(*
    ||M||  This file is part of HELM, an Hypertextual, Electronic        
    ||A||  Library of Mathematics, developed at the Computer Science     
    ||T||  Department, University of Bologna, Italy.                     
    ||I||                                                                
    ||T||  HELM is free software; you can redistribute it and/or         
    ||A||  modify it under the terms of the GNU General Public License   
    \   /  version 2 or (at your option) any later version.      
     \ /   This software is distributed as is, NO WARRANTY.     
      V_______________________________________________________________ *)

(* $Id$ *)

exception LibraryOutOfSync of string Lazy.t

type timestamp =
 (NUri.uri * NCic.obj) list *
 (NUri.uri * string * NReference.reference) list *
 NCic.obj NUri.UriMap.t;;

let time0 = [],[],NUri.UriMap.empty;;
let storage = ref [];;
let local_aliases = ref [];;
let global_aliases = ref [];;
let cache = ref NUri.UriMap.empty;;

class status =
 object
  val timestamp = (time0 : timestamp)
  method timestamp = timestamp
  method set_timestamp v = {< timestamp = v >}
  method set_library_status
   : 'status. < timestamp : timestamp; .. > as 'status -> 'self
   = fun o -> {< timestamp = o#timestamp >}
 end

let time_travel status =
 let sto,ali,cac = status#timestamp in
  storage := sto; local_aliases := ali; cache := cac
;;

let path_of_baseuri ?(no_suffix=false) baseuri =
 let uri = NUri.string_of_uri baseuri in
 let path = String.sub uri 4 (String.length uri - 4) in
 let path = Helm_registry.get "matita.basedir" ^ path in
 let dirname = Filename.dirname path in
  HExtlib.mkdir dirname;
  if no_suffix then
   path
  else
   path ^ ".ng"
;;

let magic = 0;;

let require_path path =
 let ch = open_in path in
 let mmagic,dump = Marshal.from_channel ch in
  close_in ch;
  if mmagic <> magic then
   raise (LibraryOutOfSync (lazy "The library is out of sync with the implementation. Please recompile the library."))
  else
   dump
;;

let require0 ~baseuri = require_path (path_of_baseuri baseuri);;

let db_path () = Helm_registry.get "matita.basedir" ^ "/ng_db.ng";;

let init () =
 try
  global_aliases := require_path (db_path ())
 with
  Sys_error _ -> ()
;;

let serialize ~baseuri dump =
 let ch = open_out (path_of_baseuri baseuri) in
 Marshal.to_channel ch (magic,dump) [];
 close_out ch;
 List.iter
  (fun (uri,obj) ->
    let ch = open_out (path_of_baseuri uri) in
    Marshal.to_channel ch (magic,obj) [];
    close_out ch
  ) !storage;
 global_aliases := !local_aliases @ !global_aliases;
 let ch = open_out (db_path ()) in
 Marshal.to_channel ch (magic,!global_aliases) [];
 close_out ch;
 time_travel (new status)
;;

let refresh_uri uri = NUri.uri_of_string (NUri.string_of_uri uri);;

let rec refresh_uri_in_term =
 function
    NCic.Const (NReference.Ref (u,spec)) ->
     NCic.Const (NReference.reference_of_spec (refresh_uri u) spec)
  | t -> NCicUtils.map (fun _ _ -> ()) () (fun _ -> refresh_uri_in_term) t
;;

let refresh_uri_in_obj (uri,height,metasenv,subst,obj_kind) =
 assert (metasenv = []);
 assert (subst = []);
 uri,height,metasenv,subst,
  NCicUntrusted.map_obj_kind refresh_uri_in_term obj_kind
;;

module type Serializer =
 sig
  type status
  type obj
  val register:
   string ->
    ('a -> refresh_uri_in_term:(NCic.term -> NCic.term) -> status -> status) ->
    ('a -> obj)
  val serialize: baseuri:NUri.uri -> obj list -> unit
  val require: baseuri:NUri.uri -> status -> status
 end

module Serializer(S: sig type status end) =
 struct
  type status = S.status
  type obj = string * Obj.t

  let require1 = ref (fun _ -> assert false (* unknown data*))
  let already_registered = ref []

