/**
 * The CustomEvent class lets you define events for your application
 * that can be subscribed to by one or more independent component.
 *
 * @param {String}  type The type of event, which is passed to the callback
 *                  when the event fires
 * @param {Object}  oScope The context the event will fire from.  "this" will
 *                  refer to this object in the callback.  Default value: 
 *                  the window object.  The listener can override this.
 * @param {boolean} silent pass true to prevent the event from writing to
 *                  the debugsystem
 * @param {int}     signature the signature that the custom event subscriber
 *                  will receive. YAHOO.util.CustomEvent.LIST or 
 *                  YAHOO.util.CustomEvent.FLAT.  The default is
 *                  YAHOO.util.CustomEvent.LIST.
 * @namespace YAHOO.util
 * @class CustomEvent
 * @constructor
 */
YAHOO.util.CustomEvent = function(type, oScope, silent, signature) {

    /**
     * The type of event, returned to subscribers when the event fires
     * @property type
     * @type string
     */
    this.type = type;

    /**
     * The scope the the event will fire from by default.  Defaults to the window 
     * obj
     * @property scope
     * @type object
     */
    this.scope = oScope || window;

    /**
     * By default all custom events are logged in the debug build, set silent
     * to true to disable debug outpu for this event.
     * @property silent
     * @type boolean
     */
    this.silent = silent;

    /**
     * Custom events support two styles of arguments provided to the event
     * subscribers.  
     * <ul>
     * <li>YAHOO.util.CustomEvent.LIST: 
     *   <ul>
     *   <li>param1: event name</li>
     *   <li>param2: array of arguments sent to fire</li>
     *   <li>param3: <optional> a custom object supplied by the subscriber</li>
     *   </ul>
     * </li>
     * <li>YAHOO.util.CustomEvent.FLAT
     *   <ul>
     *   <li>param1: the first argument passed to fire.  If you need to
     *           pass multiple parameters, use and array or object literal</li>
     *   <li>param2: <optional> a custom object supplied by the subscriber</li>
     *   </ul>
     * </li>
     * </ul>
     *   @property signature
     *   @type int
     */
    this.signature = signature || YAHOO.util.CustomEvent.LIST;

    /**
     * The subscribers to this event
     * @property subscribers
     * @type Subscriber[]
     */
    this.subscribers = [];

    if (!this.silent) {
        YAHOO.log( "Creating " + this, "info", "Event" );
    }

    var onsubscribeType = "_YUICEOnSubscribe";

    // Only add subscribe events for events that are not generated by 
    // CustomEvent
    if (type !== onsubscribeType) {

        /**
         * Custom events provide a custom event that fires whenever there is
         * a new subscriber to the event.  This provides an opportunity to
         * handle the case where there is a non-repeating event that has
         * already fired has a new subscriber.  
         *
         * @event subscribeEvent
         * @type YAHOO.util.CustomEvent
         * @param {Function} fn The function to execute
         * @param {Object}   obj An object to be passed along when the event 
         *                       fires
         * @param {boolean|Object}  override If true, the obj passed in becomes 
         *                                   the execution scope of the listener.
         *                                   if an object, that object becomes the
         *                                   the execution scope.
         */
        this.subscribeEvent = 
                new YAHOO.util.CustomEvent(onsubscribeType, this, true);

    } 
};

/**
 * Subscriber listener sigature constant.  The LIST type returns three
 * parameters: the event type, the array of args passed to fire, and
 * the optional custom object
 * @property YAHOO.util.CustomEvent.LIST
 * @static
 * @type int
 */
YAHOO.util.CustomEvent.LIST = 0;

/**
 * Subscriber listener sigature constant.  The FLAT type returns two
 * parameters: the first argument passed to fire and the optional 
 * custom object
 * @property YAHOO.util.CustomEvent.FLAT
 * @static
 * @type int
 */
YAHOO.util.CustomEvent.FLAT = 1;

YAHOO.util.CustomEvent.prototype = {

    /**
     * Subscribes the caller to this event
     * @method subscribe
     * @param {Function} fn        The function to execute
     * @param {Object}   obj       An object to be passed along when the event 
     *                             fires
     * @param {boolean|Object}  override If true, the obj passed in becomes 
     *                                   the execution scope of the listener.
     *                                   if an object, that object becomes the
     *                                   the execution scope.
     */
    subscribe: function(fn, obj, override) {
        if (this.subscribeEvent) {
            this.subscribeEvent.fire(fn, obj, override);
        }

        this.subscribers.push( new YAHOO.util.Subscriber(fn, obj, override) );
    },

    /**
     * Unsubscribes the caller from this event
     * @method unsubscribe
     * @param {Function} fn  The function to execute
     * @param {Object}   obj  The custom object passed to subscribe (optional)
     * @return {boolean} True if the subscriber was found and detached.
     */
    unsubscribe: function(fn, obj) {
        var found = false;
        for (var i=0, len=this.subscribers.length; i<len; ++i) {
            var s = this.subscribers[i];
            if (s && s.contains(fn, obj)) {
                this._delete(i);
                found = true;
            }
        }

