From 808cb77040131b793397ff506af4841aa38970f9 Mon Sep 17 00:00:00 2001
From: SeanOMik <seanomik@gmail.com>
Date: Fri, 8 Dec 2023 18:10:08 -0500
Subject: [PATCH] Implement multiple argument fn systems

---
 lyra-ecs/src/system/mod.rs | 108 ++++++++++++++++++++++++++-----------
 1 file changed, 76 insertions(+), 32 deletions(-)

diff --git a/lyra-ecs/src/system/mod.rs b/lyra-ecs/src/system/mod.rs
index 800210f..5fc677d 100644
--- a/lyra-ecs/src/system/mod.rs
+++ b/lyra-ecs/src/system/mod.rs
@@ -41,42 +41,60 @@ pub struct FnSystem<F, Args> {
     args: Args,
 }
 
-impl<F, A> System for FnSystem<F, A>
-where
-    A: FnArgFetcher,
-    F: for<'a> FnMut(A::Arg<'a>) -> anyhow::Result<()>,
-{
-    fn world_access(&self) -> Access {
-        todo!()
-    }
+macro_rules! impl_fn_system_tuple {
+    ( $($name: ident),+ ) => (
+        #[allow(non_snake_case)]
+        impl<F, $($name: FnArgFetcher,)+> System for FnSystem<F, ($($name,)+)>
+        where
+            F: for<'a> FnMut($($name::Arg<'a>,)+) -> anyhow::Result<()>,
+        {
+            fn world_access(&self) -> Access {
+                todo!()
+            }
 
-    fn execute(&mut self, world: NonNull<World>) -> anyhow::Result<()> {
-        let mut a = A::new();
+            fn execute(&mut self, world: NonNull<World>) -> anyhow::Result<()> {
+                $(let $name = unsafe { $name::new().get(world) };)+
 
-        let a = unsafe { a.get(world) };
-
-        (self.inner)(a)?;
-        
-        Ok(())
-    }
-}
-
-impl<F, A> IntoSystem<A> for F
-where
-    A: FnArg,
-    F: FnMut(A) -> anyhow::Result<()>,
-    F: for<'a> FnMut(<A::Fetcher as FnArgFetcher>::Arg<'a>) -> anyhow::Result<()>,
-{
-    type System = FnSystem<F, A::Fetcher>;
-
-    fn into_system(self) -> Self::System {
-        FnSystem {
-            args: A::Fetcher::new(),
-            inner: self
+                (self.inner)($($name,)+)?;
+                
+                Ok(())
+            }
         }
-    }
+
+        impl<F, $($name: FnArg,)+> IntoSystem<($($name,)+)> for F
+        where
+            F: FnMut($($name,)+) -> anyhow::Result<()>,
+            F: for<'a> FnMut($(<$name::Fetcher as FnArgFetcher>::Arg<'a>,)+) -> anyhow::Result<()>,
+        {
+            type System = FnSystem<F, ($($name::Fetcher,)+)>;
+
+            fn into_system(self) -> Self::System {
+                FnSystem {
+                    args: ($($name::Fetcher::new(),)+),
+                    inner: self
+                }
+            }
+        }
+    );
 }
 
+// Hopefully up to 16 arguments in a system is good enough.
+impl_fn_system_tuple!{ A }
+impl_fn_system_tuple!{ A, B }
+impl_fn_system_tuple!{ A, B, C }
+impl_fn_system_tuple!{ A, B, C, D }
+impl_fn_system_tuple!{ A, B, C, D, E }
+impl_fn_system_tuple!{ A, B, C, D, E, F2 }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N, O }
+impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N, O, P }
+
 /// An ArgFetcher implementation for query [`View`]s
 pub struct ViewArgFetcher<Q> {
     query: Q
@@ -95,6 +113,10 @@ impl<Q: Query> FnArgFetcher for ViewArgFetcher<Q> {
         }
     }
 
+    fn world_access(&self) -> Access {
+        todo!()
+    }
+
     unsafe fn get<'a>(&mut self, world: NonNull<World>) -> Self::Arg<'a> {
         let world = &*world.as_ptr();
         let arch = world.archetypes.values().collect();
@@ -237,7 +259,7 @@ mod tests {
     }
 
     #[test]
-    fn multi_system() {
+    fn multi_view_system() {
         let mut world = World::new();
         world.spawn((Vec2::rand(), Vec3::rand()));
         world.spawn((Vec2::rand(), Vec3::rand()));
@@ -307,4 +329,26 @@ mod tests {
         let counter = world.get_resource::<SomeCounter>();
         assert_eq!(counter.0, 10);
     }
+
+    #[test]
+    fn multi_arg_system() {
+        let mut world = World::new();
+        world.spawn((Vec2::rand(), ));
+        world.spawn((Vec2::rand(), ));
+        world.add_resource(SomeCounter(0));
+
+        let test_system = |mut counter: RefMut<SomeCounter>, view: View<QueryBorrow<Vec2>>| -> anyhow::Result<()> {
+            for v2 in view.into_iter() {
+                println!("Got v2 at '{:?}'", v2);
+                counter.0 += 1;
+            }
+
+            Ok(())
+        };
+
+        test_system.into_system().execute(NonNull::from(&world)).unwrap();
+
+        let counter = world.get_resource::<SomeCounter>();
+        assert_eq!(counter.0, 2);
+    }
 }
\ No newline at end of file