async.mjs

 * }
 *
 */
function some(coll, iteratee, callback) {
    return _createTester(Boolean, res => res)(eachOf$1, coll, iteratee, callback)
}
var some$1 = awaitify(some, 3);

/**
 * The same as [`some`]{@link module:Collections.some} but runs a maximum of `limit` async operations at a time.
 *
 * @name someLimit
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.some]{@link module:Collections.some}
 * @alias anyLimit
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {AsyncFunction} iteratee - An async truth test to apply to each item
 * in the collections in parallel.
 * The iteratee should complete with a boolean `result` value.
 * Invoked with (item, callback).
 * @param {Function} [callback] - A callback which is called as soon as any
 * iteratee returns `true`, or after all the iteratee functions have finished.
 * Result will be either `true` or `false` depending on the values of the async
 * tests. Invoked with (err, result).
 * @returns {Promise} a promise, if no callback provided
 */
function someLimit(coll, limit, iteratee, callback) {
    return _createTester(Boolean, res => res)(eachOfLimit(limit), coll, iteratee, callback)
}
var someLimit$1 = awaitify(someLimit, 4);

/**
 * The same as [`some`]{@link module:Collections.some} but runs only a single async operation at a time.
 *
 * @name someSeries
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.some]{@link module:Collections.some}
 * @alias anySeries
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async truth test to apply to each item
 * in the collections in series.
 * The iteratee should complete with a boolean `result` value.
 * Invoked with (item, callback).
 * @param {Function} [callback] - A callback which is called as soon as any
 * iteratee returns `true`, or after all the iteratee functions have finished.
 * Result will be either `true` or `false` depending on the values of the async
 * tests. Invoked with (err, result).
 * @returns {Promise} a promise, if no callback provided
 */
function someSeries(coll, iteratee, callback) {
    return _createTester(Boolean, res => res)(eachOfSeries$1, coll, iteratee, callback)
}
var someSeries$1 = awaitify(someSeries, 3);

/**
 * 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$1(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;
    }
}
var sortBy$1 = awaitify(sortBy, 3);

/**
 * Sets a time limit on an asynchronous function. If the function does not call
 * its callback within the specified milliseconds, it will be called with a
 * timeout error. The code property for the error object will be `'ETIMEDOUT'`.
 *
 * @name timeout
 * @static
 * @memberOf module:Utils
 * @method
 * @category Util
 * @param {AsyncFunction} asyncFn - The async function to limit in time.
 * @param {number} milliseconds - The specified time limit.
 * @param {*} [info] - Any variable you want attached (`string`, `object`, etc)
 * to timeout Error for more information..
 * @returns {AsyncFunction} Returns a wrapped function that can be used with any
 * of the control flow functions.
 * Invoke this function with the same parameters as you would `asyncFunc`.
 * @example
 *
 * function myFunction(foo, callback) {
 *     doAsyncTask(foo, function(err, data) {
 *         // handle errors
 *         if (err) return callback(err);
 *
 *         // do some stuff ...
 *
 *         // return processed data
 *         return callback(null, data);
 *     });
 * }
 *
 * var wrapped = async.timeout(myFunction, 1000);
 *
 * // call `wrapped` as you would `myFunction`
 * wrapped({ bar: 'bar' }, function(err, data) {
 *     // if `myFunction` takes < 1000 ms to execute, `err`
 *     // and `data` will have their expected values
 *
 *     // else `err` will be an Error with the code 'ETIMEDOUT'
 * });
 */
function timeout(asyncFn, milliseconds, info) {
    var fn = wrapAsync(asyncFn);

    return initialParams((args, callback) => {
        var timedOut = false;
        var timer;

        function timeoutCallback() {
            var name = asyncFn.name || 'anonymous';
            var error  = new Error('Callback function "' + name + '" timed out.');
            error.code = 'ETIMEDOUT';
            if (info) {
                error.info = info;
            }
            timedOut = true;
            callback(error);
        }

        args.push((...cbArgs) => {
            if (!timedOut) {
                callback(...cbArgs);
                clearTimeout(timer);
            }
        });

        // setup timer and call original function
        timer = setTimeout(timeoutCallback, milliseconds);
        fn(...args);
    });
}

function range(size) {
    var result = Array(size);
    while (size--) {
        result[size] = size;
    }
    return result;
}