  let register tag require =
   assert (not (List.mem tag !already_registered));
   already_registered := tag :: !already_registered;
   require1 :=
    (fun (tag',data) as x ->
     if tag=tag' then
      require (Obj.magic data) ~refresh_uri_in_term
     else
      !require1 x);
   (fun x -> tag,Obj.repr x)

  let serialize = serialize

  let require ~baseuri status =
   let dump = require0 ~baseuri in
    List.fold_right !require1 dump status
end

let decompile ~baseuri =
 HExtlib.safe_remove (path_of_baseuri baseuri);
 let basepath = path_of_baseuri ~no_suffix:true baseuri in
 try
  let od = Unix.opendir basepath in
  let rec aux names =
   try
    let name = Unix.readdir od in
     if name <> "." && name <> ".." then aux (name::names) else aux names
   with
    End_of_file -> names in
  let names = List.map (fun name -> basepath ^ "/" ^ name) (aux []) in
   Unix.closedir od;
   List.iter Unix.unlink names;
   HExtlib.rmdir_descend basepath
 with
  Unix.Unix_error _ -> () (* raised by Unix.opendir, we hope :-) *)
;;

LibraryClean.set_decompile_cb
 (fun ~baseuri -> decompile ~baseuri:(NUri.uri_of_string baseuri));;

let fetch_obj uri =
 let obj = require0 ~baseuri:uri in
  refresh_uri_in_obj obj
;;

let resolve name =
 try
  HExtlib.filter_map
   (fun (_,name',nref) -> if name'=name then Some nref else None)
   (!local_aliases @ !global_aliases)
 with
  Not_found -> raise (NCicEnvironment.ObjectNotFound (lazy name))
;;

let aliases_of uri =
 try
  HExtlib.filter_map
   (fun (uri',_,nref) ->
     if NUri.eq uri' uri then Some nref else None) !local_aliases
 with
  Not_found -> raise (NCicEnvironment.ObjectNotFound (lazy (NUri.string_of_uri uri)))
;;

let add_obj status u obj =
 storage := (u,obj)::!storage;
  let _,height,_,_,obj = obj in
  let references =
   match obj with
      NCic.Constant (_,name,None,_,_) ->
       [u,name,NReference.reference_of_spec u NReference.Decl]
    | NCic.Constant (_,name,Some _,_,_) ->
       [u,name,NReference.reference_of_spec u (NReference.Def height)]
    | NCic.Fixpoint (is_ind,fl,_) ->
       HExtlib.list_mapi
        (fun (_,name,recno,_,_) i ->
          if is_ind then
           u,name,NReference.reference_of_spec u(NReference.Fix(i,recno,height))
          else
           u,name,NReference.reference_of_spec u (NReference.CoFix i)) fl
    | NCic.Inductive (inductive,leftno,il,_) ->
       List.flatten
        (HExtlib.list_mapi
         (fun (_,iname,_,cl) i ->
           HExtlib.list_mapi
            (fun (_,cname,_) j->
              u,cname,
               NReference.reference_of_spec u (NReference.Con (i,j+1,leftno))
            ) cl @
           [u,iname,
             NReference.reference_of_spec u
              (NReference.Ind (inductive,i,leftno))]
         ) il)
  in
  local_aliases := references @ !local_aliases;
  status#set_timestamp (!storage,!local_aliases,!cache)
;;

let get_obj u =
 try List.assq u !storage
 with Not_found ->
  try fetch_obj u
  with Sys_error _ ->
   try NUri.UriMap.find u !cache
   with Not_found ->
    let ouri = NCic2OCic.ouri_of_nuri u in
    try
      let o,_ = CicEnvironment.get_obj CicUniv.oblivion_ugraph ouri in
      let l = OCic2NCic.convert_obj ouri o in
      List.iter (fun (u,_,_,_,_ as o) -> cache:= NUri.UriMap.add u o !cache) l;
      HExtlib.list_last l
    with CicEnvironment.Object_not_found u -> 
      raise (NCicEnvironment.ObjectNotFound 
               (lazy (NUri.string_of_uri (OCic2NCic.nuri_of_ouri u))))
;;

let clear_cache () = cache := NUri.UriMap.empty;;

NCicEnvironment.set_get_obj get_obj;;
NCicPp.set_get_obj get_obj;;