Checkout by wolas

• Checkout functionality with a fully manageable discount system
• each pricing_rule has a code, matched to every item to see wether it applies, the resulting items are called selected_items
• Rules are defined by two parameters:
  • Condition: which is a function over selected_items determining wether the discount can be applied or not. Returns true or false
  • Discount: again, a function over selected_items which determines the amount to be discounted. returns an Integer
• Helper methods are present to provide more human like coding. These include buy_more_than_x_get_y_off_each and buy_x_get_y_free
• The main effort has been to provide a fully customisable discount system paired with beautiful syntax.

Considerations

I wanted to extend the PricingRule class by allowing one instance to work on multiple codes and have multiple conditions. But I think that the same functionality is achieved by having multiple PricingRule instances with the same code. This also makes for easier understanding and using.

Example

    voucher = Item.new("Cabify Voucher", 5, "VOUCHER")
    tshirt = Item.new("Cabify T-Shirt", 20, "TSHIRT")
    mug = Item.new("Cabify Coffee Mug", 7.5, "MUG")
    
    pricing_voucher = PricingRule.new("VOUCHER")
    pricing_voucher.buy_x_get_y_free 2, 1
    
    pricing_tshirt = PricingRule.new("TSHIRT")
    pricing_tshirt.buy_more_than_x_get_y_off_each 3, 1.00
    
    checkout = Checkout.new
    checkout.scan voucher
    checkout.scan voucher
    checkout.scan tshirt
    checkout.scan mug
    checkout.scan tshirt
    checkout.scan tshirt
    
    checkout.total

or, if you prefer to code your own discounts, just set the condition and discount. For example:

    voucher = Item.new("Cabify Voucher", 5, "VOUCHER")
    tshirt = Item.new("Cabify T-Shirt", 20, "TSHIRT")
    mug = Item.new("Cabify Coffee Mug", 7.5, "MUG")
    
    pricing_voucher = PricingRule.new("VOUCHER")
    
    # you must buy more than 2 and less than 10 items to get the discount
    pricing_voucher.condition = lambda do |items|
      items.size > 2 and items.size < 10
    end
    
    # you get a total discount of 3, independent of number of vouchers bought
    pricing_voucher.discount = lambda do |items|
      3
    end
    

Requirements

Ruby, Rspec