feat: use declarative callbacks for data changes

js/src/lib/firestore-particles.ts

@@ -132,6 +132,8 @@ export function subscribeToParticleChildren(
   visibilityScopes: string[] = [],
   orderByField: string = "created_at",
   orderDirection: "asc" | "desc" = "desc",
+  onAdded?: (child: Particle) => void,
+  onRemoved?: (child: Particle, updatedChildren: Particle[]) => void,
 ): Unsubscribe {
   let q = query(typedCollection(collectionPath), orderBy(orderByField, orderDirection));
   if (visibilityScopes.length > 0) {
@@ -143,11 +145,15 @@ export function subscribeToParticleChildren(
   return onSnapshot(
     q,
     (snap) => {
-      // onNext(snap.docChanges().map((change) => {
-      //   const data = change.doc.data();
-      //   return { type: change.type, data };
-      // }));
-      onData(snap.docs.map((d) => d.data()));
+      const updatedChildren = snap.docs.map((d) => d.data());
+      onData(updatedChildren);
+
+      if (onAdded || onRemoved) {
+        for (const change of snap.docChanges()) {
+          if (change.type === "added" && onAdded) onAdded(change.doc.data());
+          if (change.type === "removed" && onRemoved) onRemoved(change.doc.data(), updatedChildren);
+        }
+      }
     },
     onError,
   );