perf(config): added cache

In order to prevent traversing the YAML tree I have added a hash map (O(1) lookup) to cache already accessed config variables. I have also added a vector to store keys requested but not found so we do not need to check for those every time

src/config/private/config.cpp

@@ -29,3 +29,14 @@ bool Config::loadConfig(const std::string& configFile) {
     return true;
 }
 
+bool Config::isKeyInCache(const std::string &key) {
+    return configMap.find(key) != configMap.end();
+}
+
+void Config::addToCache(const std::string &key, const YAML::Node &node) {
+    configMap[key] = node;
+}
+
+void Config::registerUnknownKey(const std::string &key) {
+    unknownKeys.push_back(key);
+}

src/config/public/config.h

@@ -7,6 +7,7 @@
 #include <sstream>
 #include <vector>
 #include <map>
+#include <algorithm>
 
 #include "yaml-cpp/yaml.h"
 
@@ -28,6 +29,50 @@ class Config {
 
    YAML::Node yamlRoot; ///< Root node of the YAML configuration.
    std::string configFilePath; ///< Path to the configuration file.
+   bool debug = false; ///< Flag to enable debug output.
+
+   std::map<std::string, YAML::Node> configMap; ///< Cache for the location of configuration settings.
+   std::vector<std::string> unknownKeys; ///< Cache for the existence of configuration settings.
+
+   /**
+    * @brief Get a value from the configuration cache.
+    * @tparam T Type of the value to retrieve.
+    * @param key Key of the configuration value.
+    * @param defaultValue Default value to return if the key does not exist.
+    * @return Configuration value of type T.
+    */
+   template <typename T>
+   T getFromCache(const std::string &key, T defaultValue) {
+      if (configMap.find(key) != configMap.end()) {
+         try {
+               return configMap[key].as<T>();
+         } catch (const YAML::Exception& e) {
+               return defaultValue;
+         }
+      }
+      return defaultValue;
+   }
+
+
+   /**
+    * @brief Check if a key exists in the configuration cache.
+    * @param key Key to check.
+    * @return True if the key exists in the cache, false otherwise.
+    */
+   bool isKeyInCache(const std::string &key);
+
+   /**
+    * @brief Add a key-value pair to the configuration cache.
+    * @param key Key of the configuration value.
+    * @param node YAML node containing the configuration value.
+    */
+   void addToCache(const std::string &key, const YAML::Node &node);
+
+   /**
+    * @brief Register a key as not found in the configuration.
+    * @param key Key that was not found.
+    */
+   void registerUnknownKey(const std::string &key);
 
 public:
    /**
@@ -41,6 +86,8 @@ class Config {
    Config (Config&&) = delete;
    Config& operator= (Config&&) = delete;
 
+   void setDebug(bool debug) { this->debug = debug; }
+
    /**
     * @brief Load configuration from a YAML file.
     * @param configFilePath Path to the YAML configuration file.
@@ -69,23 +116,54 @@ class Config {
     */
    template <typename T>
    T get(const std::string &key, T defaultValue) {
+      // --- Check if the key has already been checked for existence 
+      if (std::find(unknownKeys.begin(), unknownKeys.end(), key) != unknownKeys.end()) {
+         return defaultValue; // If the key has already been added to the unknown cache do not traverse the YAML tree or hit the cache
+      }
+
+      // --- Check if the key is already in the cache (avoid traversing YAML nodes)
+      if (isKeyInCache(key)) {
+         return getFromCache<T>(key, defaultValue);
+      }
+      // --- If the key is not in the cache, check the YAML file
+      else {
          YAML::Node node = YAML::Clone(yamlRoot);
          std::istringstream keyStream(key);
          std::string subKey;
          while (std::getline(keyStream, subKey, ':')) {
             if (!node[subKey]) {
+                  // Key does not exist
+                  registerUnknownKey(key);
                   return defaultValue;
             }
             node = node[subKey]; // go deeper
          }
 
          try {
+            // Key exists and is of the requested type
+            addToCache(key, node);
             return node.as<T>();
          } catch (const YAML::Exception& e) {
+            // Key is not of the requested type
+            registerUnknownKey(key);
             return defaultValue; // return default value if the key does not exist
          }
       }
+   }
 
+   friend std::ostream& operator<<(std::ostream& os, const Config& config) {
+      if (!config.debug) {
+         os << "Config file: " << config.configFilePath << std::endl;
+      } else{
+         // Print entire YAML file from root
+         os << "Config file: " << config.configFilePath << std::endl;
+         os << config.yamlRoot << std::endl;
+      }
+      return os;
+   }
+
+   // Setup gTest class as a friend
+   friend class configTestPrivateAccessor;
 };
 
 #endif