(* COCANWIKI scripts.
 * Written by Richard W.M. Jones <rich@merjis.com>.
 * Copyright (C) 2004 Merjis Ltd.
 * $Id: cgi_expires.ml,v 1.2 2004/09/07 14:58:34 rich Exp $
 *)

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)))