feat(config): config class added

At many points in the code we may want configurable options, the Config class usses a yaml file to make this easy. It also allows for namespace references "opac:lowtemp:file" etc...

src/config/public/config.h

@@ -0,0 +1,91 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <vector>
+#include <map>
+
+#include "yaml-cpp/yaml.h"
+
+/**
+ * @class Config
+ * @brief Singleton class to manage configuration settings loaded from a YAML file.
+ */
+class Config {
+ private:
+    /**
+     * @brief Private constructor to prevent instantiation.
+     */
+    Config();
+
+    /**
+     * @brief Destructor.
+     */
+    ~Config();
+
+    YAML::Node yamlRoot; ///< Root node of the YAML configuration.
+    std::string configFilePath; ///< Path to the configuration file.
+
+ public:
+    /**
+     * @brief Get the singleton instance of the Config class.
+     * @return Reference to the Config instance.
+     */
+    static Config& getInstance();
+
+    Config (const Config&) = delete;
+    Config& operator= (const Config&) = delete;
+    Config (Config&&) = delete;
+    Config& operator= (Config&&) = delete;
+
+    /**
+     * @brief Load configuration from a YAML file.
+     * @param configFilePath Path to the YAML configuration file.
+     * @return True if the configuration was loaded successfully, false otherwise.
+     */
+    bool loadConfig(const std::string& configFilePath);
+
+    /**
+     * @brief Get the input table from the configuration.
+     * @return Input table as a string.
+     */
+    std::string getInputTable() const;
+
+    /**
+     * @brief Get a configuration value by key.
+     * @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.
+     * 
+     * @example
+     * @code
+     * Config& config = Config::getInstance();
+     * config.loadConfig("example.yaml");
+     * int maxIter = config.get<int>("opac:lowTemp:numeric:maxIter", 10);
+     */
+   template <typename T>
+   T get(const std::string &key, T defaultValue) {
+      YAML::Node node = YAML::Clone(yamlRoot);
+      std::istringstream keyStream(key);
+      std::string subKey;
+      while (std::getline(keyStream, subKey, ':')) {
+         if (!node[subKey]) {
+               return defaultValue;
+         }
+         node = node[subKey]; // go deeper
+      }
+
+      try {
+         return node.as<T>();
+      } catch (const YAML::Exception& e) {
+         return defaultValue; // return default value if the key does not exist
+      }
+   }
+
+};
+
+#endif