mailers_v4.rb

class BaseUserMailer
  
  def initialize(smtp_settings)
    @client = MailSendingLibrary.new(smtp_settings)
  end
  
  def send_mail(user,mail)
    @client.send_mail(user.email, mail.body)
  end
end

class TransactionalMailer
  
  SMTP_SETTINGS = ...
  
  def initialize()
    @mailer = BaseUserMailer.new(SMTP_SETTINGS)
  end
  
  def send_mail(user,mail)
    @mailer.send_mail(user.email, mail.body)
  end
end

class MarketingMailer
  
  SMTP_SETTINGS = ...
  
  def initialize()
    @mailer = BaseUserMailer.new(SMTP_SETTINGS)
  end
  
  def send_mail(user,mail)
    @mailer.send_mail(user.email, mail.body)
  end
end

class LoggingMailer
  
  def initialize(mailer)
    @mailer = mailer
  end
  
  def send_mail(user,mail)
    p "sending email to user #{user.id}"
    @mailer.send_mail(user.email, mail.body)
  end
end

class BlockingMailer
  
  def initialize(mailer)
    @mailer = mailer
  end
  
  def send_mail(user,mail)
    return unless @user.has_active_subscription?
    @mailer.send_mail(user.email, mail.body)
  end
end

# using the code would be something like:

mailer = BlockingMailer.new(LoggingMailer.new(TransactionalMailer.new()))