backend/src/controllers/authController.js

const jwt = require('jsonwebtoken');
const User = require('../models/User');
const Joi = require('joi');

// Validation schemas
const registerSchema = Joi.object({
  username: Joi.string().alphanum().min(3).max(30).required(),
  email: Joi.string().email().required(),
  password: Joi.string().min(6).required()
});

const loginSchema = Joi.object({
  email: Joi.string().email().required(),
  password: Joi.string().min(6).required()
});

// Generate JWT token
const generateToken = (userId) => {
  return jwt.sign({ userId }, process.env.JWT_SECRET, {
    expiresIn: process.env.JWT_EXPIRE || '7d'
  });
};

// Register user
exports.register = async (req, res) => {
  try {
    // Validate input
    const { error } = registerSchema.validate(req.body);
    if (error) {
      return res.status(400).json({ error: error.details[0].message });
    }

    const { username, email, password } = req.body;

    // Check if user already exists
    const existingUser = await User.findOne({
      $or: [{ email }, { username }]
    });

    if (existingUser) {
      return res.status(400).json({ 
        error: existingUser.email === email ? 'Email already registered' : 'Username already taken'
      });
    }

    // Create new user
    const user = new User({ username, email, password });
    await user.save();

    // Generate token
    const token = generateToken(user._id);

    res.status(201).json({
      message: 'User registered successfully',
      token,
      user
    });
  } catch (error) {
    console.error('Registration error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};

// Login user
exports.login = async (req, res) => {
  try {
    // Validate input
    const { error } = loginSchema.validate(req.body);
    if (error) {
      return res.status(400).json({ error: error.details[0].message });
    }

    const { email, password } = req.body;

    // Find user and include password for comparison
    const user = await User.findOne({ email }).select('+password');
    if (!user) {
      return res.status(401).json({ error: 'Invalid credentials' });
    }

    // Check password
    const isPasswordValid = await user.comparePassword(password);
    if (!isPasswordValid) {
      return res.status(401).json({ error: 'Invalid credentials' });
    }

    // Update last seen
    user.lastSeen = new Date();
    await user.save();

    // Generate token
    const token = generateToken(user._id);

    res.json({
      message: 'Login successful',
      token,
      user
    });
  } catch (error) {
    console.error('Login error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};

// Get current user
exports.getMe = async (req, res) => {
  try {
    const user = await User.findById(req.userId);
    if (!user) {
      return res.status(404).json({ error: 'User not found' });
    }

    res.json({ user });
  } catch (error) {
    console.error('Get user error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};

// Update user profile
exports.updateProfile = async (req, res) => {
  try {
    const { username, avatar } = req.body;
    const updates = {};

    if (username) {
      // Check if username is already taken
      const existingUser = await User.findOne({ 
        username, 
        _id: { $ne: req.userId } 
      });
      if (existingUser) {
        return res.status(400).json({ error: 'Username already taken' });
      }
      updates.username = username;
    }

    if (avatar) updates.avatar = avatar;

    const user = await User.findByIdAndUpdate(
      req.userId,
      updates,
      { new: true, runValidators: true }
    );

    res.json({
      message: 'Profile updated successfully',
      user
    });
  } catch (error) {
    console.error('Update profile error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};