(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Util
open Pp
open Names
open Nameops
open Term
open Termops
open Inductive
open Declarations
open Entries
open Environ
open Inductive
open Lib
open Classops
open Declare
open Libnames
open Nametab
open Decl_kinds
open Safe_typing

let strength_min l = if List.mem Local l then Local else Global

(* Errors *)

type coercion_error_kind =
  | AlreadyExists
  | NotAFunction
  | NoSource of cl_typ option
  | ForbiddenSourceClass of cl_typ
  | NotUniform
  | NoTarget
  | WrongTarget of cl_typ * cl_typ
  | NotAClass of global_reference
  | NotEnoughClassArgs of cl_typ

exception CoercionError of coercion_error_kind

let explain_coercion_error g = function
  | AlreadyExists ->
      (Printer.pr_global g ++ str" is already a coercion")
  | NotAFunction ->
      (Printer.pr_global g ++ str" is not a function")
  | NoSource (Some cl) ->
      (str "Cannot recognize " ++ pr_class cl ++ str " as a source class of "
       ++ Printer.pr_global g)
  | NoSource None ->
      (str ": cannot find the source class of " ++ Printer.pr_global g)
  | ForbiddenSourceClass cl ->
      pr_class cl ++ str " cannot be a source class"
  | NotUniform ->
      (Printer.pr_global g ++
         str" does not respect the uniform inheritance condition");
  | NoTarget ->
      (str"Cannot find the target class")
  | WrongTarget (clt,cl) ->
      (str"Found target class " ++ pr_class cl ++
       str " instead of " ++ pr_class clt)
  | NotAClass ref ->
      (str "Type of " ++ Printer.pr_global ref ++
         str " does not end with a sort")
  | NotEnoughClassArgs cl ->
      (str"Wrong number of parameters for " ++ pr_class cl)

(* Verifications pour l'ajout d'une classe *)

let check_reference_arity ref =
  if not (Reductionops.is_arity (Global.env()) Evd.empty (Global.type_of_global ref)) then
    raise (CoercionError (NotAClass ref))

let check_arity = function
  | CL_FUN | CL_SORT -> ()
  | CL_CONST cst -> check_reference_arity (ConstRef cst)
  | CL_SECVAR id -> check_reference_arity (VarRef id)
  | CL_IND kn -> check_reference_arity (IndRef kn)

(* Coercions *)

(* check that the computed target is the provided one *)
let check_target clt = function
  | Some cl when cl <> clt -> raise (CoercionError (WrongTarget(clt,cl)))
  | _ -> ()

(* condition d'heritage uniforme *)

let uniform_cond nargs lt =
  let rec aux = function
    | (0,[]) -> true
    | (n,t::l) -> (strip_outer_cast t = mkRel n) & (aux ((n-1),l))
    | _ -> false
  in
  aux (nargs,lt)

let class_of_global = function
  | ConstRef sp -> CL_CONST sp
  | IndRef sp -> CL_IND sp
  | VarRef id -> CL_SECVAR id
  | ConstructRef _ as c ->
      errorlabstrm "class_of_global"
	(str "Constructors, such as " ++ Printer.pr_global c ++
	   str ", cannot be used as a class.")

(*
lp est la liste (inverse'e) des arguments de la coercion
ids est le nom de la classe source
sps_opt est le sp de la classe source dans le cas des structures
retourne:
la classe source
nbre d'arguments de la classe
le constr de la class
la liste des variables dont depend la classe source
l'indice de la classe source dans la liste lp
*)

let get_source lp source =
  match source with
    | None ->
	let (cl1,lv1) =
          match lp with
	    | [] -> raise Not_found
            | t1::_ -> find_class_type (Global.env()) Evd.empty t1
        in
	(cl1,lv1,1)
    | Some cl ->
	let rec aux = function
	  | [] -> raise Not_found
	  | t1::lt ->
	      try
		let cl1,lv1 = find_class_type (Global.env()) Evd.empty t1 in
		if cl = cl1 then cl1,lv1,(List.length lt+1)
		else raise Not_found
              with Not_found -> aux lt
	in aux (List.rev lp)

let get_target t ind =
  if (ind > 1) then
    CL_FUN
  else
    fst (find_class_type (Global.env()) Evd.empty t)

let prods_of t =
  let rec aux acc d = match kind_of_term d with
    | Prod (_,c1,c2) -> aux (c1::acc) c2
    | Cast (c,_,_) -> aux acc c
    | _ -> (d,acc)
  in
  aux [] t

let strength_of_cl = function
  | CL_CONST kn -> Global
  | CL_SECVAR id -> Local
  | _ -> Global

let get_strength stre ref cls clt =
  let stres = strength_of_cl cls in
  let stret = strength_of_cl clt in
  let stref = strength_of_global ref in
  strength_min [stre;stres;stret;stref]

let ident_key_of_class = function
  | CL_FUN -> "Funclass"
  | CL_SORT -> "Sortclass"
  | CL_CONST sp -> string_of_label (con_label sp)
  | CL_IND (sp,_) -> string_of_label (mind_label sp)
  | CL_SECVAR id -> string_of_id id

