/*
Copyright (c) 2010, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.com/yui/license.html
version: 3.3.0
build: 3167
*/
YUI.add('event-valuechange', function(Y) {

/**
 * Adds a synthetic <code>valueChange</code> event that fires when the
 * <code>value</code> property of an input field or textarea changes as a result
 * of a keystroke, mouse operation, or input method editor (IME) input event.
 *
 * @module event-valuechange
 */

/**
 * Provides the implementation for the synthetic <code>valueChange</code> event.
 *
 * @class ValueChange
 * @static
 */

var YArray = Y.Array,

    VALUE = 'value',

// Just a simple namespace to make methods overridable.
VC = {
    // -- Static Constants -----------------------------------------------------

    /**
     * Interval (in milliseconds) at which to poll for changes to the value of
     * an element with one or more <code>valueChange</code> subscribers when the
     * user is likely to be interacting with it.
     *
     * @property POLL_INTERVAL
     * @type Number
     * @default 50
     * @static
     */
    POLL_INTERVAL: 50,

    /**
     * Timeout (in milliseconds) after which to stop polling when there hasn't
     * been any new activity (keypresses, mouse clicks, etc.) on an element.
     *
     * @property TIMEOUT
     * @type Number
     * @default 10000
     * @static
     */
    TIMEOUT: 10000,

    // -- Protected Static Properties ------------------------------------------
    _history  : {},
    _intervals: {},
    _notifiers: {},
    _timeouts : {},

    // -- Protected Static Methods ---------------------------------------------

    /**
     * Called at an interval to poll for changes to the value of the specified
     * node.
     *
     * @method _poll
     * @param {Node} node
     * @param {String} stamp
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _poll: function (node, stamp, e) {
        var domNode = node._node, // performance cheat; getValue() is a big hit when polling
            newVal  = domNode && domNode.value,
            prevVal = VC._history[stamp],
            facade;

        if (!domNode) {
            VC._stopPolling(node, stamp);
            return;
        }

        if (newVal !== prevVal) {
            VC._history[stamp] = newVal;

            facade = {
                _event : e,
                newVal : newVal,
                prevVal: prevVal
            };

            YArray.each(VC._notifiers[stamp], function (notifier) {
                notifier.fire(facade);
            });

            VC._refreshTimeout(node, stamp);
        }
    },

    /**
     * Restarts the inactivity timeout for the specified node.
     *
     * @method _refreshTimeout
     * @param {Node} node
     * @param {String} stamp
     * @protected
     * @static
     */
    _refreshTimeout: function (node, stamp) {
        VC._stopTimeout(node, stamp); // avoid dupes

        // If we don't see any changes within the timeout period (10 seconds by
        // default), stop polling.
        VC._timeouts[stamp] = setTimeout(function () {
            VC._stopPolling(node, stamp);
        }, VC.TIMEOUT);

    },

    /**
     * Begins polling for changes to the <code>value</code> property of the
     * specified node. If polling is already underway for the specified node,
     * it will not be restarted unless the <i>force</i> parameter is
     * <code>true</code>
     *
     * @method _startPolling
     * @param {Node} node Node to watch.
     * @param {String} stamp (optional) Object stamp for the node. Will be
     *   generated if not provided (provide it to improve performance).
     * @param {EventFacade} e (optional) Event facade of the event that
     *   initiated the polling (if any).
     * @param {Boolean} force (optional) If <code>true</code>, polling will be
     *   restarted even if we're already polling this node.
     * @protected
     * @static
     */
    _startPolling: function (node, stamp, e, force) {
        if (!stamp) {
            stamp = Y.stamp(node);
        }

        // Don't bother continuing if we're already polling.
        if (!force && VC._intervals[stamp]) {
            return;
        }

        VC._stopPolling(node, stamp); // avoid dupes

        // Poll for changes to the node's value. We can't rely on keyboard
        // events for this, since the value may change due to a mouse-initiated
        // paste event, an IME input event, or for some other reason that
        // doesn't trigger a key event.
        VC._intervals[stamp] = setInterval(function () {
            VC._poll(node, stamp, e);
        }, VC.POLL_INTERVAL);

        VC._refreshTimeout(node, stamp, e);

    },

    /**
     * Stops polling for changes to the specified node's <code>value</code>
     * attribute.
     *
     * @method _stopPolling
     * @param {Node} node
     * @param {String} stamp (optional)
     * @protected
     * @static
     */
    _stopPolling: function (node, stamp) {
        if (!stamp) {
            stamp = Y.stamp(node);
        }

        VC._intervals[stamp] = clearInterval(VC._intervals[stamp]);
        VC._stopTimeout(node, stamp);

    },

    /**
     * Clears the inactivity timeout for the specified node, if any.
     *
     * @method _stopTimeout
     * @param {Node} node
     * @param {String} stamp (optional)
     * @protected
     * @static
     */
    _stopTimeout: function (node, stamp) {
        if (!stamp) {
            stamp = Y.stamp(node);
        }

