cpp-engine/include/engine/config.h

//
//  config.h
//  pokemon-engine
//
//  Created by Sam Jaffe on 12/22/18.
//  Copyright © 2018 Sam Jaffe. All rights reserved.
//

#pragma once

#include <filesystem>
#include <map>
#include <memory>
#include <string>

#include <json/forwards.h>

namespace engine::env {
class Config {
private:
  std::filesystem::path config_path_{""};
  std::filesystem::path resource_path_;
  std::map<std::string, std::string> properties_;

public:
  /**
   * @brief Load this configuration from a JSON file on disk.
   * @param filepath The absolute path to a JSON config file.
   * @throws std::logic_error if any of the following:
   * - filepath is empty (i.e. Config cfg = Config("");)
   * - filepath is not an absolute UNIX-style path
   * - The file is readable and exists.
   */
  Config(std::filesystem::path const & filepath);
  ~Config();

  /**
   * @brief Obtain the absolute path to a resource, as determined by the
   * properties loaded into this object. For example,
   * @code std::string image_path = cfg.resource("sprites/nurse_joy.png");
   * @param rel_path The relative path to the resource file we are searching
   * for.
   * @return The absolute path to the file
   */
  std::filesystem::path resource(std::filesystem::path const & rel_path) const;

  /**
   * @brief Fetch a singluar property that exists within the object
   * @param name The property name being fetched
   * @param fallback A fallback value in case that the object is absent
   * @return The property being read in
   */
  std::string const & property(std::string const & name,
                               std::string const & fallback) const;

protected:
  /**
   * @brief Construct a config from a raw json blob. Primarily for testing.
   * @param json A json object containing certain properties
   */
  Config(Json::Value const & json,
         std::filesystem::path const & config_path = "/");

private:
  std::filesystem::path fix(std::filesystem::path input) const;
};
}