logging.h

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#pragma once
 
// system includes
#include <functional>
#include <sstream>
#include <string>
 
namespace display_device {
  class Logger {
  public:
    enum class LogLevel {
      verbose = 0,  
      debug,  
      info,  
      warning,  
      error,  
      fatal  
    };
 
    using Callback = std::function<void(LogLevel, std::string)>;
 
    static Logger &get();
 
    void setLogLevel(LogLevel log_level);
 
    [[nodiscard]] bool isLogLevelEnabled(LogLevel log_level) const;
 
    void setCustomCallback(Callback callback);
 
    void write(LogLevel log_level, std::string value);
 
    Logger(Logger const &) = delete;
 
    void operator=(Logger const &) = delete;
 
  private:
    explicit Logger();
 
    LogLevel m_enabled_log_level; 
    Callback m_custom_callback; 
  };
 
  class LogWriter {
  public:
    explicit LogWriter(Logger::LogLevel log_level);
 
    virtual ~LogWriter();
 
    template<class T>
    LogWriter &operator<<(T &&value) {
      m_buffer << std::forward<T>(value);
      return *this;
    }
 
  private:
    Logger::LogLevel m_log_level; 
    std::ostringstream m_buffer; 
  };
}  // namespace display_device
 
#define DD_LOG(level) \
  for (bool is_enabled {display_device::Logger::get().isLogLevelEnabled(display_device::Logger::LogLevel::level)}; is_enabled; is_enabled = false) \
  display_device::LogWriter(display_device::Logger::LogLevel::level)