(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2013     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

(* The file format is a header
 *     ("COQAUX%d %s %s\n" version hex_hash path)
 * followed by an arbitrary number of entries
 *     ("%d %d %s %S\n" loc_begin loc_end key value)  *)

open Filename

let version = 1

let oc = ref None

let aux_file_name_for vfile =
  dirname vfile ^ "/." ^ chop_extension(basename vfile) ^ ".aux"

let start_aux_file_for vfile =
  oc := Some (open_out (aux_file_name_for vfile));
  Printf.fprintf (Option.get !oc) "COQAUX%d %s %s\n"
    version (Digest.to_hex (Digest.file vfile)) (CUnix.strip_path vfile)

let stop_aux_file () =
  close_out (Option.get !oc);
  oc := None

let recording () = not (Option.is_empty !oc)

module H = Map.Make(struct type t = int * int let compare = compare end)
module M = Map.Make(String)
type data = string M.t
type aux_file = data H.t

let empty_aux_file = H.empty

let get aux loc key = M.find key (H.find (Loc.unloc loc) aux)

let record_in_aux_at loc key v =
  Option.iter (fun oc ->
    let i, j = Loc.unloc loc in
    Printf.fprintf oc "%d %d %s %S\n" i j key v)
  !oc

let current_loc = ref Loc.ghost

let record_in_aux_set_at loc = current_loc := loc

let record_in_aux key v = record_in_aux_at !current_loc key v

exception Outdated

let load_aux_file_for vfile =
  let ret3 x y z = x, y, z in
  let ret4 x y z t = x, y, z, t in
  let h = ref empty_aux_file in
  let add loc k v =
    let m = try H.find loc !h with Not_found -> M.empty in
    h := H.add loc (M.add k v m) !h in
  let aux_fname = aux_file_name_for vfile in
  try
    let ic = open_in aux_fname in
    let ver, hash, fname = Scanf.fscanf ic "COQAUX%d %s %s\n" ret3 in
    if ver <> version then raise (Failure "aux file version mismatch");
    if fname <> CUnix.strip_path vfile then
      raise (Failure "aux file name mismatch");
    if Digest.to_hex (Digest.file vfile) <> hash then raise Outdated;
    while true do
      let i, j, k, v = Scanf.fscanf ic "%d %d %s %S\n" ret4 in
      add (i,j) k v;
    done;
    raise End_of_file
  with
  | End_of_file -> !h
  | Outdated -> empty_aux_file
  | Sys_error s | Scanf.Scan_failure s
  | Failure s | Invalid_argument s ->
     Pp.(msg_error (str"Error loading file "++str aux_fname++str" : "++str s));
     empty_aux_file