Support default value for merge tags in governance rules. (#93)

* support default value in merge tags

* bump version

Author: xinghengwang

lib/governanceRulesManager.js

@@ -94,21 +94,56 @@ function doesRegexConfigMatch(regexConfig, requestFields, requestBody, requestHe
   }, false);
 }
 
+function replaceVariableNameWithValueWithDefault(inputString, variables) {
+  // This regular expression matches patterns like {{VARIABLE_NAME}} or {{VARIABLE_NAME|DEFAULT_VALUE}}
+  const variablePattern = /\{\{([^\{\}|]+)(\|([^}]+))?\}\}/g;
+
+  return inputString.replace(variablePattern, (match, variableName, _, defaultValue) => {
+    // Check if the variableName exists in the variables object and is not null/undefined
+    if (variables.hasOwnProperty(variableName) && variables[variableName] !== null && variables[variableName] !== undefined) {
+      // Replace with the variable value from the variables object
+      return variables[variableName];
+    } else {
+      // If the variable is not provided, use the default value (if available)
+      // If defaultValue is undefined (i.e., not provided in the template), this will return an empty string
+      return defaultValue || 'UNKNOWN';
+    }
+  });
+}
+// // Example usage:
+// const inputString = "This string has {{VARIABLE_NAME}} and {{MISSING_VARIABLE|default value}} to be {{foo.bar|default name}} replaced {{no_default.field}}.";
+
+// // Suppose VARIABLE_NAME is provided, but MISSING_VARIABLE is not
+// const variables = {
+//   VARIABLE_NAME: "some value",
+//   'foo.bar': 'nihao'
+//   // MISSING_VARIABLE is not provided, so its default value from the template should be used
+//   // no_default.field is not provided, the template have no default either, so it becomes "UNKNOWN"
+// };
+
+// const result = replaceVariableNameWithValueWithDefault(inputString, variables);
+// console.log(result):
+// // This string has some value and default value to be nihao replaced UNKNOWN.
+
 function recursivelyReplaceValues(tempObjectOrVal, mergeTagValues, ruleVariables) {
   if (!ruleVariables || ruleVariables.length <= 0) {
     return tempObjectOrVal;
   }
 
   if (typeof tempObjectOrVal === 'string') {
     let tempString = tempObjectOrVal;
+    const variablesAndValues = {};
     ruleVariables.forEach(function (ruleVar) {
       const varName = ruleVar.name;
-      const replacementValue = safeGet(mergeTagValues, varName) || 'UNKNOWN';
+      const replacementValue = safeGet(mergeTagValues, varName);
 
-      tempString = tempString.replace('{{' + varName + '}}', replacementValue);
+      if (replacementValue) {
+        variablesAndValues[varName] = replacementValue;
+      }
     });
 
-    return tempString;
+    const replacedString = replaceVariableNameWithValueWithDefault(tempString, variablesAndValues);
+    return replacedString;
   }
 
   if (isNil(tempObjectOrVal)) {

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "moesif-nodejs",
-  "version": "3.6.1",
+  "version": "3.6.2",
   "description": "Monitoring agent to log API calls to Moesif for deep API analytics",
   "main": "lib/index.js",
   "typings": "dist/index.d.ts",
@@ -48,7 +48,7 @@
     "assert": "^2.0.0",
     "blanket": "^1.2.3",
     "chai": "^4.3.10",
-    "express": "^4.17.2",
+    "express": "^4.19.2",
     "express-unless": "^1.0.0",
     "mocha": "^9.2.1",
     "node-mocks-http": "^1.11.0",