import contextlib
import os
import signal
import socket

import matplotlib as mpl
from matplotlib import _api, cbook
from matplotlib._pylab_helpers import Gcf
from . import _macosx
from .backend_agg import FigureCanvasAgg
from matplotlib.backend_bases import (
    _Backend, FigureCanvasBase, FigureManagerBase, NavigationToolbar2,
    ResizeEvent, TimerBase)


class TimerMac(_macosx.Timer, TimerBase):
    """Subclass of `.TimerBase` using CFRunLoop timer events."""
    # completely implemented at the C-level (in _macosx.Timer)


class FigureCanvasMac(FigureCanvasAgg, _macosx.FigureCanvas, FigureCanvasBase):
    # docstring inherited

    # Ideally this class would be `class FCMacAgg(FCAgg, FCMac)`
    # (FC=FigureCanvas) where FCMac would be an ObjC-implemented mac-specific
    # class also inheriting from FCBase (this is the approach with other GUI
    # toolkits).  However, writing an extension type inheriting from a Python
    # base class is slightly tricky (the extension type must be a heap type),
    # and we can just as well lift the FCBase base up one level, keeping it *at
    # the end* to have the right method resolution order.

    # Events such as button presses, mouse movements, and key presses are
    # handled in C and events (MouseEvent, etc.) are triggered from there.

    required_interactive_framework = "macosx"
    _timer_cls = TimerMac
    manager_class = _api.classproperty(lambda cls: FigureManagerMac)

    def __init__(self, figure):
        super().__init__(figure=figure)
        self._draw_pending = False
        self._is_drawing = False
        # Keep track of the timers that are alive
        self._timers = set()

    def draw(self):
        """Render the figure and update the macosx canvas."""
        # The renderer draw is done here; delaying causes problems with code
        # that uses the result of the draw() to update plot elements.
        if self._is_drawing:
            return
        with cbook._setattr_cm(self, _is_drawing=True):
            super().draw()
        self.update()

    def draw_idle(self):
        # docstring inherited
        if not (getattr(self, '_draw_pending', False) or
                getattr(self, '_is_drawing', False)):
            self._draw_pending = True
            # Add a singleshot timer to the eventloop that will call back
            # into the Python method _draw_idle to take care of the draw
            self._single_shot_timer(self._draw_idle)

    def _single_shot_timer(self, callback):
        """Add a single shot timer with the given callback"""
        # We need to explicitly stop and remove the timer after
        # firing, otherwise segfaults will occur when trying to deallocate
        # the singleshot timers.
        def callback_func(callback, timer):
            callback()
            self._timers.remove(timer)
            timer.stop()
        timer = self.new_timer(interval=0)
        timer.single_shot = True
        timer.add_callback(callback_func, callback, timer)
        self._timers.add(timer)
        timer.start()

    def _draw_idle(self):
        """
        Draw method for singleshot timer

        This draw method can be added to a singleshot timer, which can
        accumulate draws while the eventloop is spinning. This method will
        then only draw the first time and short-circuit the others.
        """
        with self._idle_draw_cntx():
            if not self._draw_pending:
                # Short-circuit because our draw request has already been
                # taken care of
                return
            self._draw_pending = False
            self.draw()

    def blit(self, bbox=None):
        # docstring inherited
        super().blit(bbox)
        self.update()

    def resize(self, width, height):
        # Size from macOS is logical pixels, dpi is physical.
        scale = self.figure.dpi / self.device_pixel_ratio
        width /= scale
        height /= scale
        self.figure.set_size_inches(width, height, forward=False)
        ResizeEvent("resize_event", self)._process()
        self.draw_idle()

    def start_event_loop(self, timeout=0):
        # docstring inherited
        with _maybe_allow_interrupt():
            # Call the objc implementation of the event loop after
            # setting up the interrupt handling
            self._start_event_loop(timeout=timeout)


class NavigationToolbar2Mac(_macosx.NavigationToolbar2, NavigationToolbar2):

