'''
Sandbox
=======

.. versionadded:: 1.8.0

.. warning::

    This is experimental and subject to change as long as this warning notice
    is present.

This is a widget that runs itself and all of its children in a Sandbox. That
means if a child raises an Exception, it will be caught. The Sandbox
itself runs its own Clock, Cache, etc.

The SandBox widget is still experimental and required for the Kivy designer.
When the user designs their own widget, if they do something wrong (wrong size
value, invalid python code), it will be caught correctly without breaking
the whole application. Because it has been designed that way, we are still
enhancing this widget and the :mod:`kivy.context` module.
Don't use it unless you know what you are doing.

'''

__all__ = ('Sandbox', )

from functools import wraps
from kivy.context import Context
from kivy.base import ExceptionManagerBase
from kivy.clock import Clock
from kivy.uix.widget import Widget
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.relativelayout import RelativeLayout
from kivy.lang import Builder


def sandbox(f):
    @wraps(f)
    def _f2(self, *args, **kwargs):
        ret = None
        with self:
            ret = f(self, *args, **kwargs)
        return ret
    return _f2


class SandboxExceptionManager(ExceptionManagerBase):

    def __init__(self, sandbox):
        ExceptionManagerBase.__init__(self)
        self.sandbox = sandbox

    def handle_exception(self, e):
        if not self.sandbox.on_exception(e):
            return ExceptionManagerBase.RAISE
        return ExceptionManagerBase.PASS


class SandboxContent(RelativeLayout):
    pass


class Sandbox(FloatLayout):
    '''Sandbox widget, used to trap all the exceptions raised by child
    widgets.
    '''

    def __init__(self, **kwargs):
        self._context = Context(init=True)
        self._context['ExceptionManager'] = SandboxExceptionManager(self)
        self._context.sandbox = self
        self._context.push()
        self.on_context_created()
        self._container = None
        super(Sandbox, self).__init__(**kwargs)
        self._container = SandboxContent(size=self.size, pos=self.pos)
        super(Sandbox, self).add_widget(self._container)
        self._context.pop()

        # force SandboxClock's scheduling
        Clock.schedule_interval(self._clock_sandbox, 0)
        Clock.schedule_once(self._clock_sandbox_draw, -1)
        self.main_clock = object.__getattribute__(Clock, '_obj')

    def __enter__(self):
        self._context.push()

    def __exit__(self, _type, value, traceback):
        self._context.pop()
        if _type is not None:
            return self.on_exception(value, _traceback=traceback)

    def on_context_created(self):
        '''Override this method in order to load your kv file or do anything
        else with the newly created context.
        '''
        pass

    def on_exception(self, exception, _traceback=None):
        '''Override this method in order to catch all the exceptions from
        children.

        If you return True, it will not reraise the exception.
        If you return False, the exception will be raised to the parent.
        '''
        import traceback
        traceback.print_tb(_traceback)
        return True

    on_touch_down = sandbox(Widget.on_touch_down)
    on_touch_move = sandbox(Widget.on_touch_move)
    on_touch_up = sandbox(Widget.on_touch_up)

    @sandbox
    def add_widget(self, *args, **kwargs):
        self._container.add_widget(*args, **kwargs)

    @sandbox
    def remove_widget(self, *args, **kwargs):
        self._container.remove_widget(*args, **kwargs)

    @sandbox
    def clear_widgets(self, *args, **kwargs):
        self._container.clear_widgets()

    @sandbox
    def on_size(self, *args):
        if self._container:
            self._container.size = self.size

    @sandbox
    def on_pos(self, *args):
        if self._container:
            self._container.pos = self.pos

    @sandbox
    def _clock_sandbox(self, dt):
        #import pdb; pdb.set_trace()
        Clock.tick()
        Builder.sync()

    @sandbox
    def _clock_sandbox_draw(self, dt):
        Clock.tick_draw()
        Builder.sync()
        self.main_clock.schedule_once(self._call_draw, 0)

    def _call_draw(self, dt):
        self.main_clock.schedule_once(self._clock_sandbox_draw, -1)

if __name__ == '__main__':
    from kivy.base import runTouchApp
    from kivy.uix.button import Button

    class TestButton(Button):

        def on_touch_up(self, touch):
            #raise Exception('fdfdfdfdfdfdfd')
            return super(TestButton, self).on_touch_up(touch)

        def on_touch_down(self, touch):
            #raise Exception('')
            return super(TestButton, self).on_touch_down(touch)

    s = Sandbox()
    with s:
        Builder.load_string('''
<TestButton>:
    canvas:
        Color:
            rgb: (.3, .2, 0) if self.state == 'normal' else (.7, .7, 0)
        Rectangle:
            pos: self.pos
            size: self.size
        Color:
            rgb: 1, 1, 1
        Rectangle:
            size: self.texture_size
            pos: self.center_x - self.texture_size[0] / 2.,\
                 self.center_y - self.texture_size[1] / 2.
            texture: self.texture

    # invalid... for testing.
    #on_touch_up: root.d()
    #on_touch_down: root.f()
    on_release: root.args()
    #on_press: root.args()
''')
        b = TestButton(text='Hello World')
        s.add_widget(b)

        # this exception is within the "with" block, but will be ignored by
        # default because the sandbox on_exception will return True
        raise Exception('hello')

    runTouchApp(s)
