diff --git a/src/part1/constants.py b/src/part1/constants.py index 9abfbba2..0d968954 100644 --- a/src/part1/constants.py +++ b/src/part1/constants.py @@ -1,38 +1,12 @@ -"""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). +from time import time + + +CURRENT_EPOCH_MS: int = int(time() * 1000) +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 diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py index d3abf050..9d99c64c 100644 --- a/src/part1/snowflake.py +++ b/src/part1/snowflake.py @@ -1,114 +1,44 @@ -"""Twitter Snowflake identifier generator. - -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 - EPOCH_MS_DEFAULT, - NODE_ID_DEFAULT, - NODE_ID_MAX, - SEQUENCE_ID_MAX, - TIMESTAMP_MS_MAX, -) +from .constants import * 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 - - -def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int: - """Read the timestamp field out of a Snowflake identifier. + return CURRENT_EPOCH_MS - epoch_ms - 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 +def generate_snowflake_id( + sequence_id: int, node_id: int = NODE_ID_DEFAULT, epoch_ms: int = EPOCH_MS_DEFAULT +) -> int | None: + if not (0 <= node_id <= NODE_ID_MAX): + print(f"node_id must be in [0 ; {NODE_ID_MAX}]") + return None + if not (0 <= sequence_id <= SEQUENCE_ID_MAX): + print(f"sequence_id must be in [0 ; {SEQUENCE_ID_MAX}]") + return None -def decode_node_id(snowflake_id: int) -> int: - """Read the node identifier field out of a Snowflake identifier. + timestamp_ms = read_current_millis(epoch_ms) - Args: - snowflake_id: An identifier produced by :func:`generate_snowflake_id`. + if timestamp_ms > TIMESTAMP_MS_MAX: + print("Timestamp overflows") + return None - Returns: - The node identifier packed into ``snowflake_id``, in the range - ``[0, NODE_ID_MAX]``. - """ - # TODO: реализуйте функцию - return 0 + snowflake_id: int = ( + (timestamp_ms << (NODE_ID_BITS + SEQUENCE_ID_BITS)) + | (node_id << SEQUENCE_ID_BITS) + | sequence_id + ) + return snowflake_id 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 snowflake_id & SEQUENCE_ID_MAX -def generate_snowflake_id( - 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. +def decode_node_id(snowflake_id: int) -> int: + return (snowflake_id >> SEQUENCE_ID_BITS) & NODE_ID_MAX - 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 +def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int: + return ( + (snowflake_id >> NODE_ID_BITS + SEQUENCE_ID_BITS) & TIMESTAMP_MS_MAX + ) + epoch_ms diff --git a/src/part2/cart.py b/src/part2/cart.py index 063f9aea..cbdaa539 100644 --- a/src/part2/cart.py +++ b/src/part2/cart.py @@ -1,18 +1,7 @@ -"""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 +from .crud import read_product, update_product +from .storage import ( NAME_INDEX, PRICE_INDEX, QUANTITY_INDEX, @@ -20,11 +9,22 @@ ) -type CartLine = tuple[int, int] +CartLine = tuple[int, int] + +LINE_PRODUCT_ID_INDEX: Final[int] = 0 +LINE_QUANTITY_INDEX: Final[int] = 1 + -# TODO: задайте позиции полей внутри кортежа CartLine -LINE_PRODUCT_ID_INDEX: Final = 0 -LINE_QUANTITY_INDEX: Final = 0 +def find_cart_line( + cart: list[CartLine], + product_id: int, +) -> CartLine | None: + for line in cart: + if line[LINE_PRODUCT_ID_INDEX] == product_id: + return line + + print(f"Product {product_id} is not in the cart") + return None def add_to_cart( @@ -33,28 +33,45 @@ def add_to_cart( product_id: int, quantity: int, ) -> CartLine | 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 (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) + product = read_product(storage, product_id) + + if product is None: + return None + + storage_quantity = product[QUANTITY_INDEX] + + if storage_quantity < quantity: + print( + f"Not enough stock for product {product_id}: " + f"{storage_quantity} available, " + f"{quantity} requested." + ) + return None + + new_fields = ( + product[NAME_INDEX], + product[PRICE_INDEX], + storage_quantity - quantity, + ) + + update_product( + storage, + product_id, + new_fields, + ) + + for index, line in enumerate(cart): + if line[LINE_PRODUCT_ID_INDEX] == product_id: + new_line = ( + product_id, + line[LINE_QUANTITY_INDEX] + quantity, + ) + cart[index] = new_line + return new_line + + new_line = (product_id, quantity) + cart.append(new_line) + return new_line def remove_from_cart( @@ -63,27 +80,50 @@ 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_line = find_cart_line(cart, product_id) + + if cart_line is None: + return None + + if cart_line[LINE_QUANTITY_INDEX] < quantity: + print( + f"Cart holds only {cart_line[LINE_QUANTITY_INDEX]} " + f"unit(s) of product {product_id}, " + f"cannot remove {quantity}." + ) + return None + + product = read_product(storage, product_id) + + if product is None: + return None + + new_quantity = product[QUANTITY_INDEX] + quantity + + new_fields = ( + product[NAME_INDEX], + product[PRICE_INDEX], + new_quantity, + ) + + update_product( + storage, + product_id, + new_fields, + ) + + new_line: CartLine = ( + product_id, + cart_line[LINE_QUANTITY_INDEX] - quantity, + ) + + if new_line[LINE_QUANTITY_INDEX] == 0: + cart.remove(cart_line) + return new_line + + for index, line in enumerate(cart): + if line == cart_line: + cart[index] = new_line + return new_line + + return None diff --git a/src/part2/crud.py b/src/part2/crud.py index d026cbcb..a37746cc 100644 --- a/src/part2/crud.py +++ b/src/part2/crud.py @@ -1,79 +1,58 @@ -"""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``. +def create_product( + storage: list[Product], + fields: tuple[str, Decimal, int], +) -> int | None: + product_name, product_price, product_quantity = fields - Args: - storage: The product store to inspect. + for product in storage: + if product_name == product[NAME_INDEX]: + print(f"Product name {product_name} is already taken.") + return None - 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 + product_id = generate_product_id(storage) + storage.append( + ( + product_id, + product_name, + normalize_price(product_price), + product_quantity, + ) + ) + + return product_id -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. +def generate_product_id(storage: list[Product]) -> int: + if not storage: + return PRODUCT_ID_MIN - 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 + max_id = max(product[PRODUCT_ID_INDEX] for product in storage) + return max_id + 1 -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. +def read_product( + storage: list[Product], + product_id: int, +) -> Product | None: + for product in storage: + if product[PRODUCT_ID_INDEX] == product_id: + return product - 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) + print(f"No product with id {product_id}") + return None def update_product( @@ -81,40 +60,32 @@ 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) - - -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 + for index, product in enumerate(storage): + if product[PRODUCT_ID_INDEX] == product_id: + new_name, new_price, new_quantity = fields + + new_product: Product = ( + product_id, + new_name, + normalize_price(new_price), + new_quantity, + ) + + storage[index] = new_product + return new_product + + print(f"No product with id {product_id}") + return None + + +def delete_product( + storage: list[Product], + product_id: int, +) -> int | None: + for index, product in enumerate(storage): + if product[PRODUCT_ID_INDEX] == product_id: + storage.pop(index) + return product_id + + print(f"No product with id {product_id}.") + return None diff --git a/src/part2/storage.py b/src/part2/storage.py index b63d5fc7..726ab823 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] +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 11bd7a76..28fe897f 100644 --- a/src/part2/utils.py +++ b/src/part2/utils.py @@ -1,29 +1,10 @@ -"""Standalone helpers shared by the part2 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] = 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) diff --git a/src/part3/crud.py b/src/part3/crud.py index 68811d7e..2774f58c 100644 --- a/src/part3/crud.py +++ b/src/part3/crud.py @@ -1,87 +1,67 @@ -"""Create/read/update/delete operations over the in-memory product store. - -Every operation takes the store -- a list of -:data:`~src.part3.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.part3.storage.PRODUCT_ID_MIN` when the store is empty. - -Every product name that reaches the store is passed through -:func:`~src.part3.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. -""" - 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, normalize_product_name # noqa: F401 +from .utils import normalize_price, normalize_product_name + + +def check_product(storage: list[Product], product_name: str) -> bool | None: + if not (product_name): + print("product name must not be blank") + return None + + for product in storage: + if product_name == product[NAME_INDEX]: + print(f"product name '{product_name}' is already taken") + return None + return True def generate_product_id(storage: list[Product]) -> int: - """Choose the identifier for the next product added to ``storage``. + if not storage: + return PRODUCT_ID_MIN - Args: - storage: The product store to inspect. + max_id = max(product[PRODUCT_ID_INDEX] for product in storage) - Returns: - One past the greatest identifier currently held in ``storage``, or - :data:`~src.part3.storage.PRODUCT_ID_MIN` when ``storage`` is - empty. - """ - # TODO: реализуйте функцию (используйте своё решение части 2) - return 0 + return max_id + 1 def create_product( - storage: list[Product], fields: tuple[str, Decimal, int] + 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. - ``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`` - is left unchanged and an explanatory message is printed. - """ - # TODO: реализуйте функцию - return 0 + product_name, product_price, product_quantity = fields + normalized_name = normalize_product_name(product_name) + if (status := check_product(storage, normalized_name)) is None: + return status -def read_product(storage: list[Product], product_id: