# (C) Copyright 2005-2021 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!

""" The interface of a pyface GUI. """


import logging
import os


from traits.etsconfig.api import ETSConfig
from traits.api import Bool, HasTraits, Interface, Str


# Logging.
logger = logging.getLogger(__name__)


class IGUI(Interface):
    """ The interface of a pyface GUI. """

    # 'GUI' interface -----------------------------------------------------#

    #: Is the GUI busy (i.e. should the busy cursor, often an hourglass, be
    #: displayed)?
    busy = Bool(False)

    #: Has the GUI's event loop been started?
    started = Bool(False)

    #: A directory on the local file system that we can read and write to at
    #: will.  This is used to persist layout information etc.  Note that
    #: individual toolkits will have their own directory.
    state_location = Str()

    # ------------------------------------------------------------------------
    # 'object' interface.
    # ------------------------------------------------------------------------

    def __init__(self, splash_screen=None):
        """ Initialise a new GUI.

        Parameters
        ----------
        splash_screen : ISplashScreen instance or None
            An optional splash screen that will be displayed until the event
            loop is started.
        """

    # ------------------------------------------------------------------------
    # 'GUI' class interface.
    # ------------------------------------------------------------------------

    @staticmethod
    def allow_interrupt():
        """ Override SIGINT to prevent swallowing KeyboardInterrupt

        Override the SIGINT handler to ensure the process can be
        interrupted. This prevents GUI toolkits from swallowing
        KeyboardInterrupt exceptions.

        Warning: do not call this method if you intend your application to be
        run interactively.
        """

    @classmethod
    def invoke_after(cls, millisecs, callable, *args, **kw):
        """ Call a callable after a specific delay in the main GUI thread.

        Parameters
        ----------
        millisecs : float
            Delay in milliseconds
        callable : callable
            Callable to be called after the delay
        args, kwargs :
            Arguments and keyword arguments to be used when calling.
        """

    @classmethod
    def invoke_later(cls, callable, *args, **kw):
        """ Call a callable in the main GUI thread.

        Parameters
        ----------
        callable : callable
            Callable to be called after the delay
        args, kwargs :
            Arguments and keyword arguments to be used when calling.
        """

    @classmethod
    def set_trait_after(cls, millisecs, obj, trait_name, new):
        """ Sets a trait after a specific delay in the main GUI thread.

        Parameters
        ----------
        millisecs : float
            Delay in milliseconds
        obj : HasTraits instance
            Object on which the trait is to be set
        trait_name : str
            The name of the trait to set
        new : any
            The value to set.
        """

    @classmethod
    def set_trait_later(cls, obj, trait_name, new):
        """ Sets a trait in the main GUI thread.

        Parameters
        ----------
        obj : HasTraits instance
            Object on which the trait is to be set
        trait_name : str
            The name of the trait to set
        new : any
            The value to set.
        """

    @staticmethod
    def process_events(allow_user_events=True):
        """ Process any pending GUI events.

        Parameters
        ----------
        allow_user_events : bool
            If allow_user_events is ``False`` then user generated events are not
            processed.
        """

    @staticmethod
    def set_busy(busy=True):
        """Specify if the GUI is busy.

        Parameters
        ----------
        busy : bool
            If ``True`` is passed, the cursor is set to a 'busy' cursor.
            Passing ``False`` will reset the cursor to the default.
        """

    # ------------------------------------------------------------------------
    # 'GUI' interface.
    # ------------------------------------------------------------------------

    def start_event_loop(self):
        """ Start the GUI event loop. """

    def stop_event_loop(self):
        """ Stop the GUI event loop. """


class MGUI(HasTraits):
    """ The mixin class that contains common code for toolkit specific
    implementations of the IGUI interface.

    Implements: _default_state_location()
    """

    @staticmethod
    def allow_interrupt():
        """ Override SIGINT to prevent swallowing KeyboardInterrupt

        Override the SIGINT handler to ensure the process can be
        interrupted. This prevents GUI toolkits from swallowing
        KeyboardInterrupt exceptions.

        Warning: do not call this method if you intend your application to be
        run interactively.
        """
        import signal

        signal.signal(signal.SIGINT, signal.SIG_DFL)

    def _default_state_location(self):
        """ Return the default state location. """

        state_location = os.path.join(
            ETSConfig.application_home, "pyface", ETSConfig.toolkit
        )

        if not os.path.exists(state_location):
            os.makedirs(state_location)

        logger.debug("GUI state location is <%s>", state_location)

        return state_location
