(******************************************************************************)
(*                                                                            *)
(*                               PROJECT HELM                                 *)
(*                                                                            *)
(*                Claudio Sacerdoti Coen <sacerdot@cs.unibo.it>               *)
(*                                 28/12/2000                                 *)
(*                                                                            *)
(* This is the parser that reads the configuration file of helm               *)
(*                                                                            *)
(******************************************************************************)

exception MalformedDir of string

(* this should be the only hard coded constant *)
let filename =
 let prefix =
  try
   Sys.getenv "HELM_CONFIGURATION_DIR"
  with
   Not_found -> "@HELM_CONFIGURATION_DIR@"
 in
  if prefix.[(String.length prefix) - 1] = '/' then
   raise (MalformedDir prefix) ;
  prefix ^ "/configuration.xml";;

exception Warnings;;

class warner =
  object 
    method warn w =
      print_endline ("WARNING: " ^ w) ;
      (raise Warnings : unit)
  end
;;

let xml_document () =
 let module Y = Pxp_yacc in
  try 
   let config = {Y.default_config with Y.warner = new warner} in
    Y.parse_document_entity config (Y.from_file filename) Y.default_spec
  with
   e ->
     print_endline (Pxp_types.string_of_exn e) ;
     raise e
;;

exception Impossible;;

let vars = Hashtbl.create 14;;

(* resolve <value-of> tags and returns the string values of the variable tags *)
let rec resolve =
 let module D = Pxp_document in
  function
     [] -> ""
   | he::tl when he#node_type = D.T_element "value-of" ->
      (match he#attribute "var" with
          Pxp_types.Value var -> Hashtbl.find vars var
        | _ -> raise Impossible
      ) ^ resolve tl
   | he::tl when he#node_type = D.T_data ->
      he#data ^ resolve tl
   | _ -> raise Impossible
;;

(* we trust the xml file to be valid because of the validating xml parser *)
let _ =
 List.iter
  (function
      n ->
       match n#node_type with
          Pxp_document.T_element var ->
           Hashtbl.add vars var (resolve (n#sub_nodes))
        | _ -> raise Impossible
  )
  ((xml_document ())#root#sub_nodes)
;;

(* try to read a configuration variable, given its name into the
 * configuration.xml file and its name into the shell environment.
 * The shell variable, if present, has precedence over configuration.xml
 *)
let read_configuration_var_env xml_name env_name =
 try
  try
   Sys.getenv env_name
  with
   Not_found -> Hashtbl.find vars xml_name
 with
  Not_found ->
   Printf.printf "Sorry, cannot find variable `%s', please check your configuration\n" xml_name ;
   flush stdout ;
   raise Not_found

let read_configuration_var xml_name =
 try
  Hashtbl.find vars xml_name
 with
  Not_found ->
   Printf.printf "Sorry, cannot find variable `%s', please check your configuration\n" xml_name ;
   flush stdout ;
   raise Not_found

let helm_dir      = read_configuration_var     "helm_dir";;
let dtd_dir       = read_configuration_var     "dtd_dir";;
let style_dir     = read_configuration_var_env "style_dir" "HELM_STYLE_DIR";;
let servers_file  = read_configuration_var     "servers_file";;
let uris_dbm      = read_configuration_var     "uris_dbm";;
let dest          = read_configuration_var     "dest";;
let indexname     = read_configuration_var     "indexname";;
let tmp_dir       = read_configuration_var     "tmp_dir"
let helm_dir      = read_configuration_var     "helm_dir";;
let getter_url    = read_configuration_var_env "getter_url" "HELM_GETTER_URL";;
let processor_url = read_configuration_var_env "processor_url" "HELM_PROCESSOR_URL";;

let _ = Hashtbl.clear vars;;