int) -> Product | None: - """Return the product stored under ``product_id``. + product_id = generate_product_id(storage) + normalized_price = normalize_price(product_price) + + storage.append( + ( + product_id, + normalized_name, + normalized_price, + product_quantity, + ) + ) - Args: - storage: The product store to search. - product_id: The identifier to look up. + return product_id - 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 (используйте своё решение части 2) - return (0, "", Decimal(0), 0) + +def read_product(storage: list[Product], product_id: int) -> Product | None: + 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( @@ -89,43 +69,48 @@ 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 ``name`` is blank once normalised, no product - carries that identifier, or the normalised name is already taken - by another product. In every ``None`` case ``storage`` is left - unchanged and an explanatory message is printed. Renaming a - product to its own current name is allowed. - """ - # TODO: реализуйте функцию - return (0, "", Decimal(0), 0) + product_name, product_price, product_quantity = fields + normalized_name = normalize_product_name(product_name) + + if not normalized_name: + print("product name must not be blank") + return None + + product_index = None + + for index, product in enumerate(storage): + if product[PRODUCT_ID_INDEX] == product_id: + product_index = index + break + + if product_index is None: + print(f"no product with id {product_id}") + return None + + for product in storage: + if ( + product[PRODUCT_ID_INDEX] != product_id + and product[NAME_INDEX] == normalized_name + ): + print(f"product name '{normalized_name}' is already taken") + return None + + new_product: Product = ( + product_id, + normalized_name, + normalize_price(product_price), + product_quantity, + ) + + storage[product_index] = new_product + return new_product 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 (используйте своё решение части 2) - return 0 + for index, product in enumerate(storage): + if product[PRODUCT_ID_INDEX] == product_id: + storage.pop(index) + return product_id + + print(f"no product with id {product_id}") + return None diff --git a/src/part3/run_admin.py b/src/part3/run_admin.py index c5feeb0b..53847ec6 100644 --- a/src/part3/run_admin.py +++ b/src/part3/run_admin.py @@ -1,107 +1,84 @@ -"""Interactive admin console for the part3 in-memory product store. - -Running this module starts a read-eval-print loop over a single product -store that lives in memory for the lifetime of the process. Every line -typed at the prompt is stripped of surrounding whitespace and matched -against the set of known commands: - -* ``help`` -- print the list of commands and what each one does; -* ``exit`` -- leave the loop and end the program; -* ``show`` -- print the whole store as a text table; -* ``create `` -- add a product; -* ``read `` -- print one product; -* ``update `` -- overwrite a product; -* ``delete `` -- remove a product. - -For ``create`` and ``update`` the price and quantity are always the last -two words of the line; everything between the verb (and, for ``update``, -the id) and those two words is joined with single spaces into the -product name, so a multi-word name such as ``Gibson SG Junior`` needs no -quoting. - -The four CRUD commands forward to :mod:`src.part3.crud`; whatever -that call returns is printed unless it is ``None``. A line whose first -word is not a known verb, or that carries the wrong number of arguments -for its verb, prints an "is not a command" notice. A line that names a -command correctly but whose id, price or quantity argument will not -parse prints a distinct "arguments are invalid" notice. Either way the -store is left untouched and the loop keeps running; only ``exit`` stops -it. -""" - -from decimal import Decimal, InvalidOperation # noqa: F401 +from decimal import Decimal, InvalidOperation from typing import Final -from .crud import ( # noqa: F401 +from .crud import ( create_product, delete_product, read_product, update_product, ) from .storage import Product -from .utils import get_storage_str_representation # noqa: F401 +from .utils import get_storage_str_representation -# TODO: задайте приглашение и текст справки -PROMPT: Final[str] = "" -HELP_TEXT: Final[str] = "" +PROMPT: Final[str] = "admin> " +HELP_TEXT: Final[str] = """Available commands: + help show this message + exit leave the console + show print the whole store as a table + create add a product, print its new id + read print the product with that id + update overwrite that product's fields + delete remove the product with that id -def show_help() -> None: - """Print the command reference to stdout. +For create and update the price and quantity are the last two words of the +line; everything before them is the product name, so it may contain spaces +(for example "Gibson SG Junior") and needs no quoting.""" - The text is the module-level :data:`HELP_TEXT` constant, printed as - is: a heading, one line