Implemented CartContext.js

frontend/src/contexts/CartContext.js

+import React, { createContext, useContext, useReducer } from 'react';
+
+const CartContext = createContext();
+
+const initialState = {
+    items: [],
+};
+
+function cartReducer(state, action) {
+    switch (action.type) {
+        case 'ADD_TO_CART':
+            const existingIndex = state.items.findIndex(item => item.id === action.payload.id);
+            if (existingIndex >= 0) {
+                const items = state.items.map((item, index) => {
+                    if (index === existingIndex) {
+                        return { ...item, quantity: item.quantity + 1 };
+                    }
+                    return item;
+                });
+                return { ...state, items };
+            } else {
+                return { ...state, items: [...state.items, { ...action.payload, quantity: 1 }] };
+            }
+        case 'REMOVE_FROM_CART':
+            return {
+                ...state,
+                items: state.items.filter(item => item.id !== action.payload.id),
+            };
+        case 'UPDATE_QUANTITY':
+            return {
+                ...state,
+                items: state.items.map(item =>
+                    item.id === action.payload.id ? { ...item, quantity: action.payload.quantity } : item
+                ),
+            };
+        default:
+            return state;
+    }
+}
+
+export const CartProvider = ({ children }) => {
+    const [state, dispatch] = useReducer(cartReducer, initialState);
+
+    const addToCart = item => {
+        dispatch({ type: 'ADD_TO_CART', payload: item });
+    };
+
+    const removeFromCart = id => {
+        dispatch({ type: 'REMOVE_FROM_CART', payload: { id } });
+    };
+
+    const updateQuantity = (id, quantity) => {
+        dispatch({ type: 'UPDATE_QUANTITY', payload: { id, quantity } });
+    };
+
+    return (
+        <CartContext.Provider value={{ cart: state, addToCart, removeFromCart, updateQuantity }}>
+            {children}
+        </CartContext.Provider>
+    );
+};
+
+export const useCart = () => useContext(CartContext);