      return res.status(400).json({ message: 'Display name must contain letters only (no numbers)' });
    }
    admin.name = newName.trim();
  }

  if (newPassword) {
    if (newPassword.length < env.adminPasswordMinLength) {
      return res.status(400).json({ message: `New password must be at least ${env.adminPasswordMinLength} characters` });
    }

    admin.passwordHash = await bcrypt.hash(newPassword, BCRYPT_SALT_ROUNDS);
  }

  await admin.save();

  const updatedAdmin = await AdminUser.findById(admin._id).select('+sessionToken').lean();
  const user = buildAuthUser(admin);
  const token = generateToken(user, updatedAdmin?.sessionToken || undefined);

  res.cookie('token', token, {
    httpOnly: true,
    secure: env.isProduction,
    sameSite: 'strict',
  });

  return res.json({ user, message: 'Profile updated successfully' });
});

const listUsers = asyncController(async (_req, res) => {
  await ensureAdminInitialized();
  const users = await AdminUser.find({})
    .sort({ createdAt: 1 })
    .select('_id username name role isActive createdAt updatedAt')
    .lean();

  return res.json((users || []).map(buildManagedUser));
});

const createUser = asyncController(async (req, res) => {
  await ensureAdminInitialized();

  const username = normalizeUsername(req.body?.username);
  const name = String(req.body?.name || '').trim();
  const password = String(req.body?.password || '');
  const isActive = req.body?.isActive !== false;

  if (!USERNAME_PATTERN.test(username)) {
    return res.status(400).json({
      message: 'Username must be 3-30 characters using letters, numbers, dots, dashes, or underscores',
    });
  }

  if (!name) {
    return res.status(400).json({ message: 'Display name is required' });
  }

  if (!isValidPersonName(name)) {
    return res.status(400).json({ message: 'Display name must contain letters only (no numbers)' });
  }

  if (password.length < env.adminPasswordMinLength) {
    return res.status(400).json({ message: `Password must be at least ${env.adminPasswordMinLength} characters` });
  }

  const usernameInUse = await AdminUser.findOne({ username }).select('_id').lean();
  if (usernameInUse) {
    return res.status(409).json({ message: 'Username is already taken' });
  }

  const passwordHash = await bcrypt.hash(password, BCRYPT_SALT_ROUNDS);
  const admin = await AdminUser.create({
    username,
    name,
    passwordHash,
    role: 'admin',
    isActive,
  });

  return res.status(201).json(buildManagedUser(admin));
});

const updateUser = asyncController(async (req, res) => {
  await ensureAdminInitialized();

  const targetId = String(req.params?.id || '').trim();
  if (!targetId) {
    return res.status(400).json({ message: 'User id is required' });
  }

  const admin = await AdminUser.findById(targetId).select('+passwordHash');
  if (!admin) {
    return res.status(404).json({ message: 'User not found' });
  }

  const requesterId = String(req.user?.id || req.user?._id || '');

  const hasUsername = Object.prototype.hasOwnProperty.call(req.body || {}, 'username');
  const hasName = Object.prototype.hasOwnProperty.call(req.body || {}, 'name');
  const hasPassword = Object.prototype.hasOwnProperty.call(req.body || {}, 'password');
  const hasIsActive = Object.prototype.hasOwnProperty.call(req.body || {}, 'isActive');

  if (hasUsername) {
    const username = normalizeUsername(req.body?.username);
    if (!USERNAME_PATTERN.test(username)) {
      return res.status(400).json({
        message: 'Username must be 3-30 characters using letters, numbers, dots, dashes, or underscores',
      });
    }

    if (username !== admin.username) {
      const usernameInUse = await AdminUser.findOne({ username, _id: { $ne: admin._id } }).select('_id').lean();
      if (usernameInUse) {
        return res.status(409).json({ message: 'Username is already taken' });
      }
      admin.username = username;
    }
  }

  if (hasName) {
    const name = String(req.body?.name || '').trim();
    if (!name) {
      return res.status(400).json({ message: 'Display name is required' });
    }
    if (!isValidPersonName(name)) {
      return res.status(400).json({ message: 'Display name must contain letters only (no numbers)' });
    }
    admin.name = name;
  }