per command with a short description, and a - note on how multi-word names are parsed. - """ - # TODO: реализуйте функцию +def show_help() -> None: + print(HELP_TEXT) -def print_result(result: object) -> None: - """Print a CRUD result to stdout unless it is ``None``. - Args: - result: The value returned by a CRUD operation. ``None`` means the - operation already reported its own failure, so nothing is - printed in that case. - """ - # TODO: реализуйте функцию +def print_result(result: object) -> None: + if result is not None: + print(result) def run_command(storage: list[Product], line: str) -> bool: - """Parse one console line and carry out the command it names. + parts = line.split() + + match parts: + case ["help"]: + show_help() + + case ["exit"]: + return False + + case ["show"]: + print(get_storage_str_representation(storage)) + + case ["create", *args] if len(args) >= 3: + name = " ".join(args[:-2]) + price = Decimal(args[-2]) + quantity = int(args[-1]) + print_result(create_product(storage, (name, price, quantity))) + + case ["read", product_id]: + print_result(read_product(storage, int(product_id))) + + case ["update", product_id, *args] if len(args) >= 3: + name = " ".join(args[:-2]) + price = Decimal(args[-2]) + quantity = int(args[-1]) + result = update_product( + storage, + int(product_id), + (name, price, quantity), + ) + print_result(result) - Args: - storage: The product store shared across the session; mutated in - place by the ``create``, ``update`` and ``delete`` commands. - line: One line of console input, already stripped of surrounding - whitespace. + case ["delete", product_id]: + print_result(delete_product(storage, int(product_id))) - Returns: - ``True`` to keep the read-eval-print loop running, or ``False`` - once the ``exit`` command has been seen. A line that is not a - known command prints a notice and still returns ``True``. + case _: + print(f"'{line}' is not a command") - Raises: - ValueError: If an id or quantity argument of a CRUD command does - not parse as a base-10 integer. - decimal.InvalidOperation: If the price argument of ``create`` or - ``update`` does not parse as a decimal number. - """ - # TODO: реализуйте функцию - return False + return True def main() -> None: - """Run the admin console until the ``exit`` command is entered. - - A single product store is created empty and kept in memory for the - whole session. Each iteration reads one line from stdin, strips its - surrounding whitespace and hands it to :func:`run_command`. A line - that names a command but whose id, price or quantity argument does - not parse is caught here and reported without stopping the loop; only - ``exit`` ends it. - """ storage: list[Product] = [] running = True diff --git a/src/part3/storage.py b/src/part3/storage.py index c5e34be5..726ab823 100644 --- a/src/part3/storage.py +++ b/src/part3/storage.py @@ -1,35 +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.part3.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.part3.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] +Product = tuple[int, str, Decimal, int] -# TODO: задайте позиции полей внутри кортежа Product (используйте своё решение -# части 2) 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/part3/utils.py b/src/part3/utils.py index 318ded0b..f5cc90b5 100644 --- a/src/part3/utils.py +++ b/src/part3/utils.py @@ -1,95 +1,53 @@ -"""Standalone helpers shared by the part3 storage and CRUD modules. - -Normalisation: - -* :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. -* :func:`normalize_product_name` strips surrounding whitespace from a - product name, collapses every internal run of whitespace to a single - space and lower-cases it, giving every stored name a single canonical - form. - -Presentation: - -* :func:`get_storage_str_representation` renders the whole store as a - text table meant to be printed to a terminal; each column is sized to - the longest value it holds in that particular call. -""" - -from decimal import ROUND_HALF_UP, Decimal # noqa: F401 +from decimal import ROUND_HALF_UP, Decimal from typing import Final from .storage import Product -# Number of fractional digits every stored price is rounded to. -# Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01"). -# TODO: задайте число знаков после запятой и шаг квантования (используйте своё -# решение части 2) -PRICE_PRECISION: Final[int] = 0 -PRICE_STEP: Final = Decimal(0) +PRICE_PRECISION: Final[int] = 2 +PRICE_STEP: Final[Decimal] = Decimal(1).scaleb(-PRICE_PRECISION) -# Column headers of the table produced by get_storage_str_representation, -# left to right. The width of each column is not fixed here -- it is -# measured per call from the data (see the function). -# TODO: задайте заголовки столбцов таблицы -TABLE_HEADERS: Final[tuple[str, ...]] = () +TABLE_HEADERS: Final[tuple[str, str, str, str]] = ( + "ID", + "name", + "price", + "quantity", +) def normalize_price(price: Decimal) -> Decimal: - """Round a price to the precision every stored record