2. Банад Михаил .614

src/part1/constants.py

@@ -1,38 +1,10 @@
-"""Bit layout and default epoch for the Twitter Snowflake ID generator.
-
-A Snowflake identifier is a 63-bit positive integer packed as follows, from
-the most significant bit downwards:
-
-    1 bit   unused sign bit, always zero
-    41 bits milliseconds elapsed since a custom epoch
-    10 bits node identifier
-    12 bits per-millisecond sequence counter
-
-The shift and mask constants should be derived from the bit widths so that
-changing a width keeps everything else consistent.
-"""
-
-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
-
-# Node identifier used when the caller does not supply one.
-NODE_ID_DEFAULT: Final[int] = 0
-
-# Width of each field, in bits.
-TIMESTAMP_BITS: Final[int] = 0
-NODE_ID_BITS: Final[int] = 0
-SEQUENCE_ID_BITS: Final[int] = 0
-
-# 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).
+EPOCH_MS_DEFAULT: int = 1288834974657
+NODE_ID_DEFAULT: int = 1
+TIMESTAMP_BITS: int = 41
+NODE_ID_BITS: int = 10
+SEQUENCE_ID_BITS: int = 12
+TIMESTAMP_MS_MAX: int = 2**TIMESTAMP_BITS - 1
+NODE_ID_MAX: int = 2**NODE_ID_BITS - 1
+SEQUENCE_ID_MAX: int = 2**SEQUENCE_ID_BITS - 1
+NODE_ID_SHIFT: int = SEQUENCE_ID_BITS
+TIMESTAMP_SHIFT: int = SEQUENCE_ID_BITS + NODE_ID_BITS

src/part1/snowflake.py

@@ -1,114 +1,48 @@
-"""Twitter Snowflake identifier generator.
+import time
 
-Snowflake produces roughly time-ordered 64-bit integer identifiers without
-coordination between nodes. Each identifier packs the milliseconds elapsed
-since a custom epoch, a node identifier and a per-millisecond sequence counter
-into a single 63-bit positive integer (see ``constants`` for the layout).
-
-The public entry point is :func:`generate_snowflake_id`. It is stateless: the
-caller passes the sequence counter on every call and is responsible for
-advancing it within a millisecond and resetting it when the clock ticks over.
-
-Each packed field can be read back on its own with :func:`decode_timestamp_ms`,
-:func:`decode_node_id` and :func:`decode_sequence_id`.
-"""
-
-import time  # noqa: F401
-
-from .constants import (  # noqa: F401
+from .constants import (
     EPOCH_MS_DEFAULT,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    NODE_ID_SHIFT,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
+    TIMESTAMP_SHIFT,
 )
 
 
 def read_current_millis(epoch_ms: int) -> int:
-    """Read the number of milliseconds elapsed since the custom epoch.
-
-    Args:
-        epoch_ms: The custom epoch expressed as Unix milliseconds.
-
-    Returns:
-        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(int(time.time() * 1000) - epoch_ms)
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
-    """Read the timestamp field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced against the same epoch.
-        epoch_ms: The epoch the identifier was generated against. Defaults to
-            the original Twitter epoch (2010-11-04 01:42:54.657 UTC).
-
-    Returns:
-        The absolute Unix time in milliseconds at which the identifier was
-        generated.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    return int(snowflake_id // (2**TIMESTAMP_SHIFT) + epoch_ms)
 
 
-def decode_node_id(snowflake_id: int) -> int:
-    """Read the node identifier field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The node identifier packed into ``snowflake_id``, in the range
-        ``[0, NODE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+def decode_node_id(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
+    return int((
+        snowflake_id
+        - (
+            (decode_timestamp_ms(snowflake_id, epoch_ms) - epoch_ms)
+            * 2**TIMESTAMP_SHIFT
+        )
+    ) // (2**NODE_ID_SHIFT))
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
-    """Read the sequence counter field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The per-millisecond sequence counter packed into ``snowflake_id``, in
-        the range ``[0, SEQUENCE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    return int(snowflake_id - ((snowflake_id // 2**NODE_ID_SHIFT) * (2**NODE_ID_SHIFT)))
 
 
 def generate_snowflake_id(
-    sequence_id: int,
-    node_id: int = NODE_ID_DEFAULT,
-    epoch_ms: int = EPOCH_MS_DEFAULT,
+    sequence_id: int, node_id: int = NODE_ID_DEFAULT, epoch_ms: int = EPOCH_MS_DEFAULT
 ) -> int | None:
-    """Build and return a Snowflake identifier for the current millisecond.
-
-    The function is stateless: the caller passes the per-millisecond sequence
-    counter explicitly. It is the caller's responsibility to increment
-    ``sequence_id`` for identifiers minted within the same millisecond and to
-    reset it once the clock advances.
-
-    Args:
-        sequence_id: The per-millisecond sequence counter, in the range
-            ``[0, SEQUENCE_ID_MAX]``.
-        node_id: The identifier of this node, in the range ``[0, NODE_ID_MAX]``.
-            Optional; defaults to ``NODE_ID_DEFAULT``.
-        epoch_ms: The start of the epoch as Unix milliseconds. Optional;
-            defaults to the original Twitter epoch (2010-11-04 01:42:54.657
-            UTC).
-
-    Returns:
-        The Snowflake identifier as a positive 63-bit integer, or ``None`` if
-        ``node_id`` is outside ``[0, NODE_ID_MAX]``, ``sequence_id`` is outside
-        ``[0, SEQUENCE_ID_MAX]``, or the elapsed time no longer fits in the
-        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
+    current_millis = read_current_millis(epoch_ms)
+    if current_millis < 0 or current_millis > TIMESTAMP_MS_MAX:
+        raise ValueError("Превышен максимальный лимит времени")
+    if node_id < 0 or node_id > NODE_ID_MAX:
+        raise ValueError("Node Id выходит за допустимые пределы")
+    if sequence_id < 0 or sequence_id > SEQUENCE_ID_MAX:
+        raise ValueError("Sequence Id выходит за допустимые пределы")
+    return int((current_millis * (2**TIMESTAMP_SHIFT)) + (
+        node_id * (2**NODE_ID_SHIFT) + sequence_id
+    ))

