# Source code for pymunk.collision_handler

    __version__ = "$Id$"
    __docformat__ = "reStructuredText"

    from typing import TYPE_CHECKING, Any, Callable, Dict, Optional

    if TYPE_CHECKING:
        from .space import Space

    from ._chipmunk_cffi import ffi, lib
    from .arbiter import Arbiter

    _CollisionCallbackBool = Callable[[Arbiter, "Space", Any], bool]
    _CollisionCallbackNoReturn = Callable[[Arbiter, "Space", Any], None]

    class CollisionHandler(object):
        """A collision handler is a set of 4 function callbacks for the different
        collision events that Pymunk recognizes.

        Collision callbacks are closely associated with Arbiter objects. You
        should familiarize yourself with those as well.

        Note #1: Shapes tagged as sensors (Shape.sensor == true) never generate
        collisions that get processed, so collisions between sensors shapes and
        other shapes will never call the post_solve() callback. They still
        generate begin(), and separate() callbacks, and the pre_solve() callback
        is also called every frame even though there is no collision response.
        Note #2: pre_solve() callbacks are called before the sleeping algorithm
        runs. If an object falls asleep, its post_solve() callback won't be
        called until it's re-awoken.
        """

        def __init__(self, _handler: Any, space: "Space") -> None:
            """Initialize a CollisionHandler object from the Chipmunk equivalent
            struct and the Space.

            .. note::
                You should never need to create an instance of this class directly.
            """
            self._userData = ffi.new_handle(self)

            self._handler = _handler
            self._handler.userData = self._userData

            self._space = space
            self._begin: Optional[_CollisionCallbackBool] = None
            self._pre_solve: Optional[_CollisionCallbackBool] = None
            self._post_solve: Optional[_CollisionCallbackNoReturn] = None
            self._separate: Optional[_CollisionCallbackNoReturn] = None

            self._data: Dict[Any, Any] = {}

        def _reset(self) -> None:
            def allways_collide(arb: Arbiter, space: "Space", data: Any) -> bool:
                return True

            def do_nothing(arb: Arbiter, space: "Space", data: Any) -> None:
                return

            self.begin = allways_collide
            self.pre_solve = allways_collide
            self.post_solve = do_nothing
            self.separate = do_nothing

        @property
        def data(self) -> Dict[Any, Any]:
            """Data property that get passed on into the
            callbacks.

            data is a dictionary and you can not replace it, only fill it with data.

            Usefull if the callback needs some extra data to perform its function.
            """
            return self._data

        def _set_begin(self, func: Callable[[Arbiter, "Space", Any], bool]) -> None:
            self._begin = func
            self._handler.beginFunc = lib.ext_cpCollisionBeginFunc

        def _get_begin(self) -> Optional[_CollisionCallbackBool]:
            return self._begin

        begin = property(
            _get_begin,
            _set_begin,
            doc="""Two shapes just started touching for the first time this step.

            ``func(arbiter, space, data) -> bool``

            Return true from the callback to process the collision normally or
            false to cause pymunk to ignore the collision entirely. If you return
            false, the `pre_solve` and `post_solve` callbacks will never be run,
            but you will still recieve a separate event when the shapes stop
            overlapping.
            """,
        )

        def _set_pre_solve(self, func: _CollisionCallbackBool) -> None:
            self._pre_solve = func
            self._handler.preSolveFunc = lib.ext_cpCollisionPreSolveFunc

        def _get_pre_solve(self) -> Optional[Callable[[Arbiter, "Space", Any], bool]]:
            return self._pre_solve

        pre_solve = property(
            _get_pre_solve,
            _set_pre_solve,
            doc="""Two shapes are touching during this step.

            ``func(arbiter, space, data) -> bool``

            Return false from the callback to make pymunk ignore the collision
            this step or true to process it normally. Additionally, you may
            override collision values using Arbiter.friction, Arbiter.elasticity
            or Arbiter.surfaceVelocity to provide custom friction, elasticity,
            or surface velocity values. See Arbiter for more info.
            """,
        )

        def _set_post_solve(self, func: _CollisionCallbackNoReturn) -> None:

            self._post_solve = func
            self._handler.postSolveFunc = lib.ext_cpCollisionPostSolveFunc

        def _get_post_solve(self) -> Optional[_CollisionCallbackNoReturn]:
            return self._post_solve

        post_solve = property(
            _get_post_solve,
            _set_post_solve,
            doc="""Two shapes are touching and their collision response has been
            processed.

            ``func(arbiter, space, data)``

            You can retrieve the collision impulse or kinetic energy at this
            time if you want to use it to calculate sound volumes or damage
            amounts. See Arbiter for more info.
            """,
        )

        def _set_separate(self, func: _CollisionCallbackNoReturn) -> None:
            self._separate = func
            self._handler.separateFunc = lib.ext_cpCollisionSeparateFunc

        def _get_separate(self) -> Optional[_CollisionCallbackNoReturn]:
            return self._separate

        separate = property(
            _get_separate,
            _set_separate,
            doc="""Two shapes have just stopped touching for the first time this
            step.

            ``func(arbiter, space, data)``

            To ensure that begin()/separate() are always called in balanced
            pairs, it will also be called when removing a shape while its in
            contact with something or when de-allocating the space.
            """,
        )