        VC._timeouts[stamp] = clearTimeout(VC._timeouts[stamp]);
    },

    // -- Protected Static Event Handlers --------------------------------------

    /**
     * Stops polling when a node's blur event fires.
     *
     * @method _onBlur
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _onBlur: function (e) {
        VC._stopPolling(e.currentTarget);
    },

    /**
     * Resets a node's history and starts polling when a focus event occurs.
     *
     * @method _onFocus
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _onFocus: function (e) {
        var node = e.currentTarget;

        VC._history[Y.stamp(node)] = node.get(VALUE);
        VC._startPolling(node, null, e);
    },

    /**
     * Starts polling when a node receives a keyDown event.
     *
     * @method _onKeyDown
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _onKeyDown: function (e) {
        VC._startPolling(e.currentTarget, null, e);
    },

    /**
     * Starts polling when an IME-related keyUp event occurs on a node.
     *
     * @method _onKeyUp
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _onKeyUp: function (e) {
        // These charCodes indicate that an IME has started. We'll restart
        // polling and give the IME up to 10 seconds (by default) to finish.
        if (e.charCode === 229 || e.charCode === 197) {
            VC._startPolling(e.currentTarget, null, e, true);
        }
    },

    /**
     * Starts polling when a node receives a mouseDown event.
     *
     * @method _onMouseDown
     * @param {EventFacade} e
     * @protected
     * @static
     */
    _onMouseDown: function (e) {
        VC._startPolling(e.currentTarget, null, e);
    },

    /**
     * Called when event-valuechange receives a new subscriber.
     *
     * @method _onSubscribe
     * @param {Node} node
     * @param {Subscription} subscription
     * @param {SyntheticEvent.Notifier} notifier
     * @protected
     * @static
     */
    _onSubscribe: function (node, subscription, notifier) {
        var stamp     = Y.stamp(node),
            notifiers = VC._notifiers[stamp];

        VC._history[stamp] = node.get(VALUE);

        notifier._handles = node.on({
            blur     : VC._onBlur,
            focus    : VC._onFocus,
            keydown  : VC._onKeyDown,
            keyup    : VC._onKeyUp,
            mousedown: VC._onMouseDown
        });

        if (!notifiers) {
            notifiers = VC._notifiers[stamp] = [];
        }

        notifiers.push(notifier);
    },

    /**
     * Called when event-valuechange loses a subscriber.
     *
     * @method _onUnsubscribe
     * @param {Node} node
     * @param {Subscription} subscription
     * @param {SyntheticEvent.Notifier} notifier
     * @protected
     * @static
     */
    _onUnsubscribe: function (node, subscription, notifier) {
        var stamp     = Y.stamp(node),
            notifiers = VC._notifiers[stamp],
            index     = YArray.indexOf(notifiers, notifier);

        notifier._handles.detach();

        if (index !== -1) {
            notifiers.splice(index, 1);

            if (!notifiers.length) {
                VC._stopPolling(node, stamp);

                delete VC._notifiers[stamp];
                delete VC._history[stamp];
            }
        }
    }
};

/**
 * <p>
 * Synthetic event that fires when the <code>value</code> property of an input
 * field or textarea changes as a result of a keystroke, mouse operation, or
 * input method editor (IME) input event.
 * </p>
 *
 * <p>
 * Unlike the <code>onchange</code> event, this event fires when the value
 * actually changes and not when the element loses focus. This event also
 * reports IME and multi-stroke input more reliably than <code>oninput</code> or
 * the various key events across browsers.
 * </p>
 *
 * <p>
 * This event is provided by the <code>event-valuechange</code> module.
 * </p>
 *
 * <p>
 * <strong>Usage example:</strong>
 * </p>
 *
 * <code><pre>
 * YUI().use('event-valuechange', function (Y) {
 * &nbsp;&nbsp;Y.one('input').on('valueChange', function (e) {
 * &nbsp;&nbsp;&nbsp;&nbsp;// Handle valueChange events on the first input element on the page.
 * &nbsp;&nbsp;});
 * });
 * </pre></code>
 *
 * @event valueChange
 * @param {EventFacade} e Event facade with the following additional
 *   properties:
 *
 * <dl>
 *   <dt>prevVal (String)</dt>
 *   <dd>
 *     Previous value before the latest change.
 *   </dd>
 *
 *   <dt>newVal (String)</dt>
 *   <dd>
 *     New value after the latest change.
 *   </dd>
 * </dl>
 *
 * @for YUI
 */

Y.Event.define('valueChange', {
    detach: VC._onUnsubscribe,
    on    : VC._onSubscribe,

    publishConfig: {
        emitFacade: true
    }
});

Y.ValueChange = VC;


}, '3.3.0' ,{requires:['event-focus', 'event-synthetic']});
