import map from './map.js'
import wrapAsync from './internal/wrapAsync.js'
import awaitify from './internal/awaitify.js'

/**
 * Sorts a list by the results of running each `coll` value through an async
 * `iteratee`.
 *
 * @name sortBy
 * @static
 * @memberOf module:Collections
 * @method
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async function to apply to each item in
 * `coll`.
 * The iteratee should complete with a value to use as the sort criteria as
 * its `result`.
 * Invoked with (item, callback).
 * @param {Function} callback - A callback which is called after all the
 * `iteratee` functions have finished, or an error occurs. Results is the items
 * from the original `coll` sorted by the values returned by the `iteratee`
 * calls. Invoked with (err, results).
 * @returns {Promise} a promise, if no callback passed
 * @example
 *
 * // bigfile.txt is a file that is 251100 bytes in size
 * // mediumfile.txt is a file that is 11000 bytes in size
 * // smallfile.txt is a file that is 121 bytes in size
 *
 * // asynchronous function that returns the file size in bytes
 * function getFileSizeInBytes(file, callback) {
 *     fs.stat(file, function(err, stat) {
 *         if (err) {
 *             return callback(err);
 *         }
 *         callback(null, stat.size);
 *     });
 * }
 *
 * // Using callbacks
 * async.sortBy(['mediumfile.txt','smallfile.txt','bigfile.txt'], getFileSizeInBytes,
 *     function(err, results) {
 *         if (err) {
 *             console.log(err);
 *         } else {
 *             console.log(results);
 *             // results is now the original array of files sorted by
 *             // file size (ascending by default), e.g.
 *             // [ 'smallfile.txt', 'mediumfile.txt', 'bigfile.txt']
 *         }
 *     }
 * );
 *
 * // By modifying the callback parameter the
 * // sorting order can be influenced:
 *
 * // ascending order
 * async.sortBy(['mediumfile.txt','smallfile.txt','bigfile.txt'], function(file, callback) {
 *     getFileSizeInBytes(file, function(getFileSizeErr, fileSize) {
 *         if (getFileSizeErr) return callback(getFileSizeErr);
 *         callback(null, fileSize);
 *     });
 * }, function(err, results) {
 *         if (err) {
 *             console.log(err);
 *         } else {
 *             console.log(results);
 *             // results is now the original array of files sorted by
 *             // file size (ascending by default), e.g.
 *             // [ 'smallfile.txt', 'mediumfile.txt', 'bigfile.txt']
 *         }
 *     }
 * );
 *
 * // descending order
 * async.sortBy(['bigfile.txt','mediumfile.txt','smallfile.txt'], function(file, callback) {
 *     getFileSizeInBytes(file, function(getFileSizeErr, fileSize) {
 *         if (getFileSizeErr) {
 *             return callback(getFileSizeErr);
 *         }
 *         callback(null, fileSize * -1);
 *     });
 * }, function(err, results) {
 *         if (err) {
 *             console.log(err);
 *         } else {
 *             console.log(results);
 *             // results is now the original array of files sorted by
 *             // file size (ascending by default), e.g.
 *             // [ 'bigfile.txt', 'mediumfile.txt', 'smallfile.txt']
 *         }
 *     }
 * );
 *
 * // Error handling
 * async.sortBy(['mediumfile.txt','smallfile.txt','missingfile.txt'], getFileSizeInBytes,
 *     function(err, results) {
 *         if (err) {
 *             console.log(err);
 *             // [ Error: ENOENT: no such file or directory ]
 *         } else {
 *             console.log(results);
 *         }
 *     }
 * );
 *
 * // Using Promises
 * async.sortBy(['mediumfile.txt','smallfile.txt','bigfile.txt'], getFileSizeInBytes)
 * .then( results => {
 *     console.log(results);
 *     // results is now the original array of files sorted by
 *     // file size (ascending by default), e.g.
 *     // [ 'smallfile.txt', 'mediumfile.txt', 'bigfile.txt']
 * }).catch( err => {
 *     console.log(err);
 * });
 *
 * // Error handling
 * async.sortBy(['mediumfile.txt','smallfile.txt','missingfile.txt'], getFileSizeInBytes)
 * .then( results => {
 *     console.log(results);
 * }).catch( err => {
 *     console.log(err);
 *     // [ Error: ENOENT: no such file or directory ]
 * });
 *
 * // Using async/await
 * (async () => {
 *     try {
 *         let results = await async.sortBy(['bigfile.txt','mediumfile.txt','smallfile.txt'], getFileSizeInBytes);
 *         console.log(results);
 *         // results is now the original array of files sorted by
 *         // file size (ascending by default), e.g.
 *         // [ 'smallfile.txt', 'mediumfile.txt', 'bigfile.txt']
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * })();
 *
 * // Error handling
 * async () => {
 *     try {
 *         let results = await async.sortBy(['missingfile.txt','mediumfile.txt','smallfile.txt'], getFileSizeInBytes);
 *         console.log(results);
 *     }
 *     catch (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *     }
 * }
 *
 */
function sortBy (coll, iteratee, callback) {
    var _iteratee = wrapAsync(iteratee);
    return map(coll, (x, iterCb) => {
        _iteratee(x, (err, criteria) => {
            if (err) return iterCb(err);
            iterCb(err, {value: x, criteria});
        });
    }, (err, results) => {
        if (err) return callback(err);
        callback(null, results.sort(comparator).map(v => v.value));
    });

    function comparator(left, right) {
        var a = left.criteria, b = right.criteria;
        return a < b ? -1 : a > b ? 1 : 0;
    }
}
export default awaitify(sortBy, 3)