async/priorityQueue.js

'use strict';

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

exports.default = function (worker, concurrency) {
    // Start with a normal queue
    var q = (0, _queue2.default)(worker, concurrency);

    // Override push to accept second parameter representing priority
    q.push = function (data, priority, callback) {
        if (callback == null) callback = _noop2.default;
        if (typeof callback !== 'function') {
            throw new Error('task callback must be a function');
        }
        q.started = true;
        if (!(0, _isArray2.default)(data)) {
            data = [data];
        }
        if (data.length === 0) {
            // call drain immediately if there are no tasks
            return (0, _setImmediate2.default)(function () {
                q.drain();
            });
        }

        priority = priority || 0;
        var nextNode = q._tasks.head;
        while (nextNode && priority >= nextNode.priority) {
            nextNode = nextNode.next;
        }

        for (var i = 0, l = data.length; i < l; i++) {
            var item = {
                data: data[i],
                priority: priority,
                callback: callback
            };

            if (nextNode) {
                q._tasks.insertBefore(nextNode, item);
            } else {
                q._tasks.push(item);
            }
        }
        (0, _setImmediate2.default)(q.process);
    };

    // Remove unshift function
    delete q.unshift;

    return q;
};

var _isArray = require('lodash/isArray');

var _isArray2 = _interopRequireDefault(_isArray);

var _noop = require('lodash/noop');

var _noop2 = _interopRequireDefault(_noop);

var _setImmediate = require('./setImmediate');

var _setImmediate2 = _interopRequireDefault(_setImmediate);

var _queue = require('./queue');

var _queue2 = _interopRequireDefault(_queue);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

module.exports = exports['default'];

/**
 * The same as [async.queue]{@link module:ControlFlow.queue} only tasks are assigned a priority and
 * completed in ascending priority order.
 *
 * @name priorityQueue
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.queue]{@link module:ControlFlow.queue}
 * @category Control Flow
 * @param {AsyncFunction} worker - An async function for processing a queued task.
 * If you want to handle errors from an individual task, pass a callback to
 * `q.push()`.
 * Invoked with (task, callback).
 * @param {number} concurrency - An `integer` for determining how many `worker`
 * functions should be run in parallel.  If omitted, the concurrency defaults to
 * `1`.  If the concurrency is `0`, an error is thrown.
 * @returns {module:ControlFlow.QueueObject} A priorityQueue object to manage the tasks. There are two
 * differences between `queue` and `priorityQueue` objects:
 * * `push(task, priority, [callback])` - `priority` should be a number. If an
 *   array of `tasks` is given, all tasks will be assigned the same priority.
 * * The `unshift` method was removed.
 */