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(** Type of a protocol-specific mempool filter plug-in. *)
module type FILTER = sig
  (** Type of protocol-specific mempool configuration, as specifiable
      in the node's configuration file, and updatable via RPCs. *)
  type config

  (** Formatting of {!config} for the configuration file and RPCs. *)
  val config_encoding : config Data_encoding.t

  (** Default configuration value, used when none is specified. *)
  val default_config : config

  (** The protocol this plug-in understands. *)
  module Proto : Registered_protocol.T

  (** Tells if an operation should be kept and propagated before even running it. *)
  val pre_filter : config -> Proto.operation_data -> bool

  (** Tells if an operation should be kept and propagated considering its result. *)
  val post_filter :
    config ->
    validation_state_before:Proto.validation_state ->
    validation_state_after:Proto.validation_state ->
    Proto.operation_data * Proto.operation_receipt ->
    bool Lwt.t
end

(** Dummy filter that does nothing *)
module No_filter (Proto : Registered_protocol.T) :
  FILTER with module Proto = Proto

(** Registers a mempool plug-in for a specific protocol (according to its [Proto.hash]). *)
val register : (module FILTER) -> unit

(** Looks for a mempool plug-in for a specific protocol. *)
val find : Protocol_hash.t -> (module FILTER) option