/**
 * The same as [times]{@link module:ControlFlow.times} but runs a maximum of `limit` async operations at a
 * time.
 *
 * @name timesLimit
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.times]{@link module:ControlFlow.times}
 * @category Control Flow
 * @param {number} count - The number of times to run the function.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {AsyncFunction} iteratee - The async function to call `n` times.
 * Invoked with the iteration index and a callback: (n, next).
 * @param {Function} callback - see [async.map]{@link module:Collections.map}.
 * @returns {Promise} a promise, if no callback is provided
 */
function timesLimit(count, limit, iteratee, callback) {
    var _iteratee = wrapAsync(iteratee);
    return mapLimit$1(range(count), limit, _iteratee, callback);
}

/**
 * Calls the `iteratee` function `n` times, and accumulates results in the same
 * manner you would use with [map]{@link module:Collections.map}.
 *
 * @name times
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.map]{@link module:Collections.map}
 * @category Control Flow
 * @param {number} n - The number of times to run the function.
 * @param {AsyncFunction} iteratee - The async function to call `n` times.
 * Invoked with the iteration index and a callback: (n, next).
 * @param {Function} callback - see {@link module:Collections.map}.
 * @returns {Promise} a promise, if no callback is provided
 * @example
 *
 * // Pretend this is some complicated async factory
 * var createUser = function(id, callback) {
 *     callback(null, {
 *         id: 'user' + id
 *     });
 * };
 *
 * // generate 5 users
 * async.times(5, function(n, next) {
 *     createUser(n, function(err, user) {
 *         next(err, user);
 *     });
 * }, function(err, users) {
 *     // we should now have 5 users
 * });
 */
function times (n, iteratee, callback) {
    return timesLimit(n, Infinity, iteratee, callback)
}

/**
 * The same as [times]{@link module:ControlFlow.times} but runs only a single async operation at a time.
 *
 * @name timesSeries
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.times]{@link module:ControlFlow.times}
 * @category Control Flow
 * @param {number} n - The number of times to run the function.
 * @param {AsyncFunction} iteratee - The async function to call `n` times.
 * Invoked with the iteration index and a callback: (n, next).
 * @param {Function} callback - see {@link module:Collections.map}.
 * @returns {Promise} a promise, if no callback is provided
 */
function timesSeries (n, iteratee, callback) {
    return timesLimit(n, 1, iteratee, callback)
}

/**
 * A relative of `reduce`.  Takes an Object or Array, and iterates over each
 * element in parallel, each step potentially mutating an `accumulator` value.
 * The type of the accumulator defaults to the type of collection passed in.
 *
 * @name transform
 * @static
 * @memberOf module:Collections
 * @method
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {*} [accumulator] - The initial state of the transform.  If omitted,
 * it will default to an empty Object or Array, depending on the type of `coll`
 * @param {AsyncFunction} iteratee - A function applied to each item in the
 * collection that potentially modifies the accumulator.
 * Invoked with (accumulator, item, key, callback).
 * @param {Function} [callback] - A callback which is called after all the
 * `iteratee` functions have finished. Result is the transformed accumulator.
 * Invoked with (err, result).
 * @returns {Promise} a promise, if no callback provided
 * @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
 *
 * // helper function that returns human-readable size format from bytes
 * function formatBytes(bytes, decimals = 2) {
 *   // implementation not included for brevity
 *   return humanReadbleFilesize;
 * }
 *
 * const fileList = ['file1.txt','file2.txt','file3.txt'];
 *
 * // asynchronous function that returns the file size, transformed to human-readable format
 * // e.g. 1024 bytes = 1KB, 1234 bytes = 1.21 KB, 1048576 bytes = 1MB, etc.
 * function transformFileSize(acc, value, key, callback) {
 *     fs.stat(value, function(err, stat) {
 *         if (err) {
 *             return callback(err);
 *         }
 *         acc[key] = formatBytes(stat.size);
 *         callback(null);
 *     });
 * }
 *
 * // Using callbacks
 * async.transform(fileList, transformFileSize, function(err, result) {
 *     if(err) {
 *         console.log(err);
 *     } else {
 *         console.log(result);
 *         // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
 *     }
 * });
 *
 * // Using Promises
 * async.transform(fileList, transformFileSize)
 * .then(result => {
 *     console.log(result);
 *     // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * // Using async/await
 * (async () => {
 *     try {
 *         let result = await async.transform(fileList, transformFileSize);
 *         console.log(result);
 *         // [ '1000 Bytes', '1.95 KB', '2.93 KB' ]
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * })();
 *
 * @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
 *
 * // helper function that returns human-readable size format from bytes
 * function formatBytes(bytes, decimals = 2) {
 *   // implementation not included for brevity
 *   return humanReadbleFilesize;
 * }
 *
 * const fileMap = { f1: 'file1.txt', f2: 'file2.txt', f3: 'file3.txt' };
 *
 * // asynchronous function that returns the file size, transformed to human-readable format
 * // e.g. 1024 bytes = 1KB, 1234 bytes = 1.21 KB, 1048576 bytes = 1MB, etc.
 * function transformFileSize(acc, value, key, callback) {
 *     fs.stat(value, function(err, stat) {
 *         if (err) {
 *             return callback(err);
 *         }
 *         acc[key] = formatBytes(stat.size);
 *         callback(null);
 *     });
 * }
 *
 * // Using callbacks
 * async.transform(fileMap, transformFileSize, function(err, result) {
 *     if(err) {
 *         console.log(err);
 *     } else {
 *         console.log(result);
 *         // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
 *     }
 * });
 *
 * // Using Promises
 * async.transform(fileMap, transformFileSize)
 * .then(result => {
 *     console.log(result);
 *     // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * // Using async/await
 * async () => {
 *     try {
 *         let result = await async.transform(fileMap, transformFileSize);
 *         console.log(result);
 *         // { f1: '1000 Bytes', f2: '1.95 KB', f3: '2.93 KB' }
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 */
function transform (coll, accumulator, iteratee, callback) {
    if (arguments.length <= 3 && typeof accumulator === 'function') {
        callback = iteratee;
        iteratee = accumulator;
        accumulator = Array.isArray(coll) ? [] : {};
    }
    callback = once(callback || promiseCallback());
    var _iteratee = wrapAsync(iteratee);

