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

"""
This module provides support for Twisted to interact with the glib
mainloop via GObject Introspection.

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

    from twisted.internet import gireactor
    gireactor.install()

If you wish to use a GApplication, register it with the reactor::

    from twisted.internet import reactor
    reactor.registerGApplication(app)

Then use twisted.internet APIs as usual.

On Python 3, pygobject v3.4 or later is required.
"""

from __future__ import division, absolute_import

from twisted.python.compat import _PY3
from twisted.internet.error import ReactorAlreadyRunning
from twisted.internet import _glibbase
from twisted.python import runtime

if _PY3:
    # We require a sufficiently new version of pygobject, so always exists:
    _pygtkcompatPresent = True
else:
    # We can't just try to import gi.pygtkcompat, because that would import
    # gi, and the goal here is to not import gi in cases where that would
    # cause segfault.
    from twisted.python.modules import theSystemPath
    _pygtkcompatPresent = True
    try:
        theSystemPath["gi.pygtkcompat"]
    except KeyError:
        _pygtkcompatPresent = False


# Modules that we want to ensure aren't imported if we're on older versions of
# GI:
_PYGTK_MODULES = ['gobject', 'glib', 'gio', 'gtk']

def _oldGiInit():
    """
    Make sure pygtk and gi aren't loaded at the same time, and import Glib if
    possible.
    """
    # We can't immediately prevent imports, because that confuses some buggy
    # code in gi:
    _glibbase.ensureNotImported(
        _PYGTK_MODULES,
        "Introspected and static glib/gtk bindings must not be mixed; can't "
        "import gireactor since pygtk2 module is already imported.")

    global GLib
    from gi.repository import GLib
    if getattr(GLib, "threads_init", None) is not None:
        GLib.threads_init()

    _glibbase.ensureNotImported([], "",
                                preventImports=_PYGTK_MODULES)


if not _pygtkcompatPresent:
    # Older versions of gi don't have compatability layer, so just enforce no
    # imports of pygtk and gi at same time:
    _oldGiInit()
else:
    # Newer version of gi, so we can try to initialize compatibility layer; if
    # real pygtk was already imported we'll get ImportError at this point
    # rather than segfault, so unconditional import is fine.
    import gi.pygtkcompat
    gi.pygtkcompat.enable()
    # At this point importing gobject will get you gi version, and importing
    # e.g. gtk will either fail in non-segfaulty way or use gi version if user
    # does gi.pygtkcompat.enable_gtk(). So, no need to prevent imports of
    # old school pygtk modules.
    from gi.repository import GLib
    if getattr(GLib, "threads_init", None) is not None:
        GLib.threads_init()



class GIReactor(_glibbase.GlibReactorBase):
    """
    GObject-introspection event loop reactor.

    @ivar _gapplication: A C{Gio.Application} instance that was registered
        with C{registerGApplication}.
    """
    _POLL_DISCONNECTED = (GLib.IOCondition.HUP | GLib.IOCondition.ERR |
                          GLib.IOCondition.NVAL)
    _POLL_IN = GLib.IOCondition.IN
    _POLL_OUT = GLib.IOCondition.OUT

    # glib's iochannel sources won't tell us about any events that we haven't
    # asked for, even if those events aren't sensible inputs to the poll()
    # call.
    INFLAGS = _POLL_IN | _POLL_DISCONNECTED
    OUTFLAGS = _POLL_OUT | _POLL_DISCONNECTED

    # By default no Application is registered:
    _gapplication = None


    def __init__(self, useGtk=False):
        _gtk = None
        if useGtk is True:
            from gi.repository import Gtk as _gtk

        _glibbase.GlibReactorBase.__init__(self, GLib, _gtk, useGtk=useGtk)


    def registerGApplication(self, app):
        """
        Register a C{Gio.Application} or C{Gtk.Application}, whose main loop
        will be used instead of the default one.

        We will C{hold} the application so it doesn't exit on its own. In
        versions of C{python-gi} 3.2 and later, we exit the event loop using
        the C{app.quit} method which overrides any holds. Older versions are
        not supported.
        """
        if self._gapplication is not None:
            raise RuntimeError(
                "Can't register more than one application instance.")
        if self._started:
            raise ReactorAlreadyRunning(
                "Can't register application after reactor was started.")
        if not hasattr(app, "quit"):
            raise RuntimeError("Application registration is not supported in"
                               " versions of PyGObject prior to 3.2.")
        self._gapplication = app
        def run():
            app.hold()
            app.run(None)
        self._run = run

        self._crash = app.quit



class PortableGIReactor(_glibbase.PortableGlibReactorBase):
    """
    Portable GObject Introspection event loop reactor.
    """
    def __init__(self, useGtk=False):
        _gtk = None
        if useGtk is True:
            from gi.repository import Gtk as _gtk

        _glibbase.PortableGlibReactorBase.__init__(self, GLib, _gtk,
                                                   useGtk=useGtk)


    def registerGApplication(self, app):
        """
        Register a C{Gio.Application} or C{Gtk.Application}, whose main loop
        will be used instead of the default one.
        """
        raise NotImplementedError("GApplication is not currently supported on Windows.")



def install(useGtk=False):
    """
    Configure the twisted mainloop to be run inside the glib mainloop.

    @param useGtk: should GTK+ rather than glib event loop be
        used (this will be slightly slower but does support GUI).
    """
    if runtime.platform.getType() == 'posix':
        reactor = GIReactor(useGtk=useGtk)
    else:
        reactor = PortableGIReactor(useGtk=useGtk)

    from twisted.internet.main import installReactor
    installReactor(reactor)
    return reactor


__all__ = ['install']
