const { Pool } = require('pg');
const bcrypt = require('bcryptjs');
const jwt = require('jsonwebtoken');

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  ssl: process.env.NODE_ENV === 'production' ? { rejectUnauthorized: false } : false,
});

export default async function handler(req, res) {
  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  // Check environment variables
  if (!process.env.DATABASE_URL) {
    return res.status(500).json({ 
      error: 'Database configuration missing',
      details: 'DATABASE_URL environment variable not set'
    });
  }

  if (!process.env.JWT_SECRET) {
    console.warn('JWT_SECRET not set, using fallback');
  }

  const client = await pool.connect();
  
  try {
    const { username, email, password, firstName, lastName } = req.body;

    // Validate input
    if (!username || !email || !password) {
      return res.status(400).json({ 
        error: 'Username, email, and password are required' 
      });
    }

    if (password.length < 6) {
      return res.status(400).json({ 
        error: 'Password must be at least 6 characters long' 
      });
    }

    // Check if users table exists
    const tableCheck = await client.query(`
      SELECT EXISTS (
        SELECT FROM information_schema.tables 
        WHERE table_schema = 'public' 
        AND table_name = 'users'
      );
    `);

    if (!tableCheck.rows[0].exists) {
      return res.status(500).json({ 
        error: 'Database not initialized',
        details: 'Please run the setup-auth endpoint first'
      });
    }

    // Check if user already exists
    const existingUser = await client.query(
      'SELECT id FROM users WHERE username = $1 OR email = $2',
      [username, email]
    );

    if (existingUser.rows.length > 0) {
      return res.status(409).json({ 
        error: 'Username or email already exists' 
      });
    }

    // Hash password
    const saltRounds = 12;
    const passwordHash = await bcrypt.hash(password, saltRounds);

    // Create user
    const userResult = await client.query(`
      INSERT INTO users (username, email, password_hash, first_name, last_name)
      VALUES ($1, $2, $3, $4, $5)
      RETURNING id, username, email, first_name, last_name, created_at
    `, [username, email, passwordHash, firstName || null, lastName || null]);

    const user = userResult.rows[0];

    // Assign default 'user' role
    const roleResult = await client.query(
      'SELECT id FROM roles WHERE name = $1',
      ['user']
    );

    if (roleResult.rows.length > 0) {
      await client.query(
        'INSERT INTO user_roles (user_id, role_id) VALUES ($1, $2)',
        [user.id, roleResult.rows[0].id]
      );
    }

    // Generate JWT token
    const jwtSecret = process.env.JWT_SECRET || 'fallback-secret-change-in-production';
    const token = jwt.sign(
      { 
        userId: user.id, 
        username: user.username,
        email: user.email
      },
      jwtSecret,
      { expiresIn: '7d' }
    );

    // Store session
    const tokenHash = await bcrypt.hash(token, 10);
    const expiresAt = new Date(Date.now() + 7 * 24 * 60 * 60 * 1000); // 7 days

    await client.query(`
      INSERT INTO user_sessions (user_id, token_hash, expires_at, user_agent, ip_address)
      VALUES ($1, $2, $3, $4, $5)
    `, [
      user.id,
      tokenHash,
      expiresAt,
      req.headers['user-agent'] || null,
      req.headers['x-forwarded-for'] || req.headers['x-real-ip'] || null
    ]);

    // Get user roles for response
    const userRoles = await client.query(`
      SELECT r.name, r.description
      FROM roles r
      JOIN user_roles ur ON r.id = ur.role_id
      WHERE ur.user_id = $1
    `, [user.id]);

    res.status(201).json({
      success: true,
      message: 'User registered successfully',
      user: {
        id: user.id,
        username: user.username,
        email: user.email,
        firstName: user.first_name,
        lastName: user.last_name,
        roles: userRoles.rows.map(r => r.name),
        createdAt: user.created_at
      },
      token
    });

  } catch (error) {
    console.error('Registration error:', error);
    res.status(500).json({ 
      error: 'Registration failed',
      details: process.env.NODE_ENV === 'development' ? error.message : undefined
    });
  } finally {
    client.release();
  }
}