(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2017     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Names
open Term
open Univ
open Evd
open Environ

(** Reduction Functions. *)

exception Elimconst

(** Machinery to customize the behavior of the reduction *)
module ReductionBehaviour : sig
  type flag = [ `ReductionDontExposeCase | `ReductionNeverUnfold ]

(** [set is_local ref (recargs, nargs, flags)] *)
  val set :
    bool -> Globnames.global_reference -> (int list * int * flag list) -> unit
  val get :
    Globnames.global_reference -> (int list * int * flag list) option
  val print : Globnames.global_reference -> Pp.std_ppcmds
end

(** Option telling if reduction should use the refolding machinery of cbn
   (off by default) *)
val get_refolding_in_reduction : unit -> bool
val set_refolding_in_reduction : bool -> unit

(** {6 Machinery about a stack of unfolded constant }

    cst applied to params must convertible to term of the state applied to args
*)
module Cst_stack : sig
  type t
  val empty : t
  val add_param : constr -> t -> t
  val add_args : constr array -> t -> t
  val add_cst : constr -> t -> t
  val best_cst : t -> (constr * constr list) option
  val best_replace : constr -> t -> constr -> constr
  val reference : t -> Constant.t option
  val pr : t -> Pp.std_ppcmds
end


module Stack : sig
  type 'a app_node

  val pr_app_node : ('a -> Pp.std_ppcmds) -> 'a app_node -> Pp.std_ppcmds

  type cst_member =
    | Cst_const of pconstant
    | Cst_proj of projection

  type 'a member =
  | App of 'a app_node
  | Case of case_info * 'a * 'a array * Cst_stack.t
  | Proj of int * int * projection * Cst_stack.t
  | Fix of fixpoint * 'a t * Cst_stack.t
  | Cst of cst_member * int (** current foccussed arg *) * int list (** remaining args *)
    * 'a t * Cst_stack.t
  | Shift of int
  | Update of 'a
  and 'a t = 'a member list

  val pr : ('a -> Pp.std_ppcmds) -> 'a t -> Pp.std_ppcmds

  val empty : 'a t
  val is_empty : 'a t -> bool
  val append_app : 'a array -> 'a t -> 'a t
  val decomp : 'a t -> ('a * 'a t) option

  val decomp_node_last : 'a app_node -> 'a t -> ('a * 'a t)

  val compare_shape : 'a t -> 'a t -> bool
  (** [fold2 f x sk1 sk2] folds [f] on any pair of term in [(sk1,sk2)].
      @return the result and the lifts to apply on the terms *)
  val fold2 : ('a -> Term.constr -> Term.constr -> 'a) -> 'a ->
    Term.constr t -> Term.constr t -> 'a * int * int
  val map : (Term.constr -> Term.constr) -> Term.constr t -> Term.constr t
  val append_app_list : 'a list -> 'a t -> 'a t

  (** if [strip_app s] = [(a,b)], then [s = a @ b] and [b] does not
      start by App or Shift *)
  val strip_app : 'a t -> 'a t * 'a t
  (** @return (the nth first elements, the (n+1)th element, the remaining stack)  *)
  val strip_n_app : int -> 'a t -> ('a t * 'a * 'a t) option

  val not_purely_applicative : 'a t -> bool
  val list_of_app_stack : constr t -> constr list option

  val assign : 'a t -> int -> 'a -> 'a t
  val args_size : 'a t -> int
  val tail : int -> 'a t -> 'a t
  val nth : 'a t -> int -> 'a

  val best_state : constr * constr t -> Cst_stack.t -> constr * constr t
  val zip : ?refold:bool -> constr * constr t -> constr
end

