# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
This module provides wxPython event loop support for Twisted.

In order to use this support, simply do the following::

    |  from twisted.internet import wxreactor
    |  wxreactor.install()

Then, when your root wxApp has been created::

    | from twisted.internet import reactor
    | reactor.registerWxApp(yourApp)
    | reactor.run()

Then use twisted.internet APIs as usual. Stop the event loop using
reactor.stop(), not yourApp.ExitMainLoop().

IMPORTANT: tests will fail when run under this reactor. This is
expected and probably does not reflect on the reactor's ability to run
real applications.
"""

try:
    from queue import Empty, Queue
except ImportError:
    from Queue import Empty, Queue

try:
    from wx import PySimpleApp as wxPySimpleApp, CallAfter as wxCallAfter, \
         Timer as wxTimer
except ImportError:
    # older version of wxPython:
    from wxPython.wx import wxPySimpleApp, wxCallAfter, wxTimer

from twisted.python import log, runtime
from twisted.internet import _threadedselect


class ProcessEventsTimer(wxTimer):
    """
    Timer that tells wx to process pending events.

    This is necessary on macOS, probably due to a bug in wx, if we want
    wxCallAfters to be handled when modal dialogs, menus, etc.  are open.
    """
    def __init__(self, wxapp):
        wxTimer.__init__(self)
        self.wxapp = wxapp
    

    def Notify(self):
        """
        Called repeatedly by wx event loop.
        """
        self.wxapp.ProcessPendingEvents()



class WxReactor(_threadedselect.ThreadedSelectReactor):
    """
    wxPython reactor.

    wxPython drives the event loop, select() runs in a thread.
    """

    _stopping = False

    def registerWxApp(self, wxapp):
        """
        Register wxApp instance with the reactor.
        """
        self.wxapp = wxapp


    def _installSignalHandlersAgain(self):
        """
        wx sometimes removes our own signal handlers, so re-add them.
        """
        try:
            # make _handleSignals happy:
            import signal
            signal.signal(signal.SIGINT, signal.default_int_handler)
        except ImportError:
            return
        self._handleSignals()


    def stop(self):
        """
        Stop the reactor.
        """
        if self._stopping:
            return
        self._stopping = True
        _threadedselect.ThreadedSelectReactor.stop(self)


    def _runInMainThread(self, f):
        """
        Schedule function to run in main wx/Twisted thread.

        Called by the select() thread.
        """
        if hasattr(self, "wxapp"):
            wxCallAfter(f)
        else:
            # wx shutdown but twisted hasn't
            self._postQueue.put(f)


    def _stopWx(self):
        """
        Stop the wx event loop if it hasn't already been stopped.

        Called during Twisted event loop shutdown.
        """
        if hasattr(self, "wxapp"):
            self.wxapp.ExitMainLoop()


    def run(self, installSignalHandlers=True):
        """
        Start the reactor.
        """
        self._postQueue = Queue()
        if not hasattr(self, "wxapp"):
            log.msg("registerWxApp() was not called on reactor, "
                    "registering my own wxApp instance.")
            self.registerWxApp(wxPySimpleApp())

        # start select() thread:
        self.interleave(self._runInMainThread,
                        installSignalHandlers=installSignalHandlers)
        if installSignalHandlers:
            self.callLater(0, self._installSignalHandlersAgain)

        # add cleanup events:
        self.addSystemEventTrigger("after", "shutdown", self._stopWx)
        self.addSystemEventTrigger("after", "shutdown",
                                   lambda: self._postQueue.put(None))

        # On macOS, work around wx bug by starting timer to ensure
        # wxCallAfter calls are always processed. We don't wake up as
        # often as we could since that uses too much CPU.
        if runtime.platform.isMacOSX():
            t = ProcessEventsTimer(self.wxapp)
            t.Start(2) # wake up every 2ms

        self.wxapp.MainLoop()
        wxapp = self.wxapp
        del self.wxapp

        if not self._stopping:
            # wx event loop exited without reactor.stop() being
            # called.  At this point events from select() thread will
            # be added to _postQueue, but some may still be waiting
            # unprocessed in wx, thus the ProcessPendingEvents()
            # below.
            self.stop()
            wxapp.ProcessPendingEvents() # deal with any queued wxCallAfters
            while 1:
                try:
                    f = self._postQueue.get(timeout=0.01)
                except Empty:
                    continue
                else:
                    if f is None:
                        break
                    try:
                        f()
                    except:
                        log.err()


def install():
    """
    Configure the twisted mainloop to be run inside the wxPython mainloop.
    """
    reactor = WxReactor()
    from twisted.internet.main import installReactor
    installReactor(reactor)
    return reactor


__all__ = ['install']
