#! /usr/local/bin/ruby

require 'time'
require 'mailscanner'
require 'smtpforward'

TRANS = { :_begin	=> [ :_begin,		:helo, :ehlo, 		:quit ],
	  :ehlo		=> [ :xforward,		:mail_from, 		:quit ],
	  :xforward	=> [ :mail_from,				:quit ],
	  :helo		=> [ :mail_from,				:quit ],
	  :mail_from	=> [ :rcpt_to, 					:quit ],
	  :rcpt_to	=> [ :rcpt_to, 		:data, 			:quit ],
	  :data		=> [ :_end					      ],
	  :quit		=> [ 						      ],
	  :_end		=> [ :ehlo					      ] }

class SMTPFilter
	attr_accessor :client, :pstate, :state, :line, :continue, :saybye, :body, :xf
	attr_accessor :from, :to, :helo, :esmtp
	attr_accessor :proxy, :scanner
	def initialize(client)
		@client = client
		@pstate = :_begin
		@state = :_begin
		@esmtp = false
		@line = ''
		@continue = true
		@saybye = [ 221, "2.0.0 #{$apphost} #{$appname} Goodbye." ]
		@body = []
		@from = ''
		@to = []
		@xf = {}
		@helo = ''
		while(@continue)
			puts "State #{@pstate.to_s} => #{@state.to_s}"
			if(TRANS[@pstate].include? @state) then
				send(@state)
				@pstate = @state
			else
				error()
			end
			waitinput() if(@continue)
		end
		respond(*@saybye) if(@saybye.length > 0)
		puts "xforward: " + @xf.keys.collect { |k| k + "=>" + @xf[k] }.join(',')
		puts @from + " => [ " + @to.join(',') + " ] (" + @body.length.to_s + " lines)"
		puts @body.join("\n") if($DEBUG)
	end
	def respond(code, lines)
		c = code.to_s
		if(lines.respond_to? :to_ary) then
			l = lines.to_ary
		else
			l = [ lines.to_s ]
		end
		begin
			while(l.length > 1)
				p = c + '-' + l.shift
				puts '>>> ' + p if($ldebug)
				@client.print p + "\r\n"
			end
			p = c + ' ' + l.shift
			puts '>>> ' + p if($ldebug)
			@client.print p + "\r\n"
		rescue Exception => e
			puts "ERROR : client write error #{e}"
			@line = nil
			@continue = false
			@saybye = ''
		end
	end
	def error
		if(TRANS.has_key? @state) then
			respond(503, '5.5.1 Command out of sequence')
		else
			respond(502, '5.5.2 Command not recognized')	
		end
	end
	def waitinput
		while(true)
			begin
				@line = client.gets
			rescue Exception => e
				puts "ERROR : client read error #{e}"
				@line = nil
				@continue = false
				@saybye = ''
			end
			if(@line.nil?) then
				return
			end
			@line.chomp!
			puts '<<< ' + @line if($ldebug)
			if(@line.length > 1024) then
				respond(501, '5.1.7 Line too long')
			else
				if(@state == :data) then
					if(@line == '.') then
						@state = :_end
						break
					end
					@line.gsub!(/^\.\./, '.')
					@body << @line
				else
					s = @line.sub(/ /, '_').downcase
					@state = TRANS.keys.find { |k| s =~ /^#{k.to_s}(\b|_)/ }
					@state = :nil if(@state.nil?)
					break
				end
			end
		end

	end
	def _begin()
		respond(220, "#{$apphost} ESMTP #{$appname} Hello !")
	end
	def helo
		@line.scan(/^helo +(.*)$/i) { |v| @helo = v }
		@esmtp = false
		respond(250, "#{$apphost}")
	end
	def ehlo
		@line.scan(/^ehlo +(.*)$/i) { |v| @helo = v }
		@esmtp = true
		respond(250, [ "#{$apphost}",
			       'PIPELINING',
			       'ENHANCEDSTATUSCODES',
			       '8BITMIME',
			       'XFORWARD NAME ADDR PROTO HELO' ])
		#	       'SIZE',
	end
	def xforward
		# XFORWARD NAME=talisker.lacave.net ADDR=217.145.39.3 HELO=talisker.lacave.net PROTO=SMTP
		@line.scan(/([A-Z]+)=(\S+)/i) { |k, v| @xf[k] = v }
		respond(250, [ '2.5.0 Ok XFORWARD' ])
	end

	def mail_from
		@line.scan(/^mail from\s*:?\s*<?(\S+?)>?\s*(?:\s+SIZE\s*=\s*\d+)?$/i) { |t| @from = $1 }
		if(@from) then
			respond(250, "2.1.0 Sender #{@from} OK")
		else
			respond(550, '5.1.1 Invalid syntax')
			@state = @pstate
		end
	end
	def rcpt_to
		to = ''
		@line.scan(/^rcpt to\s*:?\s*<?(\S+?)>?\s*$/i) { |v| to = v }
		if(to != '')  then
			@scanner = MailScanner.new(self) if(@scanner.nil?)
			if((r = @scanner.validate_recipient(to)) == '') then
				if(@proxy.nil?) then
					@proxy = SMTPForward.new(self)
					@proxy.begin
				end
				r = @proxy.rcpt_to(to)
				if(r[0] / 100 == 2) then
					@to.push(to)
					respond(250, "2.1.5 Recipient #{to} OK")
				else
					respond(r[0], r[1])
				end
			else
				respond(550, "5.1.1 #{to} rejected your address : #{r}")
			end
		else
			respond(550, '5.1.1 Invalid syntax')
			@state = @pstate
		end
	end
	def data
		addr = @client.peeraddr
		#puts "Client connecting from #{addr[2]} <#{addr[3]}> on port #{addr[1]}"
		respond(354, 'End data with <CR><LF>.<CR><LF>')
		@body << "Received: from #{addr[2]}" +
			 (addr[3].downcase != @helo ? " (HELO #{@helo})" : "") +
			 " [#{addr[3]}]"
		@body << "\tby #{$apphost} (#{$appid}) with #{(@esmtp?'ESMTP':'SMTP')};"
		@body << "\t" + Time.now.rfc2822
		puts "||| " + @body.join("\n||| ") + "\n" if($ldebug)
	end
	def quit
		@continue = false
	end
	def _end
		@scanner.contenttag
		respond(*@proxy.data)
		#respond(250, '2.6.0 Ok, id=123456-01')
		@state = :ehlo
	end
end