"use strict";
var path = require('path')
, fs = require('fs')
, streams = require('streamroller')
, os = require('os')
, eol = os.EOL || '\n'
, openFiles = [];

//close open files on process exit.
process.on('exit', function() {
  openFiles.forEach(function (file) {
    file.end();
  });
});

module.exports = function(layouts, levels) {

  /**
   * File Appender writing the logs to a text file. Supports rolling of logs by size.
   *
   * @param file 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)
   */
  function fileAppender (file, layout, logSize, numBackups) {
    var bytesWritten = 0;
    file = path.normalize(file);
    layout = layout || layouts.basicLayout;
    numBackups = numBackups === undefined ? 5 : numBackups;
    //there has to be at least one backup if logSize has been specified
    numBackups = numBackups === 0 ? 1 : numBackups;
    
    function openTheStream(file, fileSize, numFiles) {
      var stream;
      if (fileSize) {
        stream = new streams.RollingFileStream(
          file,
          fileSize,
          numFiles
        );
      } else {
        stream = fs.createWriteStream(
          file, 
          { encoding: "utf8", 
            mode: parseInt('0644', 8), 
            flags: 'a' }
        );
      }
      stream.on("error", function (err) {
        console.error("log4js.fileAppender - Writing to file %s, error happened ", file, err);
      });
      return stream;
    }

    var logFile = openTheStream(file, logSize, numBackups);
  
    // push file to the stack of open handlers
    openFiles.push(logFile);
  
    return function(loggingEvent) {
      logFile.write(layout(loggingEvent) + eol, "utf8");
    };
  }

  return function configure(config) {
    var layout;
    if (config.layout) {
      layout = layouts.layout(config.layout.type, config.layout);
    }

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

};