/**
 * @class Ext.util.DelayedTask
 * 
 The DelayedTask class provides a convenient way to "buffer" the execution of a method,
 * performing setTimeout where a new timeout cancels the old timeout. When called, the
 * task will wait the specified time period before executing. If durng that time period,
 * the task is called again, the original call will be cancelled. This continues so that
 * the function is only called a single time for each iteration.

 * 
This method is especially useful for things like detecting whether a user has finished
 * typing in a text field. An example would be performing validation on a keypress. You can
 * use this class to buffer the keypress events for a certain number of milliseconds, and
 * perform only if they stop for that amount of time.  Usage:

var task = new Ext.util.DelayedTask(function(){
    alert(Ext.getDom('myInputField').value.length);
});
// Wait 500ms before calling our function. If the user presses another key 
// during that 500ms, it will be cancelled and we'll wait another 500ms.
Ext.get('myInputField').on('keypress', function(){
    task.{@link #delay}(500); 
});
 * 
 
 * 
Note that we are using a DelayedTask here to illustrate a point. The configuration
 * option buffer for {@link Ext.util.Observable#addListener addListener/on} will
 * also setup a delayed task for you to buffer events.
 
 * @constructor The parameters to this constructor serve as defaults and are not required.
 * @param {Function} fn (optional) The default function to timeout
 * @param {Object} scope (optional) The default scope of that timeout
 * @param {Array} args (optional) The default Array of arguments
 */
Ext.util.DelayedTask = function(fn, scope, args){
    var me = this,
        id,     
        call = function(){
                clearInterval(id);
                id = null;
                fn.apply(scope, args || []);
            };
            
    
/**
     * Cancels any pending timeout and queues a new one
     * @param {Number} delay The milliseconds to delay
     * @param {Function} newFn (optional) Overrides function passed to constructor
     * @param {Object} newScope (optional) Overrides scope passed to constructor
     * @param {Array} newArgs (optional) Overrides args passed to constructor
     */
    me.delay = function(delay, newFn, newScope, newArgs){
        me.cancel();
        fn = newFn || fn;
        scope = newScope || scope;
        args = newArgs || args;
        id = setInterval(call, delay);
    };

    
/**
     * Cancel the last queued timeout
     */
    me.cancel = function(){
        if(id){
            clearInterval(id);
            id = null;
        }
    };
};