Hallucinate a json mode implementation

processor/processor.go

@@ -300,6 +300,26 @@ func BuildLuaScript(luaExpr string) string {
 	return fullScript
 }
 
+// BuildJSONLuaScript prepares a Lua expression for JSON mode
+func BuildJSONLuaScript(luaExpr string) string {
+	buildJsonLuaScriptLogger := processorLogger.WithPrefix("BuildJSONLuaScript").WithField("inputLuaExpr", luaExpr)
+	buildJsonLuaScriptLogger.Debug("Building full Lua script for JSON mode from expression")
+
+	// Perform $var substitutions from globalVariables
+	luaExpr = replaceVariables(luaExpr)
+
+	fullScript := fmt.Sprintf(`
+		function run()
+			%s
+		end
+		local res = run()
+		modified = res == nil or res
+	`, luaExpr)
+	buildJsonLuaScriptLogger.Trace("Generated full JSON Lua script: %q", utils.LimitString(fullScript, 200))
+
+	return fullScript
+}
+
 func replaceVariables(expr string) string {
 	// $varName -> literal value
 	varNameRe := regexp.MustCompile(`\$(\w+)`)