1 files changed, 48 insertions, 0 deletions
diff --git a/ecs/src/event.rs b/ecs/src/event.rs
index 0cf6da7..01d9d80 100644
--- a/ecs/src/event.rs
+++ b/ecs/src/event.rs
@@ -2,6 +2,8 @@ use std::any::TypeId;
 use std::fmt::Debug;
 use std::hash::Hash;
 
+use seq_macro::seq;
+
 pub trait Event: Debug + 'static
 {
     fn id(&self) -> Id;
@@ -22,3 +24,49 @@ impl Id
         Self { inner: TypeId::of::<EventT>() }
     }
 }
+
+pub trait Ids
+{
+    type Iter<'a>: Iterator<Item = &'a Id>
+    where
+        Self: 'a;
+
+    fn iter(&self) -> Self::Iter<'_>;
+}
+
+/// A sequence of events.
+pub trait Sequence
+{
+    type Ids: Ids;
+
+    fn ids() -> Self::Ids;
+}
+
+macro_rules! impl_sequence {
+    ($c: tt) => {
+        seq!(I in 0..=$c {
+            impl Ids for [Id; $c + 1]
+            {
+                type Iter<'a> = std::slice::Iter<'a, Id>;
+
+                fn iter(&self) -> Self::Iter<'_> {
+                    self.into_iter()
+                }
+            }
+
+            impl<#(Event~I: Event,)*> Sequence for (#(Event~I,)*) {
+                type Ids = [Id; $c + 1];
+
+                fn ids() -> Self::Ids {
+                    [#(
+                        Id::of::<Event~I>(),
+                    )*]
+                }
+            }
+        });
+    };
+}
+
+seq!(C in 0..=64 {
+    impl_sequence!(C);
+});