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, 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;
  }

  const { id } = req.query;

  if (req.method === 'GET') {
    try {
      // Get collection details
      const collectionResult = await sql`
        SELECT 
          c.*,
          u.email as creator_email
        FROM collections c
        LEFT JOIN users u ON c.user_id = u.id
        WHERE c.id = ${id}
      `;

      if (collectionResult.rows.length === 0) {
        return res.status(404).json({ error: 'Collection not found' });
      }

      const collection = collectionResult.rows[0];

      // Get cards in the collection
      const cardsResult = await sql`
        SELECT 
          cc.*,
          cards.name,
          cards.set_name,
          cards.rarity,
          cards.type,
          cards.image_url,
          cards.market_price
        FROM collection_cards cc
        JOIN cards ON cc.card_id = cards.id
        WHERE cc.collection_id = ${id}
        ORDER BY cc.created_at ASC
      `;

      const cards = cardsResult.rows;

      // Calculate collection stats
      const totalCards = cards.reduce((sum, card) => sum + card.quantity, 0);
      const totalValue = cards.reduce((sum, card) => sum + (card.market_price * card.quantity), 0);

      res.status(200).json({
        collection: {
          ...collection,
          totalCards,
          totalValue
        },
        cards
      });

    } catch (error) {
      console.error('Error fetching collection:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'PUT') {
    // Update collection
    try {
      const { name, description, isPublic } = req.body;

      const result = await sql`
        UPDATE collections 
        SET 
          name = ${name},
          description = ${description},
          is_public = ${isPublic},
          updated_at = NOW()
        WHERE id = ${id}
        RETURNING *
      `;

      if (result.rows.length === 0) {
        return res.status(404).json({ error: 'Collection not found' });
      }

      res.status(200).json(result.rows[0]);

    } catch (error) {
      console.error('Error updating collection:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'DELETE') {
    // Delete collection
    try {
      // First delete all cards in the collection
      await sql`DELETE FROM collection_cards WHERE collection_id = ${id}`;

      // Then delete the collection
      const result = await sql`DELETE FROM collections WHERE id = ${id} RETURNING *`;

      if (result.rows.length === 0) {
        return res.status(404).json({ error: 'Collection not found' });
      }

      res.status(200).json({ message: 'Collection deleted successfully' });

    } catch (error) {
      console.error('Error deleting collection:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else {
    res.status(405).json({ error: 'Method not allowed' });
  }
}