refactor(ecs): add system trait

1 files changed, 64 insertions, 0 deletions

diff --git a/ecs/src/system.rs b/ecs/src/system.rs
new file mode 100644
index 0000000..ecf1885
--- /dev/null
+++ b/ecs/src/system.rs
@@ -0,0 +1,64 @@
+use std::any::Any;
+use std::fmt::Debug;
+
+use crate::component::Sequence as ComponentSequence;
+use crate::{ComponentStorage, Query};
+
+pub trait System<Impl>: 'static
+{
+    type Query<'a>;
+
+    fn run(&self, component_storage: &mut ComponentStorage);
+
+    fn into_type_erased(self) -> TypeErased;
+}
+
+impl<Func, Comps> System<fn(Query<Comps>)> for Func
+where
+    Func: Fn(Query<Comps>) + 'static,
+    Comps: ComponentSequence,
+{
+    type Query<'a> = Query<'a, Comps>;
+
+    fn run(&self, component_storage: &mut ComponentStorage)
+    {
+        self(Query::new(component_storage));
+    }
+
+    fn into_type_erased(self) -> TypeErased
+    {
+        TypeErased {
+            data: Box::new(self),
+            func: Box::new(|data, component_storage| {
+                let me = data.downcast_mut::<Func>().unwrap();
+
+                me.run(component_storage);
+            }),
+        }
+    }
+}
+
+pub struct TypeErased
+{
+    data: Box<dyn Any>,
+    func: Box<TypeErasedFunc>,
+}
+
+impl TypeErased
+{
+    pub fn run(&mut self, component_storage: &mut ComponentStorage)
+    {
+        (self.func)(self.data.as_mut(), component_storage);
+    }
+}
+
+impl Debug for TypeErased
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        formatter.debug_struct("TypeErased").finish_non_exhaustive()
+    }
+}
+
+/// Function in [`TypeErased`] used to run the system.
+type TypeErasedFunc = dyn Fn(&mut dyn Any, &mut ComponentStorage);