function MenuBar(div) {
    this._div = div;
    this._initializeUI();
}

MenuBar.prototype._initializeUI = function() {
    this._mode = "inactive";
    this._menuItemRecords = [];
    
    this._div.addClass("menu-bar").html(" ");
    this._innerDiv = $('<div></div>').addClass("menu-bar-inner").appendTo(this._div);

    var self = this;
    
    this._createTopLevelMenuItem("Data Set", [
        {
            label: "Export Filtered Rows",
            click: function() { self._doExportRows(); }
        }
    ]);
    this._createTopLevelMenuItem("Schemas", [
        {
            label: "Auto-Align with Freebase ...",
            click: function() { self._doAutoSchemaAlignment(); }
        },
        {
            label: "Edit Schema Alignment ...",
            click: function() {  }
        }
    ]);
    
    this._wireAllMenuItemsInactive();
};

MenuBar.prototype._createTopLevelMenuItem = function(label, submenu) {
    var self = this;
    
    var menuItem = MenuSystem.createMenuItem().text(label).appendTo(this._innerDiv);
    
    this._menuItemRecords.push({
        menuItem: menuItem,
        show: function() {
            MenuSystem.dismissUntil(self._level);
            
            menuItem.addClass("menu-expanded");
            
            MenuSystem.createAndShowStandardMenu(
                submenu,
                this,
                {
                    horizontal: false,
                    onDismiss: function() {
                        menuItem.removeClass("menu-expanded");
                    }
                }
            );
        }
    });
};

MenuBar.prototype._wireMenuItemInactive = function(record) {
    var self = this;
    var click = function() {
        self._activateMenu();
        record.show.apply(record.menuItem[0]);
    };
    
    record.menuItem.click(function() {
        // because we're going to rewire the menu bar, we have to
        // make this asynchronous, or jquery event binding won't work.
        window.setTimeout(click, 100);
    });
};

MenuBar.prototype._wireAllMenuItemsInactive = function() {
    for (var i = 0; i < this._menuItemRecords.length; i++) {
        this._wireMenuItemInactive(this._menuItemRecords[i]);
    }
};

MenuBar.prototype._wireMenuItemActive = function(record) {
    record.menuItem.mouseover(function() {
        record.show.apply(this);
    });
};

MenuBar.prototype._wireAllMenuItemsActive = function() {
    for (var i = 0; i < this._menuItemRecords.length; i++) {
        this._wireMenuItemActive(this._menuItemRecords[i]);
    }
};

MenuBar.prototype._activateMenu = function() {
    var self = this;
    
    var top = this._innerDiv.offset().top;
    
    this._innerDiv.remove().css("top", top + "px");
    this._wireAllMenuItemsActive();
    this._mode = "active";
    
    this._level = MenuSystem.showMenu(this._innerDiv, function() {
        self._deactivateMenu();
    });
};

MenuBar.prototype._deactivateMenu = function() {
    this._innerDiv.remove()
        .css("top", "0px")
        .appendTo(this._div);
        
    this._wireAllMenuItemsInactive();
    this._mode = "inactive";
};

MenuBar.prototype._doExportRows = function() {
    var form = document.createElement("form");
    $(form)
        .css("display", "none")
        .attr("method", "post")
        .attr("action", "/command/export-rows?project=" + theProject.id)
        .attr("target", "gridworks-export");

    $('<input />')
        .attr("name", "engine")
        .attr("value", JSON.stringify(ui.browsingEngine.getJSON()))
        .appendTo(form);
    
    document.body.appendChild(form);

    window.open("about:blank", "gridworks-export");
    form.submit();
    
    document.body.removeChild(form);
};

MenuBar.prototype._doAutoSchemaAlignment = function() {
    //SchemaAlignment.autoAlign();
    
    new SchemaAlignmentDialog(theProject.protograph, function(newProtograph) {
        
    });
};