import sys, string, os
 
#---------------------------------------------------------------------------------------------
class SMTPServerEngine:
	ST_INIT = 0
	ST_HELO = 1
	ST_MAIL = 2
	ST_RCPT = 3
	ST_DATA = 4
	ST_QUIT = 5
 
	def __init__(self):
		self.state = SMTPServerEngine.ST_INIT
 
	def chug(self):
		while 1:
			data = ''
			completeLine = 0
			while not completeLine:
				lump = os.read(sys.stdin.fileno(), 1024)
				if len(lump):
					data += lump
					if (len(data) >= 2) and data[-2:] == '\r\n':
						completeLine = 1
						if self.state != SMTPServerEngine.ST_DATA:
							rsp, keep = self.doCommand(data)
						else:
							rsp = self.doData(data)
 
						if rsp == None:
							continue
 
						sys.stdout.write(rsp + "\r\n")
						sys.stdout.flush()
 
						if keep == 0:	
							sys.exit(0)
							return	
				else:
					return
 
		return
 
	def doCommand(self, data):
		"""Process a single SMTP Command"""
		cmd = data[0:4]
		cmd = string.upper(cmd)
		keep = 1
		if cmd == "HELO":
			self.state = SMTPServerEngine.ST_HELO
		elif cmd == "RSET":
			self.dataAccum = ""
			self.state = SMTPServerEngine.ST_INIT
		elif cmd == "NOOP":
			pass
		elif cmd == "QUIT":
			keep = 0
		elif cmd == "MAIL":
			if self.state != SMTPServerEngine.ST_HELO:
				return ("503 Bad command sequence", 1)
			self.state = SMTPServerEngine.ST_MAIL
		elif cmd == "RCPT":
			if (self.state != SMTPServerEngine.ST_MAIL) and (self.state != SMTPServerEngine.ST_RCPT):
				return ("503 Bad command sequence", 1)
			self.state = SMTPServerEngine.ST_RCPT
		elif cmd == "DATA":
			if self.state != SMTPServerEngine.ST_RCPT:
				return ("503 Bad command sequence", 1)
			self.state = SMTPServerEngine.ST_DATA
			self.dataAccum = ""
			return ("354 OK, Enter data, terminated with a \\r\\n.\\r\\n", 1)
		else:
			return ("505 Eh? WTF was that?", 1)
 
		return("250 OK", keep)
 
	def doData(self, data):
		"""
		Process SMTP Data. Accumulates client DATA until the
		terminator is found.
		"""
		self.dataAccum = self.dataAccum + data
		if len(self.dataAccum) > 4 and self.dataAccum[-5:] == '\r\n.\r\n':
			self.dataAccum = self.dataAccum[:-5]
			self.state = SMTPServerEngine.ST_HELO
 
			return "250 OK - message accepted"
		else:
			return None
 
 
#---------------------------------------------------------------------------------------------
if __name__ == '__main__':
	try:
		sys.stdout.write("220 localhost\r\n")
		sys.stdout.flush()
		while 1:
			engine = SMTPServerEngine()
			engine.chug()
	except SystemExit:
		pass