E-Commerce-Module/backend/src/routes/cart.js

const express = require('express');
const { v4: uuidv4 } = require('uuid');
const router = express.Router();

module.exports = (pool, query, authMiddleware) => {

  router.use(authMiddleware);

  // Get user's cart
  router.get('/:userId', async (req, res, next) => {
    try {
      const { userId } = req.params;
      if (req.user.id !== userId) {
        return res.status(403).json({
          error: true,
          message: 'You can only access your own cart'
        });
      }
      // Get cart
      let cartResult = await query(
        'SELECT * FROM carts WHERE user_id = $1',
        [userId]
      );
      
      // If no cart exists, create one
      if (cartResult.rows.length === 0) {
        cartResult = await query(
          'INSERT INTO carts (id, user_id) VALUES ($1, $2) RETURNING *',
          [uuidv4(), userId]
        );
      }
      
      const cartId = cartResult.rows[0].id;
      
      // Get cart items with product details
      const cartItemsResult = await query(
        `SELECT ci.id, ci.quantity, ci.added_at, 
         p.id AS product_id, p.name, p.description, p.price,
         p.category_id, pc.name AS category_name
         FROM cart_items ci
         JOIN products p ON ci.product_id = p.id
         JOIN product_categories pc ON p.category_id = pc.id
         WHERE ci.cart_id = $1`,
        [cartId]
      );
      
      // Calculate total
      const total = cartItemsResult.rows.reduce((sum, item) => {
        
        return sum + (parseFloat(item.price) * item.quantity);
      }, 0);
      
      res.json({
        id: cartId,
        userId,
        items: cartItemsResult.rows,
        itemCount: cartItemsResult.rows.length,
        total
      });
    } catch (error) {
      next(error);
    }
  });
  
  // Add item to cart
  router.post('/add', async (req, res, next) => {
    try {
      const { userId, productId, quantity = 1 } = req.body;
      if (req.user.id !== userId) {
        return res.status(403).json({
          error: true,
          message: 'You can only modify your own cart' + req.user.id + " "+  userId
        });
      }
      // Check if product exists
      const productResult = await query(
        'SELECT * FROM products WHERE id = $1',
        [productId]
      );
      
      if (productResult.rows.length === 0) {
        return res.status(404).json({
          error: true,
          message: 'Product not found'
        });
      }
      
      // Get or create cart
      let cartResult = await query(
        'SELECT * FROM carts WHERE user_id = $1',
        [userId]
      );
      
      if (cartResult.rows.length === 0) {
        cartResult = await query(
          'INSERT INTO carts (id, user_id) VALUES ($1, $2) RETURNING *',
          [uuidv4(), userId]
        );
      }
      
      const cartId = cartResult.rows[0].id;
      
      // Check if item already in cart
      const existingItemResult = await query(
        'SELECT * FROM cart_items WHERE cart_id = $1 AND product_id = $2',
        [cartId, productId]
      );
      
      if (existingItemResult.rows.length > 0) {
        // Update quantity
        const newQuantity = existingItemResult.rows[0].quantity + quantity;
        
        await query(
          'UPDATE cart_items SET quantity = $1 WHERE id = $2',
          [newQuantity, existingItemResult.rows[0].id]
        );
      } else {
        // Add new item
        await query(
          'INSERT INTO cart_items (id, cart_id, product_id, quantity) VALUES ($1, $2, $3, $4)',
          [uuidv4(), cartId, productId, quantity]
        );
      }
      
      // Get updated cart
      const updatedCartItems = await query(
        `SELECT ci.id, ci.quantity, ci.added_at, 
         p.id AS product_id, p.name, p.description, p.price,
         p.category_id, pc.name AS category_name
         FROM cart_items ci
         JOIN products p ON ci.product_id = p.id
         JOIN product_categories pc ON p.category_id = pc.id
         WHERE ci.cart_id = $1`,
        [cartId]
      );
      
      // Calculate total
      const total = updatedCartItems.rows.reduce((sum, item) => {
        return sum + (parseFloat(item.price) * item.quantity);
      }, 0);
      
      res.json({
        id: cartId,
        userId,
        items: updatedCartItems.rows,
        itemCount: updatedCartItems.rows.length,
        total
      });
    } catch (error) {
      next(error);
    }
  });
  
