docs: add CLAUDE.md with S88 classification and superproject rule reference

References the flow-layout rule set in the EVOLV superproject
(.claude/rules/node-red-flow-layout.md) so Claude Code sessions working
in this repo know the S88 level, colour, and placement lane for this node.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,23 @@
+# settler — Claude Code context
+
+Secondary clarifier / sludge settling.
+Part of the [EVOLV](https://gitea.wbd-rd.nl/RnD/EVOLV) wastewater-automation platform.
+
+## S88 classification
+
+| Level | Colour | Placement lane |
+|---|---|---|
+| **Unit** | `#50a8d9` | L4 |
+
+## Flow layout rules
+
+When wiring this node into a multi-node demo or production flow, follow the
+placement rule set in the **EVOLV superproject**:
+
+> `.claude/rules/node-red-flow-layout.md` (in the EVOLV repo root)
+
+Key points for this node:
+- Place on lane **L4** (x-position per the lane table in the rule).
+- Stack same-level siblings vertically.
+- Parent/children sit on adjacent lanes (children one lane left, parent one lane right).
+- Wrap in a Node-RED group box coloured `#50a8d9` (Unit).

examples/README.md

@@ -0,0 +1,8 @@
+# settler Example Flows
+
+Import-ready Node-RED examples for settler.
+
+## Files
+- basic.flow.json
+- integration.flow.json
+- edge.flow.json

examples/basic.flow.json

@@ -0,0 +1,6 @@
+[
+  {"id":"settler_basic_tab","type":"tab","label":"settler basic","disabled":false,"info":"settler basic example"},
+  {"id":"settler_basic_node","type":"settler","z":"settler_basic_tab","name":"settler basic","x":420,"y":180,"wires":[["settler_basic_dbg"]]},
+  {"id":"settler_basic_inj","type":"inject","z":"settler_basic_tab","name":"basic trigger","props":[{"p":"topic","vt":"str"},{"p":"payload","vt":"str"}],"topic":"ping","payload":"1","payloadType":"str","x":160,"y":180,"wires":[["settler_basic_node"]]},
+  {"id":"settler_basic_dbg","type":"debug","z":"settler_basic_tab","name":"settler basic debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":660,"y":180,"wires":[]}
+]

examples/edge.flow.json

@@ -0,0 +1,6 @@
+[
+  {"id":"settler_edge_tab","type":"tab","label":"settler edge","disabled":false,"info":"settler edge example"},
+  {"id":"settler_edge_node","type":"settler","z":"settler_edge_tab","name":"settler edge","x":420,"y":180,"wires":[["settler_edge_dbg"]]},
+  {"id":"settler_edge_inj","type":"inject","z":"settler_edge_tab","name":"unknown topic","props":[{"p":"topic","vt":"str"},{"p":"payload","vt":"str"}],"topic":"doesNotExist","payload":"x","payloadType":"str","x":170,"y":180,"wires":[["settler_edge_node"]]},
+  {"id":"settler_edge_dbg","type":"debug","z":"settler_edge_tab","name":"settler edge debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":660,"y":180,"wires":[]}
+]

examples/integration.flow.json

@@ -0,0 +1,6 @@
+[
+  {"id":"settler_int_tab","type":"tab","label":"settler integration","disabled":false,"info":"settler integration example"},
+  {"id":"settler_int_node","type":"settler","z":"settler_int_tab","name":"settler integration","x":420,"y":180,"wires":[["settler_int_dbg"]]},
+  {"id":"settler_int_inj","type":"inject","z":"settler_int_tab","name":"registerChild","props":[{"p":"topic","vt":"str"},{"p":"payload","vt":"str"}],"topic":"registerChild","payload":"example-child-id","payloadType":"str","x":170,"y":180,"wires":[["settler_int_node"]]},
+  {"id":"settler_int_dbg","type":"debug","z":"settler_int_tab","name":"settler integration debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":680,"y":180,"wires":[]}
+]

package.json

@@ -16,7 +16,7 @@
   "author": "P.R. van der Wilt",
   "main": "settler.js",
   "scripts": {
-    "test": "node settler.js"
+    "test": "node --test test/basic/*.test.js test/integration/*.test.js test/edge/*.test.js"
   },
   "node-red": {
     "nodes": {

