package main

import (
	"encoding/json"
	"net/http"
	"sync"
)

type item struct {
	ProductID int `json:"product_id"`
	Quantity  int `json:"quantity"`
}

var (
	mu   sync.Mutex
	cart []item
)

func addToCart(w http.ResponseWriter, r *http.Request) {
	var it item
	if err := json.NewDecoder(r.Body).Decode(&it); err != nil {
		http.Error(w, "bad JSON", http.StatusBadRequest)
		return
	}
	mu.Lock()
	cart = append(cart, it)
	mu.Unlock()
	w.WriteHeader(http.StatusCreated)
}

func showCart(w http.ResponseWriter, r *http.Request) {
	mu.Lock()
	defer mu.Unlock()
	total := 0.0
	for _, it := range cart {
		for _, p := range products {
			if p.ID == it.ProductID {
				total += p.Price * float64(it.Quantity)
			}
		}
	}
	json.NewEncoder(w).Encode(map[string]any{"items": cart, "total": total})
}

func validQuantity(q int) bool { return q > 0 && q <= 99 }