4. Дьяков Григорий Александрович. 614

src/part1/constants.py

@@ -19,20 +19,20 @@
 # 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).

src/part1/snowflake.py

@@ -13,12 +13,13 @@
 :func:`decode_node_id` and :func:`decode_sequence_id`.
 """
 
-import time  # noqa: F401
+import time
 
-from .constants import (  # noqa: F401
+from .constants import (
     EPOCH_MS_DEFAULT,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
 )
@@ -34,8 +35,7 @@ def read_current_millis(epoch_ms: int) -> int:
         The count of whole milliseconds between ``epoch_ms`` and now. May be
         negative if ``epoch_ms`` lies in the future.
     """
-    # TODO: реализуйте функцию
-    return 0
+    return int(time.time() * 1000.0 - epoch_ms)
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +50,7 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         The absolute Unix time in milliseconds at which the identifier was
         generated.
     """
-    # TODO: реализуйте функцию
-    return 0
+    return (snowflake_id >> (NODE_ID_MAX + SEQUENCE_ID_MAX)) + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -64,8 +63,7 @@ def decode_node_id(snowflake_id: int) -> int:
         The node identifier packed into ``snowflake_id``, in the range
         ``[0, NODE_ID_MAX]``.
     """
-    # TODO: реализуйте функцию
-    return 0
+    return (snowflake_id >> SEQUENCE_ID_BITS) & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -78,8 +76,7 @@ def decode_sequence_id(snowflake_id: int) -> int:
         The per-millisecond sequence counter packed into ``snowflake_id``, in
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
-    # TODO: реализуйте функцию
-    return 0
+    return snowflake_id & SEQUENCE_ID_MAX
 
 
 def generate_snowflake_id(
@@ -110,5 +107,21 @@ def generate_snowflake_id(
         timestamp field (roughly 69 years after ``epoch_ms``). In each of those
         cases an explanatory message is printed to stdout first.
     """
-    # TODO: реализуйте функцию
-    return 0
+    if not (0 <= node_id <= NODE_ID_MAX):
+        print(f"node_id must be in [0, {NODE_ID_MAX}], but is {node_id}")
+        return None
+
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but is {sequence_id}")
+        return None
+
+    timestamp = read_current_millis(epoch_ms)
+    if timestamp > TIMESTAMP_MS_MAX:
+        print("timestamp overflows")
+        return None
+
+    return (
+        (timestamp << (NODE_ID_MAX + SEQUENCE_ID_MAX))
+        | (node_id << SEQUENCE_ID_BITS)
+        | sequence_id
+    )

src/part2/cart.py

@@ -11,8 +11,8 @@
 
 from typing import Final
 
-from .crud import read_product, update_product  # noqa: F401
-from .storage import (  # noqa: F401
+from .crud import read_product, update_product
+from .storage import (
     NAME_INDEX,
     PRICE_INDEX,
     QUANTITY_INDEX,
@@ -22,9 +22,19 @@
 
 type CartLine = tuple[int, int]
 
-# TODO: задайте позиции полей внутри кортежа CartLine
+
 LINE_PRODUCT_ID_INDEX: Final = 0
-LINE_QUANTITY_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
+
+
+def find_cart_line(
+    cart: list[CartLine],
+    product_id: int,
+) -> CartLine | None:
+    for cart_line in cart:
+        if cart_line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return cart_line
+    return None
 
 
 def add_to_cart(
@@ -53,8 +63,46 @@ def add_to_cart(
         The cart line for ``product_id`` after the addition, or ``None``
         when the product is unknown or the store cannot cover the request.
     """
-    # TODO: реализуйте функцию
-    return (0, 0)
+    product_in_storage = read_product(storage, product_id)
+    if product_in_storage is None:
+        return None
+
+    available_quantity = product_in_storage[QUANTITY_INDEX]
+    if available_quantity < quantity:
+        print(
+            f"not enough stock for product {product_id}: "
+            f"{available_quantity} available, {quantity} requested"
+        )
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (
+            product_in_storage[NAME_INDEX],
+            product_in_storage[PRICE_INDEX],
+            available_quantity - quantity,
+        ),
+    )
+
+    final_cartline: CartLine
+    product_already_in_cart = False
+
+    for cartline_index in range(len(cart)):
+        if product_id == cart[cartline_index][LINE_PRODUCT_ID_INDEX]:
+            final_cartline = (
+                product_id,
+                cart[cartline_index][LINE_QUANTITY_INDEX] + quantity,
+            )
+            cart[cartline_index] = final_cartline
+            product_already_in_cart = True
+            break
+
+    if not product_already_in_cart:
+        final_cartline = (product_id, quantity)
+        cart.append(final_cartline)
+
+    return final_cartline
 