uses. + return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP) - Args: - price: The raw price amount. - Returns: - ``price`` quantised to :data:`PRICE_PRECISION` fractional digits, - with halves rounded up. - """ - # TODO: реализуйте функцию (используйте своё решение части 2) - return Decimal(0) +def normalize_product_name(name: str) -> str: + return " ".join(name.split()).lower() -def normalize_product_name(name: str) -> str: - """Reduce a product name to the canonical form the store keeps. +def get_storage_str_representation(storage: list[Product]) -> str: + rows: list[list[str]] = [list(TABLE_HEADERS)] - Args: - name: The raw product name. + for p in storage: + rows.append( + [ + str(p[0]), + str(p[1]), + str(p[2]), + str(p[3]), + ] + ) - Returns: - ``name`` with every leading and trailing whitespace character - removed, every internal run of whitespace (spaces, tabs and the - like) collapsed to a single space, and the rest lower-cased. For - example ``"abc def\tghi\tjkl"`` becomes ``"abc def ghi jkl"``. - The result is an empty string when ``name`` holds nothing but - whitespace. - """ - # TODO: реализуйте функцию - return "" + col_widths = [max(len(row[i]) for row in rows) for i in range(len(TABLE_HEADERS))] + formatted_rows = [] + for row in rows: + padded_cells = [ + f" {row[i].ljust(col_widths[i])} " for i in range(len(TABLE_HEADERS)) + ] + formatted_rows.append(f"|{'|'.join(padded_cells)}|") -# TODO: при необходимости добавьте свои вспомогательные функции + dash_cells = ["-" * (w + 2) for w in col_widths] + separator_line = f"|{'|'.join(dash_cells)}|" + formatted_rows.insert(1, separator_line) -def get_storage_str_representation(storage: list[Product]) -> str: - """Render the product store as a text table with data-sized columns. - - The table has the columns named by :data:`TABLE_HEADERS` -- id, name, - price and quantity. Each column is made exactly as wide as the longest - value it carries in this call (its header counted), so the columns - line up when the string is printed to a terminal and no value is ever - truncated. - - Args: - storage: The product store to render. - - Returns: - A multi-line string: a header row, a dashed separator row, then - one row per product in ``storage`` in list order. When ``storage`` - is empty only the header and separator rows are returned, sized to - the header labels. - """ - # TODO: реализуйте функцию - return "" + return "\n".join(formatted_rows) diff --git a/src/part4/cart.py b/src/part4/cart.py index aed9bb72..05097cf7 100644 --- a/src/part4/cart.py +++ b/src/part4/cart.py @@ -1,18 +1,4 @@ -"""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 +from .storage import QUANTITY_KEY, Product def add_to_cart( @@ -22,32 +8,22 @@ def add_to_cart( product_id: str, quantity: int, ) -> int | None: - """Move ``quantity`` units of ``product_id`` from the store into ``cart``. + if product_id not in storage: + print(f"no product with id {product_id}") + return None - 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. + storage_quantity = storage[product_id][QUANTITY_KEY] + if quantity > storage_quantity: + print( + f"not enough stock for product {product_id}: " + f"{storage_quantity} available, {quantity} requested" + ) + return None - 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. + storage[product_id][QUANTITY_KEY] -= quantity + cart[product_id] = cart.get(product_id, 0) + quantity - 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 + return cart[product_id] def remove_from_cart( @@ -57,31 +33,27 @@ def remove_from_cart( 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 + if product_id not in cart: + print(f"product {product_id} is not in the cart") + return None + + cart_quantity = cart[product_id] + if quantity > cart_quantity: + print( + f"cart holds only {cart_quantity} unit(s) of product {product_id}," + f" cannot remove {quantity}" + ) + return None + + if product_id not in storage: + print(f"no product with id {product_id}") + return None + + storage[product_id][QUANTITY_KEY] += quantity + cart[product_id] -= quantity + + if cart[product_id] == 0: + del cart[product_id] + return 0 + + return cart[product_id] diff --git a/src/part4/crud.py b/src/part4/crud.py index 471eff00..a8e38e13 100644 --- a/src/part4/crud.py +++ b/src/part4/crud.py @@ -1,48 +1,17 @@ -"""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 +import uuid from typing import Any -from .storage import ( # noqa: F401 +from .storage import ( NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product, ) -from .utils import normalize_price, normalize_product_name # noqa: F401 +from .utils import normalize_price, normalize_product_name def generate_product_id() -> str: - """Generate an identifier for a new product. - - Returns: - A freshly generated UUID, stringified. - """ - # TODO: реализуйте функцию - return "" + return str(uuid.uuid4()) def create_product( @@ -50,46 +19,36 @@ def create_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 "" + normalized_name = normalize_product_name(fields[NAME_KEY]) + if not normalized_name: + print("product name must not be blank") + return None -def read_product(storage: dict[str, Product], product_id: str) -> Product | None: - """Return the product stored under ``product_id``. + if normalized_name in product_names: + print(f"product name '{normalized_name}' is already taken") + return None + + normalized_price = normalize_price(fields[PRICE_KEY]) + product_id = generate_product_id() + quantity = fields[QUANTITY_KEY] + new_product = { + NAME_KEY: normalized_name, + PRICE_KEY: normalized_price, + QUANTITY_KEY: quantity, + } + + product_names.add(normalized_name) + storage[product_id] = new_product + + return 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 read_product(storage: dict[str, Product], product_id: str) -> Product | None: + if product_id not in storage: + print(f"no product with id {product_id}") + return None + return storage[product_id] def update_product( @@ -98,39 +57,43 @@ def update_product( 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 {} + if product_id not in storage: + print(f"no product with id {product_id}") + return None + + product = storage[product_id] + normalized_fields = fields.copy() + + if NAME_KEY in normalized_fields: + normalized_name = normalize_product_name(normalized_fields[NAME_KEY]) + + if not normalized_name: + print("product name must not be blank") + return None + + current_name = product[NAME_KEY] + + if normalized_name != current_name and normalized_name in product_names: + print(f"product name '{normalized_name}' is already taken") + return None + + normalized_fields[NAME_KEY] = normalized_name + + if PRICE_KEY in normalized_fields: + normalized_fields[PRICE_KEY] = normalize_price(normalized_fields[PRICE_KEY]) + + if NAME_KEY in normalized_fields: + old_name = product[NAME_KEY] + new_name = normalized_fields[NAME_KEY] + + if old_name != new_name: + product_names.discard(old_name) + product_names.add(new_name) + + fields.update(normalized_fields) + product.update(normalized_fields) + + return product def delete_product( @@ -138,20 +101,11 @@ def delete_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 "" + if product_id not in storage: + print(f"no product with id {product_id}") + return None + + product_names.discard(storage[product_id][NAME_KEY]) + del storage[product_id] + + return product_id diff --git a/src/part4/run_admin.py b/src/part4/run_admin.py index 2247b29b..c607b637 100644 --- a/src/part4/run_admin.py +++ b/src/part4/run_admin.py @@ -1,110 +1,95 @@ -"""Interactive admin console for the part4 in-memory product store. - -Running this module starts a read-eval-print loop over a single product -store that lives in memory for the lifetime of the process. Every line -typed at the prompt is stripped of surrounding whitespace and matched, -with a ``match`` statement, against the set of known commands: - -* ``help`` -- print the list of commands and what each one does; -* ``exit`` -- leave the loop and end the program; -* ``show`` -- print the whole store as a text table; -* ``create `` -- add a product; -* ``read `` -- print one product; -* ``update `` -- overwrite a product; -* ``delete `` -- remove a product. - -For ``create`` and ``update`` the price and quantity are always the last -two words of the line; everything between the verb (and, for ``update``, -the id) and those two words is joined with single spaces into the -product name, so a multi-word name such as ``Gibson SG Junior`` needs no -quoting. - -The four CRUD commands forward to :mod:`src.part4.crud`; whatever -that call returns is printed unless it is ``None``. A line whose first -word is not a known verb, or that carries the wrong number of arguments -for its verb, prints an "is not a command" notice. A line that names a -command correctly but whose price or quantity argument will not parse -prints a distinct "arguments are invalid" notice. Either way the store -is left untouched and the loop keeps running; only ``exit`` stops it. -""" - -from decimal import Decimal, InvalidOperation # noqa: F401 +from decimal import Decimal, InvalidOperation from typing import Final -from .crud import ( # noqa: F401 +from .crud import ( create_product, delete_product, read_product, update_product, ) -from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product # noqa: F401 -from .utils import get_storage_str_representation # noqa: F401 +from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product +from .utils import ( + get_storage_str_representation, + normalize_price, + normalize_product_name, +) -# TODO: задайте приглашение и текст справки (используйте своё решение части 3) -PROMPT: Final[str] = "" -HELP_TEXT: Final[str] = "" +PROMPT: Final[str] = "admin> " +HELP_TEXT: Final[str] = """Available commands: + help show this message + exit leave the console + show print the whole store as a table + create add a product, print its new id + read print the product with that id + update overwrite that product's fields + delete