(function( $ ){

    //id hash for private properties;
    var THIS = {};
    
    /**
     * @class
     */
    $.ControlDock = function( options ){
        var layouts = [ 'topleft', 'topright', 'bottomright', 'bottomleft'],
            layout,
            i;
        
        $.extend( true, this, {
            id: 'controldock-'+(+new Date())+'-'+Math.floor(Math.random()*1000000),
            container: $.makeNeutralElement('form'),
            controls: []
        }, options );

        if( this.element ){
            this.element = $.getElement( this.element );
            this.element.appendChild( this.container );   
            this.element.style.position = 'relative'; 
            this.container.style.width = '100%';
            this.container.style.height = '100%';
        }

        for( i = 0; i < layouts.length; i++ ){
            layout = layouts[ i ];
            this.controls[ layout ] = $.makeNeutralElement( "div" );
            this.controls[ layout ].style.position = 'absolute';
            if ( layout.match( 'left' ) ){
                this.controls[ layout ].style.left = '0px';
            }
            if ( layout.match( 'right' ) ){
                this.controls[ layout ].style.right = '0px';
            }
            if ( layout.match( 'top' ) ){
                this.controls[ layout ].style.top = '0px';
            }
            if ( layout.match( 'bottom' ) ){
                this.controls[ layout ].style.bottom = '0px';
            }
        }

        this.container.appendChild( this.controls.topleft );
        this.container.appendChild( this.controls.topright );
        this.container.appendChild( this.controls.bottomright );
        this.container.appendChild( this.controls.bottomleft );
    };

    $.ControlDock.prototype = {

        /**
         * @function
         */
        addControl: function ( element, anchor ) {
            var element = $.getElement( element ),
                div = null;

            if ( getControlIndex( this, element ) >= 0 ) {
                return;     // they're trying to add a duplicate control
            }

            switch ( anchor ) {
                case $.ControlAnchor.TOP_RIGHT:
                    div = this.controls.topright;
                    element.style.position = "relative";
                    element.style.marginRight = "4px";
                    element.style.marginTop = "4px";
                    break;
                case $.ControlAnchor.BOTTOM_RIGHT:
                    div = this.controls.bottomright;
                    element.style.position = "relative";
                    element.style.marginRight = "4px";
                    element.style.marginBottom = "4px";
                    break;
                case $.ControlAnchor.BOTTOM_LEFT:
                    div = this.controls.bottomleft;
                    element.style.position = "relative";
                    element.style.marginLeft = "4px";
                    element.style.marginBottom = "4px";
                    break;
                case $.ControlAnchor.TOP_LEFT:
                    div = this.controls.topleft;
                    element.style.position = "relative";
                    element.style.marginLeft = "4px";
                    element.style.marginTop = "4px";
                    break;
                case $.ControlAnchor.NONE:
                default:
                    div = this.container;
                    element.style.margin = "0px";
                    element.style.padding = "0px";
                    break;
            }

            this.controls.push(
                new $.Control( element, anchor, div )
            );
            element.style.display = "inline-block";
        },


        /**
         * @function
         * @return {OpenSeadragon.ControlDock} Chainable.
         */
        removeControl: function ( element ) {
            var element  = $.getElement( element ),
                i        = getControlIndex( this, element );
            
            if ( i >= 0 ) {
                this.controls[ i ].destroy();
                this.controls.splice( i, 1 );
            }

            return this;
        },

        /**
         * @function
         * @return {OpenSeadragon.ControlDock} Chainable.
         */
        clearControls: function () {
            while ( this.controls.length > 0 ) {
                this.controls.pop().destroy();
            }
            
            return this;
        },


        /**
         * @function
         * @return {Boolean}
         */
        areControlsEnabled: function () {
            var i;
            
            for ( i = this.controls.length - 1; i >= 0; i-- ) {
                if ( this.controls[ i ].isVisible() ) {
                    return true;
                }
            }

            return false;
        },


        /**
         * @function
         * @return {OpenSeadragon.ControlDock} Chainable.
         */
        setControlsEnabled: function( enabled ) {
            var i;

            for ( i = this.controls.length - 1; i >= 0; i-- ) {
                this.controls[ i ].setVisible( enabled );
            }

            return this;
        }

    };


    ///////////////////////////////////////////////////////////////////////////////
    // Utility methods
    ///////////////////////////////////////////////////////////////////////////////
    function getControlIndex( dock, element ) {
        var controls = dock.controls,
            i;

        for ( i = controls.length - 1; i >= 0; i-- ) {
            if ( controls[ i ].element == element ) {
                return i;
            }
        }

        return -1;
    };

}( OpenSeadragon ));