'use strict';

Object.defineProperty(exports, "__esModule", {
    value: true
});

exports.default = function (tasks, concurrency, callback) {
    if (typeof concurrency === 'function') {
        // concurrency is optional, shift the args.
        callback = concurrency;
        concurrency = null;
    }
    callback = (0, _once2.default)(callback || _noop2.default);
    var keys = (0, _keys2.default)(tasks);
    var numTasks = keys.length;
    if (!numTasks) {
        return callback(null);
    }
    if (!concurrency) {
        concurrency = numTasks;
    }

    var results = {};
    var runningTasks = 0;
    var hasError = false;

    var listeners = Object.create(null);

    var readyTasks = [];

    // for cycle detection:
    var readyToCheck = []; // tasks that have been identified as reachable
    // without the possibility of returning to an ancestor task
    var uncheckedDependencies = {};

    (0, _baseForOwn2.default)(tasks, function (task, key) {
        if (!(0, _isArray2.default)(task)) {
            // no dependencies
            enqueueTask(key, [task]);
            readyToCheck.push(key);
            return;
        }

        var dependencies = task.slice(0, task.length - 1);
        var remainingDependencies = dependencies.length;
        if (remainingDependencies === 0) {
            enqueueTask(key, task);
            readyToCheck.push(key);
            return;
        }
        uncheckedDependencies[key] = remainingDependencies;

        (0, _arrayEach2.default)(dependencies, function (dependencyName) {
            if (!tasks[dependencyName])