1. Рустаев Самир Рустамович. 614

src/part1/constants.py

@@ -19,20 +19,22 @@
 # 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).
+NODE_ID_SHIFT: Final[int] = SEQUENCE_ID_BITS
+TIMESTAMP_SHIFT: Final[int] = NODE_ID_BITS + SEQUENCE_ID_BITS

src/part1/snowflake.py

@@ -13,14 +13,16 @@
 :func:`decode_node_id` and :func:`decode_sequence_id`.
 """
 
-import time  # noqa: F401
+from time import time
 
-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,
 )
 
 
@@ -34,8 +36,7 @@ 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() * 1000 - epoch_ms)
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +51,7 @@ 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 +64,7 @@ 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_ID_SHIFT) & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -78,8 +77,7 @@ 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_ID_MAX
 
 
 def generate_snowflake_id(
@@ -110,5 +108,17 @@ 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("overflows")
+        return None
+
+    return (elapsed_ms << TIMESTAMP_SHIFT) | (node_id << NODE_ID_SHIFT) | sequence_id

src/part4/cart.py

@@ -0,0 +1,87 @@
+"""Shopping-cart operations layered on top of the product store.
+
+The cart is a plain dictionary mapping each product identifier to the
+number of units of that product in the cart. Moving units between the
+store and the cart keeps the two sides in balance: :func:`add_to_cart` takes
+units out of stock, :func:`remove_from_cart` puts them back.
+
+Like the CRUD layer, the failure path never raises -- the operation prints
+an explanatory message to stdout and returns ``None``.
+"""
+
+from .storage import Product
+
+
+# TODO: при необходимости добавьте свои вспомогательные функции
+
+
+def add_to_cart(
+    storage: dict[str, Product],
+    product_names: set[str],
+    cart: dict[str, int],
+    product_id: str,
+    quantity: int,
+) -> int | None:
+    """Move ``quantity`` units of ``product_id`` from the store into ``cart``.
+
+    The product is looked up in ``storage``. If it is missing, a message is
+    printed and nothing changes. If the store holds fewer units than
+    requested, an explanatory message is printed and nothing changes.
+    Otherwise the store record is decremented by ``quantity`` and the cart
+    gains ``quantity`` units of ``product_id`` -- the product is added when
+    the cart had none of it.
+
+    Args:
+        storage: The product store to draw stock from; modified in place on
+            success.
+        product_names: The normalised names in ``storage``; a
+            quantity-only change never renames a product, so it is left
+            unchanged here.
+        cart: The cart to add the units to; modified in place on success.
+        product_id: The identifier of the product to add.
+        quantity: Number of units to move into the cart.
+
+    Returns:
+        The quantity of ``product_id`` in the cart after the addition, or
+        ``None`` when the product is unknown or the store cannot cover the
+        request.
+    """
+    # TODO: реализуйте функцию
+    return 0
+
+
+def remove_from_cart(
+    storage: dict[str, Product],
+    product_names: set[str],
+    cart: dict[str, int],
+    product_id: str,
+    quantity: int,
+) -> int | None:
+    """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store.
+
+    If the cart holds no units of ``product_id``, a message is printed and
+    nothing changes. If it holds fewer units than requested, an explanatory
+    message is printed and nothing changes. If the product is missing from
+    ``storage``, a message is printed and nothing changes. Otherwise the cart loses
+    ``quantity`` units of the product -- the product is dropped from the
+    cart when its quantity reaches zero -- and the store record gains
+    ``quantity`` units back.
+
+    Args:
+        storage: The product store to return stock to; modified in place on
+            success.
+        product_names: The normalised names in ``storage``; a
+            quantity-only change never renames a product, so it is left
+            unchanged here.
+        cart: The cart to take the units from; modified in place on
+            success.
+        product_id: The identifier of the product to remove.
+        quantity: Number of units to move back into the store.
+
+    Returns:
+        The quantity of ``product_id`` left in the cart after the removal
+        (zero means the product was dropped from the cart), or ``None`` when
+        the cart does not hold the product or holds too few units.
+    """
+    # TODO: реализуйте функцию
+    return 0