  // Update cart item quantity
  router.put('/update', async (req, res, next) => {
    try {
      const { userId, productId, quantity } = req.body;
      if (req.user.id !== userId) {
        return res.status(403).json({
          error: true,
          message: 'You can only modify your own cart' + req.user.id + " "+  userId
        });
      }
      // Get cart
      const cartResult = await query(
        'SELECT * FROM carts WHERE user_id = $1',
        [userId]
      );
      
      if (cartResult.rows.length === 0) {
        return res.status(404).json({
          error: true,
          message: 'Cart not found'
        });
      }
      
      const cartId = cartResult.rows[0].id;
      
      if (quantity <= 0) {
        // Remove item
        await query(
          'DELETE FROM cart_items WHERE cart_id = $1 AND product_id = $2',
          [cartId, productId]
        );
      } else {
        // Update quantity
        await query(
          'UPDATE cart_items SET quantity = $1 WHERE cart_id = $2 AND product_id = $3',
          [quantity, cartId, productId]
        );
      }
      
      // Get updated cart
      const updatedCartItems = await query(
        `SELECT ci.id, ci.quantity, ci.added_at, 
         p.id AS product_id, p.name, p.description, p.price,
         p.category_id, pc.name AS category_name
         FROM cart_items ci
         JOIN products p ON ci.product_id = p.id
         JOIN product_categories pc ON p.category_id = pc.id
         WHERE ci.cart_id = $1`,
        [cartId]
      );
      
      // Calculate total
      const total = updatedCartItems.rows.reduce((sum, item) => {
        return sum + (parseFloat(item.price) * item.quantity);
      }, 0);
      
      res.json({
        id: cartId,
        userId,
        items: updatedCartItems.rows,
        itemCount: updatedCartItems.rows.length,
        total
      });
    } catch (error) {
      next(error);
    }
  });
  
  // Clear cart
  router.delete('/clear/:userId', async (req, res, next) => {
    try {
      const { userId } = req.params;
      if (req.user.id !== userId) {
        return res.status(403).json({
          error: true,
          message: 'You can only modify your own cart' + req.user.id + " "+  userId
        });
      }
      // Get cart
      const cartResult = await query(
        'SELECT * FROM carts WHERE user_id = $1',
        [userId]
      );
      
      if (cartResult.rows.length === 0) {
        return res.status(404).json({
          error: true,
          message: 'Cart not found'
        });
      }
      
      const cartId = cartResult.rows[0].id;
      
      // Delete all items
      await query(
        'DELETE FROM cart_items WHERE cart_id = $1',
        [cartId]
      );
      
      res.json({
        id: cartId,
        userId,
        items: [],
        itemCount: 0,
        total: 0
      });
    } catch (error) {
      next(error);
    }
  });
  
  // Checkout (create order from cart)
  router.post('/checkout', async (req, res, next) => {
    try {
      const { userId, shippingAddress } = req.body;
      if (req.user.id !== userId) {
        return res.status(403).json({
          error: true,
          message: 'You can only checkout your own cart'
        });
      }
      // Get cart
      const cartResult = await query(
        'SELECT * FROM carts WHERE user_id = $1',
        [userId]
      );
      
      if (cartResult.rows.length === 0) {
        return res.status(404).json({
          error: true,
          message: 'Cart not found'
        });
      }
      
      const cartId = cartResult.rows[0].id;
      
      // Get cart items
      const cartItemsResult = await query(
        `SELECT ci.*, p.price
         FROM cart_items ci
         JOIN products p ON ci.product_id = p.id
         WHERE ci.cart_id = $1`,
        [cartId]
      );
      
      if (cartItemsResult.rows.length === 0) {
        return res.status(400).json({
          error: true,
          message: 'Cart is empty'
        });
      }
      
      // Calculate total
      const total = cartItemsResult.rows.reduce((sum, item) => {
        return sum + (parseFloat(item.price) * item.quantity);
      }, 0);
      
      // Begin transaction
      const client = await pool.connect();
      
      try {
        await client.query('BEGIN');
        
        // Create order
        const orderId = uuidv4();
        await client.query(
          'INSERT INTO orders (id, user_id, status, total_amount, shipping_address) VALUES ($1, $2, $3, $4, $5)',
          [orderId, userId, 'pending', total, shippingAddress]
        );
        
        // Create order items
        for (const item of cartItemsResult.rows) {
          await client.query(
            'INSERT INTO order_items (id, order_id, product_id, quantity, price_at_purchase) VALUES ($1, $2, $3, $4, $5)',
            [uuidv4(), orderId, item.product_id, item.quantity, item.price]
          );
          
          // Update product stock
          await client.query(
            'UPDATE products SET stock_quantity = stock_quantity - $1 WHERE id = $2',
            [item.quantity, item.product_id]
          );
        }
        
        // Clear cart
        await client.query(
          'DELETE FROM cart_items WHERE cart_id = $1',
          [cartId]
        );
        
        await client.query('COMMIT');
        
        res.status(201).json({
          success: true,
          message: 'Order created successfully',
          orderId
        });
      } catch (error) {
        await client.query('ROLLBACK');
        throw error;
      } finally {
        client.release();
      }
    } catch (error) {
      next(error);
    }
  });
  
  return router;
};