(*
copyright (c) 2013, simon cruanes
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(** {6 Action Language for command line} *)

(** {2 Command-line Actions} *)

module Action : sig
  type 'a t
    (** Action returning a 'a *)

  type trigger = string
    (** Trigger a given action, based on the next token *)

  val return : 'a -> 'a t
    (** Return a pure value *)

  val (>>=) : 'a t -> ('a -> 'b t) -> 'b t
    (** Sequence of arguments *)

  val (>>) : 'a t -> (unit -> 'b t) -> 'b t
    (** Same as {! (>>=)}, but ignores the result of left side *)

  val ( *>) : 'a t -> 'b t -> 'b t
    (** Accept left, then returns right *)

  val accept : trigger -> unit t
    (** Accept the given trigger, fails otherwise *)

  val any : string t
    (** Any token *)

  val with_string : ?trigger:trigger -> (string -> 'a t) -> 'a t
    (** Command that takes a string *)

  val with_int : ?trigger:trigger -> (int -> 'a t) -> 'a t
    (** Command that takes an integer *)

  val with_bool : ?trigger:trigger -> (bool -> 'a t) -> 'a t

  val opt : 'a t -> 'a option t
    (** Optional action *)

  val repeat : 'a t -> 'a list t
    (** Repeated action *)

  val choice : 'a t list -> 'a t
    (** Choice between options. The first option of the list that
        does not fail will be the result (backtracking is used!) *)

  val ignore : 'a t -> unit t
    (** Ignore result *)

  val fail : string -> 'a t
    (** Fail with given message *)
end

(** {2 Main interface} *)

type 'a result =
  | Ok of 'a
  | Error of string

val parse_args : string array -> 'a Action.t -> 'a result
  (** Parse given command line *)

val parse : 'a Action.t -> 'a result
  (** Parse Sys.argv *)

val print_doc : out_channel -> 'a Action.t -> unit
  (** Print documentation on given channel *)