text: /**
   * (c) 2017 cepharum GmbH, Berlin, http://cepharum.de
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2017 cepharum GmbH
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   *
   * @author: cepharum
   */
  
  "use strict";
  
  const Path = require( "path" );
  const File = require( "fs" );
  
  
  module.exports = createFile;
  
  
  /**
   * Creates file with random name in context of provided folder.
   *
   * @param {string} containerPathName path name of folder to contain created one
   * @param {string} extension extension to append optionally
   * @returns {Promise<Writable>}
   */
  function createFile( containerPathName, extension ) {
  	return new Promise( ( resolve, reject ) => {
  		_try();
  
  		/**
  		 * Tries to create file with random name in selected folder.
  		 *
  		 * @private
  		 */
  		function _try() {
  			File.readdir( containerPathName, ( error, entries ) => {
  				if ( error ) {
  					return reject( Object.assign( new Error( "failed generating random session ID" ), { httpCode: 500 } ) );
  				}
  
  				let found = 0;
  
  				for ( let i = 0, length = entries.length; i < length; i++ ) {
  					let name = entries[i];
  
  					if ( name[0] !== "." && name.slice( -extension.length ) === extension ) {
  						found++;
  					}
  				}
  
  				const pathName = Path.join( containerPathName, String( "000" + ++found ).slice( -4 ) + extension.replace( /\.\./g, "" ) );
  
  				try {
  					resolve( File.createWriteStream( pathName, {
  						flags: "wx+",
  						mode: "0600",
  					} ) );
  				} catch ( error ) {
  					if ( error.code === "EEXIST" ) {
  						// got a collision -> try another name
  						process.nextTick( _try );
  					} else {
  						return reject( Object.assign( new Error( "creating session storage failed" ), { httpCode: 500 } ) );
  					}
  				}
  			} );
  		}
  	} );
  }
  