src/part4/crud.py

@@ -0,0 +1,157 @@
+"""Create/read/update/delete operations over the in-memory product store.
+
+Every operation takes the store -- a dictionary mapping product id to its
+:data:`~src.part4.storage.Product` record -- as its first argument and
+works on it in place. ``create_product``, ``update_product`` and
+``delete_product`` additionally take ``product_names``, the ``set[str]``
+of normalised names currently in ``storage`` (see
+:mod:`src.part4.storage`), and keep it in sync with ``storage`` on
+every successful call. The failure path never raises: the operation
+prints an explanatory message to stdout and returns ``None``.
+
+The identifier of a new product is a freshly generated UUID string
+(:func:`generate_product_id`), independent of insertion order or of any
+identifier already in ``storage``.
+
+Every product name that reaches the store is passed through
+:func:`~src.part4.utils.normalize_product_name` first. A name that
+normalises to an empty string is rejected -- the operation prints a
+message and changes nothing. Names are also kept unique --
+:func:`create_product` refuses a normalised name that is already taken,
+and :func:`update_product` refuses one that is already taken by another
+product -- via an O(1) membership test against ``product_names`` rather
+than a scan over ``storage.values()``.
+"""
+
+import uuid  # noqa: F401
+from typing import Any
+
+from .storage import (  # noqa: F401
+    NAME_KEY,
+    PRICE_KEY,
+    QUANTITY_KEY,
+    Product,
+)
+from .utils import normalize_price, normalize_product_name  # noqa: F401
+
+
+def generate_product_id() -> str:
+    """Generate an identifier for a new product.
+
+    Returns:
+        A freshly generated UUID, stringified.
+    """
+    # TODO: реализуйте функцию
+    return ""
+
+
+def create_product(
+    storage: dict[str, Product],
+    product_names: set[str],
+    fields: dict[str, Any],
+) -> str | None:
+    """Add a new product to ``storage`` and return its new identifier.
+
+    Args:
+        storage: The product store to add to; modified in place on
+            success.
+        product_names: The normalised names already in ``storage``; the
+            new name is added to it in place on success.
+        fields: A dictionary with the ``name``, ``price`` and ``quantity``
+            keys (see :data:`~src.part4.storage.NAME_KEY`,
+            :data:`~src.part4.storage.PRICE_KEY` and
+            :data:`~src.part4.storage.QUANTITY_KEY`) describing the
+            product. ``name`` is normalised (surrounding whitespace
+            stripped, lower-cased) before it is stored or compared.
+            ``price`` is a :class:`~decimal.Decimal` amount and is rounded
+            to the stored money precision before it is saved.
+
+    Returns:
+        The identifier generated for the new product, or ``None`` when
+        ``name`` is blank once normalised or a product with the same
+        normalised name already exists. In the ``None`` case ``storage``
+        and ``product_names`` are left unchanged and an explanatory
+        message is printed.
+    """
+    # TODO: реализуйте функцию
+    return ""
+
+
+def read_product(storage: dict[str, Product], product_id: str) -> Product | None:
+    """Return the product stored under ``product_id``.
+
+    Args:
+        storage: The product store to search.
+        product_id: The identifier to look up.
+
+    Returns:
+        The matching product record, or ``None`` when no product carries
+        that identifier (a message is printed in that case).
+    """
+    # TODO: реализуйте функцию
+    return {}
+
+
+def update_product(
+    storage: dict[str, Product],
+    product_names: set[str],
+    product_id: str,
+    fields: dict[str, Any],
+) -> Product | None:
+    """Overwrite the fields of the product stored under ``product_id``.
+
+    The identifier itself is preserved. ``fields`` may carry any subset of
+    ``name``, ``price`` and ``quantity``; a key that is missing keeps the
+    value the product already has, so a caller can update a single field
+    without repeating the other two.
+
+    Args:
+        storage: The product store to modify; the matching record is
+            updated in place on success.
+        product_names: The normalised names already in ``storage``; on a
+            successful rename the old name is removed from it and the new
+            one added.
+        product_id: The identifier of the product to change.
+        fields: A dictionary with any of the ``name``, ``price`` and
+            ``quantity`` keys (see :data:`~src.part4.storage.NAME_KEY`,
+            :data:`~src.part4.storage.PRICE_KEY` and
+            :data:`~src.part4.storage.QUANTITY_KEY`) holding the new
+            values. ``price`` is a :class:`~decimal.Decimal` amount and is
+            rounded to the stored money precision before it is saved.
+            Mutated in place: a ``name`` or ``price`` value present in
+            ``fields`` is overwritten with its normalised form.
+
+    Returns:
+        The updated product record, or ``None`` when ``name`` is present
+        and blank once normalised, no product carries that identifier, or
+        the normalised name is already taken by another product. In every
+        ``None`` case ``storage`` and ``product_names`` are left unchanged
+        and an explanatory message is printed. Renaming a product to its
+        own current name is allowed.
+    """
+    # TODO: реализуйте функцию
+    return {}
+
+
+def delete_product(
+    storage: dict[str, Product],
+    product_names: set[str],
+    product_id: str,
+) -> str | None:
+    """Remove the product stored under ``product_id`` from ``storage``.
+
+    Args:
+        storage: The product store to remove from; modified in place on
+            success.
+        product_names: The normalised names already in ``storage``; the
+            departing product's name is removed from it in place on
+            success.
+        product_id: The identifier of the product to remove.
+
+    Returns:
+        ``product_id`` when a product was removed, or ``None`` when no
+        product carried that identifier (``storage`` and ``product_names``
+        are left unchanged and a message is printed).
+    """
+    # TODO: реализуйте функцию
+    return ""