'use strict';

import noop from 'lodash/noop';
import rest from 'lodash/rest';

/**
 * Like [`whilst`](#whilst), except the `test` is an asynchronous function that
 * is passed a callback in the form of `function (err, truth)`. If error is
 * passed to `test` or `fn`, the main callback is immediately called with the
 * value of the error.
 *
 * @name during
 * @static
 * @memberOf async
 * @see `async.whilst`
 * @category Control Flow
 * @param {Function} test - asynchronous truth test to perform before each
 * execution of `fn`. Invoked with (callback).
 * @param {Function} fn - A function which is called each time `test` passes.
 * The function is passed a `callback(err)`, which must be called once it has
 * completed with an optional `err` argument. Invoked with (callback).
 * @param {Function} [callback] - A callback which is called after the test
 * function has failed and repeated execution of `fn` has stopped. `callback`
 * will be passed an error and any arguments passed to the final `fn`'s
 * callback. Invoked with (err, [results]);
 * @example
 *
 * var count = 0;
 *
 * async.during(
 *     function (callback) {
 *         return callback(null, count < 5);
 *     },
 *     function (callback) {
 *         count++;
 *         setTimeout(callback, 1000);
 *     },
 *     function (err) {
 *         // 5 seconds have passed
 *     }
 * );
 */
export default function during(test, iteratee, cb) {
    cb = cb || noop;

    var next = rest(function(err, args) {
        if (err) {
            cb(err);
        } else {
            args.push(check);
            test.apply(this, args);
        }
    });

    var check = function(err, truth) {
        if (err) return cb(err);
        if (!truth) return cb(null);
        iteratee(next);
    };

    test(check);
}