Source code for app.cart

from app.pydantic_models import Cart




class CartManager:
    """
    Manage shopping carts using the Singleton design pattern.
    """

    _instance = None

    def __init__(self):
        """
        Block direct instantiation.

        Raises:
            RuntimeError: If instantiated directly via the constructor, to force usage of get_instance().
        """
        raise RuntimeError("You cannot use the public constructor `get_instance()` instead")

    def _init(self):
        """
        Initialize the manager with an empty cart store.
        """
        self._carts: dict[str, Cart] = {}



    @staticmethod
    def get_instance():
        """
        Return the unique CartManager instance, creating it if needed.

        Returns:
            CartManager: The singleton instance.
        """
        if CartManager._instance is None:
            CartManager._instance = CartManager.__new__(CartManager)
            CartManager._instance._init()
        return CartManager._instance




    def get_cart(self, cart_id: str = "default") -> Cart:
        """
        Return an existing cart or create a new one.

        Args:
            cart_id: The unique cart identifier. Default value to "default".

        Returns:
            Cart: The cart matching the given identifier.
        """
        if cart_id not in self._carts:
            self._carts[cart_id] = Cart(id=cart_id)
        return self._carts[cart_id]




    def clear_cart(self, cart_id: str = "default") -> None:
        """
        Clear the contents of a cart.

        Args:
            cart_id: The identifier of the cart to clear. Default value to "default".
        """
        if cart_id in self._carts:
            self._carts[cart_id].items.clear()