SupermarketCashier

This project implements a simple cashier function for a small supermarket chain. The cashier function allows adding products to a cart and displaying the total price. It is designed with flexibility to accommodate frequently changing pricing rules.

Requirements

1. Programming Language: Elixir
2. Methodology: Test-Driven Development (TDD)
3. Repository: GitHub (public)
4. Database: Not required

Product Details

The following test products are registered in the system:

Product Code	Name	Price
GR1	Green tea	£3.11
SR1	Strawberries	£5.00
CF1	Coffee	£11.23

Special Conditions

1. Green Tea (GR1): Buy-one-get-one-free offer.
2. Strawberries (SR1): Price drops to £4.50 per strawberry if 3 or more are purchased.
3. Coffee (CF1): Price drops to two-thirds of the original price if 3 or more are purchased.

Test Data

The checkout system can scan items in any order. Below are some test cases:

Basket: GR1, SR1, GR1, GR1, CF1

Total Price Expected: £22.45

Basket: GR1, GR1

Total Price Expected: £3.11

Basket: SR1, SR1, GR1, SR1

Total Price Expected: £16.61

Basket: GR1, CF1, SR1, CF1, CF1

Total Price Expected: £30.57

Setup and Installation

1. Clone the repository:

git clone https://github.com/ivanovskairena/supermarket_cashier.git
cd supermarket_cashier

2. Install dependencies:

mix deps.get

3. Run tests:

mix test

4. Run credo and dialyzer checks

mix credo

mix dialyzer

5. Generate test coverage report

mix coveralls.html

Usage in IEx

To interact with the SupermarketCashier module in IEx, follow these steps:

Test Individual Scans

1. Start IEx session

Navigate to your project directory and start an IEx session with Mix:

iex -S mix

2. Define pricing rules:

pricing_rules = [
  {SupermarketCashier.PricingRules.BuyOneGetOneFree, :apply_rule},
  {SupermarketCashier.PricingRules.BulkDiscount, :apply_rule},
  {SupermarketCashier.PricingRules.MultiDiscount, :apply_rule}
]

3. Start the Checkout process

{:ok, pid} = SupermarketCashier.Checkout.new(pricing_rules)

3. Test individual scans:

SupermarketCashier.Checkout.scan(pid, "GR1")
IO.puts("Total after scanning GR1: #{SupermarketCashier.Checkout.total(pid)}")

SupermarketCashier.Checkout.scan(pid, "SR1")
IO.puts("Total after scanning SR1: #{SupermarketCashier.Checkout.total(pid)}")

SupermarketCashier.Checkout.scan(pid, "GR1")
IO.puts("Total after scanning GR1: #{SupermarketCashier.Checkout.total(pid)}")

SupermarketCashier.Checkout.scan(pid, "GR1")
IO.puts("Total after scanning GR1: #{SupermarketCashier.Checkout.total(pid)}")

SupermarketCashier.Checkout.scan(pid, "CF1")
IO.puts("Total after scanning CF1: #{SupermarketCashier.Checkout.total(pid)}")

SupermarketCashier.Checkout.total(pid)
IO.puts("Total: #{total}")

Test with a basket of items

1. Start IEx session

Navigate to your project directory and start an IEx session with Mix:

iex -S mix

2. Alias the BasketScan Helper

alias SupermarketCashier.BasketScan

3. Define pricing rules:

pricing_rules = [
  {SupermarketCashier.PricingRules.BuyOneGetOneFree, :apply_rule},
  {SupermarketCashier.PricingRules.BulkDiscount, :apply_rule},
  {SupermarketCashier.PricingRules.MultiDiscount, :apply_rule}
]

4. Start the Checkout process

{:ok, pid} = SupermarketCashier.Checkout.new(pricing_rules)

5. Add Items to the Basket

items = ["GR1", "SR1", "GR1", "GR1", "CF1"]

6. Test the result

total = BasketScan.test_basket(pricing_rules, items)
IO.puts("Total: #{total}")