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;
  }

  if (req.method === 'GET') {
    try {
      // Get all collections with basic stats
      const result = await sql`
        SELECT 
          c.*,
          u.email as creator_email,
          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 OR c.user_id = 1
        GROUP BY c.id, u.email
        ORDER BY c.updated_at DESC
      `;

      const collections = result.rows.map(collection => ({
        id: collection.id,
        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,
        tags: collection.tags ? collection.tags.split(',') : [],
        creator: collection.creator_email
      }));

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

    } catch (error) {
      console.error('Error fetching collections:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'POST') {
    try {
      const { name, description, tcg = 'MTG', isPublic = false, tags = [] } = req.body;

      if (!name || !description) {
        return res.status(400).json({ error: 'Name and description are required' });
      }

      // For now, use user_id = 1 (should be from auth token in real implementation)
      const userId = 1;

      const result = await sql`
        INSERT INTO collections (name, description, tcg, is_public, tags, user_id)
        VALUES (${name}, ${description}, ${tcg}, ${isPublic}, ${tags.join(',')}, ${userId})
        RETURNING *
      `;

      res.status(201).json(result.rows[0]);

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