    eachOf$1(coll, (v, k, cb) => {
        _iteratee(accumulator, v, k, cb);
    }, err => callback(err, accumulator));
    return callback[PROMISE_SYMBOL]
}

/**
 * It runs each task in series but stops whenever any of the functions were
 * successful. If one of the tasks were successful, the `callback` will be
 * passed the result of the successful task. If all tasks fail, the callback
 * will be passed the error and result (if any) of the final attempt.
 *
 * @name tryEach
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {Array|Iterable|AsyncIterable|Object} tasks - A collection containing functions to
 * run, each function is passed a `callback(err, result)` it must call on
 * completion with an error `err` (which can be `null`) and an optional `result`
 * value.
 * @param {Function} [callback] - An optional callback which is called when one
 * of the tasks has succeeded, or all have failed. It receives the `err` and
 * `result` arguments of the last attempt at completing the `task`. Invoked with
 * (err, results).
 * @returns {Promise} a promise, if no callback is passed
 * @example
 * async.tryEach([
 *     function getDataFromFirstWebsite(callback) {
 *         // Try getting the data from the first website
 *         callback(err, data);
 *     },
 *     function getDataFromSecondWebsite(callback) {
 *         // First website failed,
 *         // Try getting the data from the backup website
 *         callback(err, data);
 *     }
 * ],
 * // optional callback
 * function(err, results) {
 *     Now do something with the data.
 * });
 *
 */
function tryEach(tasks, callback) {
    var error = null;
    var result;
    return eachSeries$1(tasks, (task, taskCb) => {
        wrapAsync(task)((err, ...args) => {
            if (err === false) return taskCb(err);

            if (args.length < 2) {
                [result] = args;
            } else {
                result = args;
            }
            error = err;
            taskCb(err ? null : {});
        });
    }, () => callback(error, result));
}

var tryEach$1 = awaitify(tryEach);

/**
 * Undoes a [memoize]{@link module:Utils.memoize}d function, reverting it to the original,
 * unmemoized form. Handy for testing.
 *
 * @name unmemoize
 * @static
 * @memberOf module:Utils
 * @method
 * @see [async.memoize]{@link module:Utils.memoize}
 * @category Util
 * @param {AsyncFunction} fn - the memoized function
 * @returns {AsyncFunction} a function that calls the original unmemoized function
 */
function unmemoize(fn) {
    return (...args) => {
        return (fn.unmemoized || fn)(...args);
    };
}

