Another pipeline example

pipeline_example.rb

class DraftNewLetter
  def self.build(current_user)
    @create_letter = CreateLetter.new
    @authorize = Authorize.new(current_user, @create_letter)
    @error_handler = ActiveRecordErrorHandler.new(@authorize)    
    @assign_automatic_ccs = AssignAutomaticCCs.new(@create_letter)
    @transaction = Transaction.new(@assign_automatic_ccs)
  end
end

class Transaction 
  def initialize(processor)
    @next_processor = processor
  end

  def call(params)
    ActiveRecord.transaction do
      @next_processor.call(params)
    end
  end
end

class ActiveRecordErrorHandler
  def initialize(processor)
    @next_processor = processor
  end

  def call(params)
    @next_processor = processor.call(params)
  rescue ActiveRecord::Invalid => e
    e.record
  end
end

class CreateLetter
  def initialize(processor)
    @next_processor = processor
  end
  
  def call(params)
    letter = Letter.create!(params)
    @next_processor.call(letter)
  end
end

class AssignAutomaticRecipients
  def initialize(processor)
    @next_processor = processor
  end

  def call(letter)
    remove_automatic_ccs(letter)
    add_patient_as_cc(letter)
    add_doctor_as_cc(letter)

    @next_processor.call(letter)
  end

  private

  def remove_automatic_ccs(letter)
    letter.cc_recipients = letter.manual_cc_recipients
  end

  def add_patient_as_cc(letter)
    return if letter.main_recipient.patient?
    add_source_as_cc(letter.patient) if patient.cc_on_letter?(letter)
  end

  def add_doctor_as_cc(letter)
    return if letter.main_recipient.doctor?
    add_source_as_cc(letter.patient.doctor)
  end

  def add_source_as_cc(source)
    recipient = letter.cc_recipients.build(source: source)
    recipient.name = source.full_name
  end
end