feat: persist and cache all known devices; discovery only adds/updates

- Store.mergeDevices(): updates existing by UDN, adds new, keeps offline devices
- platform.js: merges discovered into cache; registers cached-offline devices
  in HomeKit so they remain visible; only removes truly orphaned accessories
- server.js: discover endpoint merges and returns full known device list

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/homebridge-plugin/homebridge-ui/server.js

@@ -45,8 +45,8 @@ class DibbyWemoUiServer extends HomebridgePluginUiServer {
     this.onRequest('/devices/discover', async ({ timeout } = {}) => {
       const ms = typeof timeout === 'number' ? timeout : 10_000;
       const devices = await wemoClient.discoverDevices(ms);
-      // Persist updated list
+      // Merge into cached list — previously known devices stay even if not found this scan
-      this._store.saveDevices(devices.map((d) => ({
+      this._store.mergeDevices(devices.map((d) => ({
         host: d.host,
         port: d.port,
         udn:  d.udn ?? `${d.host}:${d.port}`,
@@ -54,7 +54,8 @@ class DibbyWemoUiServer extends HomebridgePluginUiServer {
         productModel: d.productModel ?? 'Wemo Device',
         firmwareVersion: d.firmwareVersion ?? null,
       })));
-      return devices;
+      // Return the full merged list so the UI shows all known devices
+      return this._store.getDevices();
     });
 
     this.onRequest('/devices/state', async ({ host, port }) => {

packages/homebridge-plugin/lib/platform.js

@@ -114,25 +114,36 @@ class WemoPlatform {
 
     this.log.info(`Found ${discovered.length} Wemo device(s)`);
 
-    // Save discovered device list for the custom UI
+    // Merge discovered devices into the cached list — keep offline devices too
-    this._store.saveDevices(discovered.map((d) => ({
+    const freshForStore = discovered.map((d) => ({
       host: d.host,
       port: d.port,
       udn:  d.udn ?? `${d.host}:${d.port}`,
       friendlyName: d.friendlyName ?? d.host,
       productModel: d.productModel ?? 'Wemo Device',
       firmwareVersion: d.firmwareVersion ?? null,
-    })));
+    }));
+    const allKnown = this._store.mergeDevices(freshForStore);
 
+    // Register newly discovered devices in HomeKit
     for (const device of discovered) {
       this._registerDevice(device, pollInterval);
     }
 
-    // Remove stale accessories (devices no longer discovered)
+    // Register previously cached devices that weren't discovered (may be offline)
-    const activeUUIDs = new Set(discovered.map((d) => this._uuidForDevice(d)));
+    // so HomeKit still knows about them
+    const discoveredUDNs = new Set(discovered.map((d) => d.udn ?? `${d.host}:${d.port}`));
+    for (const cached of allKnown) {
+      if (!discoveredUDNs.has(cached.udn)) {
+        this.log.info(`Device offline/not found during discovery, keeping cached: ${cached.friendlyName}`);
+        this._registerDevice(cached, pollInterval);
+      }
+    }
+
+    // Remove orphaned accessories — those with no device context at all
     for (const [uuid, acc] of this._accessories) {
-      if (!activeUUIDs.has(uuid)) {
+      if (!acc.context?.device?.host) {
-        this.log.info('Removing stale accessory: ' + acc.displayName);
+        this.log.info('Removing orphaned accessory (no device context): ' + acc.displayName);
         this._handlers.get(uuid)?.stopPolling();
         this._handlers.delete(uuid);
         this.api.unregisterPlatformAccessories(PLUGIN_NAME, PLATFORM_NAME, [acc]);

packages/homebridge-plugin/lib/store.js

@@ -56,6 +56,33 @@ class DwmStore {
   getDeviceGroups()         { return this._load().deviceGroups ?? []; }
   saveDeviceGroups(groups)  { const d = this._load(); d.deviceGroups = groups; this._save(d); }
 
+  /**
+   * Merge freshly discovered devices into the cached list.
+   * - Existing devices are updated with fresh data (host/port/name/firmware).
+   * - Previously cached devices NOT in the new scan are kept as-is (offline ≠ removed).
+   * - Newly found devices are appended.
+   * Returns the merged list.
+   */
+  mergeDevices(fresh) {
+    const d       = this._load();
+    const cached  = d.devices ?? [];
+    const byUdn   = new Map(cached.map((dev) => [dev.udn, dev]));
+
+    for (const f of fresh) {
+      const udn = f.udn ?? `${f.host}:${f.port}`;
+      if (byUdn.has(udn)) {
+        // Update existing entry with latest network data
+        byUdn.set(udn, { ...byUdn.get(udn), ...f, udn });
+      } else {
+        byUdn.set(udn, { ...f, udn });
+      }
+    }
+
+    d.devices = Array.from(byUdn.values());
+    this._save(d);
+    return d.devices;
+  }
+
   // ── Disabled-rule backups ─────────────────────────────────────────────────
 
   getDisabledRules()                    { return this._load().disabledRules ?? {}; }