/**
 * Repeatedly call `iteratee`, while `test` returns `true`. Calls `callback` when
 * stopped, or an error occurs.
 *
 * @name whilst
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {AsyncFunction} test - asynchronous truth test to perform before each
 * execution of `iteratee`. Invoked with ().
 * @param {AsyncFunction} iteratee - An async function which is called each time
 * `test` passes. Invoked with (callback).
 * @param {Function} [callback] - A callback which is called after the test
 * function has failed and repeated execution of `iteratee` has stopped. `callback`
 * will be passed an error and any arguments passed to the final `iteratee`'s
 * callback. Invoked with (err, [results]);
 * @returns {Promise} a promise, if no callback is passed
 * @example
 *
 * var count = 0;
 * async.whilst(
 *     function test(cb) { cb(null, count < 5); },
 *     function iter(callback) {
 *         count++;
 *         setTimeout(function() {
 *             callback(null, count);
 *         }, 1000);
 *     },
 *     function (err, n) {
 *         // 5 seconds have passed, n = 5
 *     }
 * );
 */
function whilst(test, iteratee, callback) {
    callback = onlyOnce(callback);
    var _fn = wrapAsync(iteratee);
    var _test = wrapAsync(test);
    var results = [];

    function next(err, ...rest) {
        if (err) return callback(err);
        results = rest;
        if (err === false) return;
        _test(check);
    }

    function check(err, truth) {
        if (err) return callback(err);
        if (err === false) return;
        if (!truth) return callback(null, ...results);
        _fn(next);
    }

    return _test(check);
}
var whilst$1 = awaitify(whilst, 3);

/**
 * Repeatedly call `iteratee` until `test` returns `true`. Calls `callback` when
 * stopped, or an error occurs. `callback` will be passed an error and any
 * arguments passed to the final `iteratee`'s callback.
 *
 * The inverse of [whilst]{@link module:ControlFlow.whilst}.
 *
 * @name until
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.whilst]{@link module:ControlFlow.whilst}
 * @category Control Flow
 * @param {AsyncFunction} test - asynchronous truth test to perform before each
 * execution of `iteratee`. Invoked with (callback).
 * @param {AsyncFunction} iteratee - An async function which is called each time
 * `test` fails. Invoked with (callback).
 * @param {Function} [callback] - A callback which is called after the test
 * function has passed and repeated execution of `iteratee` has stopped. `callback`
 * will be passed an error and any arguments passed to the final `iteratee`'s
 * callback. Invoked with (err, [results]);
 * @returns {Promise} a promise, if a callback is not passed
 *
 * @example
 * const results = []
 * let finished = false
 * async.until(function test(cb) {
 *     cb(null, finished)
 * }, function iter(next) {
 *     fetchPage(url, (err, body) => {
 *         if (err) return next(err)
 *         results = results.concat(body.objects)
 *         finished = !!body.next
 *         next(err)
 *     })
 * }, function done (err) {
 *     // all pages have been fetched
 * })
 */
function until(test, iteratee, callback) {
    const _test = wrapAsync(test);
    return whilst$1((cb) => _test((err, truth) => cb (err, !truth)), iteratee, callback);
}

/**
 * Runs the `tasks` array of functions in series, each passing their results to
 * the next in the array. However, if any of the `tasks` pass an error to their
 * own callback, the next function is not executed, and the main `callback` is
 * immediately called with the error.
 *
 * @name waterfall
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {Array} tasks - An array of [async functions]{@link AsyncFunction}
 * to run.
 * Each function should complete with any number of `result` values.
 * The `result` values will be passed as arguments, in order, to the next task.
 * @param {Function} [callback] - An optional callback to run once all the
 * functions have completed. This will be passed the results of the last task's
 * callback. Invoked with (err, [results]).
 * @returns {Promise} a promise, if a callback is omitted
 * @example
 *
 * async.waterfall([
 *     function(callback) {
 *         callback(null, 'one', 'two');
 *     },
 *     function(arg1, arg2, callback) {
 *         // arg1 now equals 'one' and arg2 now equals 'two'
 *         callback(null, 'three');
 *     },
 *     function(arg1, callback) {
 *         // arg1 now equals 'three'
 *         callback(null, 'done');
 *     }
 * ], function (err, result) {
 *     // result now equals 'done'
 * });
 *
 * // Or, with named functions:
 * async.waterfall([
 *     myFirstFunction,
 *     mySecondFunction,
 *     myLastFunction,
 * ], function (err, result) {
 *     // result now equals 'done'
 * });
 * function myFirstFunction(callback) {
 *     callback(null, 'one', 'two');
 * }
 * function mySecondFunction(arg1, arg2, callback) {
 *     // arg1 now equals 'one' and arg2 now equals 'two'
 *     callback(null, 'three');
 * }
 * function myLastFunction(arg1, callback) {
 *     // arg1 now equals 'three'
 *     callback(null, 'done');
 * }
 */
function waterfall (tasks, callback) {
    callback = once(callback);
    if (!Array.isArray(tasks)) return callback(new Error('First argument to waterfall must be an array of functions'));
    if (!tasks.length) return callback();
    var taskIndex = 0;

