YUI.add('io-queue', function (Y, NAME) {

/**

Extends IO to implement Queue for synchronous

transaction processing.

@module io

@submodule io-queue

@for IO

**/

var io = Y.io._map['io:0'] || new Y.IO();

Y.mix(Y.IO.prototype, {

   /**

    * Array of transactions queued for processing

    *

    * @property _q

    * @private

    * @static

    * @type {Object}

    */

    _q: new Y.Queue(),

    _qActiveId: null,

    _qInit: false,

   /**

    * Property to determine whether the queue is set to

    * 1 (active) or 0 (inactive).  When inactive, transactions

    * will be stored in the queue until the queue is set to active.

    *

    * @property _qState

    * @private

    * @static

    * @type {Number}

    */

    _qState: 1,

   /**

    * Method Process the first transaction from the

    * queue in FIFO order.

    *

    * @method _qShift

    * @private

    * @static

    */

    _qShift: function() {

        var io = this,

            o = io._q.next();

        io._qActiveId = o.id;

        io._qState = 0;

        io.send(o.uri, o.cfg, o.id);

    },

   /**

    * Method for queueing a transaction before the request is sent to the

    * resource, to ensure sequential processing.

    *

    * @method queue

    * @static

    * @return {Object}

    */

    queue: function(uri, c) {

        var io = this,

            o = { uri: uri, cfg:c, id: this._id++ };

        if(!io._qInit) {

            Y.on('io:complete', function(id, o) { io._qNext(id); }, io);

            io._qInit = true;

        }

        io._q.add(o);

        if (io._qState === 1) {

            io._qShift();

        }

        return o;

    },

    _qNext: function(id) {

        var io = this;

        io._qState = 1;

        if (io._qActiveId === id && io._q.size() > 0) {

            io._qShift();

        }

    },

   /**

    * Method for promoting a transaction to the top of the queue.

    *

    * @method promote

    * @static

    */

    qPromote: function(o) {

        this._q.promote(o);

    },

   /**

    * Method for removing a specific, pending transaction from

    * the queue.

    *

    * @method remove

    * @private

    * @static

    */

    qRemove: function(o) {

        this._q.remove(o);

    },

   /**

    * Method for cancel all pending transaction from

    * the queue.

    *

    * @method empty

    * @static

    * @since 3.7.3

    */

    qEmpty: function() {

        this._q = new Y.Queue();

    },

    qStart: function() {

        var io = this;

        io._qState = 1;

        if (io._q.size() > 0) {

            io._qShift();

        }

    },

   /**

    * Method for setting queue processing to inactive.

    * Transaction requests to YUI.io.queue() will be stored in the queue, but

    * not processed until the queue is reset to "active".

    *

    * @method _stop

    * @private

    * @static

    */

    qStop: function() {

        this._qState = 0;

    },

   /**

    * Method to query the current size of the queue.

    *

    * @method _size

    * @private

    * @static

    * @return {Number}

    */

    qSize: function() {

        return this._q.size();

    }

}, true);

function _queue(u, c) {

    return io.queue.apply(io, [u, c]);

}

_queue.start = function () { io.qStart(); };

_queue.stop = function () { io.qStop(); };

_queue.promote = function (o) { io.qPromote(o); };

_queue.remove = function (o) { io.qRemove(o); };

_queue.size = function () { io.qSize(); };

_queue.empty = function () { io.qEmpty(); };

Y.io.queue = _queue;

}, '@VERSION@', {"requires": ["io-base", "queue-promote"]});