nips/34seen.md

NIP-34seen

Seen At

draft optional author:arthurfranca author:mikedilger

Events are desc sorted by first seen at timestamp.

Motivation

Some clients may want to check if relay has recently received old events created before last time they checked.

Implementation

Relay computes nip34seen field once upon receiving the event.

The event field is set with the timestamp of the moment the relay first became aware of it.

Javascript

// Use this same value even if your programming language allows a higher one
// It is ok because it is lower than Number.MAX_SAFE_INTEGER
const maxDateNowSeconds = 8640000000000 // 8.64e15 ms / 1000
const maxSecondsLength = maxDateNowSeconds.toString().length

function getNip34seen (id = '') {
  // The id length must always be the same to not affect sorting
  // All relays must use the same length
  if (id.length !== 64) { throw new Error('Wrong id length') }
  let seconds = Math.trunc(Date.now() / 1000) // Make sure it is int instead of float
  // don't allow negative timestamp as new Date(-1) is on year 1969
  if (seconds < 0) { throw new Error('Wrong server clock') }
  seconds = Math.min(seconds, maxDateNowSeconds) // Keep max limit
  // '10' is wrongly lower then '2' while '10' is higher than padded '02'
  const paddedTsSeconds = seconds.toString().padStart(maxSecondsLength, '0')

  // Event id is used as a fixed length unique identifier
  return `${paddedTsSeconds}${id}`
}

event.nip34seen = getNip34seen(event.id)