(************************************************************************)

type state = constr * constr Stack.t

type contextual_reduction_function = env -> evar_map -> constr -> constr
type reduction_function = contextual_reduction_function
type local_reduction_function = evar_map -> constr -> constr

type e_reduction_function = { e_redfun : 'r. env -> 'r Sigma.t -> constr -> (constr, 'r) Sigma.sigma }

type contextual_stack_reduction_function =
    env -> evar_map -> constr -> constr * constr list
type stack_reduction_function = contextual_stack_reduction_function
type local_stack_reduction_function =
    evar_map -> constr -> constr * constr list

type contextual_state_reduction_function =
    env -> evar_map -> state -> state
type state_reduction_function = contextual_state_reduction_function
type local_state_reduction_function = evar_map -> state -> state

val pr_state : state -> Pp.std_ppcmds

(** {6 Reduction Function Operators } *)

val strong : reduction_function -> reduction_function
val local_strong : local_reduction_function -> local_reduction_function
val strong_prodspine : local_reduction_function -> local_reduction_function
(*i
val stack_reduction_of_reduction :
  'a reduction_function -> 'a state_reduction_function
i*)
val stacklam : (state -> 'a) -> constr list -> constr -> constr Stack.t -> 'a

val whd_state_gen : ?csts:Cst_stack.t -> refold:bool -> tactic_mode:bool ->
  CClosure.RedFlags.reds -> Environ.env -> Evd.evar_map -> state -> state * Cst_stack.t

val iterate_whd_gen : bool -> CClosure.RedFlags.reds ->
  Environ.env -> Evd.evar_map -> Term.constr -> Term.constr

(** {6 Generic Optimized Reduction Function using Closures } *)

val clos_norm_flags : CClosure.RedFlags.reds -> reduction_function

(** Same as [(strong whd_beta[delta][iota])], but much faster on big terms *)
val nf_beta : local_reduction_function
val nf_betaiota : local_reduction_function
val nf_betaiotazeta : local_reduction_function
val nf_all : reduction_function
val nf_evar : evar_map -> constr -> constr

(** Lazy strategy, weak head reduction *)

val whd_evar :  evar_map -> constr -> constr
val whd_nored : local_reduction_function
val whd_beta : local_reduction_function
val whd_betaiota : local_reduction_function
val whd_betaiotazeta : local_reduction_function
val whd_all :  contextual_reduction_function
val whd_allnolet :  contextual_reduction_function
val whd_betalet : local_reduction_function

(** Removes cast and put into applicative form *)
val whd_nored_stack : local_stack_reduction_function
val whd_beta_stack : local_stack_reduction_function
val whd_betaiota_stack : local_stack_reduction_function
val whd_betaiotazeta_stack : local_stack_reduction_function
val whd_all_stack : contextual_stack_reduction_function
val whd_allnolet_stack : contextual_stack_reduction_function
val whd_betalet_stack : local_stack_reduction_function

val whd_nored_state : local_state_reduction_function
val whd_beta_state : local_state_reduction_function
val whd_betaiota_state : local_state_reduction_function
val whd_betaiotazeta_state : local_state_reduction_function
val whd_all_state : contextual_state_reduction_function
val whd_allnolet_state : contextual_state_reduction_function
val whd_betalet_state : local_state_reduction_function

(** {6 Head normal forms } *)

val whd_delta_stack :  stack_reduction_function
val whd_delta_state :  state_reduction_function
val whd_delta :  reduction_function
val whd_betadeltazeta_stack :  stack_reduction_function
val whd_betadeltazeta_state :  state_reduction_function
val whd_betadeltazeta :  reduction_function
val whd_zeta_stack : local_stack_reduction_function
val whd_zeta_state : local_state_reduction_function
val whd_zeta : local_reduction_function

val shrink_eta : constr -> constr

(** Various reduction functions *)

val safe_evar_value : evar_map -> existential -> constr option

val beta_applist : constr * constr list -> constr

val hnf_prod_app     : env ->  evar_map -> constr -> constr -> constr
val hnf_prod_appvect : env ->  evar_map -> constr -> constr array -> constr
val hnf_prod_applist : env ->  evar_map -> constr -> constr list -> constr
val hnf_lam_app      : env ->  evar_map -> constr -> constr -> constr
val hnf_lam_appvect  : env ->  evar_map -> constr -> constr array -> constr
val hnf_lam_applist  : env ->  evar_map -> constr -> constr list -> constr

