(* Copyright (C) 2004, HELM Team.
 * 
 * This file is part of HELM, an Hypertextual, Electronic
 * Library of Mathematics, developed at the Computer Science
 * Department, University of Bologna, Italy.
 * 
 * HELM is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * HELM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HELM; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA  02111-1307, USA.
 * 
 * For details, see the HELM World-Wide-Web page,
 * http://helm.cs.unibo.it/
 *)

open Printf

let debug = false
let debug_print s =
  if debug then prerr_endline ("Helm_registry debugging: " ^ s)

exception Malformed_key of string
exception Key_not_found of string
exception Cyclic_definition of string
exception Type_error of string * string * string (* expected type, value, msg *)
exception Parse_error of string * int * int * string  (* file, line, col, msg *)
exception Invalid_value of (string * string) * string (* key, value, descr *)

type validator_id = int

let get_next_validator_id =
  let next_id = ref 0 in
  fun () ->
    incr next_id;
    !next_id

let magic_size = 127
let validators = Hashtbl.create magic_size
let registry = Hashtbl.create magic_size

let backup_registry () = Hashtbl.copy registry
let restore_registry backup =
  Hashtbl.clear registry;
  Hashtbl.iter (fun key value -> Hashtbl.replace registry key value) backup

  (* as \\w but:
   * - no sequences of '_' longer than 1 are permitted
   * - no uppercase letter are permitted
   *)
(*
let valid_step_rex_raw = "[a-z0-9]+(_[a-z0-9]+)*"
let valid_key_rex_raw =
  sprintf "^%s(\\.%s)*$" valid_step_rex_raw valid_step_rex_raw
let valid_key_rex = Pcre.regexp valid_key_rex_raw
let dot_rex = Pcre.regexp "\\."
let spaces_rex = Pcre.regexp "\\s+"
let heading_spaces_rex = Pcre.regexp "^\\s+"
*)
let valid_step_rex_raw = "[a-z0-9]+\\(_[a-z0-9]+\\)*"
let valid_key_rex_raw =
  sprintf "%s\(\\.%s\)*" valid_step_rex_raw valid_step_rex_raw
let valid_key_rex = Str.regexp ("^" ^ valid_key_rex_raw ^ "$")
let interpolated_key_rex = Str.regexp ("\\$(" ^ valid_key_rex_raw ^ ")")
let dot_rex = Str.regexp "\\."
let spaces_rex = Str.regexp "[ \t\n\r]+"
let heading_spaces_rex = Str.regexp "^[ \t\n\r]+"

  (* escapes for xml configuration file *)
let (escape, unescape) =
  let (in_enc, out_enc) = (`Enc_utf8, `Enc_utf8) in
  (Netencoding.Html.encode ~in_enc ~out_enc (),
   Netencoding.Html.decode ~in_enc ~out_enc ~entity_base:`Xml ())

let key_is_valid key =
(*   if not (Pcre.pmatch ~rex:valid_key_rex key) then *)
  if not (Str.string_match valid_key_rex key 0) then
    raise (Malformed_key key)

let value_is_valid ~key ~value =
  List.iter
    (fun (validator, descr) ->
      if not (validator value) then
        raise (Invalid_value ((key, value), descr)))
    (Hashtbl.find_all validators key)

let set' registry ~key ~value =
  debug_print (sprintf "Setting %s = %s" key value);
  key_is_valid key;
  value_is_valid ~key ~value;
  Hashtbl.replace registry key value

let env_var_of_key key =
(*   Pcre.replace ~rex:dot_rex ~templ:"__" (String.uppercase key) *)
  Str.global_replace dot_rex "__" (String.uppercase key)

let get key =
  let rec aux stack key =
    key_is_valid key;
    if List.mem key stack then begin
      let msg = (String.concat " -> " (List.rev stack)) ^ " -> " ^ key in
      raise (Cyclic_definition msg)
    end;
    let registry_value =  (* internal value *)
      try
        Some (Hashtbl.find registry key)
      with Not_found -> None
    in
    let env_value = (* environment value *)
      try
        Some (Sys.getenv (env_var_of_key key))
      with Not_found -> None
    in
    let value = (* resulting value *)
      match (registry_value, env_value) with
      | Some reg, Some env  -> env
      | Some reg, None      -> reg
      | None,     Some env  -> env
      | None,     None      -> raise (Key_not_found key)
    in
    interpolate (key :: stack) value
  and interpolate stack value =
    Str.global_substitute interpolated_key_rex
      (fun s ->
        let matched = Str.matched_string s in
          (* "$(var)" -> "var" *)
        let key = String.sub matched 2 (String.length matched - 3) in
        aux stack key)
      value
  in
  aux [] key

let set = set' registry

let string_list_of_string s =
  (* trailing blanks are removed per default by split *)
(*   Pcre.split ~res:spaces_rex (Pcre.replace ~rex:heading_spaces_rex s) *)
  Str.split spaces_rex (Str.global_replace heading_spaces_rex "" s)
let string_of_string_list l = String.concat " " l

let mk_get_set type_name (from_string: string -> 'a) (to_string: 'a -> string) =
  let getter key =
    let value = get key in
    try
      from_string value
    with exn ->
      raise (Type_error (type_name, value, Printexc.to_string exn))
  in
  let setter ~key ~value = set ~key ~value:(to_string value) in
  (getter, setter)

let (get_string, set_string) = (get, set)
let (get_int, set_int) = mk_get_set "int" int_of_string string_of_int
let (get_float, set_float) = mk_get_set "float" float_of_string string_of_float
let (get_string_list, set_string_list) =
  mk_get_set "string list" string_list_of_string string_of_string_list

let save_to fname =
  debug_print ("Saving configuration to " ^ fname);
  let oc = open_out fname in
  output_string oc "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
  output_string oc "<helm_registry>\n";
  try
    Hashtbl.iter
      (fun key value ->
        fprintf oc "  <value key=\"%s\">%s</value>\n" key (escape value))
      registry;
    output_string oc "</helm_registry>";
    close_out oc
  with e ->
    close_out oc;
    raise e

let add_validator ~key ~validator ~descr =
  let id = get_next_validator_id () in
  Hashtbl.add validators key (validator, descr);
  id

open Pxp_document
open Pxp_types
open Pxp_yacc

let load_from =
  let config = default_config in
  let entry = `Entry_document [ `Extend_dtd_fully; `Parse_xml_decl ] in
  fun fname ->
    debug_print ("Loading configuration from " ^ fname);
    let document =
      parse_wfdocument_entity config (from_file fname) default_spec
    in
    let fill_registry () =
      document#root#iter_nodes (fun n ->
        try
          (match n#node_type with
          | T_element "value" ->
              let key = n#required_string_attribute "key" in
              let value = n#data in
              set ~key ~value
          | _ -> ())
        with exn ->
          let (fname, line, pos) = n#position in
          raise (Parse_error (fname, line, pos,
            "Uncaught exception: " ^ Printexc.to_string exn)))
    in
    let backup = backup_registry () in
    Hashtbl.clear registry;
    try
      fill_registry ()
    with exn ->
      restore_registry backup;
      raise exn

  (* DEBUGGING ONLY *)

let dump () = Hashtbl.iter (fun k v -> printf "%s = %s\n" k v) registry