file.js

const debug = require('debug')('log4js:file');
const path = require('path');
const streams = require('streamroller');
const os = require('os');

const eol = os.EOL;

let mainSighupListenerStarted = false;
const sighupListeners = new Set();
function mainSighupHandler() {
  sighupListeners.forEach((app) => {
    app.sighupHandler();
  });
}

/**
 * File Appender writing the logs to a text file. Supports rolling of logs by size.
 *
 * @param file the file log messages will be written to
 * @param layout a function that takes a logEvent and returns a string
 *   (defaults to basicLayout).
 * @param logSize - the maximum size (in bytes) for a log file,
 *   if not provided then logs won't be rotated.
 * @param numBackups - the number of log files to keep after logSize
 *   has been reached (default 5)
 * @param options - options to be passed to the underlying stream
 * @param timezoneOffset - optional timezone offset in minutes (default system local)
 */
function fileAppender(
  file,
  layout,
  logSize,
  numBackups,
  options,
  timezoneOffset
) {
  if (typeof file !== 'string' || file.length === 0) {
    throw new Error(`Invalid filename: ${file}`);
  } else if (file.endsWith(path.sep)) {
    throw new Error(`Filename is a directory: ${file}`);
  } else if (file.indexOf(`~${path.sep}`) === 0) {
    // handle ~ expansion: https://github.com/nodejs/node/issues/684
    // exclude ~ and ~filename as these can be valid files
    file = file.replace('~', os.homedir());
  }
  file = path.normalize(file);
  numBackups = !numBackups && numBackups !== 0 ? 5 : numBackups;

  debug(
    'Creating file appender (',
    file,
    ', ',
    logSize,
    ', ',
    numBackups,
    ', ',
    options,
    ', ',
    timezoneOffset,
    ')'
  );

  function openTheStream(filePath, fileSize, numFiles, opt) {
    const stream = new streams.RollingFileStream(
      filePath,
      fileSize,
      numFiles,
      opt
    );
    stream.on('error', (err) => {
      // eslint-disable-next-line no-console
      console.error(
        'log4js.fileAppender - Writing to file %s, error happened ',
        filePath,
        err
      );
    });
    stream.on('drain', () => {
      process.emit('log4js:pause', false);
    });
    return stream;
  }

  let writer = openTheStream(file, logSize, numBackups, options);

  const app = function (loggingEvent) {
    if (!writer.writable) {
      return;
    }
    if (options.removeColor === true) {
      // eslint-disable-next-line no-control-regex
      const regex = /\x1b[[0-9;]*m/g;
      loggingEvent.data = loggingEvent.data.map((d) => {
        if (typeof d === 'string') return d.replace(regex, '');
        return d;
      });
    }
    if (!writer.write(layout(loggingEvent, timezoneOffset) + eol, 'utf8')) {
      process.emit('log4js:pause', true);
    }
  };

  app.reopen = function () {
    writer.end(() => {
      writer = openTheStream(file, logSize, numBackups, options);
    });
  };

  app.sighupHandler = function () {
    debug('SIGHUP handler called.');
    app.reopen();
  };

  app.shutdown = function (complete) {
    sighupListeners.delete(app);
    if (sighupListeners.size === 0 && mainSighupListenerStarted) {
      process.removeListener('SIGHUP', mainSighupHandler);
      mainSighupListenerStarted = false;
    }
    writer.end('', 'utf-8', complete);
  };

  // On SIGHUP, close and reopen all files. This allows this appender to work with
  // logrotate. Note that if you are using logrotate, you should not set
  // `logSize`.
  sighupListeners.add(app);
  if (!mainSighupListenerStarted) {
    process.on('SIGHUP', mainSighupHandler);
    mainSighupListenerStarted = true;
  }

  return app;
}

function configure(config, layouts) {
  let layout = layouts.basicLayout;
  if (config.layout) {
    layout = layouts.layout(config.layout.type, config.layout);
  }

  // security default (instead of relying on streamroller default)
  config.mode = config.mode || 0o600;

  return fileAppender(
    config.filename,
    layout,
    config.maxLogSize,
    config.backups,
    config,
    config.timezoneOffset
  );
}

module.exports.configure = configure;