val splay_prod : env ->  evar_map -> constr -> (Name.t * constr) list * constr
val splay_lam : env ->  evar_map -> constr -> (Name.t * constr) list * constr
val splay_arity : env ->  evar_map -> constr -> (Name.t * constr) list * sorts
val sort_of_arity : env -> evar_map -> constr -> sorts
val splay_prod_n : env ->  evar_map -> int -> constr -> Context.Rel.t * constr
val splay_lam_n : env ->  evar_map -> int -> constr -> Context.Rel.t * constr
val splay_prod_assum :
  env ->  evar_map -> constr -> Context.Rel.t * constr

type 'a miota_args = {
  mP      : constr;     (** the result type *)
  mconstr : constr;     (** the constructor *)
  mci     : case_info;  (** special info to re-build pattern *)
  mcargs  : 'a list;    (** the constructor's arguments *)
  mlf     : 'a array }  (** the branch code vector *)

val reducible_mind_case : constr -> bool
val reduce_mind_case : constr miota_args -> constr

val find_conclusion : env -> evar_map -> constr -> (constr,constr) kind_of_term
val is_arity : env ->  evar_map -> constr -> bool
val is_sort : env -> evar_map -> types -> bool

val contract_fix : ?env:Environ.env -> ?reference:Constant.t -> fixpoint -> constr
val fix_recarg : fixpoint -> constr Stack.t -> (int * constr) option

(** {6 Querying the kernel conversion oracle: opaque/transparent constants } *)
val is_transparent : Environ.env -> constant tableKey -> bool

(** {6 Conversion Functions (uses closures, lazy strategy) } *)

type conversion_test = constraints -> constraints

val pb_is_equal : conv_pb -> bool
val pb_equal : conv_pb -> conv_pb

val is_conv : ?reds:transparent_state -> env -> evar_map -> constr -> constr -> bool
val is_conv_leq : ?reds:transparent_state -> env ->  evar_map -> constr -> constr -> bool
val is_fconv : ?reds:transparent_state -> conv_pb -> env ->  evar_map -> constr -> constr -> bool

(** [check_conv] Checks universe constraints only.
    pb defaults to CUMUL and ts to a full transparent state.
 *)
val check_conv : ?pb:conv_pb -> ?ts:transparent_state -> env ->  evar_map -> constr -> constr -> bool

(** [infer_conv] Adds necessary universe constraints to the evar map.
    pb defaults to CUMUL and ts to a full transparent state.
    @raises UniverseInconsistency iff catch_incon is set to false, 
    otherwise returns false in that case.
 *)
val infer_conv : ?catch_incon:bool -> ?pb:conv_pb -> ?ts:transparent_state -> 
  env -> evar_map -> constr -> constr -> evar_map * bool

(** Conversion with inference of universe constraints *)
val set_vm_infer_conv : (?pb:conv_pb -> env -> evar_map -> constr -> constr ->
  evar_map * bool) -> unit
val vm_infer_conv : ?pb:conv_pb -> env -> evar_map -> constr -> constr ->
  evar_map * bool


(** [infer_conv_gen] behaves like [infer_conv] but is parametrized by a
conversion function. Used to pretype vm and native casts. *)
val infer_conv_gen : (conv_pb -> l2r:bool -> evar_map -> transparent_state ->
    (constr, evar_map) Reduction.generic_conversion_function) ->
  ?catch_incon:bool -> ?pb:conv_pb -> ?ts:transparent_state -> env ->
  evar_map -> constr -> constr -> evar_map * bool

(** {6 Special-Purpose Reduction Functions } *)

val whd_meta : evar_map -> constr -> constr
val plain_instance : constr Metamap.t -> constr -> constr
val instance : evar_map -> constr Metamap.t -> constr -> constr
val head_unfold_under_prod : transparent_state -> reduction_function
val betazetaevar_applist : evar_map -> int -> constr -> constr list -> constr

(** {6 Heuristic for Conversion with Evar } *)

val whd_betaiota_deltazeta_for_iota_state :
  transparent_state -> Environ.env -> Evd.evar_map -> Cst_stack.t -> state ->
  state * Cst_stack.t

(** {6 Meta-related reduction functions } *)
val meta_instance : evar_map -> constr freelisted -> constr
val nf_meta       : evar_map -> constr -> constr
val meta_reducible_instance : evar_map -> constr freelisted -> constr
