serializer.py

from rest_framework import serializers # type: ignore
from .models import Product, Cart, CartItem

class ProductSerializer(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = '__all__'

class CartItemSerializer(serializers.ModelSerializer):
    product = ProductSerializer()
    total_price = serializers.SerializerMethodField()

    class Meta:
        model = CartItem
        fields = ['id', 'product', 'quantity', 'total_price']

    def get_total_price(self, obj):
        return obj.total_price()

class CartSerializer(serializers.ModelSerializer):
    items = CartItemSerializer(many=True)
    total = serializers.SerializerMethodField()

    class Meta:
        model = Cart
        fields = ['id', 'items', 'total']

    def get_total(self, obj):
        return sum(item.total_price() for item in obj.items.all())