cpp-logger/src/loggers/pattern_layout_format.cxx

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

#include <cstdint>
#include <cstring>
#include <ctime>
#include <iomanip>
#include <iostream>
#include <map>
#include <stdexcept>
#include <string>

#include "common.h"
#include "logger/exception.h"
#include "logger/logger.h"
#include "logger/logpacket.h"
#include "logger/message.h"
#include "pattern_layout.h"

namespace logging { namespace {
  struct log_handle_gen : public format::generator_t {
    std::string str(logpacket const & lp) const override {
      return lp.logger;
    }
    void write(logpacket const & lp, std::ostream & os) const override {
      os << lp.logger;
    }
  };

  struct level_gen : public format::generator_t {
    std::string str(logpacket const & lp) const override {
      return to_string(lp.level, true);
    }
  };

  struct location_info_gen : public format::generator_t {
    enum { method, line, file } where;
    constexpr static const decltype(where) format_codes[] = {
      ['F'] = file,
      ['M'] = method,
      ['L'] = line,
    };

    location_info_gen(char wh) : where(format_codes[wh]) {}
    std::string str(logpacket const & lp) const override {
      switch (where) {
        case file:
          return lp.info.filename;
        case line:
          return std::to_string(lp.info.line);
        case method:
          return lp.info.function;
      }
    }
  };

  struct message_gen : public format::generator_t {
    std::string str(logpacket const & lp) const override {
      return lp.message.str();
    }
  };
  
  struct literal_gen : public format::generator_t {
    literal_gen(std::string const & value) : value(value) {}
    std::string str(logpacket const & lp) const override {
      return value;
    }
    void write(logpacket const & lp, std::ostream & os) const override {
      os << value;
    }
    std::string value;
  };
  
  struct bounds_gen : public format::generator_t {
    bounds_gen(format::generator impl, bool is_left, int min, size_t max)
    : impl(impl), is_left(is_left), min(min), max(max) {}
    std::string str(logpacket const & lp) const override {
      return impl->str(lp);
    }
    void write(logpacket const & lp, std::ostream & os) const override {
      auto align = is_left ? std::left : std::right;
      std::string str = this->str(lp);
      if (str.length() > max) {
        str.erase(str.begin()+max, str.end());
      }
      os << align << std::setw(min) << str;
    }
    format::generator impl;
    bool is_left;
    int min;
    size_t max;
  };
} }

namespace logging {
#define is( chr ) *next == chr
#define is_string( str ) ! strncmp(next, str, strlen(str))
  format::generator date_token(char const * next);

  format::generator handle( char const * & next ) {
    if (is('c')) {
      return std::make_shared<log_handle_gen>();
    } else if (is('p')) {
      return std::make_shared<level_gen>();
    } else if (is('m')) {
      return std::make_shared<message_gen>();
    } else if (is('t')) {
      return std::make_shared<literal_gen>("???");
    } else if (is('F') || is('M') || is('L')) {
      return std::make_shared<location_info_gen>(*next);
    } else {
      std::string error_msg{"unknown format character: '"};
      throw unknown_format_specifier{error_msg + *next + "'"};
    }
  }
  
  int eat(char const * & token) {
    size_t chars = 0;
    int rval = std::stoi(token, &chars);
    token += chars;
    return rval;
  }
  
  std::pair<int, size_t> get_bounds(char const * & next) {
    int min = *next == '.' ? 0 : eat(next);
    size_t max = *next == '.' ? eat(++next) : std::string::npos;
    return std::make_pair(min, max);
  }
  
  format::generator parse_with_bounds(char const * & next) {
    bool const is_left = *next == '-';
    if (is_left) ++next;
    
    auto bounds = get_bounds(next);
    
    bounds_gen gen{handle(next), is_left, bounds.first, bounds.second};
    return std::make_shared<bounds_gen>(gen);
  }
  
  format format::parse_format_string( std::string const & fmt ) {
    format out;
    char const * curr = fmt.c_str();
    char const * next = nullptr;
    char const * const end = curr + fmt.size();
    
    while ((next = std::strchr(curr, '%')) != nullptr) {
      ++next;
      if (end == next) {
        std::string error_msg{"expected format specifier, got end of string"};
        throw format_parsing_exception{error_msg}; // TODO
      }
      
      if (curr < next-1) {
        std::string lit{curr, next - 1};
        out.gen.push_back(std::make_shared<literal_gen>(lit));
      }

      if (is('d')) {
        ++next;
        out.gen.push_back(date_token(next));
        if (is('{')) next = std::strchr(next, '}');
      } else if (is('n')) {
        out.gen.push_back(std::make_shared<literal_gen>(NEWLINE_TOKEN));
      } else if (is('%')) {
        out.gen.push_back(std::make_shared<literal_gen>("%"));
      } else if (is('.') || is('-') || isdigit( *next )) {
        out.gen.push_back(parse_with_bounds(next));
      } else {
        out.gen.push_back(handle(next));
      }
      curr = ++next;
    }
    if (curr < end) {
      std::string lit{curr, end};
      out.gen.push_back(std::make_shared<literal_gen>(lit));
    }
    return out;
  }
#undef is
  
  void format::process(logpacket const & pkt, std::ostream & os) const {
    for (auto func : gen) { func->write(pkt, os); }
  }
  
  std::string format::process(logpacket const & pkt) const {
    std::stringstream ss;
    process(pkt, ss);
    return ss.str();
  }
}