// userController.js
const User = require('../model/Cart');

exports.addToCart = async (req, res) => {
  try {
    const { userId, productId, quantity } = req.body;

    // Check if the user exists
    const user = await User.findById(userId);
    if (!user) {
      return res.status(404).json({ message: 'User not found.' });
    }

    // Check if the product exists
    const product = await Product.findById(productId);
    if (!product) {
      return res.status(404).json({ message: 'Product not found.' });
    }

    // Check if the product is active
    if (!product.isActive) {
      return res.status(400).json({ message: 'Product is not active.' });
    }

    // Check if the quantity is valid
    if (quantity <= 0) {
      return res.status(400).json({ message: 'Invalid quantity.' });
    }

    // Check if the user already has a cart
    let cart = await Cart.findOne({ userId });

    // If the user doesn't have a cart, create a new one
    if (!cart) {
      cart = new Cart({ userId, products: [], totalAmount: 0 });
    }

    // Check if the product is already in the cart
    const existingProduct = cart.products.find(
      (cartProduct) => cartProduct.productId.toString() === productId
    );

    // If the product is already in the cart, update the quantity and subtotal
    if (existingProduct) {
      existingProduct.quantity += quantity;
      existingProduct.subtotal = existingProduct.quantity * existingProduct.price;
    } else {
      // If the product is not in the cart, add it
      cart.products.push({
        productId,
        productName: product.name,
        quantity,
        price: product.price,
        subtotal: quantity * product.price,
      });
    }

    // Update the total amount in the cart
    cart.totalAmount = cart.products.reduce(
      (total, product) => total + product.subtotal,
      0
    );

    // Save the updated cart
    await cart.save();

    return res.status(200).json({ message: 'Product added to cart successfully.' });
  } catch (error) {
    console.error(error);
    return res.status(500).json({ message: 'Internal server error.' });
  }
}