#!/usr/bin/ruby

# call it from inetd

from = nil
to = []
data = nil

def response line
  $stdout.puts line
  $stdout.flush
end

site = `hostname`.chomp

response "220 #{site} FakeSMTPd"

for line in $stdin
  if data.nil?
    case line
    when /^(HELO|EHLO)/i then
      response "250 ok\r"
    when /^MAIL FROM:\s*<([^>]+)>/i then
      from = $1
      response "250 ok\r"
    when /^MAIL FROM:/i then
      from = $'.strip
      response "250 ok\r"
    when /^RCPT TO:\s*<([^>]+)>\s*$/i then
      to.push $1
      response "250 ok\r"
    when /^RCPT TO:/i then
      to.push $'.strip
      response "250 ok\r"
    when /^DATA/i then
      response "354 go ahead\r"
      data = []
    when /^NOOP/i then
      response "250 ok\r"
    when /^RSET/i then
      from = nil
      to = []
      response "250 ok\r"
    when /^QUIT/i then
      response "221 #{site}\r"
      exit 0
    else
      response "500 syntax error\r"
    end
  else
    case line
    when /^\.\r?$/ then
      cmd = "/usr/sbin/sendmail #{to.join(' ')}"
      begin
        IO.popen(cmd, 'w') {|fp| data.each { |line| fp.write line } }
        response "250 ok\r"
      rescue Exception => e
        response "500 #{e.class}\r"
      end
      data = nil
    else
      data.push line
    end
  end
end