(*
 * <COPYRIGHT>
 * Copyright 2003 Gerd Stolpmann
 *
 * <GPL>
 * This file is part of WTimer.
 *
 * WTimer 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.
 *
 * WTimer 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 WDialog; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * </>
 *)

(* $Id$
 * ----------------------------------------------------------------------
 *
 *)

(* This module defines a virtual class "error_behaviour" for two 
 * purposes:
 * - uniform handling of error situations
 * - basic authentication checks that should be done for each click
 *
 * The dialogs (except startpage) should inherit from error_behaviour,
 * and they should define these methods:
 * - try_prepare_page instead of "prepare_page"
 * - try_handle instead of "handle"
 * - check_auth to get the basic auth checks
 *
 * There is a function check_auth that can be used as an implementation
 * for the method check_auth. It checks that the user account still
 * exists, and that (in the case of basic authentication) the variable
 * REMOTE_USER has a valid value.
 *)


open Wd_dialog
open Wd_run_cgi
open Wd_types

open Db_types.Types
open Db_types
open Db.Types

open Printf

exception Login_not_permitted

let errid_of_error error =
  match error with
      Db_ac.Types.Permission_denied        -> "permission-denied"
    | Db.Session.Session_not_found         -> "session-not-found"
    | Db.Session.Invalid_session_checksum  -> "invalid-session-checksum"
    | Db.Types.No_such_user _              -> "no-such-user"
    | Db.Types.User_already_exists _       -> "user-already-exists"
    | Db.Types.No_such_instance _          -> "no-such-instance"
    | Db.Types.Instance_already_exists _   -> "instance-already-exists"
    | Login_not_permitted                  -> "login-not-permitted"
    | _                                    -> "internal-error"
;;


let check_auth db (session_opt : dialog_type option) =
  (* This is called for all dialogs except "startpage" to verify that
   * the user still has an account.
   *)
  let session =
    match session_opt with Some s -> s | None -> assert false in
  let dtd = session # application # dtd in
  let option name =
    try
      let (e,_) = dtd # gen_entity name in
      Pxp_dtd.Entity.replacement_text e
    with
	_ ->
          failwith ("Cannot find configuration option " ^ name) in
  let login_dialog = (option "login-dialog" = "yes") in
  let login_user = session # string_variable "login-user" in
  
  if not login_dialog then begin
    (* check that login_user matches REMOTE_USER *)
    let cgi = (session # environment).cgi in
    let cgienv = cgi # environment in
    if cgienv # cgi_remote_user <> login_user then
      raise Login_not_permitted
  end;

  (* Check that the user account exists and permits login *)
  let user_passes =
    ( try
        let urec = Db.User.get db (User login_user) in
        urec.u_login
      with
          No_such_user _ -> false
        | Not_found -> false
    ) in
 if not user_passes then 
   raise Login_not_permitted
;;


class virtual error_behaviour =
object(self)

  method private virtual try_prepare_page : unit -> unit

  method private virtual try_handle : unit -> unit

  method private virtual check_auth : unit -> unit

  method private prepare_error_page error =
    let errid = errid_of_error error in
    self # set_variable "runtime-error" (String_value errid);
    self # set_next_page "runtime-error"

  method private handle_error error =
    self # prepare_error_page error;
    ()

  method prepare_page() =
    try
      self # check_auth();
      self # try_prepare_page()
    with
      ( Db_ac.Types.Permission_denied
      | Db.Session.Session_not_found
      | Db.Session.Invalid_session_checksum
      | Db.Types.No_such_user _
      | Db.Types.User_already_exists _
      | Db.Types.No_such_instance _
      | Db.Types.Instance_already_exists _ 
      | Login_not_permitted as error ) ->
	  self # prepare_error_page error

  method handle() =
    try
      self # check_auth();
      self # try_handle()
    with
      ( Db_ac.Types.Permission_denied
      | Db.Session.Session_not_found
      | Db.Session.Invalid_session_checksum
      | Db.Types.No_such_user _
      | Db.Types.User_already_exists _
      | Db.Types.No_such_instance _
      | Db.Types.Instance_already_exists _
      | Login_not_permitted as error ) ->
	  self # handle_error error

end