add_to_cart.rb

require_relative "inet2"

cart = Cart.new(ARGV.delete_at(0))
ARGV.each do |a|
	@items.each { |i| cart.add_items(i) if a == i.name }
end

cart.read_from_file
cart.save_to_file

cart.rb

class Cart

	attr_reader :items

	include ItemContainer
	
	def initialize(owner)
		@items = Array.new
		@owner = owner
	end


	def save_to_file
		File.open("#{@owner}_cart.txt" , "w") do |f|
		@items.each{ |i| f.puts i}
		end
	end

	def read_from_file
		File.readlines("#{@owner}_cart.txt").each {|i| @items << i.to_real_item}		
		@items.uniq!
	rescue Errno::ENOENT
		File.open("#{@owner}_cart.txt" , "w") {}
		puts "file #{@owner}_cart.txt created"
	end
end

inet2.rb

require_relative "string"
require_relative "item_container"
require_relative "cart"
require_relative "item"
require_relative "order"
require_relative "virtual_item"
require_relative "real_item"

@items = []
@items<< RealItem.new( { :price=>109, :weight=>100, :name=> "car"} )
@items<< RealItem.new( { :price=>101, :weight=>100, :name=> "kettle"} )
@items<< RealItem.new( { :weight=>100, :name=> "dishwasher", :price=>100} )

item.rb

class Item

	@@discount = 0.05
	def self.discount
		if Time.now.month == 3
			return @@discount +0.1
		else
			return @@discount
		end	
	end

	def initialize(options={})
		@real_price = options[:price]
		@name = options[:name]
	end

	def info
		yield(price)
		yield(name)
	end

	attr_reader :real_price, :name
	attr_writer :price

	def price
		(@real_price - @real_price*self.class.discount) + tax if @real_price
	end

	def to_s
		"#{self.name}:#{self.price}:#{self.weight}"
	end


       private

	def tax
		type_tax = if self.class == VirtualItem
			1
		else
			2
		end
	cost_tax = if @real_price>5
		@real_price*0.2
		else
			@real_price*0.1
		end
	cost_tax +type_tax
	end
end

item_container.rb

module ItemContainer

   module ClassMethods

	def min_price
		50
	end

   end

   module InstantMethods

	def add_items(item)
		unless item.price < self.class.min_price	
		@items.push item
	        end
	end

	def remove_item
		@items.pop
	end

	def validate
		@items.each{ |i| puts "Item has no price" if i.price.nil? }
	end

	def delete_invalid_items
		@items.delete_if { |i| i.price.nil? }
	end

	
	def count_valid_items
		@items.count { |i| i.price }
	end
	
 
   end

   def self.included(base)

      base.extend ClassMethods
      base.class_eval do
	include InstantMethods
      end

    end

end

real_item.rb

class RealItem < Item

	attr_reader :weight
	attr_writer :weight

	def initialize(options )
		@weight = options [:weight]
		super
	end

	def info
		yield (weight)
		super
	end

end

string.rb

class String
	def to_real_item
		fields = self.chomp
		fields = fields.split(":")
		RealItem.new(name: fields[0], price: fields[1].to_i, weight: fields[2].to_i)
	end
end

virtual_item.rb

class VirtualItem < Item

end