# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

import logging
import mozinfo
import os
import select
import signal
import subprocess
import sys
import threading
import time
import traceback
from Queue import Queue
from datetime import datetime, timedelta
__all__ = ['ProcessHandlerMixin', 'ProcessHandler']

# Set the MOZPROCESS_DEBUG environment variable to 1 to see some debugging output
MOZPROCESS_DEBUG = os.getenv("MOZPROCESS_DEBUG")

if mozinfo.isWin:
    import ctypes, ctypes.wintypes, msvcrt
    from ctypes import sizeof, addressof, c_ulong, byref, POINTER, WinError, c_longlong
    import winprocess
    from qijo import JobObjectAssociateCompletionPortInformation,\
    JOBOBJECT_ASSOCIATE_COMPLETION_PORT, JobObjectExtendedLimitInformation,\
    JOBOBJECT_BASIC_LIMIT_INFORMATION, JOBOBJECT_EXTENDED_LIMIT_INFORMATION, IO_COUNTERS

class ProcessHandlerMixin(object):
    """Class which represents a process to be executed."""

    class Process(subprocess.Popen):
        """
        Represents our view of a subprocess.
        It adds a kill() method which allows it to be stopped explicitly.
        """

        MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY = 180
        MAX_PROCESS_KILL_DELAY = 30

        def __init__(self,
                     args,
                     bufsize=0,
                     executable=None,
                     stdin=None,
                     stdout=None,
                     stderr=None,
                     preexec_fn=None,
                     close_fds=False,
                     shell=False,
                     cwd=None,
                     env=None,
                     universal_newlines=False,
                     startupinfo=None,
                     creationflags=0,
                     ignore_children=False):

            # Parameter for whether or not we should attempt to track child processes
            self._ignore_children = ignore_children

            if not self._ignore_children and not mozinfo.isWin:
                # Set the process group id for linux systems
                # Sets process group id to the pid of the parent process
                # NOTE: This prevents you from using preexec_fn and managing
                #       child processes, TODO: Ideally, find a way around this
                def setpgidfn():
                    os.setpgid(0, 0)
                preexec_fn = setpgidfn

            try:
                subprocess.Popen.__init__(self, args, bufsize, executable,
                                          stdin, stdout, stderr,
                                          preexec_fn, close_fds,
                                          shell, cwd, env,
                                          universal_newlines, startupinfo, creationflags)
            except OSError, e:
                print >> sys.stderr, args
                raise

        def __del__(self, _maxint=sys.maxint):
            if mozinfo.isWin:
                if self._handle:
                    if hasattr(self, '_internal_poll'):
                        self._internal_poll(_deadstate=_maxint)
                    else:
                        self.poll(_deadstate=sys.maxint)
                if self._handle or self._job or self._io_port:
                    self._cleanup()
            else:
                subprocess.Popen.__del__(self)

        def kill(self):
            self.returncode = 0
            if mozinfo.isWin:
                if not self._ignore_children and self._handle and self._job:
                    winprocess.TerminateJobObject(self._job, winprocess.ERROR_CONTROL_C_EXIT)
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                elif self._handle:
                    err = None
                    try:
                        winprocess.TerminateProcess(self._handle, winprocess.ERROR_CONTROL_C_EXIT)
                    except:
                        err = "Could not terminate process"
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    self._cleanup()
                    if err is not None:
                        raise OSError(err)
                else:
                    pass
            else:
                if not self._ignore_children:
                    try:
                        os.killpg(self.pid, signal.SIGKILL)
                    except BaseException, e:
                        if getattr(e, "errno", None) != 3:
                            # Error 3 is "no such process", which is ok
                            print >> sys.stdout, "Could not kill process, could not find pid: %s, assuming it's already dead" % self.pid
                else:
                    os.kill(self.pid, signal.SIGKILL)
                if self.returncode is None:
                    self.returncode = subprocess.Popen._internal_poll(self)

            self._cleanup()
            return self.returncode

        def wait(self):
            """ Popen.wait
                Called to wait for a running process to shut down and return
                its exit code
                Returns the main process's exit code
            """
            # This call will be different for each OS
            self.returncode = self._wait()
            self._cleanup()
            return self.returncode

