2. Безымянный Сергей. 613

Solve Task 2/cart.py

@@ -0,0 +1,99 @@
+from typing import Final
+from crud import (
+    read_product,
+    update_product,
+)
+from storage import (
+    QUANTITY_INDEX,
+    NAME_INDEX,
+    PRICE_INDEX,
+    Product)
+
+CartLine = tuple[int, int]
+LINE_PRODUCT_ID_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
+
+
+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(storage: list[Product],
+                cart: list[CartLine],
+                product_id: int,
+                quantity: int) -> CartLine | None:
+    product = read_product(storage, product_id)
+    if product is None:
+        return product
+    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_field = (
+        product[NAME_INDEX],
+        product[PRICE_INDEX],
+        storage_quantity - quantity
+    )
+    update_product(storage, product_id, new_field)
+
+    for index, line in enumerate(cart):
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            new_line: CartLine = (
+                product_id,
+                line[LINE_QUANTITY_INDEX] + quantity
+            )
+            cart[index] = new_line
+            return new_line
+    new_line: CartLine = (product_id, quantity)
+    cart.append(new_line)
+    return new_line
+
+
+def remove_from_cart(storage: list[Product],
+                     cart: list[CartLine],
+                     product_id: int,
+                     quantity: int) -> CartLine | None:
+    cart_line = find_cart_line(cart, product_id)
+    product = read_product(storage, product_id)
+    if cart_line is None:
+        return cart_line
+    if cart_line[LINE_QUANTITY_INDEX] < quantity:
+        print(f"Cart holds only {cart_line[LINE_QUANTITY_INDEX]} "
+              f"unit(s) of product {product_id}, cannot remove {quantity}.")
+        return None
+    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,
+    )
+    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

Solve Task 2/crud.py

@@ -0,0 +1,65 @@
+from decimal import Decimal
+from storage import (
+    PRODUCT_ID_MIN,
+    PRODUCT_ID_INDEX,
+    NAME_INDEX,
+    Product,
+)
+from utils import normalize_price
+
+
+def create_product(storage: list[Product],
+                   fields: tuple[str, Decimal, int]) -> int | None:
+    product_name, product_price, product_quantity = fields
+    for product in storage:
+        if product_name == product[NAME_INDEX]:
+            print(f"Product name {product_name} is already taken.")
+            return None
+    product_id = generate_product_id(storage)
+    storage.append((
+        product_id,
+        product_name,
+        normalize_price(product_price),
+        product_quantity
+    ))
+    return product_id
+
+
+def generate_product_id(storage: list[Product]) -> int:
+    if not storage:
+        return PRODUCT_ID_MIN
+    MAX_INDEX = max(product[PRODUCT_ID_INDEX] for product in storage)
+    return MAX_INDEX + 1
+
+
+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(
+    storage: list[Product],
+    product_id: int,
+    fields: tuple[str, Decimal, int],
+) -> Product | None:
+    for index, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            new_name, new_price, new_quantity = fields
+            norm_price = normalize_price(new_price)
+            NEW_PRODUCT = (product_id, new_name, norm_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

Solve Task 2/storage.py

@@ -0,0 +1,11 @@
+from decimal import Decimal
+from typing import Final
+
+Product = tuple[int, str, Decimal, int]
+
+PRODUCT_ID_INDEX: Final[int] = 0
+NAME_INDEX: Final[int] = 1
+PRICE_INDEX: Final[int] = 2
+QUANTITY_INDEX: Final[int] = 3
+
+PRODUCT_ID_MIN: Final[int] = 1

Solve Task 2/utils.py

@@ -0,0 +1,9 @@
+from typing import Final
+from decimal import Decimal, ROUND_HALF_UP
+
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
+
+
+def normalize_price(price: Decimal) -> Decimal:
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)

src/part2/cart.py

@@ -0,0 +1,129 @@
+from typing import Final
+
+from .crud import read_product, update_product
+from .storage import (
+    NAME_INDEX,
+    PRICE_INDEX,
+    QUANTITY_INDEX,
+    Product,
+)
+
+
+CartLine = tuple[int, int]
+
+LINE_PRODUCT_ID_INDEX: Final[int] = 0
+LINE_QUANTITY_INDEX: Final[int] = 1
+
+
+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(
+    storage: list[Product],
+    cart: list[CartLine],
+    product_id: int,
+    quantity: int,
+) -> CartLine | None:
+    product = read_product(storage, product_id)
+
+    if product is None:
+        return None
+
+    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(
+    storage: list[Product],
+    cart: list[CartLine],
+    product_id: int,
+    quantity: int,
+) -> CartLine | None:
+    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