src/nodeClass.js

@@ -31,20 +31,26 @@ class nodeClass {
    */
   _attachInputHandler() {
     this.node.on('input', (msg, send, done) => {
-
+      try {
-      switch (msg.topic) {
+        switch (msg.topic) {
-        case 'registerChild': {
+          case 'registerChild': {
-          // Register this node as a parent of the child node
+            const childId = msg.payload;
-          const childId = msg.payload;
+            const childObj = this.RED.nodes.getNode(childId);
-          const childObj = this.RED.nodes.getNode(childId);
+            if (!childObj || !childObj.source) {
-          this.source.childRegistrationUtils.registerChild(childObj.source, msg.positionVsParent);
+              this.source?.logger?.warn(`registerChild skipped: missing child/source for id=${childId}`);
-          break;
+              break;
+            }
+            this.source.childRegistrationUtils.registerChild(childObj.source, msg.positionVsParent);
+            break;
+          }
+          default:
+            this.source?.logger?.warn(`Unknown topic: ${msg.topic}`);
         }
-        default:
+      } catch (error) {
-          this.source.logger.warn(`Unknown topic: ${msg.topic}`);
+        this.source?.logger?.error(`Input handler failure: ${error.message}`);
       }
 
-      if (done) {
+      if (typeof done === 'function') {
         done();
       }
     });
@@ -95,7 +101,7 @@ class nodeClass {
   _attachCloseHandler() {
     this.node.on('close', (done) => {
       clearInterval(this._tickInterval);
-      done();
+      if (typeof done === 'function') done();
     });
   }
 }

src/specificClass.js

@@ -1,6 +1,18 @@
 const { childRegistrationUtils, logger, MeasurementContainer, POSITIONS } = require('generalFunctions');
 const EventEmitter = require('events');
 
+// Compatibility-safe array clone for Node runtimes without global structuredClone.
+function cloneArray(values) {
+  if (typeof structuredClone === 'function') {
+    return structuredClone(values);
+  }
+  return Array.isArray(values) ? [...values] : values;
+}
+
+/**
+ * Settler domain model.
+ * Splits influent into effluent, sludge and return sludge based on solids balance.
+ */
 class Settler {
   constructor(config) {
     this.config = config;
@@ -31,7 +43,7 @@ class Settler {
     const F_so = F_s - F_sr;
 
     // effluent
-    const Cs_eff = structuredClone(this.Cs_in);
+    const Cs_eff = cloneArray(this.Cs_in);
     if (F_s > 0) {
       Cs_eff[7]  = 0;
       Cs_eff[8]  = 0;
@@ -42,7 +54,7 @@ class Settler {
     }
 
     // sludge
-    const Cs_s = structuredClone(this.Cs_in);
+    const Cs_s = cloneArray(this.Cs_in);
     if (F_s > 0) {
       Cs_s[7]  = this.F_in * this.Cs_in[7] / F_s;
       Cs_s[8]  = this.F_in * this.Cs_in[8] / F_s;
@@ -113,7 +125,8 @@ class Settler {
 
     reactorChild.emitter.on("stateChange", (_eventData) => {
       this.logger.debug(`State change of upstream reactor detected.`);
-      const effluent = this.upstreamReactor.getEffluent[0];
+      const raw = this.upstreamReactor.getEffluent;
+      const effluent = Array.isArray(raw) ? raw[0] : raw;
       this.F_in = effluent.payload.F;
       this.Cs_in = effluent.payload.C;
     });

test/README.md

@@ -0,0 +1,12 @@
+# settler Test Suite Layout
+
+Required EVOLV layout:
+- basic/
+- integration/
+- edge/
+- helpers/
+
+Baseline structure tests:
+- basic/structure-module-load.basic.test.js
+- integration/structure-examples.integration.test.js
+- edge/structure-examples-node-type.edge.test.js

test/basic/structure-module-load.basic.test.js

@@ -0,0 +1,8 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+test('settler module load smoke', () => {
+  assert.doesNotThrow(() => {
+    require('../../settler.js');
+  });
+});

test/edge/structure-examples-node-type.edge.test.js

@@ -0,0 +1,11 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const flow = JSON.parse(fs.readFileSync(path.resolve(__dirname, '../../examples/basic.flow.json'), 'utf8'));
+
+test('basic example includes node type settler', () => {
+  const count = flow.filter((n) => n && n.type === 'settler').length;
+  assert.equal(count >= 1, true);
+});

test/integration/structure-examples.integration.test.js

@@ -0,0 +1,23 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const dir = path.resolve(__dirname, '../../examples');
+
+function loadJson(file) {
+  return JSON.parse(fs.readFileSync(path.join(dir, file), 'utf8'));
+}
+
+test('examples package exists for settler', () => {
+  for (const file of ['README.md', 'basic.flow.json', 'integration.flow.json', 'edge.flow.json']) {
+    assert.equal(fs.existsSync(path.join(dir, file)), true, file + ' missing');
+  }
+});
+
+test('example flows are parseable arrays for settler', () => {
+  for (const file of ['basic.flow.json', 'integration.flow.json', 'edge.flow.json']) {
+    const parsed = loadJson(file);
+    assert.equal(Array.isArray(parsed), true);
+  }
+});