# Source code for pypdevs.realtime.threadingBackend

    # Copyright 2014 Modelling, Simulation and Design Lab (MSDL) at
    # McGill University and the University of Antwerp (http://msdl.cs.mcgill.ca/)
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #    http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.

    import threading

    class ThreadingBackend(object):
        """
        Wrapper around the actual threading backend. It will also handle interrupts and the passing of them to the calling thread.
        """
        def __init__(self, subsystem, args):
            """
            Constructor

            :param subsystem: string specifying the subsystem to use: python, tkinter or loop
            :param args: all additional arguments that should be passed to the subsystem's constructor (must be a list)
            """
            self.interrupted_value = None
            self.value_lock = threading.Lock()
            if subsystem == "python":
                from pypdevs.realtime.threadingPython import ThreadingPython
                self.subsystem = ThreadingPython(*args)
            elif subsystem == "tkinter":
                from pypdevs.realtime.threadingTkInter import ThreadingTkInter
                self.subsystem = ThreadingTkInter(*args)
            elif subsystem == "loop":
                from pypdevs.realtime.threadingGameLoop import ThreadingGameLoop
                self.subsystem = ThreadingGameLoop(*args)
            else:
                raise Exception("Realtime subsystem not found: " + str(subsystem))

        def wait(self, time, func):
            """
            A non-blocking call, which will call the *func* parameter after *time* seconds. It will use the provided backend to do this.

            :param time: time to wait in seconds, a float is possible
            :param func: the function to call after the time has passed
            """
            self.subsystem.wait(time, func)

        def interrupt(self, value):
            """
            Interrupt a running wait call, overwriting any previous interrupts.

            :param value: the value that interrupts
            """
            self.interrupted_value = value
            self.subsystem.interrupt()

        def setInterrupt(self, value):
            """
            Sets the value of the interrupt. This should not be used manually and is only required to prevent the asynchronous combo generator from making *interrrupt()* calls.

            :param value: value with which the interrupt variable should be set
            """
            with self.value_lock:
                if self.interrupted_value is None:
                    self.interrupted_value = value
                    return True
                else:
                    # The interrupt was already set, indicating a collision!
                    return False

        def getInterrupt(self):
            """
            Return the value of the interrupt and clear it internally.

            :returns: the interrupt
            """
            with self.value_lock:
                val = self.interrupted_value
                self.interrupted_value = None
            return val

        def step(self):
            """
            Perform a step in the backend; only supported for the game loop backend.
            """
            self.subsystem.step()