    function nextTask(args) {
        var task = wrapAsync(tasks[taskIndex++]);
        task(...args, onlyOnce(next));
    }

    function next(err, ...args) {
        if (err === false) return
        if (err || taskIndex === tasks.length) {
            return callback(err, ...args);
        }
        nextTask(args);
    }

    nextTask([]);
}

var waterfall$1 = awaitify(waterfall);

/**
 * An "async function" in the context of Async is an asynchronous function with
 * a variable number of parameters, with the final parameter being a callback.
 * (`function (arg1, arg2, ..., callback) {}`)
 * The final callback is of the form `callback(err, results...)`, which must be
 * called once the function is completed.  The callback should be called with a
 * Error as its first argument to signal that an error occurred.
 * Otherwise, if no error occurred, it should be called with `null` as the first
 * argument, and any additional `result` arguments that may apply, to signal
 * successful completion.
 * The callback must be called exactly once, ideally on a later tick of the
 * JavaScript event loop.
 *
 * This type of function is also referred to as a "Node-style async function",
 * or a "continuation passing-style function" (CPS). Most of the methods of this
 * library are themselves CPS/Node-style async functions, or functions that
 * return CPS/Node-style async functions.
 *
 * Wherever we accept a Node-style async function, we also directly accept an
 * [ES2017 `async` function]{@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function}.
 * In this case, the `async` function will not be passed a final callback
 * argument, and any thrown error will be used as the `err` argument of the
 * implicit callback, and the return value will be used as the `result` value.
 * (i.e. a `rejected` of the returned Promise becomes the `err` callback
 * argument, and a `resolved` value becomes the `result`.)
 *
 * Note, due to JavaScript limitations, we can only detect native `async`
 * functions and not transpilied implementations.
 * Your environment must have `async`/`await` support for this to work.
 * (e.g. Node > v7.6, or a recent version of a modern browser).
 * If you are using `async` functions through a transpiler (e.g. Babel), you
 * must still wrap the function with [asyncify]{@link module:Utils.asyncify},
 * because the `async function` will be compiled to an ordinary function that
 * returns a promise.
 *
 * @typedef {Function} AsyncFunction
 * @static
 */

var index = {
    apply,
    applyEach: applyEach$1,
    applyEachSeries,
    asyncify,
    auto,
    autoInject,
    cargo,
    cargoQueue: cargo$1,
    compose,
    concat: concat$1,
    concatLimit: concatLimit$1,
    concatSeries: concatSeries$1,
    constant,
    detect: detect$1,
    detectLimit: detectLimit$1,
    detectSeries: detectSeries$1,
    dir,
    doUntil,
    doWhilst: doWhilst$1,
    each,
    eachLimit: eachLimit$2,
    eachOf: eachOf$1,
    eachOfLimit: eachOfLimit$2,
    eachOfSeries: eachOfSeries$1,
    eachSeries: eachSeries$1,
    ensureAsync,
    every: every$1,
    everyLimit: everyLimit$1,
    everySeries: everySeries$1,
    filter: filter$1,
    filterLimit: filterLimit$1,
    filterSeries: filterSeries$1,
    forever: forever$1,
    groupBy,
    groupByLimit: groupByLimit$1,
    groupBySeries,
    log,
    map: map$1,
    mapLimit: mapLimit$1,
    mapSeries: mapSeries$1,
    mapValues,
    mapValuesLimit: mapValuesLimit$1,
    mapValuesSeries,
    memoize,
    nextTick,
    parallel: parallel$1,
    parallelLimit,
    priorityQueue,
    queue: queue$1,
    race: race$1,
    reduce: reduce$1,
    reduceRight,
    reflect,
    reflectAll,
    reject: reject$2,
    rejectLimit: rejectLimit$1,
    rejectSeries: rejectSeries$1,
    retry,
    retryable,
    seq,
    series,
    setImmediate: setImmediate$1,
    some: some$1,
    someLimit: someLimit$1,
    someSeries: someSeries$1,
    sortBy: sortBy$1,
    timeout,
    times,
    timesLimit,
    timesSeries,
    transform,
    tryEach: tryEach$1,
    unmemoize,
    until,
    waterfall: waterfall$1,
    whilst: whilst$1,

