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(** The bootstrap pipeline works as follows:
    1. From a locator, it computes a list of subchains (identified by
       a [Block_locator.step]) to fetch.
    2. A worker starts to fetch all the headers (top to bottom) from a subchain,
       starting with the top subchain.
    3. A worker starts to download the list of operations by batch of blocks
       once a batch of headers is available.
    4. A worker validates blocks one by one (bottom to top).

    These three workers work concurrently.
*)

type t

(** [create ?notify_new_block ~block_header_timeout
    ~block_operations_timeout validator peer ddb locator] initializes a
    [bootstrap_pipeline] for a [locator] sent by [peer]. It uses the
    [Distributed_db] to fetch the data needed and [validator] to
    validate blocks one by one with the function
    [Block_validator.validate].

    Moreover:
    - [notify_new_block] is a called everytime a valid block
    is received.
    - [block_header_timeout] is the timeout to fetch a [block_header].
    - [block_operations_timeout] is the timeout to fetch a block
    operation.

    If a timeout is triggered, the whole [bootstrap_pipeline] is
    canceled.*)
val create :
  ?notify_new_block:(Block_validator.new_block -> unit) ->
  block_header_timeout:Time.System.Span.t ->
  block_operations_timeout:Time.System.Span.t ->
  Block_validator.t ->
  P2p_peer.Id.t ->
  Distributed_db.chain_db ->
  Block_locator.t ->
  t

val wait : t -> unit tzresult Lwt.t

val cancel : t -> unit Lwt.t

(** [length pipeline] returns the number of the headers and blocks fetched *)
val length : t -> Peer_validator_worker_state.pipeline_length

val length_zero : Peer_validator_worker_state.pipeline_length