class Logger
{
 public:
  static const std::string kLogLevelDebug;
  static const std::string kLogLevelInfo;
  static const std::string kLogLevelError;

  // Returns a reference to the singleton Logger object
  static Logger& instance();

  // Logs a single message at the given log level
  void log(const std::string& inMessage, 
           const std::string& inLogLevel);

  // Logs a vector of messages at the given log level
  void log(const std::vector& inMessages, 
           const std::string& inLogLevel);

 protected:
  // Static variable for the one-and-only instance  
  static Logger sInstance;

  // Constant for the file namename
  static const char* const kLogFileName;

  // Data member for the output stream
  std::ofstream mOutputStream;

 private:
  Logger();
  ~Logger();

};