Hola Shopping Cart 🛍️

Challenge

Build an app that supports adding products to a shopping cart and displaying a total price. | Product code | Name | Price | | -------------- | -------------- | --------- | | GR1 | Green Tea | 3.11 € | | SR1 | Strawberries | 5.00 € | | CF1 | Coffee | 11.23 € |

Special conditions

• Green Tea has buy-one-get-one-free offer

• Strawberries price changes to 4.50€ if you buy 3 or more

• Coffee price drops to 2/3 of the original price if you buy 3 or more

Shopping cart can accept items in any order and be flexible regarding pricing rules.

Test data

Basket	Total price expected
GR1, GR1	3.11€
SR1, SR1, GR1, SR1	16.61€
GR1, CF1, SR1, CF1, CF1	30.57€

Solution

Hola Shopping Cart 🛍️

Are you tired of shopping on over-designed webshops? Hola Shopping Cart is a simple, eyes-friendly CLI application to browse products and fill the shopping cart. Don't leave your favorite terminal to go shopping.

Installation

Requirements: Ruby >= 3.0.0 installed

Available as a gem through RubyGems, install it:

$ gem install hola_shopping_cart

Usage

In order to start shopping, run the command:

$ hola

Use your keyboard's Up/Down arrow keys to navigate the product list. Press Enter to select a product. Select a quantity by inserting a number. When you want to finish shopping, press n to see the shopping cart.

Arhitecture

Three primary actions happen in the life cycle of the app:

• User input capture
• Processing items in a cart
• Rendering a cart to display it

User input

The underlying library TTY::Prompt is used to ease up gathering user input from the command line. The library has a number of handy prompt types; one of them is select, which is used to show a list of available products and make a selection. The command line immediately displays a user selection for a great user experience. After that, it's up to the processing action to take over.

Processing

Processing action is responsible for fetching necessary data, processing the product offers, and answering with Cart::Item. The item is then stored in the Cart, and processing is complete. The processing is done intentionally before adding an item to the cart to avoid big performance spikes at the end when the cart is rendered. That brings additional benefits. For example, if the product price or offer changes in the middle of the user's shopping, the total price will respect the price shown when the product is added to the cart.

Sequence diagram of processing an item:

Cart render

The TTY::Table table formatting component is used to perform rendering. The table is rendered with an ASCII-type border.

+------------+------+--------+--------+------------------------+
|Item        |Price |Quantity|Subtotal|Offer                   |
+------------+------+--------+--------+------------------------+
|Green Tea   |3.11€ |1       |3.11€   |                        |
|Strawberries|5.00€ |1       |5.00€   |                        |
|Coffee      |11.23€|3       |22.46€  |Two-Thirds Bulk Discount|
+------------+------+--------+--------+------------------------+
|Total       |      |        |30.57€  |                        |
+------------+------+--------+--------+------------------------+

Flexibility

The architecture is designed to be flexible as much as possible when comes to adding new special offers or modifying existing ones.

To add a new special offer, you must create a new file inside hola/offers. The example below shows adding a price reduction of 20%.

module Hola
  class Offer
    class NewSpecialDiscount < Offer
      def price
        super * 0.8
      end
    end
  end
end

The last step is to add a newly created special offer to a product.

product.apply_offer("NewSpecialDiscount")

Tests

rspec ./spec
.............................................................................................

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