#! /usr/bin/env python

import os
import sys
import signal
import errno
import copy
import pty
import optparse
import termios
import asyncore

class FileDispatcher(asyncore.file_dispatcher):
    def __init__(self, in_fd, out_fd, quit_char=None):
        asyncore.file_dispatcher.__init__(self, in_fd)
        self.out_fd = out_fd
        self.quit_char = quit_char

    def writable(self):
        return False

    def handle_read(self):
        # called from the select loop whenever data is available
        try:
            data = self.recv(1024)
            # terminate the select loop
            if data == self.quit_char:
                raise asyncore.ExitNow(
                        '\n%s terminated.' % os.path.basename(sys.argv[0]))
            os.write(self.out_fd, data)
        except OSError, err:
            if err[0] != errno.EAGAIN:
                raise asyncore.ExitNow(err)

def parse_options(argv):
    formatter = optparse.IndentedHelpFormatter(max_help_position=30)
    parser = optparse.OptionParser(
                    usage='usage: python %prog [options]',
                    formatter=formatter)
    parser.add_option('-e', '--exec',
            type='string', dest='pgm',
            help='program to spawn in a new xterm terminal '
            'that will use the slave pseudo terminal')
    parser.add_option('-t', '--tty',
            type='string', default='-tty', metavar='TTY_OPT',
            help='pass to PGM the slave pseudo terminal name using'
            ' the TTY_OPT option (default \'%default\')')
    parser.add_option('-a', '--args',
            type='string',
            help='PGM arguments (must be quoted)')
    parser.add_option('-m', '--master_fd',
            type='int', metavar='FD',
            help='master pseudo terminal file descriptor to use')
    (options, args) = parser.parse_args(args=argv)
    return options

def spawn_xterm(options, ptyname, slave_fd, master_fd):
    argv = ['xterm', '-e', options.pgm, options.tty, ptyname]
    if options.args is not None:
        # FIXME quotes in args are not handled
        argv.extend(options.args.split())
    pid = os.fork()
    if pid == 0:
        os.close(slave_fd)
        os.close(master_fd)
        os.setsid()
        os.execvp(argv[0], argv)

master_fd = None

def sigint_handler(signum, frame):
    # write a C-c character
    if master_fd is not None:
        os.write(master_fd, chr(3))

def main():
    global master_fd
    options = parse_options(sys.argv[1:])
    master_fd = options.master_fd
    if not isinstance(master_fd, int):
        master_fd, slave_fd = pty.openpty()
        ptyname = os.ttyname(slave_fd)
        print "Slave pseudo terminal to use: '%s'" % ptyname
        if options.pgm is not None:
            spawn_xterm(options, ptyname, slave_fd, master_fd)
    print 'Type C-a to exit.\n'

    signal.signal(signal.SIGINT, sigint_handler)

    # no echo, no canonical processing
    attr = termios.tcgetattr(0)
    init_attr = copy.deepcopy(attr)
    attr[3] = attr[3] & ~termios.ECHO
    attr[3] = attr[3] & ~termios.ICANON
    termios.tcsetattr(0, termios.TCSADRAIN, attr)

    # interconnect stdin to master_fd, and master_fd to stdout
    # with an asyncore select loop
    # C-a is the Quit character
    master_slave = FileDispatcher(0, master_fd, chr(1))
    slave_master = FileDispatcher(master_fd, 1)

    err = ''
    try:
        while asyncore.socket_map:
            asyncore.poll()
    except asyncore.ExitNow, err:
        pass

    os.close(slave_fd)
    os.close(master_fd)
    termios.tcsetattr(0, termios.TCSADRAIN, init_attr)
    if err:
        print err

if __name__ == '__main__':
        main()