frontend/lib/cart-context.tsx

"use client";

import type { Product } from "@/lib/types";
import { createContext, useContext, useEffect, useMemo, useState } from "react";

export interface CartItem {
  id: number;
  name: string;
  description: string;
  price: number;
  quantity: number;
}

interface CartContextValue {
  items: CartItem[];
  totalItems: number;
  totalPrice: number;
  addToCart: (product: Product) => void;
  increaseQty: (id: number) => void;
  decreaseQty: (id: number) => void;
  removeFromCart: (id: number) => void;
  setQuantity: (id: number, quantity: number) => void;
}

const STORAGE_KEY = "coffee-shop-cart";
const CartContext = createContext<CartContextValue | null>(null);

export function CartProvider({ children }: { children: React.ReactNode }) {
  const [items, setItems] = useState<CartItem[]>([]);

  useEffect(() => {
    try {
      const raw = localStorage.getItem(STORAGE_KEY);
      if (!raw) return;
      const parsed = JSON.parse(raw) as CartItem[];
      if (Array.isArray(parsed)) {
        setItems(parsed.filter((i) => i && i.id && i.quantity > 0));
      }
    } catch {
      localStorage.removeItem(STORAGE_KEY);
    }
  }, []);

  useEffect(() => {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(items));
  }, [items]);

  const addToCart = (product: Product) => {
    setItems((prev) => {
      const index = prev.findIndex((i) => i.id === product.id);
      if (index === -1) {
        return [
          ...prev,
          {
            id: product.id,
            name: product.name,
            description: product.description,
            price: product.price,
            quantity: 1,
          },
        ];
      }

      const next = [...prev];
      next[index] = { ...next[index], quantity: next[index].quantity + 1 };
      return next;
    });
  };

  const increaseQty = (id: number) => {
    setItems((prev) =>
      prev.map((item) =>
        item.id === id ? { ...item, quantity: item.quantity + 1 } : item,
      ),
    );
  };

  const decreaseQty = (id: number) => {
    setItems((prev) =>
      prev
        .map((item) =>
          item.id === id
            ? { ...item, quantity: Math.max(0, item.quantity - 1) }
            : item,
        )
        .filter((item) => item.quantity > 0),
    );
  };

  const removeFromCart = (id: number) => {
    setItems((prev) => prev.filter((item) => item.id !== id));
  };

  const setQuantity = (id: number, quantity: number) => {
    const safeQty = Number.isFinite(quantity)
      ? Math.max(0, Math.floor(quantity))
      : 0;
    if (safeQty === 0) {
      removeFromCart(id);
      return;
    }

    setItems((prev) =>
      prev.map((item) =>
        item.id === id ? { ...item, quantity: safeQty } : item,
      ),
    );
  };

  const totalItems = useMemo(
    () => items.reduce((sum, item) => sum + item.quantity, 0),
    [items],
  );

  const totalPrice = useMemo(
    () => items.reduce((sum, item) => sum + item.price * item.quantity, 0),
    [items],
  );

  const value = useMemo(
    () => ({
      items,
      totalItems,
      totalPrice,
      addToCart,
      increaseQty,
      decreaseQty,
      removeFromCart,
      setQuantity,
    }),
    [items, totalItems, totalPrice],
  );

  return <CartContext.Provider value={value}>{children}</CartContext.Provider>;
}

export function useCart() {
  const context = useContext(CartContext);
  if (!context) {
    throw new Error("useCart must be used within CartProvider");
  }
  return context;
}