#!/usr/local/bin/python

import sys, os
import re

import tempfile
import subprocess
import logging 
import time
import signal

import util

class local_segment:
    """
    Base class for starting a segments on a local testbed accessed directly
    through commands rather than ssh connections.  Code repository for
    executing commands with timeouts and other utility functions.
    """
    class cmd_timeout(RuntimeError): pass

    def __init__(self, log=None, keyfile=None, debug=False):
	"""
	Parameters are a logger to use for updates, an unused key file, and a
	flag indicating that commands should not actually be carried out.
	"""
	self.log = log or logging.getLogger(\
		'fedd.access.proxy_emulab_segment')
	self.certfile = keyfile
	self.debug = debug
	self.cmd_timeout = local_segment.cmd_timeout

    def copy_file(self, src, dest, size=1024):
        """
        Exceedingly simple file copy.
        """
	if not self.debug:
	    util.copy_file(src, dest, size)
	else:
	    self.log.debug("Copy %s to %s" % (src, dest))

    def cmd_with_timeout(self, cmd, wname=None, timeout=None):
	"""
	Run a command.  If debug is set, the action
	is only logged.  Commands are run without stdin, to avoid stray
	SIGTTINs. If timeout is given and the command runs longer, a
	cmd_timeout exception is thrown.
	"""

	try:
	    dnull = open("/dev/null", "w")
	except EnvironmentError:
	    self.log.debug("[cmd_with_timeout]: failed to open /dev/null " + \
		    "for redirect")
	    dnull = Null

	self.log.debug("[cmd_with_timeout]: %s" % cmd)
	if not self.debug:
	    if dnull:
		sub = subprocess.Popen(cmd, shell=True, stdout=dnull,
			stderr=dnull, close_fds=True)
	    else:
		sub = subprocess.Popen(cmd, shell=True, close_fds=True)
	    if timeout:
		i = 0
		rv = sub.poll()
		while i < timeout:
		    if rv is not None: break
		    else:
			time.sleep(1)
			rv = sub.poll()
			i += 1
		else:
		    self.log.debug("Process exceeded runtime: %s" % cmd)
		    os.kill(sub.pid, signal.SIGKILL)
		    raise self.cmd_timeout();
		return rv == 0
	    else:
		return sub.wait() == 0
	else:
	    if timeout == 0:
		self.log.debug("debug timeout raised on %s " % cmd)
		raise self.cmd_timeout()
	    else:
		return True