feat(ecs): re-add support for component events

1 files changed, 16 insertions, 82 deletions

diff --git a/ecs/src/event/component.rs b/ecs/src/event/component.rs
index b4edffc..ef09480 100644
--- a/ecs/src/event/component.rs
+++ b/ecs/src/event/component.rs
@@ -1,84 +1,18 @@
 //! Component events.
 
-use std::fmt::{Debug, Formatter};
-use std::marker::PhantomData;
-
-use ecs_macros::Component;
-
-use crate::component::Component;
-
-/// Event emitted when:
-/// a) A entity with component `ComponentT` is spawned.
-/// b) A component `ComponentT` is added to a entity.
-#[derive(Clone, Component)]
-pub struct Added<ComponentT>
-where
-    ComponentT: Component,
-{
-    _pd: PhantomData<ComponentT>,
-}
-
-impl<ComponentT> Debug for Added<ComponentT>
-where
-    ComponentT: Component,
-{
-    fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result
-    {
-        formatter
-            .debug_struct("Added")
-            .field("_pd", &self._pd)
-            .finish()
-    }
-}
-
-impl<ComponentT> Default for Added<ComponentT>
-where
-    ComponentT: Component,
-{
-    fn default() -> Self
-    {
-        Self { _pd: PhantomData }
-    }
-}
-
-/// Event emitted when:
-/// a) A `ComponentT` component is removed from a entity.
-/// b) A entity with component `ComponentT` is despawned.
-#[derive(Clone, Component)]
-pub struct Removed<ComponentT>
-where
-    ComponentT: Component,
-{
-    _pd: PhantomData<ComponentT>,
-}
-
-impl<ComponentT> Debug for Removed<ComponentT>
-where
-    ComponentT: Component,
-{
-    fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result
-    {
-        formatter
-            .debug_struct("Removed")
-            .field("_pd", &self._pd)
-            .finish()
-    }
-}
-
-impl<ComponentT> Default for Removed<ComponentT>
-where
-    ComponentT: Component,
-{
-    fn default() -> Self
-    {
-        Self { _pd: PhantomData }
-    }
-}
-
-/// Specifies a kind of component event UID.
-#[derive(Debug, Clone, Copy)]
-#[non_exhaustive]
-pub enum Kind
-{
-    Removed,
-}
+use std::convert::Infallible;
+use std::fmt::Debug;
+
+use crate::Component;
+
+/// Pair relation for events emitted when:
+/// a) A entity with the target component is spawned.
+/// b) The target component is added to a entity.
+#[derive(Debug, Component)]
+pub struct Added(Infallible);
+
+/// Pair relation for events emitted when:
+/// a) The target component is removed from a entity.
+/// b) A entity with the target component is despawned.
+#[derive(Debug, Component)]
+pub struct Removed(Infallible);