fix: resolve custom threshold dropdown validation error

- Client now uses 'auto-detect' placeholder when node can't be determined
- Server handles node auto-detection by looking up VM/LXC in current state
- Fixes 'Please select a VM/LXC from the dropdown first' error in v3.17.3
- Addresses issue #110

data/custom-thresholds.json

@@ -1 +1,16 @@
-{}
+{
+  "primary:103": {
+    "endpointId": "primary",
+    "nodeId": "auto-detect",
+    "vmid": "103",
+    "thresholds": {
+      "disk": {
+        "warning": 70,
+        "critical": 80
+      }
+    },
+    "enabled": true,
+    "createdAt": "2025-06-01T19:50:34.784Z",
+    "updatedAt": "2025-06-01T19:50:34.784Z"
+  }
+}

server/thresholdRoutes.js

@@ -56,7 +56,7 @@ function setupThresholdRoutes(app) {
     // Set custom thresholds for VM/LXC
     app.post('/api/thresholds/:endpointId/:nodeId/:vmid', async (req, res) => {
         try {
-            const { endpointId, nodeId, vmid } = req.params;
+            let { endpointId, nodeId, vmid } = req.params;
             const { thresholds } = req.body;
             
             if (!thresholds) {
@@ -66,6 +66,25 @@ function setupThresholdRoutes(app) {
                 });
             }
             
+            // Handle auto-detect node
+            if (nodeId === 'auto-detect') {
+                const state = require('./state');
+                // Find the VM/LXC in the current state
+                const allGuests = [...(state.vms || []), ...(state.containers || [])];
+                const guest = allGuests.find(g => 
+                    g.endpointId === endpointId && g.id === vmid
+                );
+                
+                if (guest && guest.node) {
+                    nodeId = guest.node;
+                    console.log(`[ThresholdRoutes] Auto-detected node '${nodeId}' for ${endpointId}:${vmid}`);
+                } else {
+                    // If we can't find the node, use a wildcard that will match any node
+                    nodeId = '*';
+                    console.log(`[ThresholdRoutes] Could not auto-detect node for ${endpointId}:${vmid}, using wildcard`);
+                }
+            }
+            
             if (!customThresholdManager.initialized) {
                 await customThresholdManager.init();
             }
@@ -84,7 +103,7 @@ function setupThresholdRoutes(app) {
     // Update existing custom thresholds
     app.put('/api/thresholds/:endpointId/:nodeId/:vmid', async (req, res) => {
         try {
-            const { endpointId, nodeId, vmid } = req.params;
+            let { endpointId, nodeId, vmid } = req.params;
             const { thresholds } = req.body;
             
             if (!thresholds) {
@@ -94,6 +113,25 @@ function setupThresholdRoutes(app) {
                 });
             }
             
+            // Handle auto-detect node
+            if (nodeId === 'auto-detect') {
+                const state = require('./state');
+                // Find the VM/LXC in the current state
+                const allGuests = [...(state.vms || []), ...(state.containers || [])];
+                const guest = allGuests.find(g => 
+                    g.endpointId === endpointId && g.id === vmid
+                );
+                
+                if (guest && guest.node) {
+                    nodeId = guest.node;
+                    console.log(`[ThresholdRoutes] Auto-detected node '${nodeId}' for ${endpointId}:${vmid}`);
+                } else {
+                    // If we can't find the node, use a wildcard that will match any node
+                    nodeId = '*';
+                    console.log(`[ThresholdRoutes] Could not auto-detect node for ${endpointId}:${vmid}, using wildcard`);
+                }
+            }
+            
             if (!customThresholdManager.initialized) {
                 await customThresholdManager.init();
             }

src/public/js/ui/settings.js

@@ -1712,14 +1712,24 @@ PulseApp.ui.settings = (() => {
                 
                 // Find the current node for this VM (for display purposes)
                 const selectedGuest = allGuests.find(g => g.endpointId === selectedEndpoint && g.id === selectedVmid);
-                nodeField.value = selectedGuest ? selectedGuest.node : '';
+                
+                // If we can't find the guest or it doesn't have a node, use a placeholder
+                // The server will handle finding the actual node
+                if (selectedGuest && selectedGuest.node) {
+                    nodeField.value = selectedGuest.node;
+                } else {
+                    // Use a placeholder value that will pass validation
+                    // The server can determine the actual node from endpointId and vmid
+                    nodeField.value = 'auto-detect';
+                }
                 
                 // Debug logging
                 console.log('[Settings] Guest selector changed:', {
                     selectedEndpoint,
                     selectedVmid,
                     selectedGuest,
-                    nodeValue: selectedGuest ? selectedGuest.node : 'MISSING'
+                    nodeValue: nodeField.value,
+                    allGuestsCount: allGuests.length
                 });
             } else {
                 endpointField.value = '';