logos-storage-nim/codex/contracts/clock.nim

import std/times
import pkg/ethers
import pkg/chronos
import pkg/stint
import ../clock

export clock

logScope:
  topics = "contracts clock"

type
  OnChainClock* = ref object of Clock
    provider: Provider
    subscription: Subscription
    started: bool
    newBlock: AsyncEvent
    lastBlockTime: UInt256

proc new*(_: type OnChainClock, provider: Provider): OnChainClock =
  OnChainClock(provider: provider, newBlock: newAsyncEvent())

method start*(clock: OnChainClock) {.async.} =
  if clock.started:
    return
  clock.started = true

  proc onBlock(blck: Block) {.upraises:[].} =
    clock.lastBlockTime = blck.timestamp
    clock.newBlock.fire()

  if latestBlock =? (await clock.provider.getBlock(BlockTag.latest)):
    onBlock(latestBlock)

  clock.subscription = await clock.provider.subscribe(onBlock)

method stop*(clock: OnChainClock) {.async.} =
  if not clock.started:
    return
  clock.started = false

  await clock.subscription.unsubscribe()

method now*(clock: OnChainClock): SecondsSince1970 =
  try:
    if queriedBlock =? (waitFor clock.provider.getBlock(BlockTag.latest)):
      if queriedBlock.timestamp != clock.lastBlockTime:
        trace "queried block and event block are not in sync",
          queriedBlockLessThanEventBlock = queriedBlock.timestamp < clock.lastBlockTime
      return queriedBlock.timestamp.truncate(int64)
  except CatchableError as e:
    warn "failed to get latest block timestamp"
    return clock.lastBlockTime.truncate(int64)

method waitUntil*(clock: OnChainClock, time: SecondsSince1970) {.async.} =
  while (let difference = time - clock.now(); difference > 0):
    clock.newBlock.clear()
    discard await clock.newBlock.wait().withTimeout(chronos.seconds(difference))