        """ Private Members of Process class """

        if mozinfo.isWin:
            # Redefine the execute child so that we can track process groups
            def _execute_child(self, args, executable, preexec_fn, close_fds,
                               cwd, env, universal_newlines, startupinfo,
                               creationflags, shell,
                               p2cread, p2cwrite,
                               c2pread, c2pwrite,
                               errread, errwrite):
                if not isinstance(args, basestring):
                    args = subprocess.list2cmdline(args)

                # Always or in the create new process group
                creationflags |= winprocess.CREATE_NEW_PROCESS_GROUP

                if startupinfo is None:
                    startupinfo = winprocess.STARTUPINFO()

                if None not in (p2cread, c2pwrite, errwrite):
                    startupinfo.dwFlags |= winprocess.STARTF_USESTDHANDLES
                    startupinfo.hStdInput = int(p2cread)
                    startupinfo.hStdOutput = int(c2pwrite)
                    startupinfo.hStdError = int(errwrite)
                if shell:
                    startupinfo.dwFlags |= winprocess.STARTF_USESHOWWINDOW
                    startupinfo.wShowWindow = winprocess.SW_HIDE
                    comspec = os.environ.get("COMSPEC", "cmd.exe")
                    args = comspec + " /c " + args

                # determine if we can create create a job
                canCreateJob = winprocess.CanCreateJobObject()

                # Ensure we write a warning message if we are falling back
                if not canCreateJob and not self._ignore_children:
                    # We can't create job objects AND the user wanted us to
                    # Warn the user about this.
                    print >> sys.stderr, "ProcessManager UNABLE to use job objects to manage child processes"

                # set process creation flags
                creationflags |= winprocess.CREATE_SUSPENDED
                creationflags |= winprocess.CREATE_UNICODE_ENVIRONMENT
                if canCreateJob:
                    creationflags |= winprocess.CREATE_BREAKAWAY_FROM_JOB
                else:
                    # Since we've warned, we just log info here to inform you
                    # of the consequence of setting ignore_children = True
                    print "ProcessManager NOT managing child processes"

                # create the process
                hp, ht, pid, tid = winprocess.CreateProcess(
                    executable, args,
                    None, None, # No special security
                    1, # Must inherit handles!
                    creationflags,
                    winprocess.EnvironmentBlock(env),
                    cwd, startupinfo)
                self._child_created = True
                self._handle = hp
                self._thread = ht
                self.pid = pid
                self.tid = tid

                if canCreateJob:
                    try:
                        # We create a new job for this process, so that we can kill
                        # the process and any sub-processes
                        # Create the IO Completion Port
                        self._io_port = winprocess.CreateIoCompletionPort()
                        self._job = winprocess.CreateJobObject()

                        # Now associate the io comp port and the job object
                        joacp = JOBOBJECT_ASSOCIATE_COMPLETION_PORT(winprocess.COMPKEY_JOBOBJECT,
                                                                    self._io_port)
                        winprocess.SetInformationJobObject(self._job,
                                                          JobObjectAssociateCompletionPortInformation,
                                                          addressof(joacp),
                                                          sizeof(joacp)
                                                          )

                        # Allow subprocesses to break away from us - necessary for
                        # flash with protected mode
                        jbli = JOBOBJECT_BASIC_LIMIT_INFORMATION(
                                                c_longlong(0), # per process time limit (ignored)
                                                c_longlong(0), # per job user time limit (ignored)
                                                winprocess.JOB_OBJECT_LIMIT_BREAKAWAY_OK,
                                                0, # min working set (ignored)
                                                0, # max working set (ignored)
                                                0, # active process limit (ignored)
                                                None, # affinity (ignored)
                                                0, # Priority class (ignored)
                                                0, # Scheduling class (ignored)
                                                )

                        iocntr = IO_COUNTERS()
                        jeli = JOBOBJECT_EXTENDED_LIMIT_INFORMATION(
                                                jbli, # basic limit info struct
                                                iocntr,    # io_counters (ignored)
                                                0,    # process mem limit (ignored)
                                                0,    # job mem limit (ignored)
                                                0,    # peak process limit (ignored)
                                                0)    # peak job limit (ignored)
                                                
                        winprocess.SetInformationJobObject(self._job,
                                                           JobObjectExtendedLimitInformation,
                                                           addressof(jeli),
                                                           sizeof(jeli)
                                                           )

