4. Смолянинов Станислав Александрович. 613

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 +13,14 @@
 :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_MS_MAX,
 )
@@ -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
+    current_ms = time.time_ns() // 1_000_000
+    return current_ms - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +52,10 @@ 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
+    bits_shift = NODE_ID_BITS + SEQUENCE_ID_BITS
+    timestamp_part = snowflake_id >> bits_shift
+
+    return timestamp_part + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -64,8 +68,10 @@ 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
+    bits_mask = (1 << NODE_ID_BITS) - 1
+    node_id = (snowflake_id >> SEQUENCE_ID_BITS) & bits_mask
+
+    return node_id
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -78,8 +84,9 @@ 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
+    bits_mask = (1 << SEQUENCE_ID_BITS) - 1
+
+    return snowflake_id & bits_mask
 
 
 def generate_snowflake_id(
@@ -110,5 +117,23 @@ 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 < 0 or node_id > NODE_ID_MAX:
+        print(f"node_id must be in [0, {NODE_ID_MAX}], got {node_id}")
+        return None
+
+    if sequence_id < 0 or sequence_id > SEQUENCE_ID_MAX:
+        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("TIMESTAMP_MS_MAX overflows")
+        return None
+
+    snowflake_id = (
+        (current_millis << (SEQUENCE_ID_BITS + NODE_ID_BITS))
+        | (node_id << SEQUENCE_ID_BITS)
+        | sequence_id
+    )
+
+    return snowflake_id

src/part2/TASK.md

@@ -187,7 +187,7 @@ delete) над единым хранилищем, аккуратная рабо
    печатается сообщение об ошибке, содержащее идентификатор (например:
    `product <id> is not in the cart`), возвращается `None`, ничего не меняется.
 2. Иначе количество в строке корзины сравнивается с запрошенным. Если в корзине
-   строго меньше, чем `quantity` — печатается сообщение об ошибке с
+   строго меньше, чем `quantity` — печатается сообщение об ошибке с   
    идентификатором (например:
    `cart holds only <в корзине> unit(s) of product <id>, cannot remove <quantity>`),
    возвращается `None`, ничего не меняется.

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 +24,7 @@
 
 # TODO: задайте позиции полей внутри кортежа CartLine
 LINE_PRODUCT_ID_INDEX: Final = 0
-LINE_QUANTITY_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
 
 
 def add_to_cart(
@@ -53,8 +53,82 @@ 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 not product:
+        return None
+
+    if product[QUANTITY_INDEX] < quantity:
+        print(
+            f"not enough stock for product {product_id}: storage available, {product[QUANTITY_INDEX]} requested"
+        )
+
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] - quantity),
+    )
+
+    for index_cart_line in range(len(cart)):
+        if cart[index_cart_line][LINE_PRODUCT_ID_INDEX] == product_id:
+            cart[index_cart_line] = (
+                product_id,
+                quantity + cart[index_cart_line][LINE_QUANTITY_INDEX],
+            )
+            return cart[index_cart_line]
+
+    cart.append((product_id, quantity))
+    return (product_id, quantity)
+
+
+def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None:
+    """Find line of the product from cart
+
+    Find first entry in cart line with necassery product_id.
+
+    Args:
+        cart: user's shopping cart
+        product_id: The identifier of the product to find.
+
+    Returns:
+        cart_line if all correct
+        `None` if identifier of the product don't found
+    """
+    for cart_line in cart:
+        if cart_line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return cart_line
+
+    print(f"product {product_id} is not in the cart")
+    return None
+
+
+def update_cart_line(
+    cart: list[CartLine], product_id: int, quantity: int
+) -> CartLine | None:
+    """Update line of the product in the cart
+
+    If quantity = 0 line in the cart is remove. Else his quantity update.
+
+    Args:
+        cart: user's shopping cart
+        product_id: The identifier of the product to find.
+        quantity: New product quantity value
+
+    Returns:
+        cart_line if all correct
+        `None` if identifier of the product don't found
+    """
+    for index_cart_line in range(len(cart)):
+        if cart[index_cart_line][LINE_PRODUCT_ID_INDEX] == product_id:
+            if quantity == 0:
+                del cart[index_cart_line]
+            else:
+                cart[index_cart_line] = (product_id, quantity)
+            return (product_id, quantity)
+
+    print(f"product {product_id} is not in the cart")
+    return None
 
 
 def remove_from_cart(
@@ -85,5 +159,30 @@ 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 not cart_line:
+        return None
+
+    if cart_line[LINE_QUANTITY_INDEX] < quantity:
+        print(
+            f"cart holds only {cart_line[LINE_QUANTITY_INDEX]} unit(s) "
+            f"of product {product_id}, cannot remove {quantity}"
+        )
+
+        return None
+
+    product = read_product(storage, product_id)
+    if not product:
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] + quantity),
+    )
+
+    new_cart_line = update_cart_line(
+        cart, product_id, cart_line[LINE_QUANTITY_INDEX] - quantity
+    )
+
+    return new_cart_line

src/part2/crud.py

@@ -14,13 +14,16 @@
 
 from decimal import Decimal
 
-from .storage import (  # noqa: F401
+from .storage import (
+    FIELDS_NAME_INDEX,
+    FIELDS_PRICE_INDEX,
+    FIELDS_QUANTITY_INDEX,
     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 +37,10 @@ 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 +61,18 @@ def create_product(
         ``storage`` is left unchanged and a message naming the clashing
         name is printed.
     """
-    # TODO: реализуйте функцию
-    return 0
+    if any(fields[FIELDS_NAME_INDEX] == product[NAME_INDEX] for product in storage):
+        print(f"product name {fields[FIELDS_NAME_INDEX]} is already taken")
+        return None
+
+    new_id = generate_product_id(storage)
+    new_price = normalize_price(fields[FIELDS_PRICE_INDEX])
+
+    storage.append(
+        (new_id, fields[FIELDS_NAME_INDEX], new_price, fields[FIELDS_QUANTITY_INDEX])
+    )
+
+    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[PRODUCT_ID_INDEX] == product_id:
+            return product
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -97,10 +116,33 @@ def update_product(
     Returns:
         The updated ``(product_id, name, price, quantity)`` record, or
         ``None`` when no product carries that identifier (``storage`` is
-        left unchanged and a message is printed).
+        left unchanged and a message is printed). Also ``None`` when
+        product name is already taken.
     """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    index_modifiable_product = -1
+
+    for index in range(len(storage)):
+        if storage[index][NAME_INDEX] == fields[FIELDS_NAME_INDEX]:
+            print(f"product name {fields[FIELDS_NAME_INDEX]} is already taken")
+            return None
+
+        if storage[index][PRODUCT_ID_INDEX] == product_id:
+            index_modifiable_product = index
+
+    if index_modifiable_product == -1:
+        print(f"no product with id {product_id}")
+        return None
+
+    new_price = normalize_price(fields[FIELDS_PRICE_INDEX])
+
+    storage[index_modifiable_product] = (
+        product_id,
+        fields[FIELDS_NAME_INDEX],
+        new_price,
+        fields[FIELDS_QUANTITY_INDEX],
+    )
+
+    return storage[index_modifiable_product]
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -116,5 +158,10 @@ 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:
+            del storage[i]
+            return product_id
+
+    print(f"no product with id {product_id}")
+    return None