config2.2.hpp

config2.2.hpp

  /// non-templated base class for all config definition types.
  struct ConfigDefinitionBase 
  {
    ConfigDefinitionBase(std::string section_,
                         std::string name_,
                         bool required_,
                         bool multiValued_);

    virtual ~ConfigDefinitionBase();

    /// subclasses should provide their default value as a string
    virtual std::string defaultValueAsString() = 0;

    /// subclasses should parse and store the provided input
    virtual void parseValue(const std::string& input) = 0;

    /// subclasess should write their parsed value (not default value) as a string
    virtual std::string writeValue() = 0;

    std::string section;
    std::string name;
    bool required = false;
    bool multiValued = false;
  };

  // NEW
  template<typename T>
  struct ConfigDefinition : public ConfigDefinitionBase
  {
    ConfigDefinition(std::string section_,
                           std::string name_,
                           bool required_,
                           bool multiValued_,
                           nonstd::optional<T> defaultValue);

    // NEW
    T getValue();

    // TODO: override virtual functions

    // NEW
    std::optional<T> parsedValue; // needs to be set when parseValue() called
  };


  using ConfigDefinition_ptr = std::unique_ptr<ConfigDefinitionBase>;

  /// A configuration holds an ordered set of ConfigDefinitions defining the allowable values and
  /// their constraints and an optional set defining overrides of those values (e.g. the results
  /// of a parsed config file).
  struct Configuration {
    std::unordered_map<std::string, std::set<ConfigDefinition_ptr>> definitions;
    std::unordered_map<std::string, ConfigDefinition_ptr>> configItems;

    Configuration& addDefinition(ConfigDefinition_ptr def);

    Configuration& addConfigItem(ConfigDefinition_ptr item);

    // NEW
    template<typename t>
    getValue(string_view section, string_view name)

    std::string
    generateDefaultConfig();

    std::string
    generateOverridenConfig();
  };

  void defineSomeConig()
  {
    Configuration config;
    config.addDefinition(std::make_unique<IntConfigDefinition>(
          "router",
          "threads",
          false,
          false,
          4);

    config.addDefinition(std::make_unique<StringConfigDefinition>(
        "router",
        "contact-file",
        true,
        false,
        nullptr);
  }