// Keep only the newest generation's result visible to the browser.
export const createRegenerationQueue = ({ generate, onSuccess, onError, delay = 100 }) => {
  let timer
  let running = false
  let revision = 0
  let closed = false

  const run = async () => {
    if (closed || running) return
    running = true
    const started = revision
    try {
      await generate()
      if (!closed && started === revision) onSuccess()
    } catch (error) {
      if (!closed && started === revision) onError(error)
    } finally {
      running = false
      if (!closed && started !== revision) schedule()
    }
  }

  const schedule = () => {
    clearTimeout(timer)
    timer = setTimeout(run, delay)
  }

  return {
    request() {
      if (closed) return
      revision += 1
      schedule()
    },
    close() {
      closed = true
      clearTimeout(timer)
    },
  }
}