        return found;
    },

    /**
     * Notifies the subscribers.  The callback functions will be executed
     * from the scope specified when the event was created, and with the 
     * following parameters:
     *   <ul>
     *   <li>The type of event</li>
     *   <li>All of the arguments fire() was executed with as an array</li>
     *   <li>The custom object (if any) that was passed into the subscribe() 
     *       method</li>
     *   </ul>
     * @method fire 
     * @param {Object*} arguments an arbitrary set of parameters to pass to 
     *                            the handler.
     * @return {boolean} false if one of the subscribers returned false, 
     *                   true otherwise
     */
    fire: function() {
        var len=this.subscribers.length;
        if (!len && this.silent) {
            return true;
        }

        var args=[], ret=true, i;

        for (i=0; i<arguments.length; ++i) {
            args.push(arguments[i]);
        }

        var argslength = args.length;

        if (!this.silent) {
            YAHOO.log( "Firing "       + this  + ", " + 
                       "args: "        + args  + ", " +
                       "subscribers: " + len,                 
                       "info", "Event"                  );
        }

        for (i=0; i<len; ++i) {
            var s = this.subscribers[i];
            if (s) {
                if (!this.silent) {
                    YAHOO.log( this.type + "->" + (i+1) + ": " +  s, 
                                "info", "Event" );
                }

                var scope = s.getScope(this.scope);

                if (this.signature == YAHOO.util.CustomEvent.FLAT) {
                    var param = null;
                    if (args.length > 0) {
                        param = args[0];
                    }
                    ret = s.fn.call(scope, param, s.obj);
                } else {
                    ret = s.fn.call(scope, this.type, args, s.obj);
                }
                if (false === ret) {
                    if (!this.silent) {
                        YAHOO.log("Event cancelled, subscriber " + i + 
                                  " of " + len);
                    }

                    //break;
                    return false;
                }
            }
        }

        return true;
    },

    /**
     * Removes all listeners
     * @method unsubscribeAll
     */
    unsubscribeAll: function() {
        for (var i=0, len=this.subscribers.length; i<len; ++i) {
            this._delete(len - 1 - i);
        }
    },

    /**
     * @method _delete
     * @private
     */
    _delete: function(index) {
        var s = this.subscribers[index];
        if (s) {
            delete s.fn;
            delete s.obj;
        }

        // delete this.subscribers[index];
        this.subscribers.splice(index, 1);
    },

    /**
     * @method toString
     */
    toString: function() {
         return "CustomEvent: " + "'" + this.type  + "', " + 
             "scope: " + this.scope;

    }
};

/////////////////////////////////////////////////////////////////////

/**
 * Stores the subscriber information to be used when the event fires.
 * @param {Function} fn       The function to execute
 * @param {Object}   obj      An object to be passed along when the event fires
 * @param {boolean}  override If true, the obj passed in becomes the execution
 *                            scope of the listener
 * @class Subscriber
 * @constructor
 */
YAHOO.util.Subscriber = function(fn, obj, override) {

    /**
     * The callback that will be execute when the event fires
     * @property fn
     * @type function
     */
    this.fn = fn;

    /**
     * An optional custom object that will passed to the callback when
     * the event fires
     * @property obj
     * @type object
     */
    this.obj = obj || null;

    /**
     * The default execution scope for the event listener is defined when the
     * event is created (usually the object which contains the event).
     * By setting override to true, the execution scope becomes the custom
     * object passed in by the subscriber.  If override is an object, that 
     * object becomes the scope.
     * @property override
     * @type boolean|object
     */
    this.override = override;

};

/**
 * Returns the execution scope for this listener.  If override was set to true
 * the custom obj will be the scope.  If override is an object, that is the
 * scope, otherwise the default scope will be used.
 * @method getScope
 * @param {Object} defaultScope the scope to use if this listener does not
 *                              override it.
 */
YAHOO.util.Subscriber.prototype.getScope = function(defaultScope) {
    if (this.override) {
        if (this.override === true) {
            return this.obj;
        } else {
            return this.override;
        }
    }
    return defaultScope;
};

/**
 * Returns true if the fn and obj match this objects properties.
 * Used by the unsubscribe method to match the right subscriber.
 *
 * @method contains
 * @param {Function} fn the function to execute
 * @param {Object} obj an object to be passed along when the event fires
 * @return {boolean} true if the supplied arguments match this 
 *                   subscriber's signature.
 */
YAHOO.util.Subscriber.prototype.contains = function(fn, obj) {
    if (obj) {
        return (this.fn == fn && this.obj == obj);
    } else {
        return (this.fn == fn);
    }
};

/**
 * @method toString
 */
YAHOO.util.Subscriber.prototype.toString = function() {
    return "Subscriber { obj: " + (this.obj || "")  + 
           ", override: " +  (this.override || "no") + " }";
};