(** 
    This module describe the type an analyzer must implement in order to be
    used with the parser. 

    The module is divided in three modules :
        - Expression : the finest part of the QSP syntax.
        - Instruction : if/act block, 
        - Location
 *)

(** {1 Generic types used in the module } *)

type pos = Lexing.position * Lexing.position
(** The type pos is used to track the starting and ending position for the
    given location. *)

type ('a, 'b) variable = { pos : 'a; name : string; index : 'b option }
(** Describe a variable, using the name in capitalized text, and an optionnal
    index.

    If missing, the index should be considered as [0].*)

type ('a, 'b) clause = pos * 'a * 'b list

(** {1 Checker Signature} *)

(** Represent the evaluation over an expression *)
module type Expression = sig
  type t
  (** Internal type used in the evaluation *)

  type t'
  (** External type used outside of the module *)

  val v : t -> t'
  val ident : (pos, t) variable -> t

  (*
        Basic values, text, number…
   *)

  val integer : pos -> string -> t
  val literal : pos -> t T.literal list -> t

  val function_ : pos -> T.function_ -> t list -> t
  (** Call a function. The functions list is hardcoded in lib/lexer.mll *)

  val uoperator : pos -> T.uoperator -> t -> t
  (** Unary operator like [-123] or [+'Text']*)

  val boperator : pos -> T.boperator -> t -> t -> t
  (** Binary operator, for a comparaison, or an operation *)
end

module type Instruction = sig
  type t
  (** Internal type used in the evaluation *)

  type t'
  (** External type used outside of the module *)

  val v : t -> t'

  type expression

  val call : pos -> T.keywords -> expression list -> t
  (** Call for an instruction like [GT] or [*CLR] *)

  val location : pos -> string -> t
  (** Label for a loop *)

  val comment : pos -> t
  (** Comment *)

  val expression : expression -> t
  (** Raw expression *)

  val if_ :
    pos ->
    (expression, t) clause ->
    elifs:(expression, t) clause list ->
    else_:(pos * t list) option ->
    t

  val act : pos -> label:expression -> t list -> t

  val assign :
    pos ->
    (pos, expression) variable ->
    T.assignation_operator ->
    expression ->
    t
end

module type Location = sig
  type t
  type instruction

  val v : t -> Report.t list
  val location : pos -> instruction list -> t
end

(** {1 Unified module used by the parser } *)

module type Analyzer = sig
  val identifier : string
  (** Identifier for the module *)

  val description : string
  (** Short description*)

  val active : bool ref
  (** Is the test active or not *)

  module Expression : Expression
  module Instruction : Instruction with type expression = Expression.t'
  module Location : Location with type instruction = Instruction.t'
end

(** Helper module used in order to convert elements from the differents
    representation levels. 

    Thoses functions are intended to be used in the menhir parser, in order to
    limit the code in the mly file.
*)
module Helper (E : sig
  type t
  (** Internal type used in the evaluation *)

  type t'
  (** External type used outside of the module *)

  val v : t -> t'
end) : sig
  val variable : (pos, E.t) variable -> (pos, E.t') variable
  (** Convert a variable from the [Expression.t] into [Expression.t'] *)
end = struct
  let variable : (pos, E.t) variable -> (pos, E.t') variable =
   fun variable -> { variable with index = Option.map E.v variable.index }
end