From de5c3ff1320ea0f0452afde4c1f42676d9eeab52 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Fri, 16 Feb 2024 19:58:53 +0100
Subject: feat: add entity component system library

---
 ecs/src/component.rs | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 ecs/src/component.rs

(limited to 'ecs/src/component.rs')

diff --git a/ecs/src/component.rs b/ecs/src/component.rs
new file mode 100644
index 0000000..4829050
--- /dev/null
+++ b/ecs/src/component.rs
@@ -0,0 +1,114 @@
+use std::any::{Any, TypeId};
+use std::fmt::Debug;
+
+use seq_macro::seq;
+
+pub trait Component: Any
+{
+    #[doc(hidden)]
+    fn as_any_mut(&mut self) -> &mut dyn Any;
+
+    #[doc(hidden)]
+    fn as_any(&self) -> &dyn Any;
+}
+
+impl<Value: Any> Component for Value
+{
+    fn as_any_mut(&mut self) -> &mut dyn Any
+    {
+        self
+    }
+
+    fn as_any(&self) -> &dyn Any
+    {
+        self
+    }
+}
+
+impl dyn Component
+{
+    pub fn downcast_mut<Real: 'static>(&mut self) -> Option<&mut Real>
+    {
+        self.as_any_mut().downcast_mut()
+    }
+
+    pub fn is<Other: 'static>(&self) -> bool
+    {
+        self.as_any().is::<Other>()
+    }
+}
+
+impl Debug for dyn Component
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        formatter.debug_struct("Component").finish_non_exhaustive()
+    }
+}
+
+/// A sequence of components.
+pub trait Sequence
+{
+    type MutRefs<'component>
+    where
+        Self: 'component;
+
+    fn into_vec(self) -> Vec<Box<dyn Component>>;
+
+    fn type_ids() -> Vec<TypeId>;
+
+    fn from_components<'components>(
+        components: &'components mut [Box<dyn Component>],
+    ) -> Self::MutRefs<'components>;
+}
+
+macro_rules! inner {
+    ($c: tt) => {
+        seq!(I in 0..=$c {
+            impl<#(Comp~I: Component,)*> Sequence for (#(Comp~I,)*) {
+                type MutRefs<'component> = (#(&'component mut Comp~I,)*)
+                    where Self: 'component;
+
+                fn into_vec(self) -> Vec<Box<dyn Component>> {
+                    Vec::from_iter([#(Box::new(self.I) as Box<dyn Component>,)*])
+                }
+
+                fn type_ids() -> Vec<TypeId> {
+                    vec![
+                        #(
+                            TypeId::of::<Comp~I>(),
+                        )*
+                    ]
+                }
+
+                fn from_components<'components>(
+                    components: &'components mut [Box<dyn Component>],
+                ) -> Self::MutRefs<'components>
+                {
+                    #(
+                        let mut comp_~I = None;
+                    )*
+
+                    for comp in components.iter_mut() {
+                        #(
+                            if comp.is::<Comp~I>() {
+                                comp_~I = Some(comp);
+                                continue;
+                            }
+
+                        )*
+                    }
+
+
+                    (#(
+                        comp_~I.unwrap().downcast_mut::<Comp~I>().unwrap(),
+                    )*)
+                }
+            }
+        });
+    };
+}
+
+seq!(C in 0..=64 {
+    inner!(C);
+});
-- 
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