                        # Assign the job object to the process
                        winprocess.AssignProcessToJobObject(self._job, int(hp))

                        # It's overkill, but we use Queue to signal between threads
                        # because it handles errors more gracefully than event or condition.
                        self._process_events = Queue()

                        # Spin up our thread for managing the IO Completion Port
                        self._procmgrthread = threading.Thread(target = self._procmgr)
                    except:
                        print >> sys.stderr, """Exception trying to use job objects;
falling back to not using job objects for managing child processes"""
                        tb = traceback.format_exc()
                        print >> sys.stderr, tb
                        # Ensure no dangling handles left behind
                        self._cleanup_job_io_port()
                else:
                    self._job = None

                winprocess.ResumeThread(int(ht))
                if getattr(self, '_procmgrthread', None):
                    self._procmgrthread.start()
                ht.Close()

                for i in (p2cread, c2pwrite, errwrite):
                    if i is not None:
                        i.Close()

            # Windows Process Manager - watches the IO Completion Port and
            # keeps track of child processes
            def _procmgr(self):
                if not (self._io_port) or not (self._job):
                    return

                try:
                    self._poll_iocompletion_port()
                except KeyboardInterrupt:
                    raise KeyboardInterrupt

            def _poll_iocompletion_port(self):
                # Watch the IO Completion port for status
                self._spawned_procs = {}
                countdowntokill = 0

                if MOZPROCESS_DEBUG:
                    print "DBG::MOZPROC Self.pid value is: %s" % self.pid
                
                while True:
                    msgid = c_ulong(0)
                    compkey = c_ulong(0)
                    pid = c_ulong(0)
                    portstatus = winprocess.GetQueuedCompletionStatus(self._io_port,
                                                                      byref(msgid),
                                                                      byref(compkey),
                                                                      byref(pid),
                                                                      5000)

                    # If the countdowntokill has been activated, we need to check
                    # if we should start killing the children or not.
                    if countdowntokill != 0:
                        diff = datetime.now() - countdowntokill
                        # Arbitrarily wait 3 minutes for windows to get its act together
                        # Windows sometimes takes a small nap between notifying the
                        # IO Completion port and actually killing the children, and we
                        # don't want to mistake that situation for the situation of an unexpected
                        # parent abort (which is what we're looking for here).
                        if diff.seconds > self.MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY:
                            print >> sys.stderr, "Parent process exited without \
                                                  killing children, attempting to kill children"
                            self.kill()
                            self._process_events.put({self.pid: 'FINISHED'})

                    if not portstatus:
                        # Check to see what happened
                        errcode = winprocess.GetLastError()
                        if errcode == winprocess.ERROR_ABANDONED_WAIT_0:
                            # Then something has killed the port, break the loop
                            print >> sys.stderr, "IO Completion Port unexpectedly closed"
                            break
                        elif errcode == winprocess.WAIT_TIMEOUT:
                            # Timeouts are expected, just keep on polling
                            continue
                        else:
                            print >> sys.stderr, "Error Code %s trying to query IO Completion Port, exiting" % errcode
                            raise WinError(errcode)
                            break

                    if compkey.value == winprocess.COMPKEY_TERMINATE.value:
                        if MOZPROCESS_DEBUG:
                            print "DBG::MOZPROC compkeyterminate detected"
                        # Then we're done
                        break

                    # Check the status of the IO Port and do things based on it
                    if compkey.value == winprocess.COMPKEY_JOBOBJECT.value:
                        if msgid.value == winprocess.JOB_OBJECT_MSG_ACTIVE_PROCESS_ZERO:
                            # No processes left, time to shut down
                            # Signal anyone waiting on us that it is safe to shut down
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC job object msg active processes zero"
                            self._process_events.put({self.pid: 'FINISHED'})
                            break
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_NEW_PROCESS:
                            # New Process started
                            # Add the child proc to our list in case our parent flakes out on us
                            # without killing everything.
                            if pid.value != self.pid:
                                self._spawned_procs[pid.value] = 1
                                if MOZPROCESS_DEBUG:
                                    print "DBG::MOZPROC new process detected with pid value: %s" % pid.value
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_EXIT_PROCESS:
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC process id %s exited normally" % pid.value
                            # One process exited normally
                            if pid.value == self.pid and len(self._spawned_procs) > 0:
                                # Parent process dying, start countdown timer
                                countdowntokill = datetime.now()
                            elif pid.value in self._spawned_procs:
                                # Child Process died remove from list
                                del(self._spawned_procs[pid.value])
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_ABNORMAL_EXIT_PROCESS:
                            # One process existed abnormally
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC process id %s existed abnormally" % pid.value
                            if pid.value == self.pid and len(self._spawned_procs) > 0:
                                # Parent process dying, start countdown timer
                                countdowntokill = datetime.now()
                            elif pid.value in self._spawned_procs:
                                # Child Process died remove from list
                                del self._spawned_procs[pid.value]
                        else:
                            # We don't care about anything else
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC We got a message %s" % msgid.value
                            pass

