json-field-handler.hpp

#ifndef JSON_FIELD_HANDLER_HPP
#define JSON_FIELD_HANDLER_HPP

#include <string>
#include <unordered_map>
#include <nlohmann/json.hpp>
#include <utility>

/**
 * JsonFieldHandler class is a utility class that provides field names for the JSON configuration file.
 *
 * It also provides methods to retrieve the field values from the JSON configuration file.
 *
 * It is a kind of wrapper around the JSON object of the nlohmann::json library.
 */
class JsonFieldHandler {
public:
  /**
   * Enum class for the field names in the JSON configuration file.
   */
  enum class Field {
    SignalDomain,
    SignalLength,
    HzFrequency,
    Phase,
    Noise,
    Seed
  };

  /**
   * Returns true if the field is a valid field in the JSON configuration file.
   * @param field The field name as a string.
   * @return True if the field is valid, false otherwise.
   */
  static bool hasField(const std::string &field);

  /**
   * Get the field name from the field enum.
   * @param field The field enum.
   * @return The field name.
   */
  static std::string getFieldName(Field field);

  /**
   * Constructor that takes a JSON configuration data.
   * @param json The JSON configuration data.
   * @throw std::runtime_error If the JSON cannot be parsed.
   * @throw std::invalid_argument If the JSON is not valid or the required fields are missing.
   */
  explicit JsonFieldHandler(nlohmann::json json) : configurationLoaded(std::move(json)) {
    // validate the configuration data, throw an exception if it is not valid
    validation();
  }
  // use std::move to move the json object to the configurationLoaded field
  // to avoid copying (or deep copying) the json object

  /**
   * Get the configuration data that was loaded as a JSON object.
   * Not modifiable and not recommended. Use the getter methods instead.
   * @return The configuration data as a JSON object.
   */
  [[nodiscard]] const nlohmann::json &getConfigurationLoaded() const;

  /**
   * Get the signal domain fields from the configuration data.
   * @return The signal domain.
   * @throw std::runtime_error If the signal domain is null.
   */
  [[nodiscard]] std::string getSignalDomain() const;

  /**
   * Get the signal length fields from the configuration data.
   * @return The signal length.
   * @throw std::runtime_error If the signal length is null.
   */
  [[nodiscard]] int getSignalLength() const;

  /**
   * Get the Hz frequency fields from the configuration data.
   * @return The Hz frequency.
   */
  [[nodiscard]] double getHzFrequency() const;

  /**
   * Get the phase fields from the configuration data.
   * @return The phase.
   */
  [[nodiscard]] double getPhase() const;

  /**
   * Get the noise fields from the configuration data.
   * @return The noise.
   */
  [[nodiscard]] double getNoise() const;

  /**
   * Get the seed fields from the configuration data.
   * @return The seed.
   * @throw std::runtime_error If the seed is null.
   */
  [[nodiscard]] int getSeed() const;

  /**
   * Check if the configuration data has a seed. Because the seed is optional, it may not be present.
   * @return True if the configuration data has a seed; false otherwise.
   */
  [[nodiscard]] bool hasSeed() const;

private:
  /**
   * Unordered map that maps the field enum to the field name.
   */
  static const std::unordered_map<Field, std::string> fieldNames;
  nlohmann::json configurationLoaded;

  /**
   * Validate the configuration data.
   *
   * TODO: The json schema should be used to validate the configuration data.
   * @throw std::invalid_argument If the configuration data is not valid or the required fields are missing.
   */
  void validation() const;
};

#endif //JSON_FIELD_HANDLER_HPP