(* Ocsigen
 * http://www.ocsigen.org
 * Module redirectmod.ml
 * Copyright (C) 2007 Vincent Balat
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, with linking exception;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *)

(* Define page redirections in the configuration file *)

module Pcre = Re.Pcre

let section = Lwt_log.Section.make "ocsigen:ext:redirectmod"

(* The table of redirections for each virtual server *)
type redirection =
  { r_regexp : Pcre.regexp
  ; r_dest : string
  ; r_full : [`Yes | `No | `Maybe]
  ; r_temp : bool }

let create_redirection ?(full = `Yes) ?(temporary = false) ~regexp r_dest =
  let r_regexp = Pcre.regexp ("^" ^ regexp ^ "$") in
  {r_regexp; r_dest; r_full = full; r_temp = temporary}

let attempt_redir {r_regexp; r_dest; r_full; r_temp} _err ri () =
  Lwt_log.ign_info ~section "Is it a redirection?";
  let redir =
    let find full =
      Ocsigen_extensions.find_redirection r_regexp full r_dest ri
    in
    match r_full with
    | `Yes -> find true
    | `No -> find false
    | `Maybe -> (
      try find false with Ocsigen_extensions.Not_concerned -> find true)
  in
  Lwt_log.ign_info_f ~section "YES! %s redirection to: %s"
    (if r_temp then "Temporary " else "Permanent ")
    redir;
  Lwt.return
  @@ Ocsigen_extensions.Ext_found
       (fun () ->
         Lwt.return @@ Ocsigen_response.make
         @@
         let headers = Cohttp.Header.(init_with "Location" redir)
         and status = if r_temp then `Found else `Moved_permanently in
         Cohttp.Response.make ~status ~headers ())

(** The function that will generate the pages from the request *)
let gen dir = function
  | Ocsigen_extensions.Req_found _ ->
      Lwt.return Ocsigen_extensions.Ext_do_nothing
  | Ocsigen_extensions.Req_not_found (err, {Ocsigen_extensions.request_info; _})
    -> (
      Lwt.catch (attempt_redir dir err request_info) @@ function
      | Ocsigen_extensions.Not_concerned ->
          Lwt.return (Ocsigen_extensions.Ext_next err)
      | e -> Lwt.fail e)

let parse_config config_elem =
  let regexp = ref None
  and dest = ref ""
  and mode = ref `Yes
  and temporary = ref false in
  Ocsigen_extensions.(
    Configuration.process_element ~in_tag:"host"
      ~other_elements:(fun t _ _ -> raise (Bad_config_tag_for_extension t))
      ~elements:
        [ Configuration.element ~name:"redirect"
            ~attributes:
              [ Configuration.attribute ~name:"regexp" (fun s ->
                    regexp := Some ("^" ^ s ^ "$");
                    mode := `Maybe)
              ; Configuration.attribute ~name:"fullurl" (fun s ->
                    regexp := Some s;
                    mode := `Yes)
              ; Configuration.attribute ~name:"suburl" (fun s ->
                    regexp := Some s;
                    mode := `No)
              ; Configuration.attribute ~name:"dest" ~obligatory:true (fun s ->
                    dest := s)
              ; Configuration.attribute ~name:"temporary" (function
                  | "temporary" -> temporary := true
                  | _ -> ()) ]
            () ]
      config_elem);
  match !regexp with
  | None ->
      Ocsigen_extensions.badconfig "Missing attribute regexp for <redirect>"
  | Some regexp ->
      gen (create_redirection ~full:!mode ~regexp ~temporary:!temporary !dest)

let () =
  Ocsigen_extensions.register ~name:"redirectmod"
    ~fun_site:(fun _ _ _ _ _ _ -> parse_config)
    ()

let redirection = Ocsigen_server.Site.Config.key ()

let extension =
  Ocsigen_server.Site.create_extension
    (fun {Ocsigen_server.Site.Config.accessor} ->
      match accessor redirection with
      | Some redirection -> gen redirection
      | None -> failwith "Redirectmod.redirection not set")