src/part2/cart.py

@@ -0,0 +1,47 @@
+from crud import read_product, update_product
+from storage import (
+    Product,
+    NAME_INDEX,
+    PRICE_INDEX,
+    QUANTITY_INDEX,
+)
+def find_cart_line(cart: list[CartLine], product_id: int) -> int | None:
+    for i, line in enumerate(cart):
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return i
+    return None
+
+CartLine = tuple[int, int]
+LINE_PRODUCT_ID_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
+def add_to_cart(storage: list[Product], cart: list[CartLine], product_id: int, quantity: int) -> CartLine | None:
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    stock = product[QUANTITY_INDEX]
+    if stock < quantity:
+        print(f"not enough stock for product <{product_id}>: <{stock}> available, <{quantity}> requested")
+        return None
+    new_stock = stock - quantity
+    update_product(storage, product_id, (product[NAME_INDEX], product[PRICE_INDEX], new_stock))
+
+def remove_from_cart(storage: list[Product], cart: list[CartLine], product_id: int, quantity: int) -> CartLine | None:
+    idx = find_cart_line(cart, product_id)
+    if idx is None:
+        print(f"product <{product_id}> is not in the cart")
+        return None
+    cart_qty = cart[idx][LINE_QUANTITY_INDEX]
+    if cart_qty < quantity:
+        print(f"cart holds only <{cart_qty}> unit(s) of product <{product_id}>, cannot remove <quantity>")
+        return None
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    new_stock = product[QUANTITY_INDEX] + quantity
+    update_product(storage, product_id, (product[NAME_INDEX], product[PRICE_INDEX], new_stock))
+    new_cart_qty = cart_qty - quantity
+    new_line = (product_id, new_cart_qty)
+    if new_cart_qty == 0:
+        cart.pop(idx)
+    else:
+        cart[idx] = new_line

src/part2/crud.py

@@ -0,0 +1,47 @@
+from decimal import Decimal
+from utils import normalize_price
+from storage import (
+    Product,
+    PRODUCT_ID_MIN, 
+    PRODUCT_ID_INDEX,
+    NAME_INDEX,
+    PRICE_INDEX,
+    QUANTITY_INDEX,
+)
+def generate_product_id(storage: list[Product]) -> int:
+    if not storage:
+        return PRODUCT_ID_MIN
+    return max(i[PRODUCT_ID_INDEX] for i in storage) + 1
+def create_product(storage: list[Product], fields: tuple[str, Decimal, int]) -> int | None:
+    name, price, qty = fields
+    for i in storage:
+        if i[NAME_INDEX] == name:
+            print(f"product name '<{name}>' is already taken")
+            return 0
+    new_id = generate_product_id(storage)
+    norm_price = normalize_price(price)
+    storage.append((new_id, name, norm_price, qty))
+    return new_id
+def read_product(storage: list[Product], product_id: int) -> Product | None:
+    for i in storage:
+        if i[PRODUCT_ID_INDEX] == product_id:
+            return i
+    print(f"no product with id <{product_id}>")
+    return None
+def update_product(storage: list[Product], product_id: int, fields: tuple[str, Decimal, int]) -> Product | None:
+    name, price, qty = fields
+    for i, p in enumerate(storage):
+        if p[PRODUCT_ID_INDEX] == product_id:
+            norm_price = normalize_price(price)
+            updated_product = (product_id, name, norm_price, qty)
+            storage[i] = update_product
+            return update_product
+        print(f"no product with id <{product_id}>")
+        return None
+    def delete_product(storage: list[Product], product_id: int) -> int | None:
+        for i, p in enumerate(storage):
+            if p[PRODUCT_ID_INDEX] == product_id:
+                storage.pop(i)
+                return product_id
+    print(f"no product with id <{product_id}>")
+    return None

src/part2/storage.py

@@ -0,0 +1,7 @@
+from typing import Final
+Product = tuple[int, str, Decimal, int]
+PRODUCT_ID_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
+PRODUCT_ID_MIN: Final[int] = 1

src/part2/utils.py

@@ -0,0 +1,8 @@
+from typing import Final
+from decimal import Decimal, ROUND_HALF_UP
+
+
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
+def normalize_price(price: Decimal) -> Decimal:
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)