(* COCANWIKI - a wiki written in Objective CAML.
 * Written by Richard W.M. Jones <rich@merjis.com>.
 * Copyright (C) 2004 Merjis Ltd.
 * $Id: cocanwiki_diff.ml,v 1.4 2004/09/20 10:56:47 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_files

(* Convenience code for generating diffs between versions.  See diff.ml
 * and edit.ml which both use this code.
 *)
let page_for_diff css sections =
  (String.concat ""
     (List.map (fun (sectionname, content) ->
		  "HEADING: " ^ sectionname ^ "\n\n" ^
		  content ^ "\n\n") sections)) ^
  "CSS:\n\n" ^ css

let diff_cmd old_page new_page =
  let new_filename = output_tempfile new_page in
  let old_filename = output_tempfile old_page in

  let cmd = sprintf "diff -u %s %s ||:" old_filename new_filename in
  let diff = pget cmd in

  let diff =
    match diff with
	_ :: _ :: diff -> diff
      | diff -> diff in

  unlink new_filename; unlink old_filename;
  String.concat "\n" diff

let get_version_for_diff (dbh : Dbi.connection) version =
  if version = 0 then "" else (
    let sth = dbh#prepare_cached "select coalesce (css, '') as css
                                    from pages where id = ?" in
    sth#execute [`Int version];

    let css = sth#fetch1string () in

    let sth = dbh#prepare_cached "select coalesce (sectionname, ''), content
                                    from contents where pageid = ?
                                   order by ordering" in
    sth#execute [`Int version];

    let sections =
      sth#map (function
		   [`String sectionname; `String content] ->
		     sectionname, content
		 | _ -> assert false) in
    let page = page_for_diff css sections in

    page
  )

let get_diff (dbh : Dbi.connection) hostid page ?old_version ~version () =
  let old_version =
    match old_version with
      | Some version -> version
      | None ->
	  let sth = dbh#prepare_cached "select id from pages
                                         where hostid = ?
                                           and url_deleted = ? and id < ?
                                         order by 1 desc limit 1" in
	  sth#execute [`Int hostid; `String page; `Int version];

	  try sth#fetch1int ()
	  with Not_found -> 0 in

  (* Get the two versions. *)
  let new_page = get_version_for_diff dbh version in
  let old_page = get_version_for_diff dbh old_version in

  (* Compute the diff of the two versions. *)
  let diff = diff_cmd old_page new_page in
  diff, old_version