nim-codex/codex/contracts/clock.nim

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import std/times
import pkg/ethers
import pkg/chronos
import pkg/stint
import ../clock
export clock
type
OnChainClock* = ref object of Clock
provider: Provider
subscription: Subscription
offset: int64
started: bool
proc new*(_: type OnChainClock, provider: Provider): OnChainClock =
OnChainClock(provider: provider)
proc start*(clock: OnChainClock) {.async.} =
if clock.started:
return
clock.started = true
proc onBlock(blck: Block) {.async, upraises:[].} =
let blockTime = blck.timestamp.truncate(int64)
let computerTime = getTime().toUnix
clock.offset = blockTime - computerTime
if latestBlock =? (await clock.provider.getBlock(BlockTag.latest)):
await onBlock(latestBlock)
clock.subscription = await clock.provider.subscribe(onBlock)
proc stop*(clock: OnChainClock) {.async.} =
if not clock.started:
return
clock.started = false
await clock.subscription.unsubscribe()
method now*(clock: OnChainClock): SecondsSince1970 =
doAssert clock.started, "clock should be started before calling now()"
getTime().toUnix + clock.offset