  if (hasPassword) {
    const password = String(req.body?.password || '');
    if (password && password.length < env.adminPasswordMinLength) {
      return res.status(400).json({ message: `Password must be at least ${env.adminPasswordMinLength} characters` });
    }
    if (password) {
      admin.passwordHash = await bcrypt.hash(password, BCRYPT_SALT_ROUNDS);
    }
  }

  if (hasIsActive) {
    const nextIsActive = req.body?.isActive !== false;

    if (requesterId && requesterId === String(admin._id) && !nextIsActive) {
      return res.status(400).json({ message: 'You cannot deactivate your own account' });
    }

    if (!nextIsActive && admin.isActive !== false) {
      const session = await mongoose.startSession();
      let saved;
      try {
        await session.withTransaction(async () => {
          const activeCount = await AdminUser.countDocuments(
            { isActive: { $ne: false } },
            { session }
          );
          if (activeCount <= 1) {
            throw Object.assign(new Error('At least one active admin account is required'), { statusCode: 400 });
          }
          admin.isActive = false;
          saved = await admin.save({ session });
        });
      } catch (txErr) {
        if (txErr.statusCode === 400) {
          return res.status(400).json({ message: txErr.message });
        }
        throw txErr;
      } finally {
        await session.endSession();
      }
      return res.json(buildManagedUser(saved || admin));
    }

    admin.isActive = nextIsActive;
  }

  await admin.save();
  return res.json(buildManagedUser(admin));
});

const deleteUser = asyncController(async (req, res) => {
  await ensureAdminInitialized();

  const targetId = String(req.params?.id || '').trim();
  if (!targetId) {
    return res.status(400).json({ message: 'User id is required' });
  }

  const requesterId = String(req.user?.id || req.user?._id || '');
  if (requesterId && requesterId === targetId) {
    return res.status(400).json({ message: 'You cannot delete your own account' });
  }

  const targetUser = await AdminUser.findById(targetId).select('_id isActive').lean();
  if (!targetUser) {
    return res.status(404).json({ message: 'User not found' });
  }

  if (targetUser.isActive !== false) {
    const session = await mongoose.startSession();
    try {
      await session.withTransaction(async () => {
        const activeCount = await AdminUser.countDocuments(
          { isActive: { $ne: false } },
          { session }
        );
        if (activeCount <= 1) {
          throw Object.assign(new Error('At least one active admin account is required'), { statusCode: 400 });
        }
        const deleted = await AdminUser.findByIdAndDelete(targetId, { session }).select('_id').lean();
        if (!deleted) {
          throw Object.assign(new Error('User not found'), { statusCode: 404 });
        }
      });
    } catch (txErr) {
      if (txErr.statusCode === 400) return res.status(400).json({ message: txErr.message });
      if (txErr.statusCode === 404) return res.status(404).json({ message: txErr.message });
      throw txErr;
    } finally {
      await session.endSession();
    }
    return res.status(204).send();
  }

  const deleted = await AdminUser.findByIdAndDelete(targetId).select('_id').lean();
  if (!deleted) {
    return res.status(404).json({ message: 'User not found' });
  }

  return res.status(204).send();
});

const logout = asyncController(async (req, res) => {
  const token = req.cookies?.token;
  let actorId = 'unknown';
  let actorName = 'Administrator';
  if (token) {
    try {
      const decoded = jwt.decode(token);
      if (decoded?.id) {
        actorId = String(decoded.id);
        const admin = await AdminUser.findById(actorId).select('name').lean();
        if (admin?.name) actorName = admin.name;
      }
    } catch (_) {}
  }

  if (actorId !== 'unknown') {
    try {
      await AdminUser.findByIdAndUpdate(actorId, { sessionToken: null });
    } catch (_) {}
  }

  void recordAuditTrail({
    req,
    actor: { id: actorId, name: actorName },
    action: 'logout',
    moduleName: 'auth',
    summary: 'Admin logged out',
    endpoint: 'POST /api/auth/logout',
    method: 'POST',
    statusCode: 200,
  });

  res.clearCookie('token', { httpOnly: true, secure: env.isProduction, sameSite: 'strict' });
  return res.json({ message: 'Logged out' });
});

module.exports = {
  login,
  logout,
  register,
  getMe,
  updateProfile,
  listUsers,
  createUser,
  updateUser,
  deleteUser,
};