(* COCANWIKI - a wiki written in Objective CAML.
 * Written by Richard W.M. Jones <rich@merjis.com>.
 * Copyright (C) 2004 Merjis Ltd.
 * $Id: cgi_expires.ml,v 1.3 2004/09/09 12:21:22 rich Exp $
 *
 * This program 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.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *)

open Apache
open Registry
open Cgi

open Printf

open Cocanwiki_date

(* This library should eventually be integrated with mod_caml. XXX *)

(* Expires headers.
 *
 * All content on wiki sites is dynamic, but we try to make it look static
 * for users and search engines.  We have 4 types of 'Expires' headers that
 * we can send:
 *
 * expires_past ()
 *   Send an expiry header in the past (theoretically removing content from
 *   caches).
 * expires_short ()
 *   Send a short expiry header (now + 5 minutes).  This should be used for
 *   all news pages.
 * expires_medium ()
 *   Send a medium-term expiry header (now + 24 hours).  This should be used
 *   for all "static" content.
 * expires_long ()
 *   Send a very long expiry header (now + 2 years).  This should be used for
 *   content which really never will change.
 *)
let expires_past, expires_short, expires_medium, expires_long =
  let make offset =
    let t = Unix.time () in
    let tm = Unix.gmtime (t +. float offset) in
    sprintf "%s, %02d %s %04d %02d:%02d:%02d GMT"
      (short_weekday tm.Unix.tm_wday)
      tm.Unix.tm_mday
      (short_month (tm.Unix.tm_mon + 1))
      (tm.Unix.tm_year + 1900)
      tm.Unix.tm_hour
      tm.Unix.tm_min
      tm.Unix.tm_sec
  in
  let mins m = m * 60 in
  let days d = d * 86400 in
  (fun () -> make (mins (-5))),
  (fun () -> make (mins 5)),
  (fun () -> make (days 1)),
  (fun () -> make (days (365*2)))