Function createStableFlagController

apps/sim/hooks/use-stable-flag.ts:25–89

(
  onChange: (active: boolean) => void,
  { delayMs = 0, minVisibleMs = 0 }: StableFlagOptions = {}
)

 * is safe to feed it the same value repeatedly (e.g. from React effect re-runs).
 */
export function createStableFlagController(
  onChange: (active: boolean) => void,
  { delayMs = 0, minVisibleMs = 0 }: StableFlagOptions = {}
) {
  let active = false
  let shownAt: number | null = null
  let showTimer: ReturnType<typeof setTimeout> | null = null
  let hideTimer: ReturnType<typeof setTimeout> | null = null

  const clearShow = () => {
    if (showTimer !== null) {
      clearTimeout(showTimer)
      showTimer = null
    }
  }
  const clearHide = () => {
    if (hideTimer !== null) {
      clearTimeout(hideTimer)
      hideTimer = null
    }
  }

  const show = () => {
    showTimer = null
    shownAt = Date.now()
    active = true
    onChange(true)
  }
  const hide = () => {
    hideTimer = null
    shownAt = null
    active = false
    onChange(false)
  }

  return {
    setValue(value: boolean) {
      if (value) {
        clearHide()
        if (active || showTimer !== null) {
          return
        }
        showTimer = setTimeout(show, delayMs)
        return
      }

      clearShow()
      if (!active || hideTimer !== null) {
        return
      }

      const elapsed = shownAt === null ? minVisibleMs : Date.now() - shownAt
      const remaining = minVisibleMs - elapsed
      if (remaining <= 0) {
        hide()
        return
      }
      hideTimer = setTimeout(hide, remaining)