            def _wait(self):

                # First, check to see if the process is still running
                if self._handle:
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                else:
                    # Dude, the process is like totally dead!
                    return self.returncode

                # Python 2.5 uses isAlive versus is_alive use the proper one
                threadalive = False
                if hasattr(self._procmgrthread, 'is_alive'):
                    threadalive = self._procmgrthread.is_alive()
                else:
                    threadalive = self._procmgrthread.isAlive()
                if self._job and threadalive: 
                    # Then we are managing with IO Completion Ports
                    # wait on a signal so we know when we have seen the last
                    # process come through.
                    # We use queues to synchronize between the thread and this
                    # function because events just didn't have robust enough error
                    # handling on pre-2.7 versions
                    err = None
                    try:
                        # timeout is the max amount of time the procmgr thread will wait for
                        # child processes to shutdown before killing them with extreme prejudice.
                        item = self._process_events.get(timeout=self.MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY +
                                                                self.MAX_PROCESS_KILL_DELAY)
                        if item[self.pid] == 'FINISHED':
                            self._process_events.task_done()
                    except:
                        err = "IO Completion Port failed to signal process shutdown"
                    # Either way, let's try to get this code
                    if self._handle:
                        self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    self._cleanup()

                    if err is not None:
                        raise OSError(err)


                else:
                    # Not managing with job objects, so all we can reasonably do
                    # is call waitforsingleobject and hope for the best

                    if MOZPROCESS_DEBUG:
                        print "DBG::MOZPROC NOT USING JOB OBJECTS!!!"
                    # First, make sure we have not already ended
                    if self.returncode != winprocess.STILL_ACTIVE:
                        self._cleanup()
                        return self.returncode

                    rc = None
                    if self._handle:
                        rc = winprocess.WaitForSingleObject(self._handle, -1)

                    if rc == winprocess.WAIT_TIMEOUT:
                        # The process isn't dead, so kill it
                        print "Timed out waiting for process to close, attempting TerminateProcess"
                        self.kill()
                    elif rc == winprocess.WAIT_OBJECT_0:
                        # We caught WAIT_OBJECT_0, which indicates all is well
                        print "Single process terminated successfully"
                        self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    else:
                        # An error occured we should probably throw
                        rc = winprocess.GetLastError()
                        if rc:
                            raise WinError(rc)

                    self._cleanup()

                return self.returncode

            def _cleanup_job_io_port(self):
                """ Do the job and IO port cleanup separately because there are
                    cases where we want to clean these without killing _handle
                    (i.e. if we fail to create the job object in the first place)
                """
                if getattr(self, '_job') and self._job != winprocess.INVALID_HANDLE_VALUE:
                    self._job.Close()
                    self._job = None
                else:
                    # If windows already freed our handle just set it to none
                    # (saw this intermittently while testing)
                    self._job = None

                if getattr(self, '_io_port', None) and self._io_port != winprocess.INVALID_HANDLE_VALUE:
                    self._io_port.Close()
                    self._io_port = None
                else:
                    self._io_port = None

                if getattr(self, '_procmgrthread', None):
                    self._procmgrthread = None

            def _cleanup(self):
                self._cleanup_job_io_port()
                if self._thread and self._thread != winprocess.INVALID_HANDLE_VALUE:
                    self._thread.Close()
                    self._thread = None
                else:
                    self._thread = None

                if self._handle and self._handle != winprocess.INVALID_HANDLE_VALUE:
                    self._handle.Close()
                    self._handle = None
                else:
                    self._handle = None

