import bcrypt from 'bcryptjs';
import { sql } from '@vercel/postgres';
import { generateUniqueSlug } from '../../../lib/slug-utils.js';
import { generateToken } from '../auth-utils.js';

export default async function handler(req, res) {
  // Set CORS headers
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');

  // Handle preflight requests
  if (req.method === 'OPTIONS') {
    res.status(200).end();
    return;
  }

  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  try {
    const { email, password, firstName, lastName, username, profileImage } = req.body;

    // Validate required fields
    if (!email || !password || !firstName || !lastName || !username) {
      return res.status(400).json({ error: 'All fields are required' });
    }

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

    // Validate username
    if (username.length < 3) {
      return res.status(400).json({ error: 'Username must be at least 3 characters' });
    }

    if (!/^[a-zA-Z0-9_]+$/.test(username)) {
      return res.status(400).json({ error: 'Username can only contain letters, numbers, and underscores' });
    }

    // Check if user already exists (email or username)
    const existingUser = await sql`
      SELECT id FROM users WHERE email = ${email} OR username = ${username}
    `;

    if (existingUser.rows.length > 0) {
      // Check which field conflicts
      const conflictUser = await sql`
        SELECT email, username FROM users WHERE email = ${email} OR username = ${username}
      `;
      
      const conflict = conflictUser.rows[0];
      if (conflict.email === email) {
        return res.status(409).json({ error: 'Email already exists' });
      } else {
        return res.status(409).json({ error: 'Username already taken' });
      }
    }

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

    // Create user with all fields
    const result = await sql`
      INSERT INTO users (
        email, 
        password, 
        first_name, 
        last_name, 
        username, 
        profile_image_url,
        role
      ) 
      VALUES (
        ${email}, 
        ${hashedPassword}, 
        ${firstName}, 
        ${lastName}, 
        ${username}, 
        ${profileImage || null},
        ${'user'}
      )
      RETURNING id, email, first_name, last_name, username, profile_image_url, role, created_at
    `;

    const user = result.rows[0];

    // Create the automatic "All My Cards" collection for the new user
    try {
      // Get existing slugs to ensure uniqueness
      const existingSlugsData = await sql`SELECT slug FROM collections WHERE slug IS NOT NULL`;
      const existingSlugs = (existingSlugsData.rows || []).map(row => row.slug);
      
      // Generate unique slug for "All My Cards"
      const uniqueSlug = await generateUniqueSlug("All My Cards", existingSlugs);
      
      // Create the special collection
      const collectionResult = await sql`
        INSERT INTO collections (
          name, 
          description, 
          tcg, 
          is_public, 
          user_id, 
          slug, 
          is_system_collection,
          created_at, 
          updated_at
        )
        VALUES (
          'All My Cards',
          'Automatically contains all cards you mark as owned. This collection cannot be deleted or made public.',
          'All',
          false,
          ${user.id},
          ${uniqueSlug},
          true,
          CURRENT_TIMESTAMP,
          CURRENT_TIMESTAMP
        )
        RETURNING id
      `;

      const collection = collectionResult.rows[0];

      // Create owner permission for the collection
      await sql`
        INSERT INTO collection_permissions (collection_id, user_id, role, status, created_at)
        VALUES (${collection.id}, ${user.id}, 'owner', 'active', CURRENT_TIMESTAMP)
      `;

      console.log(`✅ Created "All My Cards" collection for user ${user.email} (ID: ${collection.id})`);
    } catch (collectionError) {
      console.error('Error creating "All My Cards" collection:', collectionError);
      // Don't fail the registration if collection creation fails
    }

    // Generate JWT token
    const token = generateToken({ id: user.id, email: user.email, role: user.role });

    // Return user data without password
    const userResponse = {
      id: user.id,
      email: user.email,
      firstName: user.first_name,
      lastName: user.last_name,
      username: user.username,
      profileImage: user.profile_image_url,
      role: user.role,
      createdAt: user.created_at
    };

    res.status(201).json({
      success: true,
      user: userResponse,
      token
    });

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