ATM Ruby Studies

atm.rb

class NoSufficientPapers < StandardError
end

class Atm
  
	def initialize(notes)
		@notes = notes
	end
	
	def available_papers
		available = []
		@notes.each {|note, quantity| available << note.to_i if quantity > 0}
		available
	end
	
	def withdraw(amount)
		result = []
		notes = calculate_papers(amount)
		notes.each do |note, quantity|
			raise NoSufficientPapers if not atm_has_available?(note, quantity) #Atm has not available the required note or quantity to to the withdraw
			produce_quantity_of(note, quantity) do |note|
				result << note
			end
			decrement_quantity_of_papers_of(note, quantity)
		end
		result
	end
	
	private
		def calculate_papers(amount)
			papers = {}
			available_papers.each {|note| papers[note] = 0}
			available_papers.each do |note|
				papers[note] += amount / note
				amount = amount % note
			end
			raise NoSufficientPapers if amount > 0 #Atm has not correcty calculate amount, because it has no needed papers to do it
			papers
		end
		
		def decrement_quantity_of_papers_of(note, quantity)
			@notes["#{note}"] -= quantity
		end
		
		def atm_has_available?(note, quantity)
			@notes.has_key?("#{note}") && @notes["#{note}"] >= quantity
		end
		
		def produce_quantity_of(paper, quantity)
			if block_given?
				quantity.times { yield paper.to_i }
			end
		end
end

atm_test.rb

=begin
  Desenvolva um programa que simule a entrega de notas quando um cliente efetuar um saque em um caixa eletrônico. Os requisitos básicos são os seguintes:
	Entregar o menor número de notas;
	É possível sacar o valor solicitado com as notas disponíveis;
	Saldo do cliente infinito;
	Quantidade de notas infinito (pode-se colocar um valor finito de cédulas para aumentar a dificuldade do problema);
	Notas disponíveis de R$ 100,00; R$ 50,00; R$ 20,00 e R$ 10,00
	Exemplos:
	Valor do Saque: R$ 30,00 – Resultado Esperado: Entregar 1 nota de R$20,00 e 1 nota de R$ 10,00.
	Valor do Saque: R$ 80,00 – Resultado Esperado: Entregar 1 nota de R$50,00 1 nota de R$ 20,00 e 1 nota de R$ 10,00.

	Retirado do endereço: http://dojopuzzles.com/problemas/exibe/caixa-eletronico/
=end

require 'test/unit'
require 'atm'

class AtmTest < Test::Unit::TestCase
	
	def setup
		@atm = Atm.new '100' => 10, '50' => 10, '20' => 10, '10' => 10
	end
	
	def test_should_show_paper_money_available
		assert_equal [100, 50, 20, 10], @atm.available_papers
	end
	
	def test_should_withdraw_10
		assert_equal [10], @atm.withdraw(10)
	end
	
	def test_should_withdraw_30
		assert_equal [20, 10], @atm.withdraw(30)
	end
	
	def test_should_withdraw_80
		assert_equal [50, 20, 10], @atm.withdraw(80)
	end
	
	def test_should_withdraw_100
		assert_equal [100], @atm.withdraw(100)
	end
	
	def test_should_withdraw_200
		assert_equal [100, 100], @atm.withdraw(200)
	end
	
	
	def test_should_not_permit_withdraw_with_insufficient_papers
		atm = Atm.new '100' => 10, '50' => 10, '20' => 10
		assert_raise NoSufficientPapers do
			atm.withdraw(10)
		end
	end
	
	def test_should_not_permit_withdraw_insufficient_papers_2
		# Has 10 notes, but only 2, need 3
		atm = Atm.new '100' => 10, '50' => 10, '10' => 2 
		assert_raise NoSufficientPapers do 
			atm.withdraw(30)
		end
	end
	
	def test_should_not_permit_withdraw_insufficient_papers_3
		# Has 10 notes, but not 20
		atm = Atm.new '100' => 1, '50' => 3, '20' => 3 
		assert_raise NoSufficientPapers do 
			atm.withdraw(260)
		end
	end
	
	def test_should_withdraw_30_with_only_10_notes
		# Has 10 notes, but not 20
		atm = Atm.new '100' => 10, '50' => 10, '10' => 3 
		assert_equal [10, 10, 10], atm.withdraw(30)
		assert_equal [100, 50], atm.available_papers
	end
end