Price_calculator.rb

class PriceCalculator
  
  attr_reader :item_quantities, :item_names

  ITEM_UNIT_PRICES = {
    milk: 3.97,
    bread: 2.17,
    banana: 0.99,
    apple: 0.89	  	
  }

  SALE_PRICES = {
    milk: {
      quantity: 2,
      price: 5.00
    },
    bread: {
      quantity: 3,
      price: 7.00    	
    }
  }
  
  def set_item_quantities(item_quantities)
     @item_quantities = item_quantities
  end

  def set_item_names(item_names)
    @item_names = item_names
  end 

  def initialize
    item_quantities = {
      milk: 0, 
      bread: 0, 
      banana: 0, 
      apple: 0
    }
    item_names = []
    set_item_quantities(item_quantities)
    set_item_names(item_names)
  end

  def user_input
    puts "Please enter all the items purchased separated by a comma"
    item_names =  gets.chomp.split(',')
    set_item_names(item_names)
    remove_whitespaces_from_item_names
    convert_user_input_to_item_quantities
  end

  def calculate_price
    total_price = 0
    item_quantities.each do |item, quantity|
      if !SALE_PRICES[item].nil?
        quantity_on_sale_price = quantity / SALE_PRICES[item][:quantity]
        quantity_on_unit_price = quantity % SALE_PRICES[item][:quantity]
        sale_price = SALE_PRICES[item][:price]
        unit_price = ITEM_UNIT_PRICES[item]  	
        total_price +=  quantity_on_sale_price * sale_price + quantity_on_unit_price * unit_price 
      else
      	total_price += quantity * ITEM_UNIT_PRICES[item]
      end	
    end
    total_price.round(2) # round off to 2 digits after decimal	
  end	

  private

  def remove_whitespaces_from_item_names
    item_names.each do |item_name|
      item_name.gsub!(" ","")
    end 
  end

  def convert_user_input_to_item_quantities
    item_names.each do |item_name|
      case item_name
      when 'apple'
        @item_quantities[:apple] += 1    
      when 'milk'
        @item_quantities[:milk] += 1
      when 'bread'
        @item_quantities[:bread] += 1
      when 'banana'
        @item_quantities[:banana] += 1
      end        	
    end
  end

end

pc = PriceCalculator.new
pc.user_input
puts "Total cost: " + pc.calculate_price.to_s