2. Левинский Константин Андреевич. 614

src/part1/constants.py

@@ -15,24 +15,19 @@
 from typing import Final
 
 
-# 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
+TIMESTAMP_SHIFT: Final[int] = SEQUENCE_ID_BITS + NODE_ID_BITS
 
 # Largest value each field can hold.
-TIMESTAMP_MS_MAX: Final[int] = 0
-NODE_ID_MAX: Final[int] = 0
-SEQUENCE_ID_MAX: Final[int] = 0
-
-# Здесь можно добавить собственные вспомогательные константы
-# (например, сдвиги полей при сборке идентификатора).
+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

src/part1/snowflake.py

@@ -13,14 +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_DEFAULT,
     NODE_ID_MAX,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
+    TIMESTAMP_SHIFT,
 )
 
 
@@ -34,8 +36,8 @@ 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) - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +52,8 @@ 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 >> TIMESTAMP_SHIFT) + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -64,8 +66,8 @@ 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 +80,8 @@ 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 +112,18 @@ 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}], got {node_id}")
+        return None
+
+    if not 0 <= sequence_id <= SEQUENCE_ID_MAX:
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], got {sequence_id}")
+        return None
+
+    elapsed_ms = read_current_millis(epoch_ms)
+    if elapsed_ms > TIMESTAMP_MS_MAX:
+        print("timestamp overflows")
+        return None
+
+    return (elapsed_ms << TIMESTAMP_SHIFT) | (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 +22,16 @@
 
 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_index(cart: list[CartLine], product_id: int) -> int | None:
+    for index, line in enumerate(cart):
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return index
+    return None
 
 
 def add_to_cart(
@@ -53,8 +60,33 @@ 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 = 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}: "
+            f"{stock_quantity} available, {quantity} requested"
+        )
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], stock_quantity - quantity),
+    )
+
+    line_index = find_cart_index(cart, product_id)
+    if line_index is None:
+        new_line = (product_id, quantity)
+        cart.append(new_line)
+        return new_line
+
+    update_line = (product_id, cart[line_index][LINE_QUANTITY_INDEX] + quantity)
+    cart[line_index] = update_line
+    return update_line
 
 
 def remove_from_cart(
@@ -85,5 +117,34 @@ 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)
+    line_index = find_cart_index(cart, product_id)
+    if line_index is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    in_cart = cart[line_index][LINE_QUANTITY_INDEX]
+    if in_cart < quantity:
+        print(
+            f"cart holds only {in_cart} unit(s) of product "
+            f"{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 = in_cart - quantity
+    if new_quantity == 0:
+        cart.pop(line_index)
+        return (product_id, 0)
+
+    updated_line = (product_id, new_quantity)
+    cart[line_index] = updated_line
+    return updated_line

src/part2/crud.py

@@ -14,13 +14,20 @@
 
 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 find_product_index(storage: list[Product], product_id: int) -> int | None:
+    for index, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return index
+    return None
 
 
 def generate_product_id(storage: list[Product]) -> int:
@@ -34,8 +41,11 @@ 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 not storage:
+        return PRODUCT_ID_MIN
+
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
@@ -56,8 +66,18 @@ 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 product[NAME_INDEX] == name:
+            print(f"product name '{name}' is already taken")
+            return None
+
+    new_id = generate_product_id(storage)
+    new_product = (new_id, name, normalize_price(price), quantity)
+    storage.append(new_product)
+
+    return new_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -72,8 +92,12 @@ 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)
+
+    index = find_product_index(storage, product_id)
+    if index is None:
+        print(f"no product with id {product_id}")
+        return None
+    return storage[index]
 
 
 def update_product(
@@ -99,8 +123,16 @@ 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
+    index = find_product_index(storage, product_id)
+    if index is None:
+        print(f"no product with id {product_id}")
+        return None
+
+    updated_product = (product_id, name, normalize_price(price), quantity)
+    storage[index] = updated_product
+    return updated_product
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -116,5 +148,11 @@ 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
+
+    index = find_product_index(storage, product_id)
+    if index is None:
+        print(f"no product with id {product_id}")
+        return None
+
+    storage.pop(index)
+    return product_id

src/part2/storage.py

@@ -24,11 +24,9 @@
 
 type Product = tuple[int, str, Decimal, int]
 
-# 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 +24,5 @@ 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, rounding=ROUND_HALF_UP)

src/part3/TASK.md

@@ -1,4 +1,4 @@
-# Задача: нормализация имён, печать хранилища таблицей и админ-консоль
+  # Задача: нормализация имён, печать хранилища таблицей и админ-консоль
 
 ## Легенда