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(** History modes for the chain history storage

   History modes allow a node to require less disk storage. Indeed,
    depending on the chosen history mode, some parts of the complete
    chain history can be deleted as they are not required
    anymore. Three history modes are provided:

    - Full mode (default mode): The node stores the minimal data since
    the genesis required to reconstruct (or 'replay') the complete
    chain's ledger state.

    - Rolling mode: This is the lightest mode as it only maintains a
    minimal rolling fragment of the chain data so the node can still
    validate new blocks and synchronize with the head.

    - Archive: This is the heaviest mode as it keeps the whole chain
    data to be able to query any information stored on the chain since
    the genesis. It is particularly suitable for indexers or block
    explorers.

*)

(** The type for defining the number of additional cycles to
   preserve. *)
type additional_cycles = {offset : int}

(** The type for defining an history mode. *)
type t =
  | Archive
  | Full of additional_cycles option
  | Rolling of additional_cycles option

(** The default value for the number of additional cycles to
   preserve.*)
val default_additional_cycles : additional_cycles

(** The default full history mode value. Based on
   [default_additional_cycles]. *)
val default_full : t

(** The default rolling history mode value. Based on
   [default_additional_cycles]. *)
val default_rolling : t

(** The default history mode value. *)
val default : t

val encoding : t Data_encoding.t

(** Returns true if the modes and the number of additional cycles are
   equal. *)
val equal : t -> t -> bool

(** Returns true if the modes are equal. The number of additional
   cycles are not checked.*)
val mode_equality : t -> t -> bool

val pp : Format.formatter -> t -> unit

val pp_short : Format.formatter -> t -> unit

val tag : t Tag.def

(** The module for handling legacy history modes. It is only used for
   legacy support, see {!Tezos_store.Legacy} and {!Tezos_store.Snapshots}.
*)
module Legacy : sig
  type t = Archive | Full | Rolling

  val encoding : t Data_encoding.t

  val pp : Format.formatter -> t -> unit
end

(** [convert legacy] returns the history mode of a given [legacy]
   history mode, using the default offset values.*)
val convert : Legacy.t -> t