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(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
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type seed_computation_status =
  | Nonce_revelation_stage
  | Vdf_revelation_stage of {
      seed_discriminant : Seed_repr.seed;
      seed_challenge : Seed_repr.seed;
    }
  | Computation_finished

type error +=
  | Unknown of {
      oldest : Cycle_repr.t;
      cycle : Cycle_repr.t;
      latest : Cycle_repr.t;
    }
  | Already_accepted
  | Unverified_vdf
  | Too_early_revelation

(* `Permanent *)

(** Generates the first [preserved_cycles+2] seeds for which
    there are no nonces. *)
val init :
  ?initial_seed:State_hash.t -> Raw_context.t -> Raw_context.t tzresult Lwt.t

(** Verifies if a VDF (result, proof) is valid.

    @return [Error Too_early_revelation] if the nonce revelation
    threshold is greater than the current level cycle position.

    @return [Error Already_accepted] if a VDF seed has already been
    recorded.

    @return [Error Unverified_vdf] if the {!Seed_repr.vdf_solution} is
    not verified. *)
val check_vdf : Raw_context.t -> Seed_repr.vdf_solution -> unit tzresult Lwt.t

(** Updates the seed with a function of the VDF result. *)
val update_seed :
  Raw_context.t -> Seed_repr.vdf_solution -> Raw_context.t tzresult Lwt.t

val for_cycle : Raw_context.t -> Cycle_repr.t -> Seed_repr.seed tzresult Lwt.t

(** Computes RANDAO output for cycle #(current_cycle + preserved + 1) *)
val compute_randao : Raw_context.t -> Raw_context.t tzresult Lwt.t

(** Must be run at the end of the cycle, resets the VDF state and returns
    unrevealed nonces to know which party has to forfeit its endorsing
    rewards for that cycle.  *)
val cycle_end :
  Raw_context.t ->
  Cycle_repr.t ->
  (Raw_context.t * Nonce_storage.unrevealed list) tzresult Lwt.t

(** Return the random seed computation status, that is whether the VDF
  computation period has started, and if so the information needed, or if it has
  finished for the current cycle. *)
val get_seed_computation_status :
  Raw_context.t -> seed_computation_status tzresult Lwt.t