1. Тенишов Лев Алексеевич. 612

src/part1/constants.py

@@ -19,20 +19,24 @@
 # 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] = (1 << TIMESTAMP_BITS) - 1
+NODE_ID_MAX: Final[int] = (1 << NODE_ID_BITS) - 1
+SEQUENCE_ID_MAX: Final[int] = (1 << SEQUENCE_ID_BITS) - 1
 
 # Здесь можно добавить собственные вспомогательные константы
 # (например, сдвиги полей при сборке идентификатора).
+
+SEQUENCE_SHIFT = 0
+NODE_SHIFT = SEQUENCE_ID_BITS
+TIMESTAMP_SHIFT = SEQUENCE_ID_BITS + NODE_ID_BITS

src/part1/snowflake.py

@@ -13,14 +13,17 @@
 :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,
+    NODE_SHIFT,
     SEQUENCE_ID_MAX,
+    SEQUENCE_SHIFT,
     TIMESTAMP_MS_MAX,
+    TIMESTAMP_SHIFT,
 )
 
 
@@ -34,8 +37,8 @@ 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
+    now_ms = time.time_ns() // 1_000_000
+    return now_ms - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +53,8 @@ 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
+    current_millis = snowflake_id >> TIMESTAMP_SHIFT
+    return epoch_ms + current_millis
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -64,8 +67,7 @@ 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 >> NODE_SHIFT & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -78,8 +80,7 @@ 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_SHIFT & SEQUENCE_ID_MAX
 
 
 def generate_snowflake_id(
@@ -110,5 +111,24 @@ 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 node_id > NODE_ID_MAX or node_id < 0:
+        print(f"node_id must be in [0, {NODE_ID_MAX}], got {node_id}")
+        return None
+
+    if sequence_id > SEQUENCE_ID_MAX or sequence_id < 0:
+        print(f"sequence_id  must be in [0, {SEQUENCE_ID_MAX}], got {sequence_id}")
+        return None
+
+    current_millis = read_current_millis(epoch_ms)
+
+    if current_millis > TIMESTAMP_MS_MAX:
+        print("overflows")
+        return None
+
+    snowflake_id = (
+        current_millis << TIMESTAMP_SHIFT
+        | node_id << NODE_SHIFT
+        | sequence_id << SEQUENCE_SHIFT
+    )
+
+    return 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,
@@ -22,9 +22,58 @@
 
 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,
+) -> int | None:
+    """Check cart for cart line.
+
+    The cart line for ``product_id`` is looked up. If there is none, return None
+    else return index of required cart line in cart.
+
+    Args:
+        cart: The cart to take the units from; modified in place on
+            success.
+        product_id: The identifier of the product to remove.
+
+    Returns:
+        True if cart line was found in cart, or False
+    """
+    for i, cart_line in enumerate(cart):
+        if cart_line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return i
+    return None
+
+
+def change_cart_quantity(
+    cart: list[CartLine],
+    index: int,
+    quantity: int,
+) -> CartLine | None:
+    """Change cart quantity in cart line at ``index`` to ``quantity``.
+
+    Args:
+        cart: The cart to take the units from; modified in place on
+            success.
+        index: The index of cart line in cart (as index of list).
+        quantity: Number of units.
+
+    Returns:
+        The cart line for ``product_id`` after the changing quantity.
+        None if quantity = 0.
+    """
+
+    if quantity:
+        updated_cart_line = (cart[index][LINE_PRODUCT_ID_INDEX], quantity)
+        cart[index] = updated_cart_line
+        return updated_cart_line
+
+    cart = cart[:index] + cart[index + 1 :]
+    return None
 
 
 def add_to_cart(
@@ -53,8 +102,39 @@ 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)
+    search_product = read_product(storage, product_id)
+
+    if not search_product:
+        return None
+
+    if quantity > search_product[QUANTITY_INDEX]:
+        print(
+            f"not enough stock for product {product_id}: {search_product[QUANTITY_INDEX]} available, {quantity} requested"
+        )
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (
+            search_product[NAME_INDEX],
+            search_product[PRICE_INDEX],
+            search_product[QUANTITY_INDEX] - quantity,
+        ),
+    )
+
+    index_cart_line = find_cart_line(cart, product_id)
+
+    if not index_cart_line is None:
+        return change_cart_quantity(
+            cart, index_cart_line, cart[index_cart_line][LINE_QUANTITY_INDEX] + quantity
+        )
+
+    updated_cart_line = (product_id, quantity)
+
+    cart.append(updated_cart_line)
+
+    return updated_cart_line
 
 
 def remove_from_cart(
@@ -85,5 +165,32 @@ 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)
+    index_cart_line = find_cart_line(cart, product_id)
+
+    if index_cart_line is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    cart_line_quantity = cart[index_cart_line][LINE_QUANTITY_INDEX]
+    if cart_line_quantity < quantity:
+        print(
+            f"cart holds only {cart_line_quantity} unit(s) of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+
+    search_product = read_product(storage, product_id)
+
+    if not search_product:
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (
+            search_product[NAME_INDEX],
+            search_product[PRICE_INDEX],
+            search_product[QUANTITY_INDEX] + quantity,
+        ),
+    )
+
+    return change_cart_quantity(cart, index_cart_line, cart_line_quantity - quantity)

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 +34,10 @@ 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 +58,18 @@ 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
+    product_names = [product[NAME_INDEX] for product in storage]
+
+    if name in product_names:
+        print(f"product name {name} is already taken.")
+        return None
+
+    product_id = generate_product_id(storage)
+
+    storage.append((product_id, name, normalize_price(price), quantity))
+
+    return product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -72,8 +84,12 @@ 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[PRODUCT_ID_INDEX] == product_id:
+            return product
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -99,8 +115,16 @@ 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
+
+    for i, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            updated_product = (product_id, name, normalize_price(price), quantity)
+            storage[i] = 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:
@@ -116,5 +140,10 @@ 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 i, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage = storage[:i] + storage[i + 1 :]
+            return product_id
+
+    print(f"no product with id {product_id}")
+    return None

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