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type protocol = Nairobi | Oxford | Proto_alpha

(** [internal_message_kind] represent an internal message in a inbox. *)
type internal_message_kind =
  | Transfer (* Generic internal message. *)
  | Start_of_level
      (** Internal message put at the beginning of each inbox's level. *)
  | End_of_level  (** Internal message put at the end of each inbox's level. *)
  | Info_per_level
      (** Internal message containing the timestamp of the current block and the
          hash of the previous block. *)
  | Protocol_migration of protocol

(** A type representing messages from Layer 1 to Layer 2. Internal ones are
    originated from Layer 1 smart-contracts and external ones are messages from
    an external manager operation. Other messages represents non decodable tags.
    It aims to be future-proof and prevent discarding any new type of
    message.. *)
type t = Internal of internal_message_kind | External | Other

(** [from_raw_input input] takes a message produced by the L1 protocol and
    returns its kind. *)
val from_raw_input : string -> t

module Internal_for_tests : sig
  (** [to_binary_input kind input] returns the serialized representation of an
      [input] according to its [kind]. Internal message payloads and external
      message payloads are prefixed by their tag, and `Other` messages result in
      an exception. These messages are meant to be used in tests only, and does
      not give any guarantee on their validity according to the protocol's
      representation.

      @raise Failure on `Other` messages, and mismatches between kind and
        presence or absence of the input.
*)
  val to_binary_input : t -> string option -> string
end