=begin

= net/smtp.rb

written by Minero Aoki <aamine@dp.u-netsurf.ne.jp>

This library is distributed under the terms of the Ruby license.
You can freely distribute/modify this library.

=end


require 'net/protocol'
require 'md5'


module Net


=begin

== Net::SMTP

=== Super Class

Net::Protocol

=== Class Methods

: new( address = 'localhost', port = 25 )
  This method create new SMTP object.


=== Methods

: start( helo_domain = ENV['HOSTNAME'] || ENV['HOST'], account = nil, password = nil, authtype = nil )
  This method opens TCP connection and start SMTP.
  If protocol had been started, do nothing and return false.

  If account and password are given, is trying to get authentication
  by using AUTH command. "authtype" is :plain (symbol) or :cram_md5.

: sendmail( mailsrc, from_addr, to_addrs )
  This method sends 'mailsrc' as mail. SMTPSession read strings
  from 'mailsrc' by calling 'each' iterator, and convert them
  into "\r\n" terminated string when write.

  Exceptions which SMTP raises are:
  * Net::ProtoSyntaxError: syntax error (errno.500)
  * Net::ProtoFatalError: fatal error (errno.550)
  * Net::ProtoUnknownError: unknown error
  * Net::ProtoServerBusy: temporary error (errno.420/450)

: ready( from_addr, to_addrs ) {|adapter| .... }
  This method stands by the SMTP object for sending mail.
  In the block of this iterator, you can call ONLY 'write' method
  for 'adapter'.

    # usage example

    SMTP.start( 'localhost', 25 ) do |smtp|
      smtp.ready( from, to ) do |adapter|
        adapter.write str1
        adapter.write str2
        adapter.write str3
      end
    end

: finish
  This method ends SMTP.
  If protocol had not started, do nothind and return false.

=end

  class SMTP < Protocol

    protocol_param :port,         '25'
    protocol_param :command_type, '::Net::SMTPCommand'


    def initialize( addr = nil, port = nil )
      super
      @esmtp = true
    end


    attr :esmtp

    def sendmail( mailsrc, fromaddr, toaddrs )
      do_ready fromaddr, toaddrs
      @command.write_mail mailsrc, nil
    end

    def ready( fromaddr, toaddrs, &block )
      do_ready fromaddr, toaddrs
      @command.write_mail nil, block
    end


    private


    def do_ready( fromaddr, toaddrs )
      @command.mailfrom fromaddr
      @command.rcpt toaddrs
      @command.data
    end

    def do_start( helodom = nil,
                  user = nil, secret = nil, authtype = nil )
      unless helodom then
        helodom = ENV['HOSTNAME'] || ENV['HOST']
        unless helodom then
          raise ArgumentError, "cannot get hostname"
        end
      end

      begin
        if @esmtp then
          @command.ehlo helodom
        else
          @command.helo helodom
        end
      rescue ProtocolError
        if @esmtp then
          @esmtp = false
          retry
        else
          raise
        end
      end

      if user and secret then
        begin
          mid = 'auth_' + (authtype || 'cram_md5').to_s
          @command.send mid, user, secret
        rescue NameError
          raise ArgumentError, "wrong auth type #{authtype.to_s}"
        end
      end
    end

  end

  SMTPSession = SMTP



  class SMTPCommand < Command

    def initialize( sock )
      super
      critical {
        check_reply SuccessCode
      }
    end


    def helo( fromdom )
      critical {
        getok sprintf( 'HELO %s', fromdom )
      }
    end


    def ehlo( fromdom )
      critical {
        getok sprintf( 'EHLO %s', fromdom )
      }
    end


    # "PLAIN" authentication [RFC2554]
    def auth_plain( user, secret )
      critical {
        getok sprintf( 'AUTH PLAIN %s',
                       ["\0#{user}\0#{secret}"].pack('m').chomp )
      }
    end

    # "CRAM-MD5" authentication [RFC2195]
    def auth_cram_md5( user, secret )
      critical {
        rep = getok( 'AUTH CRAM-MD5', ContinueCode )
        challenge = rep.msg.split(' ')[1].unpack('m')[0]
        secret = MD5.new( secret ).digest if secret.size > 64

        isecret = secret + "\0" * (64 - secret.size)
        osecret = isecret.dup
        0.upto( 63 ) do |i|
          isecret[i] ^= 0x36
          osecret[i] ^= 0x5c
        end
        tmp = MD5.new( isecret + challenge ).digest
        tmp = MD5.new( osecret + tmp ).hexdigest

        getok [user + ' ' + tmp].pack('m').chomp
      }
    end


    def mailfrom( fromaddr )
      critical {
        getok sprintf( 'MAIL FROM:<%s>', fromaddr )
      }
    end


    def rcpt( toaddrs )
      toaddrs.each do |i|
        critical {
          getok sprintf( 'RCPT TO:<%s>', i )
        }
      end
    end


    def data
      return unless begin_critical
      getok 'DATA', ContinueCode
    end


    def write_mail( mailsrc, block )
      @socket.write_pendstr mailsrc, block
      check_reply SuccessCode
      end_critical
    end
    alias sendmail write_mail


    def quit
      critical {
        getok 'QUIT'
      }
    end


    private


    def get_reply
      arr = read_reply
      stat = arr[0][0,3]

      klass = case stat[0]
              when ?2 then SuccessCode
              when ?3 then ContinueCode
              when ?4 then ServerErrorCode
              when ?5 then
                case stat[1]
                when ?0 then SyntaxErrorCode
                when ?3 then AuthErrorCode
                when ?5 then FatalErrorCode
                end
              end
      klass ||= UnknownCode

      Response.new( klass, stat, arr.join('') )
    end


    def read_reply
      arr = []

      while true do
        str = @socket.readline
        break unless str[3] == ?-   # ex: "210-..."
        arr.push str
      end
      arr.push str

      return arr
    end

  end

end