(* coercion identité *)

let error_not_transparent source =
  errorlabstrm "build_id_coercion"
    (pr_class source ++ str " must be a transparent constant.")

let build_id_coercion idf_opt source =
  let env = Global.env () in
  let vs = match source with
    | CL_CONST sp -> mkConst sp
    | _ -> error_not_transparent source in
  let c = match constant_opt_value env (destConst vs) with
    | Some c -> c
    | None -> error_not_transparent source in
  let lams,t = decompose_lam_assum c in
  let val_f =
    it_mkLambda_or_LetIn
      (mkLambda (Name (id_of_string "x"),
		 applistc vs (extended_rel_list 0 lams),
		 mkRel 1))
       lams
  in
  let typ_f =
    it_mkProd_wo_LetIn
      (mkProd (Anonymous, applistc vs (extended_rel_list 0 lams), lift 1 t))
      lams
  in
  (* juste pour verification *)
  let _ =
    if not
      (Reductionops.is_conv_leq env Evd.empty
	(Typing.type_of env Evd.empty val_f) typ_f)
    then
      errorlabstrm "" (strbrk
	"Cannot be defined as coercion (maybe a bad number of arguments).")
  in
  let idf =
    match idf_opt with
      | Some idf -> idf
      | None ->
	  let cl,_ = find_class_type (Global.env()) Evd.empty t in
	  id_of_string ("Id_"^(ident_key_of_class source)^"_"^
                        (ident_key_of_class cl))
  in
  let constr_entry = (* Cast is necessary to express [val_f] is identity *)
    DefinitionEntry
      { const_entry_body = mkCast (val_f, DEFAULTcast, typ_f);
	const_entry_type = Some typ_f;
        const_entry_opaque = false;
	const_entry_boxed = Flags.boxed_definitions()} in
  let kn = declare_constant idf (constr_entry,IsDefinition IdentityCoercion) in
  ConstRef kn

let check_source = function
| Some (CL_FUN|CL_SORT as s) -> raise (CoercionError (ForbiddenSourceClass s))
| _ -> ()

(*
nom de la fonction coercion
strength de f
nom de la classe source (optionnel)
sp de la classe source (dans le cas des structures)
nom de la classe target (optionnel)
booleen "coercion identite'?"

lorque source est None alors target est None aussi.
*)

let add_new_coercion_core coef stre source target isid =
  check_source source;
  let t = Global.type_of_global coef in
  if coercion_exists coef then raise (CoercionError AlreadyExists);
  let tg,lp = prods_of t in
  let llp = List.length lp in
  if llp = 0 then raise (CoercionError NotAFunction);
  let (cls,lvs,ind) =
    try
      get_source lp source
    with Not_found ->
      raise (CoercionError (NoSource source))
  in
  check_source (Some cls);
  if not (uniform_cond (llp-ind) lvs) then
    raise (CoercionError NotUniform);
  let clt =
    try
      get_target tg ind
    with Not_found ->
      raise (CoercionError NoTarget)
  in
  check_target clt target;
  check_arity cls;
  check_arity clt;
  let stre' = get_strength stre coef cls clt in
  declare_coercion coef stre' ~isid ~src:cls ~target:clt ~params:(List.length lvs)

let try_add_new_coercion_core ref b c d e =
  try add_new_coercion_core ref b c d e
  with CoercionError e ->
      errorlabstrm "try_add_new_coercion_core"
        (explain_coercion_error ref e ++ str ".")

let try_add_new_coercion ref stre =
  try_add_new_coercion_core ref stre None None false

let try_add_new_coercion_subclass cl stre =
  let coe_ref = build_id_coercion None cl in
  try_add_new_coercion_core coe_ref stre (Some cl) None true

let try_add_new_coercion_with_target ref stre ~source ~target =
  try_add_new_coercion_core ref stre (Some source) (Some target) false

let try_add_new_identity_coercion id stre ~source ~target =
  let ref = build_id_coercion (Some id) source in
  try_add_new_coercion_core ref stre (Some source) (Some target) true

let try_add_new_coercion_with_source ref stre ~source =
  try_add_new_coercion_core ref stre (Some source) None false

let add_coercion_hook stre ref =
  try_add_new_coercion ref stre;
  Flags.if_verbose message
    (string_of_qualid (shortest_qualid_of_global Idset.empty ref)
    ^ " is now a coercion")

let add_subclass_hook stre ref =
  let cl = class_of_global ref in
  try_add_new_coercion_subclass cl stre