(************************************************************************)
(*         *   The Coq Proof Assistant / The Coq Development Team       *)
(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
(* <O___,, *       (see CREDITS file for the list of authors)           *)
(*   \VV/  **************************************************************)
(*    //   *    This file is distributed under the terms of the         *)
(*         *     GNU Lesser General Public License Version 2.1          *)
(*         *     (see LICENSE file for the text of the license)         *)
(************************************************************************)

(* Created by Bruno Barras for Benjamin Grégoire as part of the
   bytecode-based reduction machine, Oct 2004 *)
(* Bug fix #1419 by Jean-Marc Notin, Mar 2007 *)

(* This file manages the table of global symbols for the bytecode machine *)

open Util
open Names
open Vmvalues
open Cemitcodes
open Cbytecodes
open Declarations
open Pre_env
open Cbytegen

module NamedDecl = Context.Named.Declaration
module RelDecl = Context.Rel.Declaration

external eval_tcode : tcode -> values array -> values = "coq_eval_tcode"

(*******************)
(* Linkage du code *)
(*******************)

(* Table des globaux *)

(* [global_data] contient les valeurs des constantes globales
   (axiomes,definitions), les annotations des switch et les structured
   constant *)
external global_data : unit -> values array = "get_coq_global_data"

(* [realloc_global_data n] augmente de n la taille de [global_data] *)
external realloc_global_data : int -> unit = "realloc_coq_global_data"

let check_global_data n =
  if n >= Array.length (global_data()) then realloc_global_data n

let num_global = ref 0

let set_global v =
  let n = !num_global in
  check_global_data n;
  (global_data()).(n) <- v;
  incr num_global;
  n

(* table pour les structured_constant et les annotations des switchs *)

module SConstTable = Hashtbl.Make (struct
  type t = structured_constant
  let equal = eq_structured_constant
  let hash = hash_structured_constant
end)

module AnnotTable = Hashtbl.Make (struct
  type t = annot_switch
  let equal = eq_annot_switch
  let hash = hash_annot_switch
end)

let str_cst_tbl : int SConstTable.t = SConstTable.create 31

let annot_tbl : int AnnotTable.t = AnnotTable.create 31
    (* (annot_switch * int) Hashtbl.t  *)

(*************************************************************)
(*** Mise a jour des valeurs des variables et des constantes *)
(*************************************************************)

exception NotEvaluated

let key rk =
  match !rk with
  | None -> raise NotEvaluated
  | Some k ->
      try CEphemeron.get k
      with CEphemeron.InvalidKey -> raise NotEvaluated

(************************)
(* traduction des patch *)

(* slot_for_*, calcul la valeur de l'objet, la place
   dans la table global, rend sa position dans la table *)

let slot_for_str_cst key =
  try SConstTable.find str_cst_tbl key
  with Not_found ->
    let n = set_global (val_of_str_const key) in
    SConstTable.add str_cst_tbl key n;
    n

let slot_for_annot key =
  try AnnotTable.find annot_tbl key
  with Not_found ->
    let n =  set_global (val_of_annot_switch key) in
    AnnotTable.add annot_tbl key n;
    n

let rec slot_for_getglobal env kn =
  let (cb,(_,rk)) = lookup_constant_key kn env in
  try key rk
  with NotEvaluated ->
(*    Pp.msgnl(str"not yet evaluated");*)
    let pos =
      match cb.const_body_code with
      | None -> set_global (val_of_constant kn)
      | Some code ->
	 match Cemitcodes.force code with
	 | BCdefined(code,pl,fv) ->
           let v = eval_to_patch env (code,pl,fv) in
           set_global v
	 | BCalias kn' -> slot_for_getglobal env kn'
	 | BCconstant -> set_global (val_of_constant kn)
    in
(*Pp.msgnl(str"value stored at: "++int pos);*)
    rk := Some (CEphemeron.create pos);
    pos

and slot_for_fv env fv =
  let fill_fv_cache cache id v_of_id env_of_id b =
    let v,d =
      match b with
      | None -> v_of_id id, Id.Set.empty
      | Some c ->
          val_of_constr (env_of_id id env) c,
          Environ.global_vars_set (Environ.env_of_pre_env env) c in
    build_lazy_val cache (v, d); v in
  let val_of_rel i = val_of_rel (nb_rel env - i) in
  let idfun _ x = x in
  match fv with
  | FVnamed id ->
      let nv = Pre_env.lookup_named_val id env in
      begin match force_lazy_val nv with
      | None ->
	 env |> Pre_env.lookup_named id |> NamedDecl.get_value |> fill_fv_cache nv id val_of_named idfun
      | Some (v, _) -> v
      end
  | FVrel i ->
      let rv = Pre_env.lookup_rel_val i env in
      begin match force_lazy_val rv with
      | None ->
        env |> Pre_env.lookup_rel i |> RelDecl.get_value |> fill_fv_cache rv i val_of_rel env_of_rel
      | Some (v, _) -> v
      end
  | FVevar evk -> val_of_evar evk
  | FVuniv_var idu ->
    assert false

and eval_to_patch env (buff,pl,fv) =
  let slots = function
    | Reloc_annot a -> slot_for_annot a
    | Reloc_const sc -> slot_for_str_cst sc
    | Reloc_getglobal kn -> slot_for_getglobal env kn
  in
  let tc = patch buff pl slots in
  let vm_env = Array.map (slot_for_fv env) fv in
  eval_tcode tc vm_env

and val_of_constr env c =
  match compile ~fail_on_error:true env c with
  | Some v -> eval_to_patch env (to_memory v)
  | None -> assert false

let set_transparent_const kn = () (* !?! *)
let set_opaque_const kn = () (* !?! *)