coding-challenge

Implementation of the coding challenge from bitside

Assumptions

The following assumptions were made for the project:

• There can only ever be one DiscountRule for each item.
• DiscountRules are always linked to an item and independent of other items (i.e. it is not possible to say that if item A is purchased 5 times then item B is 1 time free).
• There are no discounts on the entire basket.
• If an item is no longer available in the warehouse, it will no longer be purchased and is therefore no longer listed.

How to extend

An attempt was made to implement the challenge according to the following principles:

• Strategy pattern for price calculation
• Single reponsibility principle
• Open close principle

If, for example, new rules are to apply to the entire shopping basket, a BasketDiscount rule can be inserted, which also inherits from DiscountRule. In this way, it would also be possible to define rules that apply to the entire shopping basket. However, a number of other business logics would then have to be taken into account.

Auto generated class diagram of implementation

classDiagram
    class DiscountRule {
        +apply(quantity: int): float
    }

    class NoDiscountRule {
        +apply(quantity: int): float
    }

    class PercentageDiscountRule {
        -discount_percentage: float
        +apply(quantity: int): float
    }

    class Warehouse {
        -__inventory: dict
        -__discount_rules: dict
        +add_discount_rule(item_id: str, discount_rule: DiscountRule)
        +get_discount_rule(item_id: str): DiscountRule
        +discount_available(item_id: str): bool
    }

    class Basket {
        -__user: User
        -__warehouse: Warehouse
        -__items_in_basket: dict
        +total(): float
    }

    class Item {
        -__item_id: str
        -__price: float
        +item_id: str
        +price: float
    }

    class User {
        -user_id: str
        -name: str
    }

    DiscountRule <|-- NoDiscountRule
    DiscountRule <|-- PercentageDiscountRule
    Warehouse "1" *-- "n" Item
    Warehouse "1" *-- "n" DiscountRule
    Basket "1" *-- "1" Warehouse
    Basket "1" *-- "n" Item
    Basket "1" *-- "1" User

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