import _parallel from './internal/parallel.js'
import eachOfSeries from './eachOfSeries.js'

/**
 * Run the functions in the `tasks` collection in series, each one running once
 * the previous function has completed. If any functions in the series pass an
 * error to its callback, no more functions are run, and `callback` is
 * immediately called with the value of the error. Otherwise, `callback`
 * receives an array of results when `tasks` have completed.
 *
 * It is also possible to use an object instead of an array. Each property will
 * be run as a function, and the results will be passed to the final `callback`
 * as an object instead of an array. This can be a more readable way of handling
 *  results from {@link async.series}.
 *
 * **Note** that while many implementations preserve the order of object
 * properties, the [ECMAScript Language Specification](http://www.ecma-international.org/ecma-262/5.1/#sec-8.6)
 * explicitly states that
 *
 * > The mechanics and order of enumerating the properties is not specified.
 *
 * So if you rely on the order in which your series of functions are executed,
 * and want this to work on all platforms, consider using an array.
 *
 * @name series
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {Array|Iterable|AsyncIterable|Object} tasks - A collection containing
 * [async functions]{@link AsyncFunction} to run in series.
 * Each function can complete with any number of optional `result` values.
 * @param {Function} [callback] - An optional callback to run once all the
 * functions have completed. This function gets a results array (or object)
 * containing all the result arguments passed to the `task` callbacks. Invoked
 * with (err, result).
 * @return {Promise} a promise, if no callback is passed
 * @example
 *
 * //Using Callbacks
 * async.series([
 *     function(callback) {
 *         setTimeout(function() {
 *             // do some async task
 *             callback(null, 'one');
 *         }, 200);
 *     },
 *     function(callback) {
 *         setTimeout(function() {
 *             // then do another async task
 *             callback(null, 'two');
 *         }, 100);
 *     }
 * ], function(err, results) {
 *     console.log(results);
 *     // results is equal to ['one','two']
 * });
 *
 * // an example using objects instead of arrays
 * async.series({
 *     one: function(callback) {
 *         setTimeout(function() {
 *             // do some async task
 *             callback(null, 1);
 *         }, 200);
 *     },
 *     two: function(callback) {
 *         setTimeout(function() {
 *             // then do another async task
 *             callback(null, 2);
 *         }, 100);
 *     }
 * }, function(err, results) {
 *     console.log(results);
 *     // results is equal to: { one: 1, two: 2 }
 * });
 *
 * //Using Promises
 * async.series([
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'one');
 *         }, 200);
 *     },
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'two');
 *         }, 100);
 *     }
 * ]).then(results => {
 *     console.log(results);
 *     // results is equal to ['one','two']
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * // an example using an object instead of an array
 * async.series({
 *     one: function(callback) {
 *         setTimeout(function() {
 *             // do some async task
 *             callback(null, 1);
 *         }, 200);
 *     },
 *     two: function(callback) {
 *         setTimeout(function() {
 *             // then do another async task
 *             callback(null, 2);
 *         }, 100);
 *     }
 * }).then(results => {
 *     console.log(results);
 *     // results is equal to: { one: 1, two: 2 }
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * //Using async/await
 * async () => {
 *     try {
 *         let results = await async.series([
 *             function(callback) {
 *                 setTimeout(function() {
 *                     // do some async task
 *                     callback(null, 'one');
 *                 }, 200);
 *             },
 *             function(callback) {
 *                 setTimeout(function() {
 *                     // then do another async task
 *                     callback(null, 'two');
 *                 }, 100);
 *             }
 *         ]);
 *         console.log(results);
 *         // results is equal to ['one','two']
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 * // an example using an object instead of an array
 * async () => {
 *     try {
 *         let results = await async.parallel({
 *             one: function(callback) {
 *                 setTimeout(function() {
 *                     // do some async task
 *                     callback(null, 1);
 *                 }, 200);
 *             },
 *            two: function(callback) {
 *                 setTimeout(function() {
 *                     // then do another async task
 *                     callback(null, 2);
 *                 }, 100);
 *            }
 *         });
 *         console.log(results);
 *         // results is equal to: { one: 1, two: 2 }
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 */
export default function series(tasks, callback) {
    return _parallel(eachOfSeries, tasks, callback);
}