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

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

// Middleware to verify user authentication
function verifyAuth(req) {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Bearer ')) {
    throw new Error('No token provided');
  }

  const token = authHeader.substring(7);
  const jwtSecret = process.env.JWT_SECRET || 'fallback-secret-change-in-production';
  
  try {
    const decoded = jwt.verify(token, jwtSecret);
    return decoded;
  } catch (error) {
    throw new Error('Invalid token');
  }
}

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

  const client = await pool.connect();
  
  try {
    // Verify authentication
    const user = verifyAuth(req);

    const { 
      collectionId, 
      cardId, 
      quantity = 1, 
      condition = 'near-mint',
      notes = null,
      purchasePrice = null 
    } = req.body;

    // Validate required fields
    if (!collectionId || !cardId) {
      return res.status(400).json({ 
        error: 'Collection ID and Card ID are required' 
      });
    }

    // Verify collection ownership
    const collectionCheck = await client.query(
      'SELECT id, name FROM user_collections WHERE id = $1 AND user_id = $2',
      [collectionId, user.userId]
    );

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

    // Verify card exists
    const cardCheck = await client.query(
      'SELECT id, name, game, rarity, current_price FROM cards WHERE id = $1',
      [cardId]
    );

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

    const card = cardCheck.rows[0];
    const collection = collectionCheck.rows[0];

    // Check if card already exists in collection with same condition
    const existingCard = await client.query(`
      SELECT id, quantity 
      FROM collection_cards 
      WHERE collection_id = $1 AND card_id = $2 AND condition = $3
    `, [collectionId, cardId, condition]);

    let result;

    if (existingCard.rows.length > 0) {
      // Update existing entry - increase quantity
      const newQuantity = existingCard.rows[0].quantity + quantity;
      
      await client.query(`
        UPDATE collection_cards 
        SET quantity = $1, updated_at = CURRENT_TIMESTAMP
        WHERE id = $2
      `, [newQuantity, existingCard.rows[0].id]);

      result = {
        action: 'updated',
        previousQuantity: existingCard.rows[0].quantity,
        newQuantity: newQuantity
      };
    } else {
      // Create new collection card entry
      const insertResult = await client.query(`
        INSERT INTO collection_cards (
          collection_id, card_id, quantity, condition, notes, purchase_price
        ) VALUES ($1, $2, $3, $4, $5, $6)
        RETURNING id, added_at
      `, [collectionId, cardId, quantity, condition, notes, purchasePrice]);

      result = {
        action: 'added',
        collectionCardId: insertResult.rows[0].id,
        addedAt: insertResult.rows[0].added_at
      };
    }

    // Get updated collection stats
    const statsQuery = await client.query(`
      SELECT 
        COUNT(cc.id) as total_entries,
        COALESCE(SUM(cc.quantity), 0) as total_cards,
        COALESCE(SUM(cc.quantity * COALESCE(c.current_price, 0)), 0) as total_value
      FROM collection_cards cc
      LEFT JOIN cards c ON cc.card_id = c.id
      WHERE cc.collection_id = $1
    `, [collectionId]);

    const stats = statsQuery.rows[0];

    res.status(200).json({
      success: true,
      message: `Card ${result.action} successfully`,
      result: {
        ...result,
        card: {
          id: card.id,
          name: card.name,
          game: card.game,
          rarity: card.rarity,
          currentPrice: card.current_price
        },
        collection: {
          id: collection.id,
          name: collection.name
        },
        quantity: quantity,
        condition: condition,
        collectionStats: {
          totalEntries: parseInt(stats.total_entries),
          totalCards: parseInt(stats.total_cards),
          totalValue: parseFloat(stats.total_value)
        }
      }
    });

  } catch (error) {
    console.error('Add card to collection error:', error);
    
    if (error.message === 'No token provided' || error.message === 'Invalid token') {
      res.status(401).json({ error: error.message });
    } else {
      res.status(500).json({ 
        error: 'Internal server error',
        details: error.message 
      });
    }
  } finally {
    client.release();
  }
}