remove the product with that id +For create and update the price and quantity are the last two words of the +line; everything before them is the product name, so it may contain spaces +(for example "Gibson SG Junior") and needs no quoting.""" -def show_help() -> None: - """Print the command reference to stdout. - The text is the module-level :data:`HELP_TEXT` constant, printed as - is: a heading, one line per command with a short description, and a - note on how multi-word names are parsed. - """ - # TODO: реализуйте функцию (используйте своё решение части 3) +def show_help() -> None: + print(HELP_TEXT) def print_result(result: object) -> None: - """Print a CRUD result to stdout unless it is ``None``. - - Args: - result: The value returned by a CRUD operation. ``None`` means the - operation already reported its own failure, so nothing is - printed in that case. - """ - # TODO: реализуйте функцию (используйте своё решение части 3) + if result is not None: + print(result) def run_command( storage: dict[str, Product], product_names: set[str], line: str ) -> bool: - """Parse one console line and carry out the command it names. - - Args: - storage: The product store shared across the session; mutated in - place by the ``create``, ``update`` and ``delete`` commands. - product_names: The normalised names already in ``storage``; kept - in sync by the ``create``, ``update`` and ``delete`` commands. - line: One line of console input, already stripped of surrounding - whitespace. - - Returns: - ``True`` to keep the read-eval-print loop running, or ``False`` - once the ``exit`` command has been seen. A line that is not a - known command prints a notice and still returns ``True``. - - Raises: - ValueError: If the quantity argument of a CRUD command does not - parse as a base-10 integer. - decimal.InvalidOperation: If the price argument of ``create`` or - ``update`` does not parse as a decimal number. - """ - # TODO: реализуйте функцию - return False + parts = line.split() + + match parts: + case ["help"]: + show_help() + + case ["exit"]: + return False + + case ["show"]: + print(get_storage_str_representation(storage)) + + case ["create", *args] if len(args) >= 3: + name = " ".join(args[:-2]) + price = Decimal(args[-2]) + quantity = int(args[-1]) + fields = { + NAME_KEY: normalize_product_name(name), + PRICE_KEY: normalize_price(price), + QUANTITY_KEY: quantity, + } + print_result(create_product(storage, product_names, fields)) + + case ["read", product_id]: + print_result(read_product(storage, product_id)) + + case ["update", product_id, *args] if len(args) >= 3: + name = " ".join(args[:-2]) + price = Decimal(args[-2]) + quantity = int(args[-1]) + fields = { + NAME_KEY: normalize_product_name(name), + PRICE_KEY: normalize_price(price), + QUANTITY_KEY: quantity, + } + result = update_product(storage, product_names, product_id, fields) + print_result(result) + + case ["delete", product_id]: + print_result(delete_product(storage, product_names, product_id)) + + case _: + print(f"'{line}' is not a command") + + return True def main() -> None: - """Run the admin console until the ``exit`` command is entered. - - A single product store, and the set of normalised names it holds, are - created empty and kept in memory for the whole session. Each iteration - reads one line from stdin, strips its surrounding whitespace and hands - it to :func:`run_command`. A line that names a command but whose price - or quantity argument does not parse is caught here and reported - without stopping the loop; only ``exit`` ends it. - """ storage: dict[str, Product] = {} product_names: set[str] = set() running = True diff --git a/src/part4/storage.py b/src/part4/storage.py index 9acedf07..fe192215 100644 --- a/src/part4/storage.py +++ b/src/part4/storage.py @@ -1,45 +1,8 @@ -"""In-memory product store for the shop CRUD exercise. - -The store is deliberately primitive: a plain dictionary, with no -persistence and no schema enforcement. It maps a product's ``id`` -- a -UUID string assigned by the create operation in :mod:`src.part4.crud` --- to its :data:`Product` record -- a dictionary with the keys ``name``, -``price`` and ``quantity`` -- where: - -* the ``storage`` key itself -- unique string identifier, assigned by the - create operation in :mod:`src.part4.crud`; it is not duplicated - inside the record; -* ``name`` -- human-readable product name, unique across the store, held - in normalised form (see - :func:`src.part4.utils.normalize_product_name`); -* ``price`` -- price of a single unit, held as a :class:`~decimal.Decimal` - amount rounded to a fixed number of decimal places (see - :func:`src.part4.utils.normalize_price`) so that money is never - subject to binary floating-point error; -* ``quantity`` -- number of units currently in stock. - -Field names are exposed as ``*_KEY`` constants so callers never hard-code -the dictionary keys. - -Every caller that mutates the store also threads along a second -structure, a ``set[str]`` of the normalised names