5. Васильев Егор Евгеньевич. 613

src/part5/cart.py

@@ -9,7 +9,7 @@
 an explanatory message to stdout and returns ``None``.
 """
 
-from .storage import Product
+from .storage import QUANTITY_KEY, Product
 
 
 # TODO: при необходимости добавьте свои вспомогательные функции
@@ -22,33 +22,19 @@ def add_to_cart(
     product_id: int,
     quantity: int,
 ) -> int | None:
-    """Move ``quantity`` units of ``product_id`` from the store into ``cart``.
-
-    The product is looked up in ``storage``. If it is missing, a message is
-    printed (by :func:`~src.part5.crud.read_product`) and nothing
-    changes. If the store holds fewer units than requested, an explanatory
-    message is printed and nothing changes. Otherwise the store record is
-    decremented by ``quantity`` and the cart gains ``quantity`` units of
-    ``product_id`` -- the product is added when the cart had none of it.
-
-    Args:
-        storage: The product store to draw stock from; modified in place on
-            success.
-        product_names: The normalised names in ``storage``; threaded
-            through to :func:`~src.part5.crud.update_product`, which
-            keeps it in sync (a quantity-only update never renames a
-            product, so it is left unchanged here).
-        cart: The cart to add the units to; modified in place on success.
-        product_id: The identifier of the product to add.
-        quantity: Number of units to move into the cart.
-
-    Returns:
-        The quantity of ``product_id`` in the cart after the addition, or
-        ``None`` when the product is unknown or the store cannot cover the
-        request.
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 4)
-    return 0
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    if storage[product_id][QUANTITY_KEY] < quantity:
+        print(
+            f"not enough stock for product {product_id}: "
+            f"{storage[product_id][QUANTITY_KEY]} available, "
+            f"{quantity} requested"
+        )
+        return None
+    storage[product_id][QUANTITY_KEY] -= quantity
+    cart[product_id] = cart.get(product_id, 0) + quantity
+    return cart[product_id]
 
 
 def remove_from_cart(
@@ -58,31 +44,21 @@ def remove_from_cart(
     product_id: int,
     quantity: int,
 ) -> int | None:
-    """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store.
-
-    If the cart holds no units of ``product_id``, a message is printed and
-    nothing changes. If it holds fewer units than requested, an explanatory
-    message is printed and nothing changes. Otherwise the cart loses
-    ``quantity`` units of the product -- the product is dropped from the
-    cart when its quantity reaches zero -- and the store record gains
-    ``quantity`` units back.
-
-    Args:
-        storage: The product store to return stock to; modified in place on
-            success.
-        product_names: The normalised names in ``storage``; threaded
-            through to :func:`~src.part5.crud.update_product`, which
-            keeps it in sync (a quantity-only update never renames a
-            product, so it is left unchanged here).
-        cart: The cart to take the units from; modified in place on
-            success.
-        product_id: The identifier of the product to remove.
-        quantity: Number of units to move back into the store.
-
-    Returns:
-        The quantity of ``product_id`` left in the cart after the removal
-        (zero means the product was dropped from the cart), or ``None`` when
-        the cart does not hold the product or holds too few units.
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 4)
-    return 0
+    if product_id not in cart:
+        print(f"product {product_id} is not in the cart")
+        return None
+    if cart[product_id] < quantity:
+        print(
+            f"cart holds only {cart[product_id]} unit(s) "
+            f"of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    storage[product_id][QUANTITY_KEY] += quantity
+    cart[product_id] -= quantity
+    if not cart[product_id]:
+        del cart[product_id]
+        return 0
+    return cart[product_id]

src/part5/constants.py

@@ -15,23 +15,24 @@
 from typing import Final
 
 
-# TODO: замените заглушки (0) на корректные значения (используйте своё решение
-# части 1).
+# TODO: замените заглушки (0) на корректные значения, см. TASK.md.
+# Все константы, зависящие от ёмкостей *_BITS, должны вычисляться из них.
 
 # Twitter's original Snowflake epoch: 2010-11-04 01:42:54.657 UTC.
-EPOCH_MS_DEFAULT: Final[int] = 0
+EPOCH_MS_DEFAULT: Final[int] = 1288834974657
 
 # Node identifier used when the caller does not supply one.
-NODE_ID_DEFAULT: Final[int] = 0
+NODE_ID_DEFAULT: Final[int] = 1
 
 # Width of each field, in bits.
-TIMESTAMP_BITS: Final[int] = 0
-NODE_ID_BITS: Final[int] = 0
-SEQUENCE_ID_BITS: Final[int] = 0
+TIMESTAMP_BITS: Final[int] = 41
+NODE_ID_BITS: Final[int] = 10
+SEQUENCE_ID_BITS: Final[int] = 12
 
 # Largest value each field can hold.
-TIMESTAMP_MS_MAX: Final[int] = 0
-NODE_ID_MAX: Final[int] = 0
-SEQUENCE_ID_MAX: Final[int] = 0
+TIMESTAMP_MS_MAX: Final[int] = 2**TIMESTAMP_BITS - 1
+NODE_ID_MAX: Final[int] = 2**NODE_ID_BITS - 1
+SEQUENCE_ID_MAX: Final[int] = 2**SEQUENCE_ID_BITS - 1
 
 # Здесь можно добавить собственные вспомогательные константы
+# (например, сдвиги полей при сборке идентификатора).