 
 def remove_from_cart(
@@ -85,5 +133,37 @@ def remove_from_cart(
         zero means the line was dropped), or ``None`` when the cart has no
         line for the product or holds too few units.
     """
-    # TODO: реализуйте функцию
-    return (0, 0)
+    cart_line = find_cart_line(cart, product_id)
+
+    if cart_line is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    quantity_in_cart = cart_line[LINE_QUANTITY_INDEX]
+    if quantity_in_cart < quantity:
+        print(
+            f"cart holds only {quantity_in_cart} unit(s) "
+            f"of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    quantity_in_product = product[QUANTITY_INDEX]
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], quantity_in_product + quantity),
+    )
+
+    new_cart_line: CartLine = (product_id, quantity_in_cart - quantity)
+    cart_line_index = cart.index(cart_line)
+
+    if (quantity_in_cart - quantity) != 0:
+        cart[cart_line_index] = new_cart_line
+    else:
+        cart.pop(cart_line_index)
+
+    return new_cart_line

src/part2/crud.py

@@ -14,13 +14,13 @@
 
 from decimal import Decimal
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_INDEX,
     PRODUCT_ID_INDEX,
     PRODUCT_ID_MIN,
     Product,
 )
-from .utils import normalize_price  # noqa: F401
+from .utils import normalize_price
 
 
 def generate_product_id(storage: list[Product]) -> int:
@@ -34,8 +34,13 @@ def generate_product_id(storage: list[Product]) -> int:
         :data:`~src.part2.storage.PRODUCT_ID_MIN` when ``storage`` is
         empty.
     """
-    # TODO: реализуйте функцию
-    return 0
+    if len(storage) == 0:
+        return PRODUCT_ID_MIN
+
+    max_id: int = 0
+    for product in storage:
+        max_id = max(product[PRODUCT_ID_INDEX], max_id)
+    return max_id + 1
 
 
 def create_product(
@@ -56,8 +61,18 @@ def create_product(
         ``storage`` is left unchanged and a message naming the clashing
         name is printed.
     """
-    # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+
+    for product in storage:
+        if name == product[NAME_INDEX]:
+            print(f"product name '{name}' is already taken")
+            return None
+
+    new_id = generate_product_id(storage)
+    new_price = normalize_price(price)
+    new_product_tuple = (new_id, name, new_price, quantity)
+    storage.append(new_product_tuple)
+    return new_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -72,8 +87,12 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         ``None`` when no product carries that identifier (a message is
         printed in that case).
     """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product_id == product[PRODUCT_ID_INDEX]:
+            return product
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -99,8 +118,17 @@ def update_product(
         ``None`` when no product carries that identifier (``storage`` is
         left unchanged and a message is printed).
     """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    name, price, quantity = fields
+    new_price = normalize_price(price)
+    new_product: Product = (product_id, name, new_price, quantity)
+
+    for product_index in range(len(storage)):
+        if product_id == storage[product_index][PRODUCT_ID_INDEX]:
+            storage[product_index] = new_product
+            return new_product
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -116,5 +144,10 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         product carried that identifier (``storage`` is left unchanged and
         a message is printed).
     """
-    # TODO: реализуйте функцию
-    return 0
+    for product_index in range(len(storage)):
+        if product_id == storage[product_index][PRODUCT_ID_INDEX]:
+            storage.pop(product_index)
+            return product_id
+
+    print(f"no product with id {product_id}")
+    return None

src/part2/storage.py

@@ -26,9 +26,9 @@
 
 # TODO: задайте позиции полей внутри кортежа Product
 PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 0
-PRICE_INDEX: Final = 0
-QUANTITY_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
 
 # TODO: задайте идентификатор первого товара в пустом хранилище
-PRODUCT_ID_MIN: Final[int] = 0
+PRODUCT_ID_MIN: Final[int] = 1

src/part2/utils.py

@@ -6,13 +6,12 @@
 currency values free of binary floating-point error.
 """
 
-from decimal import ROUND_HALF_UP, Decimal  # noqa: F401
+from decimal import ROUND_HALF_UP, Decimal
 from typing import Final
 
 
-# TODO: задайте число знаков после запятой и шаг квантования
-PRICE_PRECISION: Final[int] = 0
-PRICE_STEP: Final = Decimal(0)
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
 
 
 def normalize_price(price: Decimal) -> Decimal:
@@ -25,5 +24,4 @@ def normalize_price(price: Decimal) -> Decimal:
         ``price`` quantised to :data:`PRICE_PRECISION` fractional digits,
         with halves rounded up.
     """
-    # TODO: реализуйте функцию
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, ROUND_HALF_UP)