nimbus-eth1/nimbus/sync/snap/worker/com/get_block_header.nim

# Nimbus
# Copyright (c) 2021 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
#    http://www.apache.org/licenses/LICENSE-2.0)
#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
#    http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed
# except according to those terms.

import
  std/options,
  chronos,
  eth/[common/eth_types, p2p],
  "../../.."/[protocol, types],
  ../../worker_desc,
  ./com_error

{.push raises: [Defect].}

logScope:
  topics = "snap-fetch"

# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------

proc getBlockHeader*(
    buddy: SnapBuddyRef;
    num: BlockNumber;
      ): Future[Result[BlockHeader,ComError]]
      {.async.} =
  ## Get single block header
  let
    peer = buddy.peer
    reqLen = 1u
    hdrReq = BlocksRequest(
      startBlock: HashOrNum(
        isHash:   false,
        number:   num),
      maxResults: reqLen,
      skip:       0,
      reverse:    false)

  trace trEthSendSendingGetBlockHeaders, peer, startBlock=num, reqLen

  var hdrResp: Option[blockHeadersObj]
  try:
    hdrResp = await peer.getBlockHeaders(hdrReq)
  except CatchableError as e:
    trace trSnapRecvError & "waiting for GetByteCodes reply", peer,
      error=e.msg
    return err(ComNetworkProblem)

  var hdrRespLen = 0
  if hdrResp.isSome:
    hdrRespLen = hdrResp.get.headers.len
  if hdrRespLen == 0:
    trace trEthRecvReceivedBlockHeaders, peer, reqLen, respose="n/a"
    return err(ComNoHeaderAvailable)

  if hdrRespLen == 1:
    let
      header = hdrResp.get.headers[0]
      blockNumber = header.blockNumber
    trace trEthRecvReceivedBlockHeaders, peer, hdrRespLen, blockNumber
    return ok(header)

  trace trEthRecvReceivedBlockHeaders, peer, reqLen, hdrRespLen
  return err(ComTooManyHeaders)

# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------