feat: implement snapshot restore functionality and enhance graph state management

src/hooks/useGraphData.js

@@ -10,11 +10,20 @@ import * as db from '../lib/db';
  * Relation shape contract: source and target are always plain strings.
  * The normalization in db.getRelations() enforces this at the DB boundary;
  * the filter here drops any orphaned edges whose endpoints no longer exist.
+ *
+ * Snapshot contract:
+ *   bulkSave() writes a snapshot of the CURRENT state to PocketBase before
+ *   overwriting it — so the admin can always roll back one step. snapshotMeta
+ *   is non-null whenever a rollback point exists; restoreSnapshot() applies it
+ *   and then clears it so it cannot be applied twice.
  */
 export function useGraphData() {
   const [topics, setTopics] = useState([]);
   const [relations, setRelations] = useState([]);
 
+  // { ts: number, topicCount: number, relationCount: number }
+  const [snapshotMeta, setSnapshotMeta] = useState(null);
+
   // Refs that always hold the latest state — lets mutation callbacks avoid
   // stale-closure bugs without including state in their dependency arrays.
   const topicsRef = useRef([]);
@@ -41,11 +50,19 @@ export function useGraphData() {
     return () => window.removeEventListener('respellion:kb-updated', reload);
   }, [reload]);
 
+  // On mount, check whether a snapshot from a previous session exists.
+  useEffect(() => {
+    db.getGraphSnapshot().then(snap => {
+      if (snap?.ts) {
+        setSnapshotMeta({ ts: snap.ts, topicCount: snap.topicCount, relationCount: snap.relationCount });
+      }
+    });
+  }, []);
+
   // ── Single-topic mutations ───────────────────────────────────────────────────
 
   /**
    * Persist a topic update and mirror it into local state.
-   * Automatically locks learning_relevance when the admin changes it.
    * Returns the saved topic object.
    */
   const updateTopic = useCallback(async (topic) => {
@@ -74,7 +91,7 @@ export function useGraphData() {
 
   /**
    * Add a relation if not already present.
-   * Returns true if the relation was added, false if it was a duplicate.
+   * Returns true if added, false if it was a duplicate.
    */
   const addRelation = useCallback(async (relation) => {
     const isDup = relationsRef.current.some(
@@ -99,24 +116,60 @@ export function useGraphData() {
   // ── Bulk mutations (used by AI analysis) ────────────────────────────────────
 
   /**
-   * Atomically replace the entire graph in PocketBase and local state.
-   * Called by analyzeGraph after all AI actions have been applied locally.
+   * Snapshot the current graph then replace everything in PocketBase and local
+   * state. The snapshot is written BEFORE the destructive delete-all/create-all
+   * so it survives a mid-operation failure.
+   *
+   * Called by analyzeGraph after all AI actions have been applied in memory.
    */
   const bulkSave = useCallback(async (newTopics, newRelations) => {
+    // Persist a rollback point of the state we are about to overwrite.
+    await db.saveGraphSnapshot(topicsRef.current, relationsRef.current);
+    setSnapshotMeta({
+      ts: Date.now(),
+      topicCount: topicsRef.current.length,
+      relationCount: relationsRef.current.length,
+    });
+
     await db.saveTopics(newTopics);
     await db.saveRelations(newRelations);
     setTopics(newTopics);
     setRelations(newRelations);
   }, []);
 
+  /**
+   * Load the latest snapshot from PocketBase and apply it as the current graph.
+   * Clears the snapshot afterwards so the admin cannot restore the same point
+   * twice (which would silently re-apply the AI changes they just rolled back).
+   *
+   * Returns true on success, false if no snapshot exists.
+   */
+  const restoreSnapshot = useCallback(async () => {
+    const snap = await db.getGraphSnapshot();
+    if (!snap?.topics) return false;
+
+    // Apply without taking a new snapshot — we don't want to overwrite
+    // the only rollback point we have.
+    await db.saveTopics(snap.topics);
+    await db.saveRelations(snap.relations);
+    setTopics(snap.topics);
+    setRelations(snap.relations);
+
+    await db.clearGraphSnapshot();
+    setSnapshotMeta(null);
+    return true;
+  }, []);
+
   return {
     topics,
     relations,
+    snapshotMeta,
     reload,
     updateTopic,
     deleteTopic,
     addRelation,
     removeRelation,
     bulkSave,
+    restoreSnapshot,
   };
 }