import _map from './internal/map.js'
import eachOf from './eachOf.js'
import awaitify from './internal/awaitify.js'

/**
 * Produces a new collection of values by mapping each value in `coll` through
 * the `iteratee` function. The `iteratee` is called with an item from `coll`
 * and a callback for when it has finished processing. Each of these callbacks
 * takes 2 arguments: an `error`, and the transformed item from `coll`. If
 * `iteratee` passes an error to its callback, the main `callback` (for the
 * `map` function) is immediately called with the error.
 *
 * Note, that since this function applies the `iteratee` to each item in
 * parallel, there is no guarantee that the `iteratee` functions will complete
 * in order. However, the results array will be in the same order as the
 * original `coll`.
 *
 * If `map` is passed an Object, the results will be an Array.  The results
 * will roughly be in the order of the original Objects' keys (but this can
 * vary across JavaScript engines).
 *
 * @name map
 * @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 the transformed item.
 * Invoked with (item, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. Results is an Array of the
 * transformed items from the `coll`. Invoked with (err, results).
 * @returns {Promise} a promise, if no callback is passed
 * @example
 *
 * // file1.txt is a file that is 1000 bytes in size
 * // file2.txt is a file that is 2000 bytes in size
 * // file3.txt is a file that is 3000 bytes in size
 * // file4.txt does not exist
 *
 * const fileList = ['file1.txt','file2.txt','file3.txt'];
 * const withMissingFileList = ['file1.txt','file2.txt','file4.txt'];
 *
 * // 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.map(fileList, getFileSizeInBytes, function(err, results) {
 *     if (err) {
 *         console.log(err);
 *     } else {
 *         console.log(results);
 *         // results is now an array of the file size in bytes for each file, e.g.
 *         // [ 1000, 2000, 3000]
 *     }
 * });
 *
 * // Error Handling
 * async.map(withMissingFileList, getFileSizeInBytes, function(err, results) {
 *     if (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *     } else {
 *         console.log(results);
 *     }
 * });
 *
 * // Using Promises
 * async.map(fileList, getFileSizeInBytes)
 * .then( results => {
 *     console.log(results);
 *     // results is now an array of the file size in bytes for each file, e.g.
 *     // [ 1000, 2000, 3000]
 * }).catch( err => {
 *     console.log(err);
 * });
 *
 * // Error Handling
 * async.map(withMissingFileList, 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.map(fileList, getFileSizeInBytes);
 *         console.log(results);
 *         // results is now an array of the file size in bytes for each file, e.g.
 *         // [ 1000, 2000, 3000]
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 * // Error Handling
 * async () => {
 *     try {
 *         let results = await async.map(withMissingFileList, getFileSizeInBytes);
 *         console.log(results);
 *     }
 *     catch (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *     }
 * }
 *
 */
function map (coll, iteratee, callback) {
    return _map(eachOf, coll, iteratee, callback)
}
export default awaitify(map, 3);