# Temporary buffer for an SDL 2 event exposing the pseudo-class hierarchy metadata
#
# An instance of this class should be used to call `poll_event` and `to_event`.
extern class SDLEventBuffer `{SDL_Event *`}
	# Allocate memory for a new `SDLEventBuffer`
	new malloc `{ return malloc(sizeof(SDL_Event)); `}

	# Poll and event into `self`
	#
	# Returns `true` if an event was available.
	fun poll_event: Bool `{ return SDL_PollEvent(self); `}

	# Get a reference to the data at `self` as a precise `SDLEvent`
	#
	# Returns `null` if the event is unknown.
	#
	# Note: The returned `SDLEvent` is just a different Nit instance pointing to the same data.
	# A call to `poll_event` will invalidate any instances returned previously by `to_event`.
	fun to_event: SDLEvent
	do
		if is_quit then return to_quit
		if is_mouse_motion then return to_mouse_motion
		if is_mouse_button_down then return to_mouse_button_down
		if is_mouse_button_up then return to_mouse_button_up
		if is_mouse_wheel then return to_mouse_wheel
		if is_keydown then return to_keydown
		if is_keyup then return to_keyup
		if is_window then return to_window
		return to_event_direct
	end

	private fun to_event_direct: SDLEvent `{ return self; `}

	# Is this a quit event?
	fun is_quit: Bool `{ return self->type == SDL_QUIT; `}

	# Get a reference to data at `self` as a `SDLQuitEvent`
	#
	# Require: `is_quit`
	fun to_quit: SDLQuitEvent `{ return self; `}

	# Is this a mouse motion event?
	fun is_mouse_motion: Bool `{ return self->type == SDL_MOUSEMOTION; `}

	# Get a reference to data at `self` as a `SDLMouseMotionEvent`
	#
	# Require: `is_mouse_motion`
	fun to_mouse_motion: SDLMouseMotionEvent `{ return self; `}

	# Is this a mouse button down event?
	fun is_mouse_button_down: Bool `{ return self->type == SDL_MOUSEBUTTONDOWN; `}

	# Get a reference to data at `self` as a `SDLMouseButtonDownEvent`
	#
	# Require: `is_mouse_button_down`
	fun to_mouse_button_down: SDLMouseButtonDownEvent `{ return self; `}

	# Is this a mouse button up event?
	fun is_mouse_button_up: Bool `{ return self->type == SDL_MOUSEBUTTONUP; `}

	# Get a reference to data at `self` as a `SDLMouseButtonUpEvent`
	#
	# Require: `is_mouse_button_up`
	fun to_mouse_button_up: SDLMouseButtonUpEvent `{ return self; `}

	# Is this a mouse wheel event?
	fun is_mouse_wheel: Bool `{ return self->type == SDL_MOUSEWHEEL; `}

	# Get a reference to data at `self` as a `SDLMouseWheelEvent`
	#
	# Require: `is_mouse_wheel`
	fun to_mouse_wheel: SDLMouseWheelEvent `{ return self; `}

	# Is this a key presse event?
	fun is_keydown: Bool `{ return self->type == SDL_KEYDOWN; `}

	# Get a reference to data at `self` as a `SDLKeyboardDownEvent`
	#
	# Require: `is_keydown`
	fun to_keydown: SDLKeyboardDownEvent `{ return self; `}

	#  Is this a key release event?
	fun is_keyup: Bool `{ return self->type == SDL_KEYUP; `}

	# Get a reference to data at `self` as a `SDLKeyboardUpEvent`
	#
	# Require: `is_keyup`
	fun to_keyup: SDLKeyboardUpEvent `{ return self; `}

	#  Is this a window event?
	fun is_window: Bool `{ return self->type == SDL_WINDOWEVENT; `}

	# Get a reference to data at `self` as a `SDLWindowEvent`
	#
	# Require: `is_window`
	fun to_window: SDLWindowEvent `{ return self; `}

	# TODO other SDL events:
	#
	# SDL_CommonEvent common
	# SDL_WindowEvent window
	# SDL_TextEditingEvent edit
	# SDL_TextInputEvent text
	# SDL_JoyAxisEvent jaxis
	# SDL_JoyBallEvent jball
	# SDL_JoyHatEvent jhat;
	# SDL_JoyButtonEvent jbutton
	# SDL_JoyDeviceEvent jdevice
	# SDL_ControllerAxisEvent caxis
	# SDL_ControllerButtonEvent cbutton
	# SDL_ControllerDeviceEvent cdevice
	# SDL_UserEvent user
	# SDL_SysWMEvent syswm
	# SDL_TouchFingerEvent tfinger
	# SDL_MultiGestureEvent mgesture
	# SDL_DollarGestureEvent dgesture
	# SDL_DropEvent drop
end