From 0fe88ca6d34aee03e5b84fdf181c1a7cb2bd32af Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Thu, 25 Sep 2025 22:41:18 +0200
Subject: feat(ecs): add support for pairs with relation component as data

---
 ecs/src/pair.rs | 116 ++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 95 insertions(+), 21 deletions(-)

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

diff --git a/ecs/src/pair.rs b/ecs/src/pair.rs
index 985a2b3..f6d33d2 100644
--- a/ecs/src/pair.rs
+++ b/ecs/src/pair.rs
@@ -76,6 +76,23 @@ impl_multiple!(
     }
 );
 
+impl_multiple!(
+    Builder,
+    (impl<Relation> _<Relation, Uid>, impl<Relation> _<Relation, ()>)
+    (ty_param_1, ty_param_2) => {
+        pub fn relation_as_data<NewRelation: Component>(
+            self,
+            data: NewRelation,
+        ) -> Builder<NewRelation, $ty_param_2>
+        {
+            Builder {
+                relation: data,
+                target: self.target,
+            }
+        }
+    }
+);
+
 impl_multiple!(
     Builder,
     (
@@ -157,6 +174,23 @@ where
     }
 }
 
+impl<Relation> IntoComponentParts for Pair<Relation, Uid>
+where
+    Relation: Component,
+{
+    fn into_parts(self) -> ComponentParts
+    {
+        let id = Uid::new_pair(&UidPairParams {
+            relation: Relation::id(),
+            target: self.target,
+        });
+
+        ComponentParts::builder()
+            .name("Pair")
+            .build(id, self.relation)
+    }
+}
+
 impl<Relation, Target> QueryTermWithField for Pair<Relation, &Target>
 where
     Relation: Component,
@@ -168,7 +202,7 @@ where
         terms_builder: &mut QueryTermsBuilder<MAX_TERM_CNT>,
     )
     {
-        terms_builder.with_required([Self::uid()]);
+        terms_builder.with_required([Pair::<Relation, Target>::uid()]);
     }
 
     fn get_field<'world>(
@@ -177,7 +211,7 @@ where
     ) -> Self::Field<'world>
     {
         let target_component = entity_handle
-            .get_matching_components(Self::uid())
+            .get_matching_components(Pair::<Relation, Target>::uid())
             .next()
             .expect("Not possible");
 
@@ -201,7 +235,7 @@ where
         terms_builder: &mut QueryTermsBuilder<MAX_TERM_CNT>,
     )
     {
-        terms_builder.with_required([Self::uid()]);
+        terms_builder.with_required([Pair::<Relation, Target>::uid()]);
     }
 
     fn get_field<'world>(
@@ -210,7 +244,7 @@ where
     ) -> Self::Field<'world>
     {
         let target_component = entity_handle
-            .get_matching_components(Self::uid())
+            .get_matching_components(Pair::<Relation, Target>::uid())
             .next()
             .expect("Not possible");
 
@@ -225,6 +259,9 @@ where
     }
 }
 
+// TODO: implement QueryTermWithField for Pair<&Relation, Target> (or equivalent)
+// TODO: implement QueryTermWithField for Pair<&mut Relation, Target> (or equivalent)
+
 impl<Relation> QueryTermWithField for Pair<Relation, Wildcard>
 where
     Relation: Component,
@@ -256,21 +293,7 @@ where
     }
 }
 
-impl<Relation, Target> WithUid for Pair<Relation, &Target>
-where
-    Relation: Component,
-    Target: Component,
-{
-    fn uid() -> Uid
-    {
-        Uid::new_pair(&UidPairParams {
-            relation: Relation::uid(),
-            target: Target::uid(),
-        })
-    }
-}
-
-impl<Relation, Target> WithUid for Pair<Relation, &mut Target>
+impl<Relation, Target> WithUid for Pair<Relation, Target>
 where
     Relation: Component,
     Target: Component,
@@ -349,7 +372,7 @@ impl<Relation, Target> WithWildcard<'_, Relation, Target>
                     ComponentHandleError::IncorrectType => None,
                     err @ ComponentHandleError::AcquireLockFailed(_) => {
                         panic!(
-                            "Creating handle to component {} failed: {err}",
+                            "Creating handle to pair data as component {} failed: {err}",
                             type_name::<Data>()
                         );
                     }
@@ -377,7 +400,7 @@ impl<Relation, Target> WithWildcard<'_, Relation, Target>
                 ComponentHandleError::IncorrectType => None,
                 err @ ComponentHandleError::AcquireLockFailed(_) => {
                     panic!(
-                        "Creating handle to component {} failed: {err}",
+                        "Creating handle to pair data as component {} failed: {err}",
                         type_name::<Data>()
                     );
                 }
@@ -388,6 +411,8 @@ impl<Relation, Target> WithWildcard<'_, Relation, Target>
 }
 
 impl<Relation> WithWildcard<'_, Relation, Wildcard>
+where
+    Relation: Component,
 {
     /// Attempts to retrieve the target as a entity, returning `None` if not found.
     #[must_use]
@@ -407,6 +432,55 @@ impl<Relation> WithWildcard<'_, Relation, Wildcard>
 
         Some(EntityHandle::new(archetype, archetype_entity, self.world))
     }
+
+    /// Attempts to get the component data of this pair, returning `None` if the
+    /// `Relation` type is incorrect.
+    ///
+    /// # Panics
+    /// Will panic if the component data is mutably borrowed elsewhere.
+    #[must_use]
+    pub fn get_data_as_relation(&self) -> Option<ComponentHandle<'_, Relation>>
+    {
+        ComponentHandle::<Relation>::from_entity_component_ref(&self.component_ref)
+            .map_or_else(
+                |err| match err {
+                    ComponentHandleError::IncorrectType => None,
+                    err @ ComponentHandleError::AcquireLockFailed(_) => {
+                        panic!(
+                            "Creating handle to pair data as component {} failed: {err}",
+                            type_name::<Relation>()
+                        );
+                    }
+                },
+                Some,
+            )
+    }
+
+    /// Attempts to get the component data of this pair, returning `None` if the
+    /// `Relation` type is incorrect.
+    ///
+    /// # Panics
+    /// Will panic if the component data is borrowed elsewhere.
+    #[must_use]
+    pub fn get_data_as_relation_mut(&self) -> Option<ComponentHandleMut<'_, Relation>>
+    {
+        ComponentHandleMut::<Relation>::from_entity_component_ref(
+            &self.component_ref,
+            self.world,
+        )
+        .map_or_else(
+            |err| match err {
+                ComponentHandleError::IncorrectType => None,
+                err @ ComponentHandleError::AcquireLockFailed(_) => {
+                    panic!(
+                        "Creating handle to pair data as component {} failed: {err}",
+                        type_name::<Relation>()
+                    );
+                }
+            },
+            Some,
+        )
+    }
 }
 
 /// Used to access matching pairs in a entity containing zero or more matching pairs.
-- 
cgit v1.2.3-18-g5258