fix(ecs): some replacement issues

crates/comet_structs/src/column.rs

@@ -272,6 +272,22 @@ impl Column {
         }
     }
 
+    /// Overwrites an existing element in place, dropping the previous value.
+    pub fn set<T: 'static>(&mut self, index: usize, item: T) -> Option<()> {
+        assert_eq!(TypeId::of::<T>(), TypeId::of::<T>(), "Type mismatch");
+        if index >= self.data.len() {
+            return None;
+        }
+
+        unsafe {
+            let ptr = self.data.get_unchecked_mut(index) as *mut T;
+            ptr::drop_in_place(ptr);
+            ptr::write(ptr, item);
+        }
+
+        Some(())
+    }
+
     pub fn swap(&mut self, index1: usize, index2: usize) {
         assert!(
             index1 < self.data.len() && index2 < self.data.len(),

crates/comet_structs/src/componet_set.rs

@@ -67,6 +67,10 @@ impl ComponentSet {
         self.set.is_subset(&other.set)
     }
 
+    pub fn is_superset(&self, other: &ComponentSet) -> bool {
+        self.set.is_superset(&other.set)
+    }
+
     pub fn to_vec(&self) -> Vec<TypeId> {
         self.set.iter().cloned().collect()
     }

crates/comet_structs/src/flat_map.rs

@@ -44,6 +44,39 @@ impl<K: PartialEq + Clone, V: Clone> FlatMap<K, V> {
         }
     }
 
+    pub fn get_two_mut(&mut self, a: &K, b: &K) -> (Option<&mut V>, Option<&mut V>) {
+        if a == b {
+            let first = self.get_mut(a);
+            return (first, None);
+        }
+
+        let mut first_index = None;
+        let mut second_index = None;
+
+        for (idx, (key, _)) in self.map.iter().enumerate() {
+            if key == a {
+                first_index = Some(idx);
+            } else if key == b {
+                second_index = Some(idx);
+            }
+        }
+
+        match (first_index, second_index) {
+            (Some(i), Some(j)) => {
+                if i < j {
+                    let (left, right) = self.map.split_at_mut(j);
+                    (Some(&mut left[i].1), Some(&mut right[0].1))
+                } else {
+                    let (left, right) = self.map.split_at_mut(i);
+                    (Some(&mut right[0].1), Some(&mut left[j].1))
+                }
+            }
+            (Some(i), None) => (self.map.get_mut(i).map(|pair| &mut pair.1), None),
+            (None, Some(j)) => (None, self.map.get_mut(j).map(|pair| &mut pair.1)),
+            _ => (None, None),
+        }
+    }
+
     pub fn contains(&self, key: &K) -> bool {
         self.map.iter().any(|node| node.0 == *key)
     }
@@ -51,4 +84,4 @@ impl<K: PartialEq + Clone, V: Clone> FlatMap<K, V> {
     pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut (K, V)> {
         self.map.iter_mut()
     }
-}
+}

crates/comet_structs/src/sparse_set.rs

@@ -28,6 +28,12 @@ impl SparseSet {
         }
 
         if let Some(page_vec) = &mut self.sparse[page] {
+            // If there is already a mapping, overwrite the existing dense value instead of pushing.
+            if let Some(sparse_index) = page_vec[index % self.page_size] {
+                let _ = self.dense.set::<T>(sparse_index, value);
+                return;
+            }
+
             page_vec[index % self.page_size] = Some(self.dense.data.len());
         }