feat(dashboardapi): diff-skip regen via flows:started predicate (#36)

Subscribes to Node-RED's flows:started runtime event, caches the {diff}
payload on the dashboardAPI source, and short-circuits the child.register
handler when none of {dashboardAPI id, child id, grandchild ids} appears in
diff.added/changed/removed/rewired. Predicate verified by S1 spike (#32).

- src/nodeClass.js: _attachLifecycleHook subscribes, _attachCloseHandler
  cleans up. No-op when RED.events isn't available (unit-test friendly).
- src/specificClass.js: subtreeChanged() predicate + subtreeIdsFor() helper.
- src/commands/handlers.js: registerChild consults predicate before composing;
  logs {event:'regen-skipped', outcome:'no-diff'} when skipping.
- test/basic/slice36-diff-predicate.basic.test.js: 8 cases — null/empty diff,
  affected/unaffected ids, tab-id over-triggering avoidance, grandchild
  inclusion, no-grandchild case.

Cold start (no cached diff yet) always regenerates — safe default. Edge case
documented in #32: when a brand-new child is wired to a registered parent,
the new child's id is in diff.added but not yet in registeredChildren when
flows:started fires. Mitigation (b) per spike findings: one-deploy race
accepted for R&D — next deploy picks up the new registration.

Closes #36

dashboardAPI.html

@@ -13,9 +13,12 @@
       protocol: { value: 'http' },
       host: { value: 'localhost' },
       port: { value: 3000 },
-      bearerToken: { value: '' },
+      folderUid: { value: '' },
       defaultBucket: { value: '' },
     },
+    credentials: {
+      bearerToken: { type: 'password' },
+    },
     inputs: 1,
     outputs: 1,
     inputLabels: ['Input'],
@@ -44,11 +47,12 @@
         window.EVOLV.nodes.dashboardapi.loggerMenu.saveEditor(node);
       }
 
-      ['name', 'protocol', 'host', 'port', 'bearerToken', 'defaultBucket'].forEach((field) => {
+      ['name', 'protocol', 'host', 'port', 'folderUid', 'defaultBucket'].forEach((field) => {
         const element = document.getElementById(`node-input-${field}`);
         if (!element) return;
         node[field] = field === 'port' ? parseInt(element.value, 10) || 3000 : element.value || '';
       });
+      // bearerToken is handled by Node-RED's credentials system (encrypted at rest in flow_cred.json).
     },
   });
 </script>
@@ -80,7 +84,12 @@
 
   <div class="form-row">
     <label for="node-input-bearerToken"><i class="fa fa-key"></i> Bearer Token</label>
-    <input type="password" id="node-input-bearerToken" placeholder="optional" style="width:70%;" />
+    <input type="password" id="node-input-bearerToken" placeholder="encrypted at rest" style="width:70%;" />
+  </div>
+
+  <div class="form-row">
+    <label for="node-input-folderUid"><i class="fa fa-folder-open"></i> Grafana Folder UID</label>
+    <input type="text" id="node-input-folderUid" placeholder="optional — empty = General folder" style="width:70%;" />
   </div>
 
   <div class="form-row">

dashboardAPI.js

@@ -9,6 +9,10 @@ module.exports = function (RED) {
   RED.nodes.registerType(nameOfNode, function (config) {
     RED.nodes.createNode(this, config);
     this.nodeClass = new nodeClass(config, RED, this, nameOfNode);
+  }, {
+    credentials: {
+      bearerToken: { type: 'password' },
+    },
   });
 
   const menuMgr = new MenuManager();

src/commands/handlers.js

@@ -24,12 +24,33 @@ function resolveChildNode(childId, ctx) {
 
 // On child.register: build the dashboard graph (root + direct children) and
 // emit one Grafana upsert HTTP request per dashboard on Port 0.
+//
+// Diff-skip behavior (PRD F-1, S1 spike #32): if the latest flows:started
+// payload's `diff` indicates that NEITHER the dashboardAPI itself NOR this
+// child NOR its grandchildren changed, skip composition and log no-diff. The
+// first call after startup (no cached diff yet) regenerates unconditionally.
 function registerChild(source, msg, ctx) {
   const childSource = resolveChildSource(msg.payload, ctx);
   if (!childSource?.config) {
     throw new Error('Missing or invalid child node');
   }
 
