From 7e1a77c38c518f6740646f4eb0be6598186055a5 Mon Sep 17 00:00:00 2001
From: Matthias Meister <meister.matthias86@gmail.com>
Date: Fri, 3 Apr 2026 19:10:07 +0200
Subject: [PATCH] refactor(canvas): debounce and extract local snapshot
 persistence

---
 components/canvas/canvas.tsx                  |  24 ++--
 .../use-canvas-local-snapshot-persistence.ts  | 105 ++++++++++++++++++
 2 files changed, 113 insertions(+), 16 deletions(-)
 create mode 100644 components/canvas/use-canvas-local-snapshot-persistence.ts

diff --git a/components/canvas/canvas.tsx b/components/canvas/canvas.tsx
index e74f99a..6acd67c 100644
--- a/components/canvas/canvas.tsx
+++ b/components/canvas/canvas.tsx
@@ -42,11 +42,9 @@ import {
   dropCanvasOpsByEdgeIds,
   dropCanvasOpsByNodeIds,
   enqueueCanvasOp,
-  readCanvasSnapshot,
   remapCanvasOpNodeId,
   resolveCanvasOp,
   resolveCanvasOps,
-  writeCanvasSnapshot,
 } from "@/lib/canvas-local-persistence";
 import {
   ackCanvasSyncOp,
@@ -140,6 +138,7 @@ import { getImageDimensions } from "./canvas-media-utils";
 import { useCanvasReconnectHandlers } from "./canvas-reconnect";
 import { useCanvasScissors } from "./canvas-scissors";
 import { CanvasSyncProvider } from "./canvas-sync-context";
+import { useCanvasLocalSnapshotPersistence } from "./use-canvas-local-snapshot-persistence";
 
 interface CanvasInnerProps {
   canvasId: Id<"canvases">;
@@ -1907,7 +1906,6 @@ function CanvasInner({ canvasId }: CanvasInnerProps) {
   // ─── Lokaler State (für flüssiges Dragging) ───────────────────
   const nodesRef = useRef<RFNode[]>(nodes);
   nodesRef.current = nodes;
-  const [hasHydratedLocalSnapshot, setHasHydratedLocalSnapshot] = useState(false);
   const [connectionDropMenu, setConnectionDropMenu] =
     useState<ConnectionDropMenuState | null>(null);
   const connectionDropMenuRef = useRef<ConnectionDropMenuState | null>(null);
@@ -1919,19 +1917,13 @@ function CanvasInner({ canvasId }: CanvasInnerProps) {
   >(null);
   const [navTool, setNavTool] = useState<CanvasNavTool>("select");
 
-  useEffect(() => {
-    const snapshot = readCanvasSnapshot<RFNode, RFEdge>(canvasId as string);
-    if (snapshot) {
-      setNodes(snapshot.nodes);
-      setEdges(snapshot.edges);
-    }
-    setHasHydratedLocalSnapshot(true);
-  }, [canvasId]);
-
-  useEffect(() => {
-    if (!hasHydratedLocalSnapshot) return;
-    writeCanvasSnapshot(canvasId as string, { nodes, edges });
-  }, [canvasId, edges, hasHydratedLocalSnapshot, nodes]);
+  useCanvasLocalSnapshotPersistence<RFNode, RFEdge>({
+    canvasId: canvasId as string,
+    nodes,
+    edges,
+    setNodes,
+    setEdges,
+  });
 
   const handleNavToolChange = useCallback((tool: CanvasNavTool) => {
     if (tool === "scissor") {
diff --git a/components/canvas/use-canvas-local-snapshot-persistence.ts b/components/canvas/use-canvas-local-snapshot-persistence.ts
new file mode 100644
index 0000000..d37fba5
--- /dev/null
+++ b/components/canvas/use-canvas-local-snapshot-persistence.ts
@@ -0,0 +1,105 @@
+import {
+  useCallback,
+  useEffect,
+  useRef,
+  type Dispatch,
+  type SetStateAction,
+} from "react";
+import {
+  readCanvasSnapshot,
+  writeCanvasSnapshot,
+} from "@/lib/canvas-local-persistence";
+
+type UseCanvasLocalSnapshotPersistenceParams<TNode, TEdge> = {
+  canvasId: string;
+  nodes: TNode[];
+  edges: TEdge[];
+  setNodes: Dispatch<SetStateAction<TNode[]>>;
+  setEdges: Dispatch<SetStateAction<TEdge[]>>;
+  debounceMs?: number;
+};
+
+type PendingSnapshot<TNode, TEdge> = {
+  canvasId: string;
+  nodes: TNode[];
+  edges: TEdge[];
+};
+
+const DEFAULT_SNAPSHOT_DEBOUNCE_MS = 350;
+
+export function useCanvasLocalSnapshotPersistence<TNode, TEdge>({
+  canvasId,
+  nodes,
+  edges,
+  setNodes,
+  setEdges,
+  debounceMs = DEFAULT_SNAPSHOT_DEBOUNCE_MS,
+}: UseCanvasLocalSnapshotPersistenceParams<TNode, TEdge>): void {
+  const hasHydratedLocalSnapshotRef = useRef(false);
+  const timeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const pendingSnapshotRef = useRef<PendingSnapshot<TNode, TEdge> | null>(null);
+
+  const flushPendingSnapshot = useCallback(() => {
+    if (timeoutRef.current) {
+      clearTimeout(timeoutRef.current);
+      timeoutRef.current = null;
+    }
+
+    const pendingSnapshot = pendingSnapshotRef.current;
+    if (!pendingSnapshot) return;
+
+    writeCanvasSnapshot(pendingSnapshot.canvasId, {
+      nodes: pendingSnapshot.nodes,
+      edges: pendingSnapshot.edges,
+    });
+    pendingSnapshotRef.current = null;
+  }, []);
+
+  useEffect(() => {
+    hasHydratedLocalSnapshotRef.current = false;
+    flushPendingSnapshot();
+
+    const snapshot = readCanvasSnapshot<TNode, TEdge>(canvasId);
+    if (snapshot) {
+      setNodes(snapshot.nodes);
+      setEdges(snapshot.edges);
+    }
+
+    hasHydratedLocalSnapshotRef.current = true;
+  }, [canvasId, flushPendingSnapshot, setEdges, setNodes]);
+
+  useEffect(() => {
+    if (!hasHydratedLocalSnapshotRef.current) return;
+
+    pendingSnapshotRef.current = { canvasId, nodes, edges };
+
+    if (timeoutRef.current) {
+      clearTimeout(timeoutRef.current);
+    }
+
+    timeoutRef.current = setTimeout(() => {
+      const pendingSnapshot = pendingSnapshotRef.current;
+      if (!pendingSnapshot) return;
+
+      writeCanvasSnapshot(pendingSnapshot.canvasId, {
+        nodes: pendingSnapshot.nodes,
+        edges: pendingSnapshot.edges,
+      });
+      pendingSnapshotRef.current = null;
+      timeoutRef.current = null;
+    }, debounceMs);
+  }, [canvasId, debounceMs, edges, nodes]);
+
+  useEffect(() => {
+    return () => flushPendingSnapshot();
+  }, [flushPendingSnapshot]);
+
+  useEffect(() => {
+    window.addEventListener("beforeunload", flushPendingSnapshot);
+    window.addEventListener("pagehide", flushPendingSnapshot);
+    return () => {
+      window.removeEventListener("beforeunload", flushPendingSnapshot);
+      window.removeEventListener("pagehide", flushPendingSnapshot);
+    };
+  }, [flushPendingSnapshot]);
+}