import { sql } from '@vercel/postgres';

export default async function handler(req, res) {
  // Set CORS headers
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, 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 !== 'GET') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  try {
    const { limit = 6 } = req.query;

    // Get featured public collections for landing page (no auth required)
    const result = await sql`
      SELECT DISTINCT
        c.*,
        u.email as creator_email,
        u.username as creator_username,
        COUNT(cc.card_id) as card_count,
        COALESCE(SUM(cards.market_price * cc.quantity), 0) as total_value
      FROM collections c
      LEFT JOIN users u ON c.user_id = u.id
      LEFT JOIN collection_cards cc ON c.id = cc.collection_id
      LEFT JOIN cards ON cc.card_id = cards.id
      WHERE c.is_public = true 
        AND (c.is_system_collection IS NULL OR c.is_system_collection = false)
      GROUP BY c.id, u.email, u.username
      ORDER BY c.updated_at DESC, c.created_at DESC
      LIMIT ${parseInt(limit)}
    `;

    const collections = result.rows.map(collection => ({
      id: collection.id,
      slug: collection.slug,
      name: collection.name,
      description: collection.description,
      tcg: collection.tcg || 'MTG',
      cardCount: parseInt(collection.card_count) || 0,
      value: parseFloat(collection.total_value) || 0,
      lastViewed: collection.updated_at,
      createdAt: collection.created_at,
      isPublic: collection.is_public || false,
      tags: collection.tags ? collection.tags.split(',') : [],
      creator: collection.creator_username || collection.creator_email,
      image: collection.image
    }));

    res.status(200).json(collections);

  } catch (error) {
    console.error('Error fetching public collections:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
}