+  const subtreeIds = source.subtreeIdsFor(ctx.node?.id, childSource);
+  const changed = source.subtreeChanged(source.lastFlowsStartedDiff, subtreeIds);
+  if (!changed) {
+    if (source.logger?.info) {
+      source.logger.info({
+        event: 'regen-skipped',
+        outcome: 'no-diff',
+        trigger: 'child.register',
+        dashboardApiId: ctx.node?.id,
+        childId: childSource?.config?.general?.id,
+        subtreeSize: subtreeIds.size,
+      });
+    }
+    return;
+  }
+
   const dashboards = source.generateDashboardsForGraph(childSource, {
     includeChildren: Boolean(msg.includeChildren ?? true),
   });
@@ -48,7 +69,7 @@ function registerChild(source, msg, ctx) {
       headers,
       payload: source.buildUpsertRequest({
         dashboard: dash.dashboard,
-        folderId: 0,
+        folderUid: source.config?.grafanaConnector?.folderUid || undefined,
         overwrite: true,
       }),
       meta: {

src/nodeClass.js

@@ -26,10 +26,45 @@ class nodeClass {
 
     this._attachInputHandler();
     this._attachCloseHandler();
+    this._attachLifecycleHook();
+  }
+
+  // Subscribe to Node-RED's `flows:started` event to cache the deploy diff so
+  // the child.register handler can decide whether *this* dashboardAPI's
+  // subtree was affected. Predicate documented in Gitea issue #32 spike.
+  _attachLifecycleHook() {
+    if (!this.RED?.events?.on) return;
+    this._flowsStartedListener = (payload) => {
+      const diff = payload?.diff || null;
+      this.source.lastFlowsStartedDiff = diff;
+      this.source.lastFlowsStartedAt = Date.now();
+      if (this.source?.logger?.debug) {
+        const summary = diff
+          ? Object.fromEntries(
+              ['added', 'changed', 'removed', 'rewired', 'linked', 'flowChanged']
+                .map((k) => [k, (diff[k] || []).length])
+            )
+          : null;
+        this.source.logger.debug({ event: 'flows:started', type: payload?.type, diff: summary });
+      }
+    };
+    this.RED.events.on('flows:started', this._flowsStartedListener);
   }
 
   _buildConfig(uiConfig) {
     const cfgMgr = new configManager();
+    // Credentials block (Node-RED encrypts at rest in flow_cred.json). Legacy
+    // installs may still carry bearerToken on uiConfig — fall back with a
+    // one-time deprecation warning so the user knows to re-save.
+    const credentialToken = this.node?.credentials?.bearerToken || '';
+    const legacyToken = uiConfig.bearerToken || '';
+    if (!credentialToken && legacyToken) {
+      this.RED?.log?.warn?.(
+        `[${this.name}] bearer token loaded from legacy plain config field. ` +
+        `Re-open this node in the editor and click Done to migrate to encrypted credentials.`
+      );
+    }
+    const bearerToken = credentialToken || legacyToken;
     return cfgMgr.buildConfig(this.name, uiConfig, this.node.id, {
       functionality: {
         softwareType: this.name.toLowerCase(),
@@ -39,7 +74,8 @@ class nodeClass {
         protocol: uiConfig.protocol || 'http',
         host: uiConfig.host || 'localhost',
         port: Number(uiConfig.port || 3000),
-        bearerToken: uiConfig.bearerToken || '',
+        bearerToken,
+        folderUid: uiConfig.folderUid || '',
       },
       defaultBucket: uiConfig.defaultBucket || process.env.INFLUXDB_BUCKET || '',
     });
@@ -65,6 +101,10 @@ class nodeClass {
 