        elif mozinfo.isMac or mozinfo.isUnix:

            def _wait(self):
                """ Haven't found any reason to differentiate between these platforms
                    so they all use the same wait callback.  If it is necessary to
                    craft different styles of wait, then a new _wait method
                    could be easily implemented.
                """

                if not self._ignore_children:
                    try:
                        # os.waitpid returns a (pid, status) tuple
                        return os.waitpid(self.pid, 0)[1]
                    except OSError, e:
                        if getattr(e, "errno", None) != 10:
                            # Error 10 is "no child process", which could indicate normal
                            # close
                            print >> sys.stderr, "Encountered error waiting for pid to close: %s" % e
                            raise
                        return 0

                else:
                    # For non-group wait, call base class
                    subprocess.Popen.wait(self)
                    return self.returncode

            def _cleanup(self):
                pass

        else:
            # An unrecognized platform, we will call the base class for everything
            print >> sys.stderr, "Unrecognized platform, process groups may not be managed properly"

            def _wait(self):
                self.returncode = subprocess.Popen.wait(self)
                return self.returncode

            def _cleanup(self):
                pass

    def __init__(self,
                 cmd,
                 args=None,
                 cwd=None,
                 env=None,
                 ignore_children = False,
                 processOutputLine=(),
                 onTimeout=(),
                 onFinish=(),
                 **kwargs):
        """
        cmd = Command to run
        args = array of arguments (defaults to None)
        cwd = working directory for cmd (defaults to None)
        env = environment to use for the process (defaults to os.environ)
        ignore_children = when True, causes system to ignore child processes,
        defaults to False (which tracks child processes)
        processOutputLine = handlers to process the output line
        onTimeout = handlers for timeout event
        kwargs = keyword args to pass directly into Popen

        NOTE: Child processes will be tracked by default.  If for any reason
        we are unable to track child processes and ignore_children is set to False,
        then we will fall back to only tracking the root process.  The fallback
        will be logged.
        """
        self.cmd = cmd
        self.args = args
        self.cwd = cwd
        self.didTimeout = False
        self._ignore_children = ignore_children
        self.keywordargs = kwargs

        if env is None:
            env = os.environ.copy()
        self.env = env

        # handlers
        self.processOutputLineHandlers = list(processOutputLine)
        self.onTimeoutHandlers = list(onTimeout)
        self.onFinishHandlers = list(onFinish)

        # It is common for people to pass in the entire array with the cmd and
        # the args together since this is how Popen uses it.  Allow for that.
        if not isinstance(self.cmd, list):
            self.cmd = [self.cmd]

        if self.args:
            self.cmd = self.cmd + self.args

    @property
    def timedOut(self):
        """True if the process has timed out."""
        return self.didTimeout

    @property
    def commandline(self):
        """the string value of the command line"""
        return subprocess.list2cmdline([self.cmd] + self.args)

    def run(self):
        """Starts the process.  waitForFinish must be called to allow the
           process to complete.
        """
        self.didTimeout = False
        self.startTime = datetime.now()
        self.proc = self.Process(self.cmd,
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.STDOUT,
                                 cwd=self.cwd,
                                 env=self.env,
                                 ignore_children = self._ignore_children,
                                 **self.keywordargs)

    def kill(self):
        """
          Kills the managed process and if you created the process with
          'ignore_children=False' (the default) then it will also
          also kill all child processes spawned by it.
          If you specified 'ignore_children=True' when creating the process,
          only the root process will be killed.

          Note that this does not manage any state, save any output etc,
          it immediately kills the process.
        """
        return self.proc.kill()

    def readWithTimeout(self, f, timeout):
        """
          Try to read a line of output from the file object |f|.
          |f| must be a  pipe, like the |stdout| member of a subprocess.Popen
          object created with stdout=PIPE. If no output
          is received within |timeout| seconds, return a blank line.
          Returns a tuple (line, did_timeout), where |did_timeout| is True
          if the read timed out, and False otherwise.

