require "net/smtp"

# High level Interface to distribute Protocols::Mail objects.
# It is robust against network loss.
class Protocols::Smtp
  def initialize
    reset_smtp_client!
  end

  class DistributedCache < Array
    def initialize(max_size: 4096)
      @max_size = max_size
      super()
    end

    def <<(message_id)
      prepend(message_id) if !message_id.nil?
      slice! @max_size
    end
  end

  def cache
    (@cache ||= DistributedCache.new)
  end

  # @param mail [Protocols::Mail]
  def distribute(mail)
    if cache.include?(mail.cache_id)
      $logger.warn "Already distributed #{mail.message_id}"
      return
    end

    $logger.info "SEND #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
    smtp_raw = mail.to_smtp
    $logger.debug smtp_raw.join("=====")
    send_message_safe(*smtp_raw)
    cache << mail.cache_id
  rescue StandardError => e
    $logger.warn "FAILED #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
    $logger.debug e
  end

  # :nodoc:
  private def reset_smtp_client!
    @smtp = Net::SMTP.new(
      ENV["SMTP_HOST"], ENV["SMTP_PORT"], tls: ENV["SMTP_TLS"] == "true",
    ).start(
      user: ENV["SMTP_USER"],
      secret: ENV["SMTP_PASSWORD"],
      authtype: :login,
    )
  end

  # :nodoc:
  private def send_message_safe(*raw, max_tries: 3)
    return $logger.error("send_message_safe reached max_tries_limit") if max_tries == 0

    begin
      @smtp.send_message(*raw)
    rescue EOFError, Net::SMTPServerBusy => e
      $logger.warn e.message
      reset_smtp_client!
      send_message_safe(*raw, max_tries: max_tries - 1)
    rescue => e
      $logger.error e.full_message
      reset_smtp_client!
    end
  end
end