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(** This module provides middlewares that is used by the RPC servers to
    forward unsupported RPCs to a full node. *)

(** Callbacks to add side-effects to {!proxy_server_query_forwarder},
    typically used to emit events. *)
type forwarder_events = {
  on_forwarding : Cohttp.Request.t -> unit Lwt.t;
      (** Called right before an unsupported RPC gets forwarded to the node. *)
  on_locally_handled : Cohttp.Request.t -> unit Lwt.t;
      (** Called after an RPC has been handled by the server itself
          (without any forwarding). *)
}

(** A Resto middleware that transforms any callback to an other that rewrites
    queries that the proxy server cannot handle and forwards them to the full
    node at the given [Uri.t]. If [acl] parameter is provided, the forwarding
    happens only if the ACL rules are satisfied.*)
val proxy_server_query_forwarder :
  ?acl:RPC_server.Acl.t ->
  ?ctx:Cohttp_lwt_unix.Net.ctx ->
  ?forwarder_events:forwarder_events ->
  Uri.t ->
  RPC_server.callback ->
  RPC_server.callback

(** A Resto middleware that transforms any server callback to an other
    that handles RPC metrics *)
val rpc_metrics_transform_callback :
  update_metrics:
    (string ->
    string ->
    (unit -> Cohttp_lwt_unix.Server.response_action Lwt.t) ->
    Cohttp_lwt_unix.Server.response_action Lwt.t) ->
  unit Tezos_rpc.Directory.t ->
  RPC_server.callback ->
  RPC_server.callback