Update engine.js

engine.js

@@ -1,5 +1,7 @@
 // engine.js
 
+const { writeLedgerEntry } = require('./ledger');
+
 // Invariant set F1–F9
 const INVARIANTS = {
   F1_NO_SEMANTIC_INTERPRETATION: true,
@@ -13,7 +15,6 @@ const INVARIANTS = {
   F9_NO_CROSS_SIGNAL_CONTAMINATION: true,
 };
 
-// Simple invariant check function
 function checkInvariants(input) {
   const report = {
     inputType: typeof input,
@@ -22,44 +23,46 @@ function checkInvariants(input) {
     violations: [],
   };
 
-  // F1: no semantic interpretation → we only treat input as opaque string
   if (typeof input !== 'string') {
     report.violations.push('F1: input must be a string (opaque signal)');
   }
 
-  // F4: no autonomous state mutation → engine must be stateless
-  // (we just assert; no external state is touched here)
-
-  // F9: no cross-signal contamination → single input per call
-  // (enforced by API: one input argument)
-
   return report;
 }
 
-// Deterministic processing function
 function processSignal(input) {
   const invariantReport = checkInvariants(input);
 
+  let result;
   if (invariantReport.violations.length > 0) {
-    return {
+    result = {
       input,
       output: null,
       timestamp: 0,
       invariants: invariantReport,
       status: 'error',
     };
+  } else {
+    const output = `processed:${input}`;
+    result = {
+      input,
+      output,
+      timestamp: 0,
+      invariants: invariantReport,
+      status: 'ok',
+    };
   }
 
-  // Opaque, deterministic transform (no semantics)
-  const output = `processed:${input}`;
+  // Write ledger entry (deterministic, append-only)
+  const ledgerPath = writeLedgerEntry({
+    input: result.input,
+    output: result.output,
+    timestamp: result.timestamp,
+    status: result.status,
+    invariants: result.invariants,
+  });
 
-  return {
-    input,
-    output,
-    timestamp: 0,
-    invariants: invariantReport,
-    status: 'ok',
-  };
+  return { ...result, ledgerPath };
 }
 
 module.exports = { processSignal };