feat(cart): implement cart functionality with add, update, remove, and checkout features

backend/src/app.ts

@@ -8,6 +8,7 @@ import userRoutes from "./routes/user.routes";
 
 // Consolidated Imports
 import productRoutes from "./routes/product.routes";
+import cartRoutes from "./routes/cartRoutes"; 
 import mongoose from "mongoose";
 import bcrypt from "bcryptjs";
 import cookieParser from "cookie-parser";
@@ -127,6 +128,7 @@ app.get("/protected", authenticate, (req: AuthRequest, res: Response) => {
 app.use('/api/health', healthRoutes);
 app.use("/api/products", productRoutes);
 app.use("/api/users", userRoutes);
+app.use("/api/cart", cartRoutes);
 
 // Default
 app.get("/", (_req, res) => {

backend/src/controllers/cart.controller.ts

@@ -0,0 +1,151 @@
+import { Request, Response } from "express";
+import mongoose from "mongoose";
+import Cart, {  CartItemInput } from "../models/cart.model";
+
+
+export const addItem = async (req:Request, res:Response): Promise<void> => {
+  const userId = req.user?.id;
+  if (!userId) {
+    res.status(401).json({ message: "Unauthorized"}); return;
+  }
+  const {productId, name, price, quantity} = req.body as {
+    productId: string;
+    name: string;
+    price: number;
+    quantity: number;
+  };
+
+  try {
+    let cart = await Cart.findOne({ userId });
+    if (!cart) cart = new Cart({ userId, items: [], totalPrice: 0 });
+ const existingItem = cart.items.find(i => i.productId.toString() === productId);
+if (existingItem) {
+      existingItem.quantity += quantity;
+    } else {
+      const newItem: CartItemInput = {
+        productId: new mongoose.Types.ObjectId(productId),
+        name,
+        price,
+        quantity,
+      };
+      cart.items.push(newItem as any);
+    }
+cart.totalPrice = cart.items.reduce((sum, i) => sum + i.price * i.quantity, 0);
+    await cart.save();
+    res.status(200).json(cart);
+  } catch (err) {
+    console.error("Add item error:", err);
+    res.status(500).json({ message: "Server error" });
+  }
+};
+export const removeItem = async (req: Request, res: Response): Promise<void> => {
+  const userId = req.user?.id;
+  if (!userId) {
+    res.status(401).json({ message: "Unauthorized" });
+    return;
+  }
+  const { itemId } = req.params;
+  try {
+    const cart = await Cart.findOne({ userId });
+    if (!cart) {
+      res.status(404).json({ message: "Cart not found" });
+      return;
+    }
+  const itemIndex = cart.items.findIndex(i => (i as any)._id?.toString() === itemId);
+    if (itemIndex===-1) {
+      res.status(404).json({ message: "Item not found" });
+      return;
+    }
+  const item = cart.items[itemIndex];
+    cart.totalPrice -= item.price * item.quantity;
+    cart.items.splice(itemIndex, 1);
+    await cart.save();
+
+    res.status(200).json(cart);
+  } catch (err) {
+    console.error("Remove item error:", err);
+    res.status(500).json({ message: "Server error" });
+  }
+};
+export const updateQuantity = async (req: Request, res: Response): Promise<void> => {
+  const userId = req.user?.id;
+  if (!userId) {
+    res.status(401).json({ message: "Unauthorized" });
+    return;
+  }
+  const { itemId } = req.params;
+  const { quantity } = req.body as { quantity: number };
+  try {
+    const cart = await Cart.findOne({ userId });
+    if (!cart) {
+      res.status(404).json({ message: "Cart not found" });
+      return;
+    }
+    const item = cart.items.find(i => (i as any)._id?.toString() === itemId);
+    if (!item) {
+      res.status(404).json({ message: "Item not found" });
+      return;
+    }
+    item.quantity = quantity;
+    cart.totalPrice = cart.items.reduce(
+      (sum, i) => sum + i.price * i.quantity,
+      0
+    );
+
+    await cart.save();
+    res.status(200).json(cart);
+  } catch (err) {
+    console.error("Update quantity error:", err);
+    res.status(500).json({ message: "Server error" });
+  }
+  }
+  export const getCart = async (req: Request, res: Response): Promise<void> => {
+  const userId = req.user?.id;
+  if (!userId) {
+    res.status(401).json({ message: "Unauthorized" });
+    return;
+  }
+
+try {
+    const cart = await Cart.findOne({ userId }).populate("items.productId");
+    res.status(200).json(cart || { items: [], totalPrice: 0 });
+  } catch (err) {
+    console.error("Get cart error:", err);
+    res.status(500).json({ message: "Server error" });
+  }
+};
+
+export const checkout = async (req: Request, res: Response): Promise<void> => {
+  const userId = req.user?.id;
+  if (!userId) {
+    res.status(401).json({ message: "Unauthorized" });
+    return;
+  }
+
+  try {
+    const cart = await Cart.findOne({ userId });
+
+    if (!cart || cart.items.length === 0) {
+      res.status(400).json({ message: "Cart is empty" });
+      return;
+    }
+
+    const orderData = {
+      userId: new mongoose.Types.ObjectId(userId),
+      items: cart.items,
+      total: cart.totalPrice,
+      date: new Date(),
+    };
+
+    //Create order database and here push the orderData in it.
+
+    cart.items = [];
+    cart.totalPrice = 0;
+    await cart.save();
+
+    res.status(200).json({ message: "Checkout successful" });
+  } catch (err) {
+    console.error("Checkout error:", err);
+    res.status(500).json({ message: "Server error" });
+  }
+};

backend/src/models/cart.model.ts

@@ -0,0 +1,38 @@
+import mongoose, { Schema, Types } from "mongoose";
+
+export interface ICartItem {
+  _id?: Types.ObjectId;
+  productId: Types.ObjectId;
+  name: string;
+  price: number;
+  quantity: number;
+}
+
+export type CartItemInput = Omit<ICartItem, "_id">;
+
+export interface ICart extends mongoose.Document {
+  userId: Types.ObjectId;
+  items: ICartItem[];
+  totalPrice: number;
+}
+
+const cartItemSchema = new Schema<ICartItem>(
+  {
+    productId: { type: Schema.Types.ObjectId, ref: "Product", required: true },
+    name: { type: String, required: true },
+    price: { type: Number, required: true },
+    quantity: { type: Number, default: 1, min: 1 },
+  },
+  { _id: true }
+);
+
+const cartSchema = new Schema<ICart>(
+  {
+    userId: { type: Schema.Types.ObjectId, ref: "User", required: true },
+    items: [cartItemSchema],
+    totalPrice: { type: Number, default: 0 },
+  },
+  { timestamps: true }
+);
+
+export default mongoose.model<ICart>("Cart", cartSchema);

backend/src/routes/cartRoutes.ts

@@ -0,0 +1,18 @@
+import express, { Router } from "express";
+import {
+  addItem,
+  updateQuantity,
+  removeItem,
+  getCart,
+  checkout,
+} from "../controllers/cart.controller";
+
+const router: Router = express.Router();
+
+router.post("/", addItem);
+router.patch("/:itemId", updateQuantity);
+router.delete("/:itemId", removeItem);
+router.get("/", getCart);
+router.post("/checkout", checkout);
+
+export default router;

backend/src/types.d.ts

@@ -1,5 +1,5 @@
 declare namespace Express {
   export interface Request {
-    user?: { sub: string; username: string; role: string };
+    user?: { id: string; username: string; role: string };
   }
-}
+}