(* This file is part of the Catala compiler, a specification language for tax
   and social benefits computation rules. Copyright (C) 2020 Inria, contributor:
   Nicolas Chataing <nicolas.chataing@ens.fr>

   Licensed under the Apache License, Version 2.0 (the "License"); you may not
   use this file except in compliance with the License. You may obtain a copy of
   the License at

   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   License for the specific language governing permissions and limitations under
   the License. *)

(** Abstract syntax tree of the desugared representation *)

open Catala_utils
open Shared_ast

(** Inside a scope, a definition can refer either to a scope def, or a subscope
    def *)
module ScopeDef : sig
  type t =
    | Var of ScopeVar.t * StateName.t option
    | SubScopeVar of SubScopeName.t * ScopeVar.t * Pos.t

  val compare : t -> t -> int
  val get_position : t -> Pos.t
  val format_t : Format.formatter -> t -> unit
  val hash : t -> int
end

module ScopeDefMap : Map.S with type key = ScopeDef.t
module ScopeDefSet : Set.S with type elt = ScopeDef.t

(** {1 AST} *)

(** {2 Expressions} *)

type expr = (desugared, untyped mark) gexpr
(** See {!type:Shared_ast.naked_gexpr} for the complete definition *)

type location = desugared glocation

module LocationSet : Set.S with type elt = location Marked.pos
module ExprMap : Map.S with type key = expr

(** {2 Rules and scopes}*)

type exception_situation =
  | BaseCase
  | ExceptionToLabel of LabelName.t Marked.pos
  | ExceptionToRule of RuleName.t Marked.pos

type label_situation = ExplicitlyLabeled of LabelName.t Marked.pos | Unlabeled

type rule = {
  rule_id : RuleName.t;
  rule_just : expr boxed;
  rule_cons : expr boxed;
  rule_parameter : (expr Var.t * typ) list option;
  rule_exception : exception_situation;
  rule_label : label_situation;
}

module Rule : Set.OrderedType with type t = rule

val empty_rule : Pos.t -> typ list option -> rule
val always_false_rule : Pos.t -> typ list option -> rule

type assertion = expr boxed
type variation_typ = Increasing | Decreasing
type reference_typ = Decree | Law

type meta_assertion =
  | FixedBy of reference_typ Marked.pos
  | VariesWith of unit * variation_typ Marked.pos option

(** This type characterizes the three levels of visibility for a given scope
    variable with regards to the scope's input and possible redefinitions inside
    the scope.. *)
type io_input =
  | NoInput
      (** For an internal variable defined only in the scope, and does not
          appear in the input. *)
  | OnlyInput
      (** For variables that should not be redefined in the scope, because they
          appear in the input. *)
  | Reentrant
      (** For variables defined in the scope that can also be redefined by the
          caller as they appear in the input. *)

type io = {
  io_output : bool Marked.pos;
      (** [true] is present in the output of the scope. *)
  io_input : io_input Marked.pos;
}
(** Characterization of the input/output status of a scope variable. *)

type scope_def = {
  scope_def_rules : rule RuleName.Map.t;
  scope_def_typ : typ;
  scope_def_is_condition : bool;
  scope_def_io : io;
}

type var_or_states = WholeVar | States of StateName.t list

type scope = {
  scope_vars : var_or_states ScopeVar.Map.t;
  scope_sub_scopes : ScopeName.t SubScopeName.Map.t;
  scope_uid : ScopeName.t;
  scope_defs : scope_def ScopeDefMap.t;
  scope_assertions : assertion list;
  scope_meta_assertions : meta_assertion list;
}

type program = {
  program_scopes : scope ScopeName.Map.t;
  program_topdefs : (expr * typ) TopdefName.Map.t;
  program_ctx : decl_ctx;
}

(** {1 Helpers} *)

val locations_used : expr -> LocationSet.t
val free_variables : rule RuleName.Map.t -> Pos.t ScopeDefMap.t