cpp-logger/include/logger/format.hpp

//
//  format.hpp
//  logger
//
//  Created by Sam Jaffe on 8/21/16.
//

#pragma once

#include <functional>
#include <sstream>
#include <string>
#include <vector>

#include "logger_fwd.hpp"

namespace logging {
  class format {
  public:
    enum class token_id {
      DATE, PRIORITY, CATEGORY, MESSAGE, STRING, NEWLINE
    };
    
    using generator = std::function<void(logpacket const &, std::ostream &)>;
    
  private:
    static format parse_format_string(std::string const &);    
    std::vector<generator> gen;
  };
  
  inline void format_msg( std::stringstream & msg,
                         std::string const & interp, size_t pos) {
    msg << interp.substr(pos);
  }
  
  struct format_point_t {
    size_t start;
    size_t end;
  };
  
  format_point_t get_next_format_specifier( std::string const & interp, size_t pos );
  
  template <typename Arg0, typename... Args>
  inline void format_msg( std::stringstream & msg,
                         std::string const & interp, size_t pos,
                         Arg0 && arg0, Args && ...args ) {
    format_point_t next = get_next_format_specifier( interp, pos );
    msg << interp.substr(pos, next.start) << arg0;
    if ( next.start == std::string::npos ) return; // throw?
    format_msg( msg, interp, next.end,
               std::forward<Args>(args)... );
  }
  
  template <typename... Args>
  inline std::string format_msg( std::string const & interp,
                                Args && ...args ) {
    std::stringstream msg;
    format_msg<Args...>( msg, interp, 0, std::forward<Args>(args)... );
    return msg.str();
  }
}