    def __init__(self, canvas):
        data_path = cbook._get_data_path('images')
        _, tooltips, image_names, _ = zip(*NavigationToolbar2.toolitems)
        _macosx.NavigationToolbar2.__init__(
            self, canvas,
            tuple(str(data_path / image_name) + ".pdf"
                  for image_name in image_names if image_name is not None),
            tuple(tooltip for tooltip in tooltips if tooltip is not None))
        NavigationToolbar2.__init__(self, canvas)

    def draw_rubberband(self, event, x0, y0, x1, y1):
        self.canvas.set_rubberband(int(x0), int(y0), int(x1), int(y1))

    def remove_rubberband(self):
        self.canvas.remove_rubberband()

    def save_figure(self, *args):
        directory = os.path.expanduser(mpl.rcParams['savefig.directory'])
        filename = _macosx.choose_save_file('Save the figure',
                                            directory,
                                            self.canvas.get_default_filename())
        if filename is None:  # Cancel
            return
        # Save dir for next time, unless empty str (which means use cwd).
        if mpl.rcParams['savefig.directory']:
            mpl.rcParams['savefig.directory'] = os.path.dirname(filename)
        self.canvas.figure.savefig(filename)


class FigureManagerMac(_macosx.FigureManager, FigureManagerBase):
    _toolbar2_class = NavigationToolbar2Mac

    def __init__(self, canvas, num):
        self._shown = False
        _macosx.FigureManager.__init__(self, canvas)
        icon_path = str(cbook._get_data_path('images/matplotlib.pdf'))
        _macosx.FigureManager.set_icon(icon_path)
        FigureManagerBase.__init__(self, canvas, num)
        self._set_window_mode(mpl.rcParams["macosx.window_mode"])
        if self.toolbar is not None:
            self.toolbar.update()
        if mpl.is_interactive():
            self.show()
            self.canvas.draw_idle()

    def _close_button_pressed(self):
        Gcf.destroy(self)
        self.canvas.flush_events()

    def destroy(self):
        # We need to clear any pending timers that never fired, otherwise
        # we get a memory leak from the timer callbacks holding a reference
        while self.canvas._timers:
            timer = self.canvas._timers.pop()
            timer.stop()
        super().destroy()

    @classmethod
    def start_main_loop(cls):
        # Set up a SIGINT handler to allow terminating a plot via CTRL-C.
        # The logic is largely copied from qt_compat._maybe_allow_interrupt; see its
        # docstring for details.  Parts are implemented by wake_on_fd_write in ObjC.
        with _maybe_allow_interrupt():
            _macosx.show()

    def show(self):
        if not self._shown:
            self._show()
            self._shown = True
        if mpl.rcParams["figure.raise_window"]:
            self._raise()


@contextlib.contextmanager
def _maybe_allow_interrupt():
    """
    This manager allows to terminate a plot by sending a SIGINT. It is
    necessary because the running backend prevents Python interpreter to
    run and process signals (i.e., to raise KeyboardInterrupt exception). To
    solve this one needs to somehow wake up the interpreter and make it close
    the plot window. The implementation is taken from qt_compat, see that
    docstring for a more detailed description.
    """
    old_sigint_handler = signal.getsignal(signal.SIGINT)
    if old_sigint_handler in (None, signal.SIG_IGN, signal.SIG_DFL):
        yield
        return

    handler_args = None
    wsock, rsock = socket.socketpair()
    wsock.setblocking(False)
    rsock.setblocking(False)
    old_wakeup_fd = signal.set_wakeup_fd(wsock.fileno())
    _macosx.wake_on_fd_write(rsock.fileno())

    def handle(*args):
        nonlocal handler_args
        handler_args = args
        _macosx.stop()

    signal.signal(signal.SIGINT, handle)
    try:
        yield
    finally:
        wsock.close()
        rsock.close()
        signal.set_wakeup_fd(old_wakeup_fd)
        signal.signal(signal.SIGINT, old_sigint_handler)
        if handler_args is not None:
            old_sigint_handler(*handler_args)


@_Backend.export
class _BackendMac(_Backend):
    FigureCanvas = FigureCanvasMac
    FigureManager = FigureManagerMac
    mainloop = FigureManagerMac.start_main_loop
