text: // Copyright (c) 2019-2020 The Beans Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BEANS_UTIL_SETTINGS_H
  #define BEANS_UTIL_SETTINGS_H
  
  #include <fs.h>
  
  #include <map>
  #include <string>
  #include <vector>
  
  class UniValue;
  
  namespace util {
  
  //! Settings value type (string/integer/boolean/null variant).
  //!
  //! @note UniValue is used here for convenience and because it can be easily
  //!       serialized in a readable format. But any other variant type that can
  //!       be assigned strings, int64_t, and bool values and has get_str(),
  //!       get_int64(), get_bool(), isNum(), isBool(), isFalse(), isTrue() and
  //!       isNull() methods can be substituted if there's a need to move away
  //!       from UniValue. (An implementation with boost::variant was posted at
  //!       https://github.com/beans/beans/pull/15934/files#r337691812)
  using SettingsValue = UniValue;
  
  //! Stored settings. This struct combines settings from the command line, a
  //! read-only configuration file, and a read-write runtime settings file.
  struct Settings {
      //! Map of setting name to forced setting value.
      std::map<std::string, SettingsValue> forced_settings;
      //! Map of setting name to list of command line values.
      std::map<std::string, std::vector<SettingsValue>> command_line_options;
      //! Map of setting name to read-write file setting value.
      std::map<std::string, SettingsValue> rw_settings;
      //! Map of config section name and setting name to list of config file values.
      std::map<std::string, std::map<std::string, std::vector<SettingsValue>>> ro_config;
  };
  
  //! Read settings file.
  bool ReadSettings(const fs::path& path,
      std::map<std::string, SettingsValue>& values,
      std::vector<std::string>& errors);
  
  //! Write settings file.
  bool WriteSettings(const fs::path& path,
      const std::map<std::string, SettingsValue>& values,
      std::vector<std::string>& errors);
  
  //! Get settings value from combined sources: forced settings, command line
  //! arguments, runtime read-write settings, and the read-only config file.
  //!
  //! @param ignore_default_section_config - ignore values in the default section
  //!                                        of the config file (part before any
  //!                                        [section] keywords)
  //! @param get_chain_name - enable special backwards compatible behavior
  //!                         for GetChainName
  SettingsValue GetSetting(const Settings& settings,
      const std::string& section,
      const std::string& name,
      bool ignore_default_section_config,
      bool get_chain_name);
  
  //! Get combined setting value similar to GetSetting(), except if setting was
  //! specified multiple times, return a list of all the values specified.
  std::vector<SettingsValue> GetSettingsList(const Settings& settings,
      const std::string& section,
      const std::string& name,
      bool ignore_default_section_config);
  
  //! Return true if a setting is set in the default config file section, and not
  //! overridden by a higher priority command-line or network section value.
  //!
  //! This is used to provide user warnings about values that might be getting
  //! ignored unintentionally.
  bool OnlyHasDefaultSectionSetting(const Settings& settings, const std::string& section, const std::string& name);
  
  //! Accessor for list of settings that skips negated values when iterated over.
  //! The last boolean `false` value in the list and all earlier values are
  //! considered negated.
  struct SettingsSpan {
      explicit SettingsSpan() = default;
      explicit SettingsSpan(const SettingsValue& value) noexcept : SettingsSpan(&value, 1) {}
      explicit SettingsSpan(const SettingsValue* data, size_t size) noexcept : data(data), size(size) {}
      explicit SettingsSpan(const std::vector<SettingsValue>& vec) noexcept;
      const SettingsValue* begin() const; //!< Pointer to first non-negated value.
      const SettingsValue* end() const;   //!< Pointer to end of values.
      bool empty() const;                 //!< True if there are any non-negated values.
      bool last_negated() const;          //!< True if the last value is negated.
      size_t negated() const;             //!< Number of negated values.
  
      const SettingsValue* data = nullptr;
      size_t size = 0;
  };
  
  //! Map lookup helper.
  template <typename Map, typename Key>
  auto FindKey(Map&& map, Key&& key) -> decltype(&map.at(key))
  {
      auto it = map.find(key);
      return it == map.end() ? nullptr : &it->second;
  }
  
  } // namespace util
  
  #endif // BEANS_UTIL_SETTINGS_H
  