crdt.js/test/lamport-clock.js

Conflict-Free Replicated Data Types JavaScript Library

class LamportClock {
  constructor (id, time) {
    this.id = id
    this.time = time || 0
  }

  tick () {
    return new LamportClock(this.id, this.time + 1)
  }

  merge (clock) {
    this.time = Math.max(this.time, clock.time)
    return new LamportClock(this.id, this.time)
  }

  clone () {
    return new LamportClock(this.id, this.time)
  }

  static isEqual (a, b) {
    return a.id == b.id && a.time == b.time
  }

  static compare (a, b) {
    if (!a || !a.time) a = { time: 0 }
    if (!b || !b.time) b = { time: 0 }

    // Calculate the "distance" based on the clock, ie. lower or greater
    var dist = a.time - b.time

    // If the sequence number is the same (concurrent events),
    // and the IDs are different, take the one with a "lower" id
    if (dist === 0 && a.id !== b.id) return a.id < b.id ? -1 : 1

    return dist
  }
}

module.exports = LamportClock