class Mailings::HourlyThroughput
  HOUR = 1.hour
  RECENT = 15.minutes

  def initialize(project, now: Time.current)
    @project = project
    @now = now
  end

  def sent
    @sent ||= sent_since(HOUR)
  end

  def recent_sent
    @recent_sent ||= sent_since(RECENT)
  end

  def failed
    @failed ||= recipients.failed.where(updated_at: (@now - HOUR)..@now).count
  end

  def drained
    sent + failed
  end

  private

  def sent_since(window)
    recipients.sent.where(sent_at: (@now - window)..@now).count
  end

  def recipients
    MailingRecipient.joins(:mailing).merge(Mailing.for_project(@project))
  end
end