cpp-logger/src/loggers/json_layout.cxx

//
//  json_layout.cxx
//  logging
//
//  Created by Sam Jaffe on 4/7/19.
//

#include <iterator>
#include <regex>

#include "resource_factory/prototype_factory.hpp"

#include "common.h"
#include "logger/detail/layout.h"
#include "logger/log_manager.h"
#include "logger/logpacket.h"
#include "logger/properties.h"

using namespace logging;

class json_layout : public layout {
public:
  static std::shared_ptr<layout> create(properties const &);
  
  json_layout(properties const & props);
  void format(std::ostream & os, logpacket const & pkt) const override;
  
private:
  Json::StreamWriterBuilder build;
  bool eol_, log_as_json_, include_location_;
};

using namespace logging::property;
properties const DEFAULT_JSON_LAYOUT{_obj({
  {"charset", _v("en_US.UTF-8")},
  {"compact", _v(false)},
  {"eventEol", _v(false)},
  {"complete", _v(false)},
  {"locationInfo", _v(false)},
  {"includeNullDelimiter", _v(false)},
  {"objectMessageAsJsonObject", _v(false)}
})};

std::shared_ptr<layout> json_layout::create(properties const & props) {
  properties const actual = DEFAULT_JSON_LAYOUT.mergedWith(props);
  return std::make_shared<json_layout>(actual);
}

json_layout::json_layout(properties const & props)
: eol_(props["eventEol"]),
  log_as_json_(props["objectMessageAsJsonObject"]),
  include_location_(props["locationInfo"])
{
  build["indentation"] = props["compact"] ? "" : "  ";
}

char const * filename(char const * str) {
  return strrchr(str, '/')+1;
}

void json_layout::format(std::ostream & os, logpacket const & pkt) const {
  Json::Value root;
  root["instant"]["epochSecond"] = (Json::UInt64) pkt.time.tv_sec;
  root["instant"]["nanoOfSecond"] = pkt.time.tv_usec * 1000;
  root["level"] = to_string(pkt.level, true);
  root["loggerName"] = pkt.logger;
  if (log_as_json_) {
    root["message"] = pkt.message.json();
  } else {
    root["message"] = pkt.message.str();
  }
  if (include_location_) {
    root["source"]["method"] = pkt.info.function;
    root["source"]["file"] = filename(pkt.info.filename);
    root["source"]["line"] = pkt.info.line;
  }
  std::string data = Json::writeString(build, root);
  // jsoncpp is dumb and writes a newline after each ':' token if
  // the child is an object or array.
  std::regex_replace(std::ostreambuf_iterator<char>(os),
                     data.begin(), data.end(),
                     std::regex(": \n(  )*(\\{|\\[)"), ": $2");
  if (eol_) {
    os << NEWLINE_TOKEN;
  }
}

namespace {
  bool _ = layouts::instance().bind("JsonLayout", json_layout::create);
}