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

# Copyright 1999, 2000 by eGroups, Inc.
# 
#                         All Rights Reserved
# 
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# 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
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# 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: //depot/main/findmail/src/coroutine/backdoor.py#12 $'

import coro
import socket
import string
import StringIO
import sys
import traceback

# 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, line_separator='\r\n'):
		self.socket = socket
		self.buffer = ''
		self.lines = []
		self.multilines = []
		self.line_separator = line_separator

		# allow the user to change the prompts:
		if not sys.__dict__.has_key('ps1'):
			sys.ps1 = '>>> '
		if not sys.__dict__.has_key('ps2'):
			sys.ps2 = '... '

	def send (self, data):
		olb = lb = len(data)
		while lb:
			ns = self.socket.send (data)
			lb = lb - ns
		return olb
		
	def prompt (self):
		if self.multilines:
			self.send (sys.ps2)
		else:
			self.send (sys.ps1)

	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, self.line_separator)
					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 + self.line_separator)
		self.send (sys.copyright + self.line_separator)
		# 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
			elif self.multilines:
				self.multilines.append(line)
				if line == '':
					code = string.join(self.multilines, '\n')
					self.parse(code, env)
                    # we do this after the parsing so parse() knows not to do
					# a second round of multiline input if it really is an
					# unexpected EOF
					self.multilines = []
			else:
				self.parse(line, env)

	def parse(self, line, env):
		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 SyntaxError, msg:
					# this is a hack, but it is a righteous hack:
					if not self.multilines and str(msg) == 'unexpected EOF while parsing':
						self.multilines.append(line)
					else:
						traceback.print_exc()
				except:
					traceback.print_exc()
			except:
				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))
	s.listen (1024)
	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)