Object-Oriented Events for IF, including an interrupt_before method

interrupt_before.py

"""
A short example of my proposed object-oriented event framework for IF games.
Every event should implement a go() method, which calls super().go() before doing
anything else. After that, it should check whether its own go() method is
applicable by making a call to self.should_fire(<EventType>).
"""

class Event:
    """Generic Event type."""
    def __init__(self, obj):
        self.obj = obj  # Event is applied to this object.
        self._interrupts = set()  # Set of things to interrupt for.
        self._interrupt_before = set()  # Set of things to interrupt before..
        self._should_continue = True  # Has our event (not) been interrupted?

    def should_fire(self, current_type):
        """Determine whether we should apply current_type's handler."""
        if not self._should_continue:
            # We've already interrupted; don't handle the event.
            return False
        # Only fire the next event if we're not in the set of interrupts.
        self._should_continue = current_type not in self._interrupts
        # Only fire *this* event if we're not interrupted before it.
        return current_type not in self._interrupt_before

    def go(self):
        """Override this method if you want your event to do something."""

    def interrupt_after(self, *args):
        """Add an arbitrary list of event types at which we interrupt."""
        for a in args:
            self._interrupts.add(a)

    def interrupt_before(self, *args):
        """Add an arbitrary list of event types before which we interrupt."""
        for a in args:
            self._interrupts.add(a)
            self._interrupt_before.add(a)

        
class Touch(Event):
    """Sent when an object is touched."""
    def go(self):
        super().go()
        if self.should_fire(Touch):
            print(self.obj, "was touched!")

        
class Pull(Touch):
    """Sent when an object is pulled."""
    def go(self):
        super().go()
        if self.should_fire(Pull):
            print(self.obj, "was pulled!")


class LeverPull(Pull):
    """Sent when a lever is pulled."""
    def go(self):
        super().go()
        if self.should_fire(LeverPull):
            print(self.obj, "was lever-pulled!")


class ElectrifiedLeverPull(LeverPull):
    """Sent when an electrified lever is pulled."""
    def __init__(self, obj):
        super().__init__(obj)
        self.interrupt_after(Touch)

    def go(self):
        super().go()
        if self.should_fire(ElectrifiedLeverPull):
            print(self.obj, "was electric-lever-pulled!")
        else:
            print("ZAP!")


class ForcefieldLeverPull(LeverPull):
    """Sent when the user tries to pull a forcefield lever."""
    def __init__(self, obj):
        super().__init__(obj)
        if self.obj.forcefield_active:
            self.interrupt_before(Touch)

    def go(self):
        super().go()
        if self.should_fire(ForcefieldLeverPull):
            print(self.obj, "was forcefield-lever-pulled!")
        else:  # self.obj.forcefield_active is True
            print("You hit the forcefield around the lever!")
        

class WorkingLever:
    def __str__(self):
        return "Working Lever"


class ElectrifiedLever:
    def __str__(self):
        return "Electrified Lever"


class ForcefieldLever:
    def __init__(self):
        self.forcefield_active = True

    def __str__(self):
        return "Forcefield Lever"

        
LeverPull(WorkingLever()).go()
print()

ElectrifiedLeverPull(ElectrifiedLever()).go()
print()

forcefield_lever = ForcefieldLever()
ForcefieldLeverPull(forcefield_lever).go()
print()

forcefield_lever.forcefield_active = False
ForcefieldLeverPull(forcefield_lever).go()
print()