fix(frontend): remote sync improvements, save all elements, block drop backend sync (Issues #9, #10, #11)

frontend/src/App.tsx

@@ -310,36 +310,66 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
 
     // Only update local state if remote data differs AND local is not ahead of remote
     // (prevents race condition where local element is overwritten by stale Yjs sync)
+    // Merge: update local elements with remote version when properties differ, add remote-only elements
     const localIds = new Set(elements.map(e => e.id));
     const remoteIds = new Set(collab.elements.map(e => e.id));
-    const localHasExtra = elements.some(e => !remoteIds.has(e.id));
-    const remoteHasExtra = collab.elements.some(e => !localIds.has(e.id));
-    // Only sync from remote if remote has elements local doesn't have AND local doesn't have unsaved elements
-    if (remoteHasExtra && !localHasExtra) {
-      setElements(collab.elements);
-    } else if (remoteHasExtra && localHasExtra) {
-      // Merge: keep local elements, update any that changed remotely
-      const merged = elements.map(el => {
-        const remote = collab.elements.find(e => e.id === el.id);
-        return remote || el;
-      });
-      // Add remote-only elements
-      collab.elements.forEach(el => { if (!localIds.has(el.id)) merged.push(el); });
+    const remoteMap = new Map(collab.elements.map(e => [e.id, e]));
+    let changed = false;
+    const merged = elements.map(el => {
+      const remote = remoteMap.get(el.id);
+      if (remote && JSON.stringify(remote) !== JSON.stringify(el)) {
+        changed = true;
+        return remote;
+      }
+      return el;
+    });
+    // Add remote-only elements
+    collab.elements.forEach(el => {
+      if (!localIds.has(el.id)) {
+        changed = true;
+        merged.push(el);
+      }
+    });
+    if (changed) {
       setElements(merged);
     }
 
     // Never overwrite local layers with empty remote layers (prevents losing initialLayers)
     if (collab.layers.length > 0) {
-      const sameLayers = collab.layers.length === layers.length &&
-        collab.layers.every((l, i) => l.id === layers[i]?.id);
-      if (!sameLayers) setLayers(collab.layers);
+      // Compare by ID set, not by index ordering. Update if any layer properties differ.
+      const localLayerMap = new Map(layers.map(l => [l.id, l]));
+      let layersChanged = false;
+      const mergedLayers = collab.layers.map(rl => {
+        const local = localLayerMap.get(rl.id);
+        if (!local || JSON.stringify(local) !== JSON.stringify(rl)) {
+          layersChanged = true;
+        }
+        return rl;
+      });
+      // Also check if local has layers not in remote
+      if (!layersChanged && layers.length !== collab.layers.length) {
+        layersChanged = true;
+      }
+      if (layersChanged) setLayers(mergedLayers);
     }
 
     // Never overwrite local blocks with empty remote blocks (prevents losing defaultBlocks)
     if (collab.blocks.length > 0) {
-      const sameBlocks = collab.blocks.length === blocks.length &&
-        collab.blocks.every((b, i) => b.id === blocks[i]?.id);
-      if (!sameBlocks) setBlocks(collab.blocks);
+      // Compare by ID set, not by index ordering. Update if any block properties differ.
+      const localBlockMap = new Map(blocks.map(b => [b.id, b]));
+      let blocksChanged = false;
+      const mergedBlocks = collab.blocks.map(rb => {
+        const local = localBlockMap.get(rb.id);
+        if (!local || JSON.stringify(local) !== JSON.stringify(rb)) {
+          blocksChanged = true;
+        }
+        return rb;
+      });
+      // Also check if local has blocks not in remote
+      if (!blocksChanged && blocks.length !== collab.blocks.length) {
+        blocksChanged = true;
+      }
+      if (blocksChanged) setBlocks(mergedBlocks);
     }
 
     // Sync groups from remote → local
@@ -574,8 +604,22 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     if (instance) {
       setElements((prev) => [...prev, instance]);
       setCommandHistory((prev) => [...prev, { prefix: '·', text: `Block platziert: ${blockId} bei (${x.toFixed(2)}, ${y.toFixed(2)})`, type: 'info' }]);
+      // Push to Yjs CRDT for real-time sync
+      if (collab.status === 'connected') {
+        collab.setElement(instance);
+      }
+      // Save to backend
+      if (drawingId && token) {
+        setSavedStatus('Speichert…');
+        createElementTyped(token, drawingId, instance).then(() => {
+          setSavedStatus('gespeichert');
+        }).catch((err) => {
+          console.error('Failed to save block instance:', err);
+          setSavedStatus('Fehler beim Speichern');
+        });
+      }
     }
-  }, [blocks, activeLayerId]);
+  }, [blocks, activeLayerId, collab, drawingId, token]);
 
   const handleSelectionChange = useCallback((selectedIds: string[]) => {
     if (selectedIds.length === 1) {
@@ -646,7 +690,6 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
       // Save elements to backend if drawingId exists
       if (drawingId && token) {
         elements.forEach((el) => {
-          if (!el.id.startsWith('el-')) return;
           updateElement(token, el.id, el).catch(() => {});
         });
       }