/**
 * @class Ext.util.TaskRunner
 * Provides the ability to execute one or more arbitrary tasks in a multithreaded
 * manner.  Generally, you can use the singleton {@link Ext.TaskMgr} instead, but
 * if needed, you can create separate instances of TaskRunner.  Any number of
 * separate tasks can be started at any time and will run independently of each
 * other. Example usage:
 * 

// Start a simple clock task that updates a div once per second
var updateClock = function(){
    Ext.fly('clock').update(new Date().format('g:i:s A'));
} 
var task = {
    run: updateClock,
    interval: 1000 //1 second
}
var runner = new Ext.util.TaskRunner();
runner.start(task);

// equivalent using TaskMgr
Ext.TaskMgr.start({
    run: updateClock,
    interval: 1000
});

 * 
 * 
See the {@link #start} method for details about how to configure a task object.
 * Also see {@link Ext.util.DelayedTask}. 
 * 
 * @constructor
 * @param {Number} interval (optional) The minimum precision in milliseconds supported by this TaskRunner instance
 * (defaults to 10)
 */
Ext.ns('Ext.util');

Ext.util.TaskRunner = function(interval) {
    interval = interval || 10;
    var tasks = [],
    removeQueue = [],
    id = 0,
    running = false,

    // private
    stopThread = function() {
        running = false;
        clearInterval(id);
        id = 0;
    },

    // private
    startThread = function() {
        if (!running) {
            running = true;
            id = setInterval(runTasks, interval);
        }
    },

    // private
    removeTask = function(t) {
        removeQueue.push(t);
        if (t.onStop) {
            t.onStop.apply(t.scope || t);
        }
    },

    // private
    runTasks = function() {
        var rqLen = removeQueue.length,
            now = new Date().getTime(),
            i;

        if (rqLen > 0) {
            for (i = 0; i < rqLen; i++) {
                Ext.Array.remove(tasks, removeQueue[i]);
            }
            removeQueue = [];
            if (tasks.length < 1) {
                stopThread();
                return;
            }
        }
        i = 0;
        var t,
            itime,
            rt,
            len = tasks.length;
        for (; i < len; ++i) {
            t = tasks[i];
            itime = now - t.taskRunTime;
            if (t.interval <= itime) {
                rt = t.run.apply(t.scope || t, t.args || [++t.taskRunCount]);
                t.taskRunTime = now;
                if (rt === false || t.taskRunCount === t.repeat) {
                    removeTask(t);
                    return;
                }
            }
            if (t.duration && t.duration <= (now - t.taskStartTime)) {
                removeTask(t);
            }
        }
    };

    
/**
     * Starts a new task.
     * @method start
     * @param {Object} task 
A config object that supports the following properties:

     * 
run : Function
The function to execute each time the task is invoked. The
     * function will be called at each interval and passed the args argument if specified, and the
     * current invocation count if not.
     * 
If a particular scope (this reference) is required, be sure to specify it using the scope argument.
     * 
Return false from this function to terminate the task.
     * 
interval : Number
The frequency in milliseconds with which the task
     * should be invoked.
     * 
args : Array
(optional) An array of arguments to be passed to the function
     * specified by run. If not specified, the current invocation count is passed.
     * 
scope : Object
(optional) The scope (this reference) in which to execute the
     * run function. Defaults to the task config object.
     * 
duration : Number
(optional) The length of time in milliseconds to invoke
     * the task before stopping automatically (defaults to indefinite).
     * 
repeat : Number
(optional) The number of times to invoke the task before
     * stopping automatically (defaults to indefinite).
     * 

     * 
Before each invocation, Ext injects the property taskRunCount into the task object so
     * that calculations based on the repeat count can be performed.
     * @return {Object} The task
     */
    this.start = function(task) {
        tasks.push(task);
        task.taskStartTime = new Date().getTime();
        task.taskRunTime = 0;
        task.taskRunCount = 0;
        startThread();
        return task;
    };

    
/**
     * Stops an existing running task.
     * @method stop
     * @param {Object} task The task to stop
     * @return {Object} The task
     */
    this.stop = function(task) {
        removeTask(task);
        return task;
    };

    
/**
     * Stops all tasks that are currently running.
     * @method stopAll
     */
    this.stopAll = function() {
        stopThread();
        for (var i = 0, len = tasks.length; i < len; i++) {
            if (tasks[i].onStop) {
                tasks[i].onStop();
            }
        }
        tasks = [];
        removeQueue = [];
    };
};

/**
 * @class Ext.TaskMgr
 * @extends Ext.util.TaskRunner
 * A static {@link Ext.util.TaskRunner} instance that can be used to start and stop arbitrary tasks.  See
 * {@link Ext.util.TaskRunner} for supported methods and task config properties.
 * 

// Start a simple clock task that updates a div once per second
var task = {
    run: function(){
        Ext.fly('clock').update(new Date().format('g:i:s A'));
    },
    interval: 1000 //1 second
}
Ext.TaskMgr.start(task);

 * 
See the {@link #start} method for details about how to configure a task object.
 * @singleton
 */
Ext.TaskMgr = new Ext.util.TaskRunner();