/*
 * OpenSeadragon - EventHandler
 *
 * Copyright (C) 2009 CodePlex Foundation
 * Copyright (C) 2010-2013 OpenSeadragon contributors
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of CodePlex Foundation nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

(function($){

/**
 * For use by classes which want to support custom, non-browser events.
 * TODO: This is an awful name!  This thing represents an "event source",
 *       not an "event handler".  PLEASE change the to EventSource. Also please
 *       change 'addHandler', 'removeHandler' and 'raiseEvent' to 'bind',
 *       'unbind', and 'trigger' respectively.  Finally add a method 'one' which
 *       automatically unbinds a listener after the first triggered event that
 *       matches.
 * @class
 */
$.EventHandler = function() {
    this.events = {};
};

$.EventHandler.prototype = {

    /**
     * Add an event handler for a given event.
     * @function
     * @param {String} eventName - Name of event to register.
     * @param {Function} handler - Function to call when event is triggered.
     * @param {Object} optional userData - Arbitrary object to be passed to the handler.
     */
    addHandler: function ( eventName, handler, userData ) {
        var events = this.events[ eventName ];
        if ( !events ) {
            this.events[ eventName ] = events = [];
        }
        if ( handler && $.isFunction( handler ) ) {
            events[ events.length ] = { handler: handler, userData: userData || null };
        }
    },

    /**
     * Remove a specific event handler for a given event.
     * @function
     * @param {String} eventName - Name of event for which the handler is to be removed.
     * @param {Function} handler - Function to be removed.
     */
    removeHandler: function ( eventName, handler ) {
        var events = this.events[ eventName ],
            handlers = [],
            i;
        if ( !events ) {
            return;
        }
        if ( $.isArray( events ) ) {
            for ( i = 0; i < events.length; i++ ) {
                if ( events[i].handler !== handler ) {
                    handlers.push( events[ i ] );
                }
            }
            this.events[ eventName ] = handlers;
        }
    },


    /**
     * Remove all event handlers for a given event type. If no type is given all
     * event handlers for every event type are removed.
     * @function
     * @param {String} eventName - Name of event for which all handlers are to be removed.
     */
    removeAllHandlers: function( eventName ) {
        if ( eventName ){
            this.events[ eventName ] = [];
        } else{
            for ( var eventType in this.events ) {
                this.events[ eventType ] = [];
            }
        }
    },

    /**
     * Retrive the list of all handlers registered for a given event.
     * @function
     * @param {String} eventName - Name of event to get handlers for.
     */
    getHandler: function ( eventName ) {
        var events = this.events[ eventName ];
        if ( !events || !events.length ) {
            return null;
        }
        events = events.length === 1 ?
            [ events[ 0 ] ] :
            Array.apply( null, events );
        return function ( source, args ) {
            var i,
            length = events.length;
            for ( i = 0; i < length; i++ ) {
                if (events[ i ]) {
                    args.userData = events[ i ].userData;
                    events[ i ].handler( source, args );
                }
            }
        };
    },

    /**
     * Trigger an event, optionally passing additional information.
     * @function
     * @param {String} eventName - Name of event to register.
     * @param {Function} handler - Function to call when event is triggered.
     */
    raiseEvent: function( eventName, eventArgs ) {
        //uncomment if you want to get a log of all events
        //$.console.log( eventName );
        var handler = this.getHandler( eventName );

        if ( handler ) {
            if ( !eventArgs ) {
                eventArgs = {};
            }

            handler( this, eventArgs );
        }
    }
};

}( OpenSeadragon ));