class Cycle {
  constructor(iterable) {
    const arr = [...iterable]
    this.size = arr.length
    this.cycle = function* () {
      let i = 0
      while (true) {
        i = (i + (yield arr[i])) % arr.length
      }
    }()
  }
  *[Symbol.iterator]() {
    yield* Array.from(Array(this.size), (_, i) => this.cycle.next(+!!i).value)
  }
  prev() {
    return this.cycle.next(-1).value
  }
  next() {
    return this.cycle.next(1).value
  }
}