# -*- Mode: Python; tab-width: 4 -*-

# Copyright 1999 by eGroups, Inc.
# 
#                         All Rights Reserved
# 
# Permission to use, copy, modify, and distribute this software and
# its documentation for any purpose and without fee is hereby
# granted, provided that the above copyright notice appear in all
# copies and that both that copyright notice and this permission
# notice appear in supporting documentation, and that the name of
# eGroups not be used in advertising or publicity pertaining to
# distribution of the software without specific, written prior
# permission.
# 
# EGROUPS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
# NO EVENT SHALL EGROUPS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

VERSION_STRING = '$Id: backdoor.py,v 1.2 2000/10/06 16:35:36 hassan Exp $'

import coro
import socket
import string
import StringIO
import sys

# TODO: implement multi-line input!

# Originally, this object implemented the file-output api, and set
# sys.stdout and sys.stderr to 'self'.  However, if any other
# coroutine ran, it would see the captured definition of sys.stdout,
# and would send its output here, instead of the expected place.  Now
# the code captures all output using StringIO.  A little less
# flexible, a little less efficient, but much less surprising!
# [Note: this is exactly the same problem addressed by Scheme's
#  dynamic-wind facility]

class backdoor:

	def __init__ (self, socket):
		self.socket = socket
		self.buffer = ''
		self.lines = []

	def send (self, data):
		olb = lb = len(data)
		while lb:
			ns = self.socket.send (data)
			lb = lb - ns
		return olb
		
	def prompt (self):
		self.send ('>>> ')

	def read_line (self):
		if self.lines:
			l = self.lines[0]
			self.lines = self.lines[1:]
			return l
		else:
			while not self.lines:
				block = self.socket.recv (8192)
				if not block:
					return None
				elif block == '\004':
					self.socket.close()
					return None
				else:
					self.buffer = self.buffer + block
					lines = string.split (self.buffer, '\r\n')
					for l in lines[:-1]:
						self.lines.append (l)
					self.buffer = lines[-1]
			return self.read_line()
		
	def read_eval_print_loop (self):
		self.send ('Python ' + sys.version + '\r\n')
		self.send (sys.copyright + '\r\n')
		# this does the equivalent of 'from __main__ import *'
		env = sys.modules['__main__'].__dict__.copy()
		while 1:
			self.prompt()
			line = self.read_line()
			if line is None:
				break
			else:
				save = sys.stdout, sys.stderr
				output = StringIO.StringIO()
				try:
					try:
						sys.stdout = sys.stderr = output
						co = compile (line, repr(self), 'eval')
						result = eval (co, env)
						if result is not None:
							print repr(result)
							env['_'] = result
					except SyntaxError:
						try:
							co = compile (line, repr(self), 'exec')
							exec co in env
						except:
							import traceback
							traceback.print_exc()
					except:
						import traceback
						traceback.print_exc()
				finally:
					sys.stdout, sys.stderr = save
					self.send (output.getvalue())
					del output

def client (conn, addr):
	b = backdoor (conn)
	b.read_eval_print_loop()

def serve (port=8023):
	s = coro.coroutine_socket()
	s.create_socket (socket.AF_INET, socket.SOCK_STREAM)
	s.set_reuse_addr()
	s.bind (('', port))
	if port == 0:
	  sys.stderr.write("coro.backdoor listening on port: %s\n" % s.socket.getsockname()[1])
	s.listen (128)
	while 1:
		conn, addr = s.accept()
		print 'incoming connection from', addr
		coro.spawn (client, conn, addr)

if __name__ == '__main__':
	coro.spawn (serve)
	coro.event_loop (30.0)