require 'net/imap'
require 'tmail'

class ImapChecker
  include Singleton

  SERVER = 'secure.emailsrvr.com'
  USERNAME = 'A'
  PASSWORD = 'A'
  SEARCH_CRITERIA = %w{ TO offset }

  attr_accessor :exiting

  def say(message)
    STDERR.puts message
  end

  # inspired by Delayed::Worker
  def start
    say "Starting imap checker"
    trap('TERM') { say 'Exiting...'; ImapChecker.instance.exiting = true }
    trap('INT')  { say 'Exiting...'; ImapChecker.instance.exiting = true }
    loop do
      counter = nil
      realtime = Benchmark.realtime do
        counter = scan
      end
      if counter.nonzero?
        say "#{counter} emails scanned at %.4f e/s" % [counter / realtime]
      end
      break if exiting
      sleep 10
    end
  ensure
    close_connection
    self.exiting = false
  end

  def connection
    return @_connection if @_connection.is_a?(Net::IMAP)
    @_connection = Net::IMAP.new SERVER, '993', true
    @_connection.login USERNAME, PASSWORD
    @_connection.examine 'INBOX'
    @_connection
  end

  def close_connection
    connection.logout
    connection.disconnect
    @_connection = nil
  end

  def scan
    counter = 0
    connection.check
    uids = connection.uid_search SEARCH_CRITERIA
    connection.uid_fetch(uids, %w{ ENVELOPE BODY[] }).each do |message|
      envelope = message.attr['ENVELOPE']
      from = "#{envelope.from[0].mailbox}@#{envelope.from[0].host}"
      body = TMail::Mail.parse(message.attr['BODY[]']).body
      incoming_message = IncomingMessage.new from, body
      counter += 1 if incoming_message.newly_processed?
    end if uids.length > 0
    counter
  end
end