From 85ed89df486858984f0936086205efc23fd32d24 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Thu, 2 Jan 2025 17:02:25 +0100
Subject: refactor(ecs): make component::Sequence return metadata as array

---
 ecs/src/actions.rs   |  6 +++---
 ecs/src/component.rs | 18 +++++++++++++-----
 ecs/src/lib.rs       |  2 +-
 ecs/src/util.rs      | 18 ++++++++++++++++++
 4 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/ecs/src/actions.rs b/ecs/src/actions.rs
index c062472..3988a77 100644
--- a/ecs/src/actions.rs
+++ b/ecs/src/actions.rs
@@ -44,7 +44,7 @@ impl<'world> Actions<'world>
     {
         debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
 
-        if Comps::metadata().len() == 0 {
+        if Comps::COUNT == 0 {
             return;
         }
 
@@ -62,13 +62,13 @@ impl<'world> Actions<'world>
     {
         debug_assert_eq!(entity_uid.kind(), UidKind::Entity);
 
-        if Comps::metadata().len() == 0 {
+        if Comps::COUNT == 0 {
             return;
         }
 
         self.action_queue.push(Action::RemoveComponents(
             entity_uid,
-            Comps::metadata(),
+            Comps::metadata().into_iter().collect(),
             EventIds { ids: Comps::removed_event_ids() },
         ));
     }
diff --git a/ecs/src/component.rs b/ecs/src/component.rs
index 1fde5b4..bf19c9e 100644
--- a/ecs/src/component.rs
+++ b/ecs/src/component.rs
@@ -12,6 +12,7 @@ use crate::lock::{ReadGuard, WriteGuard};
 use crate::system::{ComponentRef, ComponentRefMut, Input as SystemInput};
 use crate::type_name::TypeName;
 use crate::uid::Uid;
+use crate::util::Array;
 use crate::{EntityComponent, World};
 
 pub mod local;
@@ -170,9 +171,12 @@ pub trait Sequence
     where
         Self: 'component;
 
+    /// The number of components in this component sequence.
+    const COUNT: usize;
+
     fn into_vec(self) -> Vec<Box<dyn Component>>;
 
-    fn metadata() -> Vec<Metadata>;
+    fn metadata() -> impl Array<Metadata>;
 
     fn added_event_ids() -> Vec<Uid>;
 
@@ -271,14 +275,16 @@ macro_rules! inner {
                 type Refs<'component> = (#(Comp~I::Ref<'component>,)*)
                     where Self: 'component;
 
+                const COUNT: usize = $c + 1;
+
                 fn into_vec(self) -> Vec<Box<dyn Component>>
                 {
                     Vec::from_iter([#(Box::new(self.I) as Box<dyn Component>,)*])
                 }
 
-                fn metadata() -> Vec<Metadata>
+                fn metadata() -> impl Array<Metadata>
                 {
-                    vec![
+                    [
                         #(
                             Metadata {
                                 id: Comp~I::id(),
@@ -357,14 +363,16 @@ impl Sequence for ()
     type MutRefs<'component> = ();
     type Refs<'component> = ();
 
+    const COUNT: usize = 0;
+
     fn into_vec(self) -> Vec<Box<dyn Component>>
     {
         Vec::new()
     }
 
-    fn metadata() -> Vec<Metadata>
+    fn metadata() -> impl Array<Metadata>
     {
-        Vec::new()
+        []
     }
 
     fn added_event_ids() -> Vec<Uid>
diff --git a/ecs/src/lib.rs b/ecs/src/lib.rs
index 43a00f1..ae5fd19 100644
--- a/ecs/src/lib.rs
+++ b/ecs/src/lib.rs
@@ -45,12 +45,12 @@ pub mod system;
 pub mod tuple;
 pub mod type_name;
 pub mod uid;
+pub mod util;
 
 #[doc(hidden)]
 pub mod private;
 
 mod archetype;
-mod util;
 
 pub use ecs_macros::{Component, Sole};
 
diff --git a/ecs/src/util.rs b/ecs/src/util.rs
index 0344e89..4ba8597 100644
--- a/ecs/src/util.rs
+++ b/ecs/src/util.rs
@@ -1,5 +1,18 @@
 use std::ops::BitAnd;
 
+pub trait Array<Item>:
+    AsRef<[Item]>
+    + AsMut<[Item]>
+    + IntoIterator<Item = Item>
+    + Sortable<Item = Item>
+    + sealed::Sealed
+{
+}
+
+impl<Item, const CNT: usize> Array<Item> for [Item; CNT] {}
+
+impl<Item, const CNT: usize> sealed::Sealed for [Item; CNT] {}
+
 pub trait Sortable
 {
     type Item;
@@ -115,6 +128,11 @@ macro_rules! gen_mask_64 {
 
 pub(crate) use gen_mask_64;
 
+mod sealed
+{
+    pub trait Sealed {}
+}
+
 #[cfg(test)]
 mod tests
 {
-- 
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