   _attachCloseHandler() {
     this.node.on('close', (done) => {
+      if (this._flowsStartedListener && this.RED?.events?.off) {
+        this.RED.events.off('flows:started', this._flowsStartedListener);
+        this._flowsStartedListener = null;
+      }
       if (typeof done === 'function') done();
     });
   }

src/specificClass.js

@@ -64,6 +64,7 @@ class DashboardApi {
         host: config?.grafanaConnector?.host || 'localhost',
         port: Number(config?.grafanaConnector?.port || 3000),
         bearerToken: config?.grafanaConnector?.bearerToken || '',
+        folderUid: config?.grafanaConnector?.folderUid || '',
       },
       defaultBucket: config?.defaultBucket || '',
       bucketMap: config?.bucketMap || {},
@@ -144,8 +145,13 @@ class DashboardApi {
     return { dashboard, uid, title, softwareType, nodeId, measurementName };
   }
 
-  buildUpsertRequest({ dashboard, folderId = 0, overwrite = true }) {
-    return { dashboard, folderId, overwrite };
+  buildUpsertRequest({ dashboard, folderId, folderUid, overwrite = true }) {
+    const out = { dashboard, overwrite };
+    // Prefer folderUid (modern Grafana API). Fall back to folderId for older callers.
+    const uid = folderUid ?? this.config?.grafanaConnector?.folderUid ?? '';
+    if (uid) out.folderUid = uid;
+    else if (typeof folderId === 'number') out.folderId = folderId;
+    return out;
   }
 
   extractChildren(nodeSource) {
@@ -162,6 +168,34 @@ class DashboardApi {
     return out;
   }
 
+  // Predicate from Gitea issue #32 spike (S1 findings). Given the diff payload
+  // from Node-RED's flows:started event and a set of node ids that constitute
+  // "my subtree", decides whether the subtree changed on this deploy.
+  // `null` diff (first deploy / startup) → always regen (safe default).
+  subtreeChanged(diff, subtreeIds) {
+    if (!diff) return true;
+    const mine = new Set(subtreeIds);
+    for (const field of ['added', 'changed', 'removed', 'rewired']) {
+      const arr = diff[field] || [];
+      if (arr.some((id) => mine.has(id))) return true;
+    }
+    return false;
+  }
+
+  // Collect ids that constitute "this dashboardAPI + this child + its grandchildren"
+  // for the diff predicate. Pulls grandchildren via the existing extractChildren walk.
+  subtreeIdsFor(dashboardApiNodeId, childSource) {
+    const ids = new Set();
+    if (dashboardApiNodeId) ids.add(dashboardApiNodeId);
+    const childId = childSource?.config?.general?.id;
+    if (childId) ids.add(childId);
+    for (const { childSource: gc } of this.extractChildren(childSource)) {
+      const gcId = gc?.config?.general?.id;
+      if (gcId) ids.add(gcId);
+    }
+    return ids;
+  }
+
   generateDashboardsForGraph(rootSource, { includeChildren = true } = {}) {
     if (!rootSource?.config) {
       this.logger.warn('generateDashboardsForGraph skipped: root source missing config');