currently in use -- -see, for example, the ``product_names`` parameter of -:func:`src.part4.crud.create_product`. Keeping that name index as a -plain set passed next to ``storage``, rather than bundling the two into -an object, lets a name-uniqueness check become an O(1) membership test -against the set instead of a linear scan over ``storage.values()``. The -set must always mirror the normalised names present in ``storage``; the -functions in :mod:`src.part4.crud` keep the two in sync on every -successful create, update and delete. -""" - from typing import Any, Final type Product = dict[str, Any] -# Name of each field inside a Product record. -# TODO: задайте имена полей записи -NAME_KEY: Final = "" -PRICE_KEY: Final = "" -QUANTITY_KEY: Final = "" +NAME_KEY: Final = "name" +PRICE_KEY: Final = "price" +QUANTITY_KEY: Final = "quantity" diff --git a/src/part4/utils.py b/src/part4/utils.py index d2a940ea..b4141237 100644 --- a/src/part4/utils.py +++ b/src/part4/utils.py @@ -1,27 +1,7 @@ -"""Standalone helpers shared by the part4 storage and CRUD modules. - -Normalisation: - -* :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. -* :func:`normalize_product_name` strips surrounding whitespace from a - product name, collapses every internal run of whitespace to a single - space and lower-cases it, giving every stored name a single canonical - form. - -Presentation: - -* :func:`get_storage_str_representation` renders the whole store as a - text table meant to be printed to a terminal; each column is sized to - the longest value it holds in that particular call. -""" - -from decimal import ROUND_HALF_UP, Decimal # noqa: F401 +from decimal import ROUND_HALF_UP, Decimal from typing import Final -from .storage import ( # noqa: F401 +from .storage import ( NAME_KEY, PRICE_KEY, QUANTITY_KEY, @@ -29,72 +9,49 @@ ) -# Number of fractional digits every stored price is rounded to. -# Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01"). -# TODO: задайте число знаков после запятой и шаг квантования (используйте своё -# решение части 3) -PRICE_PRECISION: Final[int] = 0 -PRICE_STEP: Final = Decimal(0) +PRICE_PRECISION: Final[int] = 2 +PRICE_STEP: Final[Decimal] = Decimal(1).scaleb(-PRICE_PRECISION) -# Column headers of the table produced by get_storage_str_representation, -# left to right. The width of each column is not fixed here -- it is -# measured per call from the data (see the function). -# TODO: задайте заголовки столбцов таблицы (используйте своё решение части 3) -TABLE_HEADERS: Final[tuple[str, ...]] = () +TABLE_HEADERS: Final[tuple[str, str, str, str]] = ( + "ID", + "name", + "price", + "quantity", +) 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 (используйте своё решение части 3) - return Decimal(0) + return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP) def normalize_product_name(name: str) -> str: - """Reduce a product name to the canonical form the store keeps. - - Args: - name: The raw product name. - - Returns: - ``name`` with every leading and trailing whitespace character - removed, every internal run of whitespace (spaces, tabs and the - like) collapsed to a single space, and the rest lower-cased. For - example ``"abc def\tghi\tjkl"`` becomes ``"abc def ghi jkl"``. - The result is an empty string when ``name`` holds nothing but - whitespace. - """ - # TODO: реализуйте функцию (используйте своё решение части 3) - return "" - - -# TODO: при необходимости добавьте свои вспомогательные функции + return " ".join(name.split()).lower() def get_storage_str_representation(storage: dict[str, Product]) -> str: - """Render the product store as a text table with data-sized columns. - - The table has the columns named by :data:`TABLE_HEADERS` -- id, name, - price and quantity. Each column is made exactly as wide as the longest - value it carries in this call (its header counted), so the columns - line up when the string is printed to a terminal and no value is ever - truncated. - - Args: - storage: The product store to render. - - Returns: - A multi-line string: a header row, a dashed separator row, then - one row per product in ``storage``, in insertion order. When - ``storage`` is empty only the header and separator rows are - returned, sized to the header labels. - """ - # TODO: реализуйте функцию (используйте своё решение части 3) - return "" + rows: list[list[str]] = [list(TABLE_HEADERS)] + + for product_id, product in storage.items(): + rows.append( + [ + product_id, + product[NAME_KEY], + str(product[PRICE_KEY]), + str(product[QUANTITY_KEY]), + ] + ) + + col_widths = [max(len(row[i]) for row in rows) for i in range(len(TABLE_HEADERS))] + + formatted_rows = [] + for row in rows: + padded_cells = [ + f" {row[i].ljust(col_widths[i])} " for i in range(len(TABLE_HEADERS)) + ] + formatted_rows.append(f"|{'|'.join(padded_cells)}|") + + dash_cells = ["-" * (w + 2) for w in col_widths] + separator_line = f"|{'|'.join(dash_cells)}|" + formatted_rows.insert(1, separator_line) + + return "\n".join(formatted_rows)