          Calls a private member because this is a different function based on
          the OS
        """
        return self._readWithTimeout(f, timeout)

    def processOutputLine(self, line):
        """Called for each line of output that a process sends to stdout/stderr.
        """
        for handler in self.processOutputLineHandlers:
            handler(line)

    def onTimeout(self):
        """Called when a process times out."""
        for handler in self.onTimeoutHandlers:
            handler()

    def onFinish(self):
        """Called when a process finishes without a timeout."""
        for handler in self.onFinishHandlers:
            handler()

    def waitForFinish(self, timeout=None, outputTimeout=None):
        """
        Handle process output until the process terminates or times out.

        If timeout is not None, the process will be allowed to continue for
        that number of seconds before being killed.

        If outputTimeout is not None, the process will be allowed to continue
        for that number of seconds without producing any output before
        being killed.
        """

        if not hasattr(self, 'proc'):
            self.run()

        self.didTimeout = False
        logsource = self.proc.stdout

        lineReadTimeout = None
        if timeout:
            lineReadTimeout = timeout - (datetime.now() - self.startTime).seconds
        elif outputTimeout:
            lineReadTimeout = outputTimeout

        (line, self.didTimeout) = self.readWithTimeout(logsource, lineReadTimeout)
        while line != "" and not self.didTimeout:
            self.processOutputLine(line.rstrip())
            if timeout:
                lineReadTimeout = timeout - (datetime.now() - self.startTime).seconds
            (line, self.didTimeout) = self.readWithTimeout(logsource, lineReadTimeout)

        if self.didTimeout:
            self.proc.kill()
            self.onTimeout()
        else:
            self.onFinish()

        status = self.proc.wait()
        return status


    ### Private methods from here on down. Thar be dragons.

    if mozinfo.isWin:
        # Windows Specific private functions are defined in this block
        PeekNamedPipe = ctypes.windll.kernel32.PeekNamedPipe
        GetLastError = ctypes.windll.kernel32.GetLastError

        def _readWithTimeout(self, f, timeout):
            if timeout is None:
                # shortcut to allow callers to pass in "None" for no timeout.
                return (f.readline(), False)
            x = msvcrt.get_osfhandle(f.fileno())
            l = ctypes.c_long()
            done = time.time() + timeout
            while time.time() < done:
                if self.PeekNamedPipe(x, None, 0, None, ctypes.byref(l), None) == 0:
                    err = self.GetLastError()
                    if err == 38 or err == 109: # ERROR_HANDLE_EOF || ERROR_BROKEN_PIPE
                        return ('', False)
                    else:
                        raise OSError("readWithTimeout got error: %d", err)
                if l.value > 0:
                    # we're assuming that the output is line-buffered,
                    # which is not unreasonable
                    return (f.readline(), False)
                time.sleep(0.01)
            return ('', True)

    else:
        # Generic
        def _readWithTimeout(self, f, timeout):
            try:
                (r, w, e) = select.select([f], [], [], timeout)
            except:
                # return a blank line
                return ('', True)

            if len(r) == 0:
                return ('', True)
            return (f.readline(), False)


### default output handlers
### these should be callables that take the output line

def print_output(line):
    print line

class StoreOutput(object):
    """accumulate stdout"""

    def __init__(self):
        self.output = []

    def __call__(self, line):
        self.output.append(line)

class LogOutput(object):
    """pass output to a file"""

    def __init__(self, filename):
        self.filename = filename
        self.file = None

    def __call__(self, line):
        if self.file is None:
            self.file = file(self.filename, 'a')
        self.file.write(line + '\n')
        self.file.flush()

    def __del__(self):
        if self.file is not None:
            self.file.close()


### front end class with the default handlers

class ProcessHandler(ProcessHandlerMixin):

    def __init__(self, cmd, logfile=None, storeOutput=True, **kwargs):
        """
        If storeOutput=True, the output produced by the process will be saved
        as self.output.

        If logfile is not None, the output produced by the process will be
        appended to the given file.
        """

        kwargs.setdefault('processOutputLine', [])

        # Print to standard output only if no outputline provided
        if not kwargs['processOutputLine']:
            kwargs['processOutputLine'].append(print_output)

        if logfile:
            logoutput = LogOutput(logfile)
            kwargs['processOutputLine'].append(logoutput)

        self.output = None
        if storeOutput:
            storeoutput = StoreOutput()
            self.output = storeoutput.output
            kwargs['processOutputLine'].append(storeoutput)

        ProcessHandlerMixin.__init__(self, cmd, **kwargs)
