'use strict';

/**
 * @license
 * Copyright 2016 Leif Olsen. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * A javascript utility for conditionally creating a list of strings.
 * The function takes any number of arguments which can be a string or object.
 * Inspired by (but not copied from) JedWatson/classnames, https://github.com/JedWatson/classnames
 *
 * @param  {*} args the strings and/or objects to
 * @return {Array} a list of strings
 * @example
 * // Returns ['foo', 'bar', 'baz', 'quux']
 * stringList(', ', 'foo', { bar: true, duck: false }, 'baz', { quux: true });
 * @example see the tests for more examples
 */
const stringList = (...args) => {

  const isString = str => str != null && typeof str === 'string';

  const flatten = list => list.reduce((a, b) => a.concat(Array.isArray(b) ? flatten(b) : b), []);

  const objectToStrings = arg =>
    Object.keys(arg)
      .filter(key => arg[key])
      .map(key => key);

  return args
    .filter(arg => !!arg)
    .map(arg => isString(arg) ? arg : objectToStrings(arg))
    .reduce((result, arg) => result.concat(Array.isArray(arg) ? flatten(arg) : arg), []);
};

/**
 * A simple javascript utility for conditionally joining strings together.
 * The function takes a delimiter string and any number of arguments which can be a string or object.
 *
 * @param delimiter delimiter to separate joined strings
 * @param  {*} args the strings and/or objects to join
 * @return {String} the joined strings
 * @example
 * // Returns 'foo, bar, baz, quux'
 * joinStrings(', ', 'foo', { bar: true, duck: false }, 'baz', { quux: true });
 * @example see the tests for more examples
 */
const joinStrings = (delimiter = ' ', ...args) => stringList(...args).join(delimiter);

/**
 * Generates a random string with a given length
 * @param n {Integer} length of generated string
 * @see http://stackoverflow.com/questions/1349404/generate-random-string-characters-in-javascript
 * @return {String} the random string
 * @example
 * // Returns e.g. 'pd781w0y'
 * randomString(8);
 * @example see the tests for more examples
 */
const randomString = ( n=12 ) => Array( n+1 ).join((`${Math.random().toString(36)}00000000000000000`).slice(2, 18)).slice(0, n);

export { joinStrings, randomString, stringList };