# Nimbus
# Copyright (c) 2023 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
# at your option.
# This file may not be copied, modified, or distributed except according to
# those terms.

import
  eth/common,
  stew/results,
  ../web3_eth_conv,
  ../beacon_engine,
  ../execution_types,
  ../payload_conv,
  ./api_utils,
  chronicles

{.push gcsafe, raises:[CatchableError].}

template validateVersion(com, timestamp, version, apiVersion) =
  if apiVersion == Version.V3:
    if not com.isCancunOrLater(timestamp):
      raise unsupportedFork("newPayloadV3 expect payload timestamp fall within Cancun")

  if com.isCancunOrLater(timestamp):
    if version != Version.V3:
      raise invalidParams("if timestamp is Cancun or later, " &
        "payload must be ExecutionPayloadV3")

  elif com.isShanghaiOrLater(timestamp):
    if version != Version.V2:
      raise invalidParams("if timestamp is Shanghai or later, " &
        "payload must be ExecutionPayloadV2")

  elif version != Version.V1:
    if com.syncReqRelaxV2:
      trace "Relaxed mode, treating payload as V1"
      discard
    else:
      raise invalidParams("if timestamp is earlier than Shanghai, " &
        "payload must be ExecutionPayloadV1")

  if apiVersion == Version.V3:
    if version != apiVersion:
      raise invalidParams("newPayload" & $apiVersion &
      " expect ExecutionPayload" & $apiVersion &
      " but got ExecutionPayload" & $version)


proc newPayload*(ben: BeaconEngineRef,
                 apiVersion: Version,
                 payload: ExecutionPayload,
                 beaconRoot = none(Web3Hash)): PayloadStatusV1 =

  trace "Engine API request received",
    meth = "newPayload",
    number = payload.blockNumber,
    hash = payload.blockHash

  if apiVersion == Version.V3:
    if beaconRoot.isNone:
      raise invalidParams("newPayloadV3 expect beaconRoot but got none")

  let
    com = ben.com
    db  = com.db
    timestamp = ethTime payload.timestamp
    version = payload.version

  validateVersion(com, timestamp, version, apiVersion)

  var header = blockHeader(payload, ethHash beaconRoot)
  let blockHash = ethHash payload.blockHash
  header.validateBlockHash(blockHash, version).isOkOr:
    return error


  # If we already have the block locally, ignore the entire execution and just
  # return a fake success.
  if db.getBlockHeader(blockHash, header):
    warn "Ignoring already known beacon payload",
      number = header.blockNumber, hash = blockHash.short
    return validStatus(blockHash)

  # If the parent is missing, we - in theory - could trigger a sync, but that
  # would also entail a reorg. That is problematic if multiple sibling blocks
  # are being fed to us, and even moreso, if some semi-distant uncle shortens
  # our live chain. As such, payload execution will not permit reorgs and thus
  # will not trigger a sync cycle. That is fine though, if we get a fork choice
  # update after legit payload executions.
  var parent: common.BlockHeader
  if not db.getBlockHeader(header.parentHash, parent):
    # Stash the block away for a potential forced forckchoice update to it
    # at a later time.
    ben.put(blockHash, header)

    # Although we don't want to trigger a sync, if there is one already in
    # progress, try to extend if with the current payload request to relieve
    # some strain from the forkchoice update.
    #if err := api.eth.Downloader().BeaconExtend(api.eth.SyncMode(), block.Header()); err == nil {
    #  log.Debug("Payload accepted for sync extension", "number", params.Number, "hash", params.BlockHash)
    #  return beacon.PayloadStatusV1{Status: beacon.SYNCING}, nil

    # Either no beacon sync was started yet, or it rejected the delivered
    # payload as non-integratable on top of the existing sync. We'll just
    # have to rely on the beacon client to forcefully update the head with
    # a forkchoice update request.
    warn "Ignoring payload with missing parent",
      number = header.blockNumber,
      hash   = blockHash.short,
      parent = header.parentHash.short
    return acceptedStatus()

  # We have an existing parent, do some sanity checks to avoid the beacon client
  # triggering too early
  let ttd = com.ttd.get(high(common.BlockNumber))

  if version == Version.V1:
    let td  = db.getScore(header.parentHash)
    if (not com.forkGTE(MergeFork)) and td < ttd:
      warn "Ignoring pre-merge payload",
        number = header.blockNumber, hash = blockHash, td, ttd
      return invalidStatus()

  if header.timestamp <= parent.timestamp:
    warn "Invalid timestamp",
      number = header.blockNumber, parentNumber = parent.blockNumber,
      parent = parent.timestamp, header = header.timestamp
    return invalidStatus(parent.blockHash, "Invalid timestamp")

  if not db.haveBlockAndState(header.parentHash):
    ben.put(blockHash, header)
    warn "State not available, ignoring new payload",
      hash   = blockHash,
      number = header.blockNumber
    let blockHash = latestValidHash(db, parent, ttd)
    return acceptedStatus(blockHash)

  trace "Inserting block without sethead",
    hash = blockHash, number = header.blockNumber
  let body = blockBody(payload, removeBlobs = true)
  let vres = ben.chain.insertBlockWithoutSetHead(header, body)
  if vres != ValidationResult.OK:
    let blockHash = latestValidHash(db, parent, ttd)
    return invalidStatus(blockHash, "Failed to insert block")

  # We've accepted a valid payload from the beacon client. Mark the local
  # chain transitions to notify other subsystems (e.g. downloader) of the
  # behavioral change.
  if not ben.ttdReached():
    ben.reachTTD()
    # TODO: cancel downloader

  return validStatus(blockHash)