refactoring patterns

## Form Template Method (http://refactoring.com/catalog/formTemplateMethod.html)

class Site
	
end

class ResidentialSite < Site
  def initialize
    @units = 1.0
    @rate  = 2.0
  end
  
  def billable_amount
    base = @units * @rate * 0.5
    tax  = base * 0.2
    base + tax
  end
end

class LifelineSite < Site
  def initialize
    @units = 2.0
    @rate  = 2.2
  end
  
  def billable_amount
    base = @units * @rate * 0.5
    tax  = base * 0.2
    base + tax
  end
end

# Refactored

module Site
  def base_amount
    @units * @rate * 0.5
  end
  
  def tax_amount
    base_amount * 0.2
  end
  
  def billable_amount
    base_amount + tax_amount
  end
end

class ResidentialSite
  include Site
  
  def initialize
    @units = 2.0
    @rate  = 2.2
  end
end

class LifelineSite
  include Site
  
  def initialize
    @units = 1.0
    @rate  = 2.0
  end
end