    // aliases
    all: every$1,
    allLimit: everyLimit$1,
    allSeries: everySeries$1,
    any: some$1,
    anyLimit: someLimit$1,
    anySeries: someSeries$1,
    find: detect$1,
    findLimit: detectLimit$1,
    findSeries: detectSeries$1,
    flatMap: concat$1,
    flatMapLimit: concatLimit$1,
    flatMapSeries: concatSeries$1,
    forEach: each,
    forEachSeries: eachSeries$1,
    forEachLimit: eachLimit$2,
    forEachOf: eachOf$1,
    forEachOfSeries: eachOfSeries$1,
    forEachOfLimit: eachOfLimit$2,
    inject: reduce$1,
    foldl: reduce$1,
    foldr: reduceRight,
    select: filter$1,
    selectLimit: filterLimit$1,
    selectSeries: filterSeries$1,
    wrapSync: asyncify,
    during: whilst$1,
    doDuring: doWhilst$1
};

export default index;
export { apply, applyEach$1 as applyEach, applyEachSeries, asyncify, auto, autoInject, cargo, cargo$1 as cargoQueue, compose, concat$1 as concat, concatLimit$1 as concatLimit, concatSeries$1 as concatSeries, constant, detect$1 as detect, detectLimit$1 as detectLimit, detectSeries$1 as detectSeries, dir, doUntil, doWhilst$1 as doWhilst, each, eachLimit$2 as eachLimit, eachOf$1 as eachOf, eachOfLimit$2 as eachOfLimit, eachOfSeries$1 as eachOfSeries, eachSeries$1 as eachSeries, ensureAsync, every$1 as every, everyLimit$1 as everyLimit, everySeries$1 as everySeries, filter$1 as filter, filterLimit$1 as filterLimit, filterSeries$1 as filterSeries, forever$1 as forever, groupBy, groupByLimit$1 as groupByLimit, groupBySeries, log, map$1 as map, mapLimit$1 as mapLimit, mapSeries$1 as mapSeries, mapValues, mapValuesLimit$1 as mapValuesLimit, mapValuesSeries, memoize, nextTick, parallel$1 as parallel, parallelLimit, priorityQueue, queue$1 as queue, race$1 as race, reduce$1 as reduce, reduceRight, reflect, reflectAll, reject$2 as reject, rejectLimit$1 as rejectLimit, rejectSeries$1 as rejectSeries, retry, retryable, seq, series, setImmediate$1 as setImmediate, some$1 as some, someLimit$1 as someLimit, someSeries$1 as someSeries, sortBy$1 as sortBy, timeout, times, timesLimit, timesSeries, transform, tryEach$1 as tryEach, unmemoize, until, waterfall$1 as waterfall, whilst$1 as whilst, every$1 as all, everyLimit$1 as allLimit, everySeries$1 as allSeries, some$1 as any, someLimit$1 as anyLimit, someSeries$1 as anySeries, detect$1 as find, detectLimit$1 as findLimit, detectSeries$1 as findSeries, concat$1 as flatMap, concatLimit$1 as flatMapLimit, concatSeries$1 as flatMapSeries, each as forEach, eachSeries$1 as forEachSeries, eachLimit$2 as forEachLimit, eachOf$1 as forEachOf, eachOfSeries$1 as forEachOfSeries, eachOfLimit$2 as forEachOfLimit, reduce$1 as inject, reduce$1 as foldl, reduceRight as foldr, filter$1 as select, filterLimit$1 as selectLimit, filterSeries$1 as selectSeries, asyncify as wrapSync, whilst$1 as during, doWhilst$1 as doDuring };