(* NAVBAR provides services to construct and pretty print to xml typical
 * menu items (of a visible text and a url link) and menu bars assembled
 * from them.  It is intended to be used as a low-level component in
 * constructing navigation related widgets and theme parts. *)

type navItem
(* Items in the navigation menu. *)

con navBar :: Type -> Type
(* A menu bar of navigation links. Up to one link may be active. *)

type build
type print
(* These track the current navbar mode. *)

class mode
(* To make sure we always print the navbar correctly. *)

val navToXml_build : mode build
val navToXml_print : mode print
(* How to print both modes. *)

val printingNavBar : navBar build -> navBar print
(* This switches the navbar from building mode to printing mode.  Normally not
 * necessary to call this, but is in the signature in case the programmer will
 * pass the same navbar to several components wanting to print it.  Then by
 * using this first multiple (redundant) calls to List.rev can be avoided.
 * Mode tracking makes this optimization safe. *)

val emptyNavBar : navBar build
(* An empty menu bar. *)

val mkNavItem : string -> url -> navItem
(* Make a menu item with visible text given by the string and linking to url. *)

val navAdd : navItem -> navBar build -> navBar build
(* Add an unactive item to the right end of the navbar. *)

val navAddActive : navItem -> navBar build -> navBar build
(* Add an active item to the right end of the navbar.  If there already
 * was an active item it will be deactivated. *)

val navItemToXml : option css_class -> navItem -> xbody
(* Pretty print a navItem with an optional style to a piece of <a>...</a> xml. *)

val navBarToXml : t ::: Type -> mode t -> navBar t -> xbody
(* Pretty print the navigation menu as a piece of xml made of
 * a chain <li><a>...</a></li> repeated. *)

style active
style last
(* CSS classes to mark the active and last menu item. *)