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(** Extention of the open type [error] with the errors that could be raised by
    the DAL node. *)
type error +=
  | Decoding_failed of Types.Store.kind
  | Profile_incompatibility
  | Invalid_slot_index of {slot_index : int; number_of_slots : int}

(** The errors below are used to extend tzresult/tztrace monad/errors with Some
    specific errors on which we'd like to match in the DAL node's code. *)

(** We would like to match decoding errors as they are sometimes expected
    (e.g. when decoding data from the network) and we want to enable callers to
    catch and handle them. On the other hand, encoding errors only happen in
    unexpected circumstances (e.g. out of memory) so we don't expect callers to
    catch and handle them. *)
type decoding = [`Decoding_failed of Types.Store.kind * tztrace]

(** We would like to match [`Not_found] as we would want to return 404 HTTP code
    to clients. *)
type not_found = [`Not_found]

(** We will use [`Other] to wrap other {!tztrace} errors in the new
    polymorphic-variants based monad. *)
type other = [`Other of tztrace]

(** [other l] wraps the give tztrace [l] in [`Other]. *)
val other : tztrace -> [> other]

(** [other_result r] casts the given value [r] from the ['a tzresult] monad into
    [('a, [> other_error]) result]. *)
val other_result : 'a tzresult -> ('a, [> other]) result

(** [other_lwt_result r] casts the given value [r] from the ['a tzresult Lwt.t]
    monad into [('a, [> other]) result Lwt.t]. *)
val other_lwt_result : 'a tzresult Lwt.t -> ('a, [> other]) result Lwt.t

(** [to_option_tzresult v] transforms the given value [v] to another value in
    the regular ['a option tzresult Lwt.t] monad.

    Asuming the Lwt monad [v] successfully resolves, then:

    - If it yields a value [Ok w], the function returns an Lwt monad whose
    payload is [Ok (Some w)].

    - If it yields a value [Error `Not_found], the function returns an Lwt monad
    whose payload is [Ok (None)] so that {!Tezos_rpc_http} returns 404 HTTP code.

    - If it yields a value [Error `Decoding_failed], the function returns an Lwt
    monad whose payload is the tzresult of [Decoding_failed] concatenated to the
    tztrance carried by [`Decoding_failed].

    - Otherwise, it yields a value [Error `Other u]. In this case, the function
    returns an Lwt monad whose payload is [Error u].

    Note that an {!Event.decoding_data_failed} is emitted. in case a
    [`Decoding_failed] is encountered. *)
val to_option_tzresult :
  ?none:(([< decoding | not_found | other] as 'b) -> bool) ->
  ('a, 'b) result Lwt.t ->
  'a option tzresult Lwt.t

(** [to_tzresult v] is quite similar to {!to_option_tzresult}. Except that the
    [`Not_found] case cannot happen, in which case the use of [option] for the
    non-failing case is not needed. *)
val to_tzresult : ('a, [< decoding | other]) result Lwt.t -> 'a tzresult Lwt.t