(******************************************************************************)
(*  SXSI : XPath evaluator                                                    *)
(*  Kim Nguyen (Kim.Nguyen@nicta.com.au)                                      *)
(*  Copyright NICTA 2008                                                      *)
(*  Distributed under the terms of the LGPL (see LICENCE)                     *)
(******************************************************************************)
(*  maybe utf8 string... *)


type t = int
type pool

external null_pool : unit -> pool = "caml_xml_tree_nullt"
external null_tag : unit -> t = "caml_xml_tree_nullt"
external register_tag : pool -> string -> t = "caml_xml_tree_register_tag"
external tag_name : pool -> t -> string = "caml_xml_tree_get_tag_name"

let nullt = null_tag ()   
let dummy = nullt
(* Defined in XMLTree.cpp *)
let document_node = 0
let attribute = 1
let pcdata = 2
let attribute_data= 3
let document_node_close = 4
let attribute_close = 5
let pcdata_close = 6
let attribute_data_close= 7


let pool = Weak.create 1

let init p = Weak.set pool 0 (Some p)

let get_pool () =  match Weak.get pool 0 with
  | Some x -> x
  | None -> failwith "Tag.ml: Uninitialized Document"

let tag s = match s with
  | "<$>" -> pcdata
  | "<@>" -> attribute
  | "" -> document_node
  | "<@$>" -> attribute_data
  | _ -> register_tag (get_pool()) s

let compare = (-)
let equal = (==)

let hash x = x


let to_string t = 
  if t == pcdata then "<$>"
  else if t == attribute_data then "<@$>"
  else if t == attribute then "<@>"
  else if t == nullt then "<!NIL!>"
  else tag_name (get_pool()) t


let print ppf t = Format.fprintf ppf "%s" (to_string t)
(* Check internal invariants *)
let check t = 
  if (t != tag (to_string t))
  then failwith "module Tag: internal check failed"

let dump = print