4. Пятина Эвелина Павловна. 613

src/part1/constants.py

@@ -19,20 +19,19 @@
 # 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

@@ -13,13 +13,16 @@
 :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_BITS,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
+    TIMESTAMP_BITS,
     TIMESTAMP_MS_MAX,
 )
 
@@ -35,7 +38,7 @@ def read_current_millis(epoch_ms: int) -> int:
         negative if ``epoch_ms`` lies in the future.
     """
     # TODO: реализуйте функцию
-    return 0
+    return int(time.time() * 1000 - epoch_ms)
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -51,7 +54,8 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         generated.
     """
     # TODO: реализуйте функцию
-    return 0
+    timestamp_ms = (snowflake_id >> 22) & (2**TIMESTAMP_BITS - 1)
+    return int(timestamp_ms + epoch_ms)
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -65,7 +69,7 @@ def decode_node_id(snowflake_id: int) -> int:
         ``[0, NODE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    return int((snowflake_id >> 12) & (2**NODE_ID_BITS - 1))
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -79,7 +83,7 @@ def decode_sequence_id(snowflake_id: int) -> int:
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    return int(snowflake_id & (2**SEQUENCE_ID_BITS - 1))
 
 
 def generate_snowflake_id(
@@ -111,4 +115,17 @@ def generate_snowflake_id(
         cases an explanatory message is printed to stdout first.
     """
     # TODO: реализуйте функцию
-    return 0
+    if node_id < 0 or NODE_ID_MAX < node_id:
+        print(f"node_id must be in [{0}; {NODE_ID_MAX}]")
+
+    if 0 < sequence_id or sequence_id < SEQUENCE_ID_MAX:
+        print(f"node_id must be in [{0}; {NODE_ID_MAX}]")
+
+    timestamp_ms = int(time.time() * 1000 - epoch_ms)
+    if timestamp_ms > TIMESTAMP_MS_MAX:
+        print("overflows")
+        return None
+
+    snowflake_id = (0b0 << 63) | (timestamp_ms << 22) | (node_id << 12) | (sequence_id)
+
+    return int(snowflake_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,
@@ -24,7 +24,17 @@
 
 # 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 line in cart:
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return line
+    return None
 
 
 def add_to_cart(
@@ -54,7 +64,36 @@ def add_to_cart(
         when the product is unknown or the store cannot cover the request.
     """
     # TODO: реализуйте функцию
-    return (0, 0)
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    stock_quantity = product[QUANTITY_INDEX]
+    if stock_quantity < quantity:
+        print(
+            f"not enough stock for product {product_id}: {stock_quantity} available, {quantity} requested"
+        )
+        return None
+
+    new_stock_quantity = stock_quantity - quantity
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], new_stock_quantity),
+    )
+
+    index = 0
+    for line in cart:
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            updated_product = (product_id, line[LINE_PRODUCT_ID_INDEX] + quantity)
+            cart[index] = updated_product
+            return updated_product
+
+    new_line = (product_id, quantity)
+    cart.append(new_line)
+
+    return new_line
 
 
 def remove_from_cart(
@@ -86,4 +125,33 @@ def remove_from_cart(
         line for the product or holds too few units.
     """
     # TODO: реализуйте функцию
-    return (0, 0)
+    line = find_cart_line(cart, product_id)
+    if line is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    cart_quantity = line[LINE_QUANTITY_INDEX]
+    if cart_quantity < quantity:
+        print(
+            f"cart holds only {cart_quantity} unit(s) of product <{product_id}, cannot remove {quantity}"
+        )
+        return None
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] + quantity),
+    )
+
+    new_quantity = cart_quantity - quantity
+    for index in range(len(cart)):
+        if cart[index][LINE_PRODUCT_ID_INDEX] == product_id:
+            if new_quantity == 0:
+                del cart[index]
+                return (product_id, 0)
+            updated_product = (product_id, new_quantity)
+            cart[index] = updated_product
+            return updated_product
+    return None

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:
@@ -35,7 +35,9 @@ def generate_product_id(storage: list[Product]) -> int:
         empty.
     """
     # TODO: реализуйте функцию
-    return 0
+    if not storage:
+        return PRODUCT_ID_MIN
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
@@ -57,7 +59,17 @@ def create_product(
         name is printed.
     """
     # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+
+    for product in storage:
+        if product[NAME_INDEX] == name:
+            print(f"product name '{name}' is already taken.")
+            return None
+
+    product_id = generate_product_id(storage)
+    normalized_price = normalize_price(price)
+    storage.append((product_id, name, normalized_price, quantity))
+    return product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -73,7 +85,11 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         printed in that case).
     """
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return product
+        print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -99,8 +115,18 @@ def update_product(
         ``None`` when no product carries that identifier (``storage`` is
         left unchanged and a message is printed).
     """
+    name, price, quantity = fields
+    normalized_price = normalize_price(price)
+
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+
+    for index, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            updated_product = (product_id, name, normalized_price, quantity)
+            storage[index] = updated_product
+            return updated_product
+    print(f"no product with id {product_id}")
+    return None
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -117,4 +143,9 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         a message is printed).
     """
     # TODO: реализуйте функцию
-    return 0
+    for index, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            del storage[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 +6,13 @@
 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:
@@ -26,4 +26,4 @@ def normalize_price(price: Decimal) -> Decimal:
         with halves rounded up.
     """
     # TODO: реализуйте функцию
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)