import system

# Entities that need animation get an AnimationComponent
class AnimationComponent(object):

    __slots__ = ('animations', 'enabled')

    def __init__(self, *, animations=[]):

        # List of currently applied (not necessarily running!) animations
        self.animations = animations

        # Enable/disable animations with a single flag (i.e. for pausing the game)
        self.enabled = True

class AnimationSystem(system.System):

    def __init__(self, mgr):

        super().__init__(mgr)

        # Boilerplate for the main Entity Manager to know how to interact with the AnimationSystem
        self.component = AnimationComponent
        self.component_name = 'Animation'

        # Specifies the priority it gets to run.
        # Different Systems run on different tick rates, but if they occur on the frame update,
        self.priority = 25

    def startup(self):

        super().startup()

    def shutdown(self):

        super().shutdown()

    def update(self, tick):

        # Receive a "tick" which is a time delta from the last game loop
        super().update(tick)

        # For each AnimationComponent and each active animation, update it.
        # self._data is an entity->component lookup table for every System
        entities = [ (entity, self._mgr.get_component(entity,'Render'), animation_comp.animations)
                     for entity, animation_comp in self._data.items() if animation_comp.enabled ]

        # Loop over the active animation entities
        for entity, render, animations in entities:

            # Entities may have multiple simultaneous animations, run them in order
            for animation in animations:
                animation.update(tick)

    def handle_event(self, event):
        pass