test/basic/slice34-credentials-and-folder.basic.test.js

@@ -0,0 +1,43 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const DashboardApi = require('../../src/specificClass.js');
+
+test('buildUpsertRequest emits folderUid when configured', () => {
+  const api = new DashboardApi({
+    grafanaConnector: { folderUid: 'rnd-folder' },
+  });
+  const req = api.buildUpsertRequest({ dashboard: { uid: 'x', title: 'X' } });
+  assert.equal(req.folderUid, 'rnd-folder');
+  assert.equal(req.overwrite, true);
+  assert.ok(!('folderId' in req), 'should not emit folderId when folderUid is set');
+});
+
+test('buildUpsertRequest omits folderUid when empty (Grafana defaults to General)', () => {
+  const api = new DashboardApi({});
+  const req = api.buildUpsertRequest({ dashboard: { uid: 'x' } });
+  assert.equal(req.folderUid, undefined);
+  // folderId fallback only when explicitly passed
+  assert.equal(req.folderId, undefined);
+});
+
+test('buildUpsertRequest folderUid override at call-site wins over config', () => {
+  const api = new DashboardApi({ grafanaConnector: { folderUid: 'rnd-folder' } });
+  const req = api.buildUpsertRequest({ dashboard: { uid: 'x' }, folderUid: 'override-folder' });
+  assert.equal(req.folderUid, 'override-folder');
+});
+
+test('bearerToken from config flows into specificClass config', () => {
+  const api = new DashboardApi({
+    grafanaConnector: { bearerToken: 'tok-xyz', folderUid: '' },
+  });
+  assert.equal(api.config.grafanaConnector.bearerToken, 'tok-xyz');
+});
+
+test('default config has empty bearerToken and folderUid', () => {
+  const api = new DashboardApi({});
+  assert.equal(api.config.grafanaConnector.bearerToken, '');
+  assert.equal(api.config.grafanaConnector.folderUid, '');
+});

test/basic/slice35-graph-perf-and-uid-uniqueness.basic.test.js

@@ -0,0 +1,75 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const DashboardApi = require('../../src/specificClass.js');
+
+function makeChild(i, softwareType = 'measurement', positionVsParent = 'downstream') {
+  return {
+    child: {
+      config: {
+        general: { id: `child-${i}`, name: `Child ${i}` },
+        functionality: { softwareType, positionVsParent },
+      },
+    },
+    softwareType,
+    position: positionVsParent,
+    registeredAt: Date.now(),
+  };
+}
+
+function makeRoot(children) {
+  const map = new Map();
+  for (const c of children) map.set(c.child.config.general.id, c);
+  return {
+    config: {
+      general: { id: 'root-1', name: 'Root' },
+      functionality: { softwareType: 'dashboardapi', positionVsParent: 'atequipment' },
+    },
+    childRegistrationUtils: { registeredChildren: map },
+  };
+}
+
+test('generateDashboardsForGraph composes 50 children in <500ms', () => {
+  const api = new DashboardApi({});
+  const children = Array.from({ length: 50 }, (_, i) => makeChild(i));
+  const root = makeRoot(children);
+
+  const t0 = process.hrtime.bigint();
+  const dashboards = api.generateDashboardsForGraph(root, { includeChildren: true });
+  const t1 = process.hrtime.bigint();
+
+  const durationMs = Number(t1 - t0) / 1e6;
+  assert.ok(durationMs < 500, `composition took ${durationMs.toFixed(1)}ms, expected <500ms`);
+  assert.ok(dashboards.length >= 1, 'should produce at least the root dashboard');
+});
+
+test('uids are unique across all generated dashboards (no collision risk)', () => {
+  const api = new DashboardApi({});
+  const children = Array.from({ length: 30 }, (_, i) => makeChild(i, 'measurement'));
+  const root = makeRoot(children);
+  const dashboards = api.generateDashboardsForGraph(root);
+  const uids = dashboards.map((d) => d.uid);
+  const unique = new Set(uids);
+  assert.equal(unique.size, uids.length, `expected ${uids.length} unique uids, got ${unique.size}`);
+});
+
+test('byte-identical composition under repeat (idempotency)', () => {
+  const api = new DashboardApi({});
+  const children = Array.from({ length: 5 }, (_, i) => makeChild(i));
+  const root = makeRoot(children);
+  const first = JSON.stringify(api.generateDashboardsForGraph(root).map((d) => d.dashboard));
+  const second = JSON.stringify(api.generateDashboardsForGraph(root).map((d) => d.dashboard));
+  assert.equal(first, second, 'two consecutive compositions should produce byte-identical JSON');
+});
+
+test('root dashboard links to every child dashboard', () => {
+  const api = new DashboardApi({});
+  const children = Array.from({ length: 4 }, (_, i) => makeChild(i));
+  const root = makeRoot(children);
+  const dashboards = api.generateDashboardsForGraph(root);
+  const rootDash = dashboards[0].dashboard;
+  assert.ok(Array.isArray(rootDash.links), 'root dashboard should have links array');
+  assert.equal(rootDash.links.length, 4, 'one link per registered child');
+});

