refactor(ecs): store local components as system entity components

1 files changed, 34 insertions, 80 deletions

diff --git a/ecs/src/system.rs b/ecs/src/system.rs
index 603c015..a7ca4df 100644
--- a/ecs/src/system.rs
+++ b/ecs/src/system.rs
@@ -1,37 +1,31 @@
-use std::any::Any;
-use std::convert::Infallible;
 use std::fmt::Debug;
 
 use ecs_macros::Component;
 use seq_macro::seq;
 
-use crate::component::{Component, HandleMut as ComponentHandleMut};
-use crate::tuple::{ReduceElement as TupleReduceElement, Tuple};
+use crate::uid::Uid;
 use crate::World;
 
+pub mod initializable;
 pub mod stateful;
 
-pub trait System<'world, Impl>: 'static
+/// Metadata of a system.
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct Metadata
 {
-    type Input;
+    pub ent_id: Uid,
+}
 
-    #[must_use]
-    fn initialize(self, input: Self::Input) -> Self;
+pub trait System<'world, Impl>: 'static
+{
+    type Callbacks: Callbacks;
 
-    fn run<'this>(&'this self, world: &'world World)
+    fn run<'this>(&'this self, world: &'world World, metadata: Metadata)
     where
         'this: 'world;
 
-    fn into_type_erased(self) -> TypeErased;
-
-    fn get_local_component_mut<LocalComponent: Component>(
-        &self,
-    ) -> Option<ComponentHandleMut<LocalComponent>>;
-
-    fn set_local_component<LocalComponent: Component>(
-        &mut self,
-        local_component: LocalComponent,
-    );
+    fn finish(self) -> (TypeErased, Self::Callbacks);
 }
 
 macro_rules! impl_system {
@@ -43,58 +37,34 @@ macro_rules! impl_system {
                 Func: Fn(#(TParam~I,)*) + Copy + 'static,
                 #(TParam~I: Param<'world, Input = ()>,)*
             {
-                type Input = Infallible;
+                type Callbacks = NoCallbacks;
 
-                fn initialize(self, _input: Self::Input) -> Self
-                {
-                    self
-                }
-
-                fn run<'this>(&'this self, world: &'world World)
+                fn run<'this>(&'this self, world: &'world World, metadata: Metadata)
                 where
                     'this: 'world
                 {
                     let func = *self;
 
                     func(#({
-                        TParam~I::new(self, world)
+                        TParam~I::new(world, &metadata)
                     },)*);
                 }
 
-                fn into_type_erased(self) -> TypeErased
+                fn finish(self) -> (TypeErased, Self::Callbacks)
                 {
-                    TypeErased {
-                        data: Box::new(self),
-                        run: Box::new(|data, world| {
-                            // SAFETY: The caller of TypeErased::run ensures the lifetime
-                            // is correct
-                            let data = unsafe { &*std::ptr::from_ref(data) };
-
-                            let me = data
-                                .downcast_ref::<Func>()
-                                .expect("Function downcast failed");
-
+                    let type_erased = TypeErased {
+                        run: Box::new(move |world, metadata| {
                             // SAFETY: The caller of TypeErased::run ensures the lifetime
                             // is correct
                             let world = unsafe { &*std::ptr::from_ref(world) };
 
-                            me.run(world);
+                            self(#({
+                                TParam~I::new(world, &metadata)
+                            },)*);
                         }),
-                    }
-                }
+                    };
 
-                fn get_local_component_mut<LocalComponent: Component>(
-                    &self,
-                ) -> Option<ComponentHandleMut<LocalComponent>>
-                {
-                    panic!("System does not have any local components");
-                }
-
-                fn set_local_component<LocalComponent: Component>(
-                    &mut self,
-                    _local_component: LocalComponent,
-                ) {
-                    panic!("System does not have any local components");
+                    (type_erased, NoCallbacks)
                 }
             }
         });
@@ -114,7 +84,6 @@ pub trait Into<Impl>
 
 pub struct TypeErased
 {
-    data: Box<dyn Any>,
     run: Box<TypeErasedRunFn>,
 }
 
@@ -124,12 +93,9 @@ impl TypeErased
     ///
     /// # Safety
     /// `world_data` must live at least as long as the [`World`] the system belongs to.
-    pub unsafe fn run(&self, world: &World)
+    pub unsafe fn run(&self, world: &World, metadata: Metadata)
     {
-        // You have to dereference for downcasting to work for some reason
-        let data = &*self.data;
-
-        (self.run)(data, world);
+        (self.run)(world, metadata);
     }
 }
 
@@ -142,41 +108,29 @@ impl Debug for TypeErased
 }
 
 /// Function in [`TypeErased`] used to run the system.
-type TypeErasedRunFn = dyn Fn(&dyn Any, &World);
+type TypeErasedRunFn = dyn Fn(&World, Metadata);
 
 /// A parameter to a [`System`].
 pub trait Param<'world>
 {
     type Input;
 
-    fn initialize<SystemImpl>(
-        system: &mut impl System<'world, SystemImpl>,
-        input: Self::Input,
-    );
-
-    fn new<SystemImpl>(
-        system: &'world impl System<'world, SystemImpl>,
-        world: &'world World,
-    ) -> Self;
+    fn new(world: &'world World, system_metadata: &Metadata) -> Self;
 }
 
 /// A type which can be used as input to a [`System`].
 pub trait Input: 'static {}
 
-/// Component tuple reducing operation to get the parameters that takes input.
-pub struct ParamWithInputFilter;
-
-impl<InputT: Input, Accumulator> TupleReduceElement<Accumulator, ParamWithInputFilter>
-    for InputT
-where
-    Accumulator: Tuple,
+pub trait Callbacks
 {
-    type Return = Accumulator::WithElementAtEnd<Self>;
+    fn on_created(&mut self, world: &mut World, metadata: Metadata);
 }
 
-impl<Accumulator> TupleReduceElement<Accumulator, ParamWithInputFilter> for ()
+pub struct NoCallbacks;
+
+impl Callbacks for NoCallbacks
 {
-    type Return = Accumulator;
+    fn on_created(&mut self, _world: &mut World, _metadata: Metadata) {}
 }
 
 #[derive(Debug, Component)]