cpp-logger/include/logger/format.h

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

#pragma once

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

#include "logger_fwd.h"

namespace logging {
  class format {
  public:
    enum class token_id {
      DATE, PRIORITY, CATEGORY, MESSAGE, STRING, NEWLINE
    };
    
    using generator = std::function<void(logpacket const &, std::ostream &)>;
    
    static format parse_format_string(std::string const &);
    void process(logpacket const & pkt, std::ostream & os) const;
    std::string process(logpacket const & pkt) const;
  private:
    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);
    if (next.start == std::string::npos) {
      return; // throw?
    } else if (!strncmp(interp.c_str() + next.start - 1, "{{}}", 4)) {
      format_msg(msg, interp, next.end, std::forward<Arg0>(arg0),
                 std::forward<Args>(args)... );
    } else {
      msg << arg0;
      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();
  }
}