Let us start here, from square one. No, from Zero!

api/module.cpp

@@ -0,0 +1,43 @@
+#include <utility>
+
+#include "util/logging.h"
+
+#include "module.h"
+
+using namespace rapidjson;
+
+namespace api {
+
+    // logging setting
+    bool LOGGING = false;
+
+    Module::Module(std::string name, bool password_force) {
+        this->name = std::move(name);
+        this->password_force = password_force;
+    }
+
+    void Module::handle(Request &req, Response &res) {
+
+        // log module access
+        if (LOGGING)
+            log_info("api::" + this->name, "handling request");
+
+        // find function
+        auto pos = functions.find(req.function);
+        if (pos == functions.end())
+            return error_function_unknown(res);
+
+        // call function
+        pos->second(req, res);
+    }
+
+    void Module::error(Response &res, std::string err) {
+
+        // log the warning
+        log_warning("api::" + this->name, "error: {}", err);
+
+        // add error to response
+        Value val(err.c_str(), res.doc()->GetAllocator());
+        res.add_error(val);
+    }
+}