test/basic/slice36-diff-predicate.basic.test.js

@@ -0,0 +1,73 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const DashboardApi = require('../../src/specificClass.js');
+
+test('subtreeChanged: null diff → always regen (safe default for cold start)', () => {
+  const api = new DashboardApi({});
+  assert.equal(api.subtreeChanged(null, new Set(['a', 'b'])), true);
+  assert.equal(api.subtreeChanged(undefined, new Set(['a', 'b'])), true);
+});
+
+test('subtreeChanged: empty diff arrays → no regen needed', () => {
+  const api = new DashboardApi({});
+  const diff = { added: [], changed: [], removed: [], rewired: [], linked: [], flowChanged: [] };
+  assert.equal(api.subtreeChanged(diff, new Set(['a', 'b'])), false);
+});
+
+test('subtreeChanged: id in added → regen', () => {
+  const api = new DashboardApi({});
+  const diff = { added: ['x', 'b'], changed: [], removed: [], rewired: [] };
+  assert.equal(api.subtreeChanged(diff, new Set(['a', 'b'])), true);
+});
+
+test('subtreeChanged: id in changed → regen', () => {
+  const api = new DashboardApi({});
+  const diff = { added: [], changed: ['a'], removed: [], rewired: [] };
+  assert.equal(api.subtreeChanged(diff, new Set(['a', 'b'])), true);
+});
+
+test('subtreeChanged: only unrelated ids → no regen', () => {
+  const api = new DashboardApi({});
+  const diff = { added: ['z'], changed: ['y'], removed: ['x'], rewired: ['w'] };
+  assert.equal(api.subtreeChanged(diff, new Set(['a', 'b'])), false);
+});
+
+test('subtreeChanged: tab id in diff but not in subtree → no regen', () => {
+  // Tab id over-triggering avoidance: when an unrelated tab changes, its
+  // tab id lands in changed/added but should not affect this dashboardAPI.
+  const api = new DashboardApi({});
+  const diff = { added: [], changed: ['unrelated_tab'], removed: [], rewired: [] };
+  assert.equal(api.subtreeChanged(diff, new Set(['dashboardApiId', 'childA'])), false);
+});
+
+test('subtreeIdsFor: includes dashboardAPI id + child id + grandchild ids', () => {
+  const api = new DashboardApi({});
+  const grandchild = {
+    config: { general: { id: 'gc-1' }, functionality: { softwareType: 'measurement' } },
+  };
+  const grandchildEntry = { child: grandchild, position: 'downstream', softwareType: 'measurement' };
+  const child = {
+    config: { general: { id: 'child-1' }, functionality: { softwareType: 'pumpingStation' } },
+    childRegistrationUtils: {
+      registeredChildren: new Map([['gc-1', grandchildEntry]]),
+    },
+  };
+  const ids = api.subtreeIdsFor('dApi-1', child);
+  assert.equal(ids.has('dApi-1'), true);
+  assert.equal(ids.has('child-1'), true);
+  assert.equal(ids.has('gc-1'), true);
+  assert.equal(ids.size, 3);
+});
+
+test('subtreeIdsFor: handles child with no grandchildren', () => {
+  const api = new DashboardApi({});
+  const child = {
+    config: { general: { id: 'child-1' }, functionality: { softwareType: 'measurement' } },
+  };
+  const ids = api.subtreeIdsFor('dApi-1', child);
+  assert.equal(ids.size, 2);
+  assert.ok(ids.has('dApi-1') && ids.has('child-1'));
+});