diff --git a/src/part1/constants.py b/src/part1/constants.py index 9abfbba2..7a112a77 100644 --- a/src/part1/constants.py +++ b/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). diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py index d3abf050..047bd76b 100644 --- a/src/part1/snowflake.py +++ b/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, ) @@ -35,7 +37,8 @@ def read_current_millis(epoch_ms: int) -> int: negative if ``epoch_ms`` lies in the future. """ # TODO: реализуйте функцию - return 0 + now_ms = int(time.time() * 1000) + 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 + snowflake_id_time = snowflake_id >> (NODE_ID_BITS + SEQUENCE_ID_BITS) + return snowflake_id_time + epoch_ms def decode_node_id(snowflake_id: int) -> int: @@ -65,7 +68,9 @@ def decode_node_id(snowflake_id: int) -> int: ``[0, NODE_ID_MAX]``. """ # TODO: реализуйте функцию - return 0 + snowflake_id_knot = snowflake_id >> SEQUENCE_ID_BITS + snowflake_id_knot = snowflake_id_knot & NODE_ID_MAX + return snowflake_id_knot def decode_sequence_id(snowflake_id: int) -> int: @@ -79,7 +84,7 @@ def decode_sequence_id(snowflake_id: int) -> int: the range ``[0, SEQUENCE_ID_MAX]``. """ # TODO: реализуйте функцию - return 0 + return snowflake_id & SEQUENCE_ID_MAX def generate_snowflake_id( @@ -111,4 +116,17 @@ def generate_snowflake_id( 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 + time_ms = read_current_millis(epoch_ms) + if time_ms > TIMESTAMP_MS_MAX: + print("overflows") + return None + snowflake_id = sequence_id + snowflake_id |= node_id << SEQUENCE_ID_BITS + snowflake_id |= time_ms << (NODE_ID_BITS + SEQUENCE_ID_BITS) + return snowflake_id diff --git a/src/part2/cart.py b/src/part2/cart.py index 063f9aea..cd84d5ec 100644 --- a/src/part2/cart.py +++ b/src/part2/cart.py @@ -1,20 +1,10 @@ -"""Shopping-cart operations layered on top of the product store. - -The cart is a plain list of tuples, one :data:`CartLine` -- -``(product_id, quantity)`` -- per distinct product. 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 typing import Final from .crud import read_product, update_product # noqa: F401 from .storage import ( # noqa: F401 NAME_INDEX, PRICE_INDEX, + PRODUCT_ID_INDEX, QUANTITY_INDEX, Product, ) @@ -24,37 +14,65 @@ # 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( - storage: list[Product], +def change_cart_quantity( cart: list[CartLine], product_id: int, quantity: int, ) -> CartLine | None: - """Move ``quantity`` units of ``product_id`` from the store into ``cart``. + for i, cart_i in enumerate(cart): + if cart_i[LINE_PRODUCT_ID_INDEX] == product_id: + if cart_i[LINE_QUANTITY_INDEX] + quantity == 0: + del cart[i] + return (product_id, 0) + cart[i] = (cart_i[0], cart_i[1] + quantity) + return cart[i] + return None - The product is looked up in ``storage``. If it is missing, a message is - printed (by :func:`~src.part2.crud.read_product`) 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 line for ``product_id`` gains - ``quantity`` units -- a new line is created when the cart had none. - Args: - storage: The product store to draw stock from; modified in place on - success. - 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 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) +def add_to_cart( + storage: list[Product], + cart: list[CartLine], + product_id: int, + quantity: int, +) -> CartLine | None: + product_new = read_product(storage, product_id) + if product_new is None: + return None + if product_new[QUANTITY_INDEX] < quantity: + print( + f"not enough stock for product {product_id}: {product_new[QUANTITY_INDEX]} available, {quantity} requested" + ) + return None + index = next( + (i for i, p in enumerate(storage) if p[PRODUCT_ID_INDEX] == product_id), None + ) + if index is None: + return None + storage[index] = ( + product_new[0], + product_new[1], + product_new[2], + product_new[3] - quantity, + ) + change = change_cart_quantity(cart, product_id, quantity) + if change is None: + cart.append((product_id, quantity)) + return (product_id, quantity) + else: + return change + + +def find_cart_line( + cart: list[CartLine], + product_id: int, +) -> CartLine | None: + for cart_i in cart: + if cart_i[LINE_PRODUCT_ID_INDEX] == product_id: + return cart_i + return None def remove_from_cart( @@ -63,27 +81,27 @@ def remove_from_cart( product_id: int, quantity: int, ) -> CartLine | None: - """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store. - - The cart line for ``product_id`` is looked up. If there is none, a - message is printed and nothing changes. If the line holds fewer units - than requested, an explanatory message is printed and nothing changes. - Otherwise the cart line loses ``quantity`` units -- the line is dropped - when it reaches zero -- and the store record gains ``quantity`` units - back. - - Args: - storage: The product store to return stock to; modified in place on - success. - 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 cart line for ``product_id`` after the removal (a quantity of - 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_find = find_cart_line(cart, product_id) + if cart_find is None: + print(f"product {product_id} is not in the cart") + return None + if cart_find[LINE_QUANTITY_INDEX] < quantity: + print( + f"cart holds only {cart_find[LINE_QUANTITY_INDEX]} unit(s) of product {product_id}, cannot remove {quantity}" + ) + return None + product_new = read_product(storage, product_id) + if product_new == None: + return None + index = next( + (i for i, p in enumerate(storage) if p[PRODUCT_ID_INDEX] == product_id), None + ) + if index is None: + return None + storage[index] = ( + product_new[0], + product_new[1], + product_new[2], + product_new[3] + quantity, + ) + return change_cart_quantity(cart, product_id, -quantity) diff --git a/src/part2/crud.py b/src/part2/crud.py index d026cbcb..a91620a7 100644 --- a/src/part2/crud.py +++ b/src/part2/crud.py @@ -1,79 +1,38 @@ -"""Create/read/update/delete operations over the in-memory product store. - -Every operation takes the store -- a list of -:data:`~src.part2.storage.Product` tuples -- as its first argument and -works on it in place. The failure path never raises: the operation prints -an explanatory message to stdout and returns ``None``. - -The identifier of a new product is derived from the store itself -(:func:`generate_product_id`): one past the greatest identifier in use, or -:data:`~src.part2.storage.PRODUCT_ID_MIN` when the store is empty. -Product names are kept unique -- :func:`create_product` refuses a name that -is already taken. -""" - 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: - """Choose the identifier for the next product added to ``storage``. - - Args: - storage: The product store to inspect. - - Returns: - One past the greatest identifier currently held in ``storage``, or - :data:`~src.part2.storage.PRODUCT_ID_MIN` when ``storage`` is - empty. - """ - # TODO: реализуйте функцию - return 0 + if len(storage) == 0: + return PRODUCT_ID_MIN + return max(p[PRODUCT_ID_INDEX] for p in storage) + 1 def create_product( storage: list[Product], fields: tuple[str, Decimal, int] ) -> int | None: - """Append a new product to ``storage`` and return its new identifier. - - Args: - storage: The product store to append to; modified in place on - success. - fields: A ``(name, price, quantity)`` tuple describing the product. - ``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 a - product with the same name already exists. In the ``None`` case - ``storage`` is left unchanged and a message naming the clashing - name is printed. - """ - # TODO: реализуйте функцию - return 0 + for cor in storage: + if cor[NAME_INDEX] == fields[0]: + print(f"product name '{fields[0]}' is already taken.") + return None + new_id = generate_product_id(storage) + storage.append((new_id, fields[0], normalize_price(fields[1]), fields[2])) + return new_id def read_product(storage: list[Product], product_id: int) -> 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_id, name, price, quantity)`` record, or - ``None`` when no product carries that identifier (a message is - printed in that case). - """ - # TODO: реализуйте функцию - return (0, "", Decimal(0), 0) + for cor in storage: + if cor[PRODUCT_ID_INDEX] == product_id: + return cor + print(f"no product with id {product_id}") + return None def update_product( @@ -81,40 +40,23 @@ def update_product( product_id: int, fields: tuple[str, Decimal, int], ) -> Product | None: - """Overwrite the fields of the product stored under ``product_id``. - - The identifier itself is preserved; only ``name``, ``price`` and - ``quantity`` are replaced. - - Args: - storage: The product store to modify; the matching record is - replaced in place on success. - product_id: The identifier of the product to change. - fields: A ``(name, price, quantity)`` tuple with the new values. - ``price`` is a :class:`~decimal.Decimal` amount and is rounded - to the stored money precision before it is saved. - - 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). - """ - # TODO: реализуйте функцию - return (0, "", Decimal(0), 0) + index = next( + (i for i, p in enumerate(storage) if p[PRODUCT_ID_INDEX] == product_id), None + ) + if index is None: + print(f"no product with id {product_id}") + return None + fields_new = (product_id, fields[0], normalize_price(fields[1]), fields[2]) + storage[index] = fields_new + return fields_new def delete_product(storage: list[Product], product_id: int) -> int | None: - """Remove the product stored under ``product_id`` from ``storage``. - - Args: - storage: The product store to remove from; modified 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`` is left unchanged and - a message is printed). - """ - # TODO: реализуйте функцию - return 0 + index = next( + (i for i, p in enumerate(storage) if p[PRODUCT_ID_INDEX] == product_id), None + ) + if index is None: + print(f"no product with id {product_id}") + return None + storage.pop(index) + return product_id diff --git a/src/part2/storage.py b/src/part2/storage.py index b63d5fc7..81651a75 100644 --- a/src/part2/storage.py +++ b/src/part2/storage.py @@ -1,34 +1,12 @@ -"""In-memory product store for the shop CRUD exercise. - -The store is deliberately primitive: a plain list of tuples, with no -persistence, no indexing and no schema enforcement. Each element is a -:data:`Product` record -- a ``(product_id, name, price, quantity)`` tuple -where: - -* ``product_id`` -- unique positive integer key, assigned by the create - operation in :mod:`src.part2.crud`; -* ``name`` -- human-readable product name, unique across the store; -* ``price`` -- price of a single unit, held as a :class:`~decimal.Decimal` - amount rounded to a fixed number of decimal places (see - :func:`src.part2.utils.normalize_price`) so that money is never - subject to binary floating-point error; -* ``quantity`` -- number of units currently in stock. - -Field positions are exposed as ``*_INDEX`` constants so callers never -hard-code tuple offsets. -""" - from decimal import Decimal from typing import Final 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 diff --git a/src/part2/utils.py b/src/part2/utils.py index ec0348d3..bf080d5f 100644 --- a/src/part2/utils.py +++ b/src/part2/utils.py @@ -1,29 +1,11 @@ -"""Standalone helpers shared by the hw4 storage and CRUD modules. - -For now this is limited to money handling: :func:`normalize_price` rounds a -raw :class:`~decimal.Decimal` amount to the fixed number of fractional -digits (:data:`PRICE_PRECISION`) that every stored price uses, keeping -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: - """Round a price to the precision every stored record uses. - - Args: - price: The raw price amount. - - Returns: - ``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)