Function ToastProvider

packages/emcn/src/components/toast/toast.tsx:387–640

({ children }: { children?: ReactNode })

 * ```
 */
export function ToastProvider({ children }: { children?: ReactNode }) {
  const pathname = usePathname()
  const reduceMotion = useReducedMotion() ?? false
  /** On the workflow editor (`/w/[id]` and the `/w` index) the stack insets by `--panel-width` / `--terminal-height` to clear the panel and terminal. */
  const isWorkflowPage = pathname ? /\/w(\/|$)/.test(pathname) : false

  const [toasts, setToasts] = useState<ToastData[]>([])
  const [heights, setHeights] = useState<Record<string, number>>({})
  const [expanded, setExpanded] = useState(false)
  const [mounted, setMounted] = useState(false)
  const timersRef = useRef(new Map<string, ReturnType<typeof setTimeout>>())

  useEffect(() => {
    setMounted(true)
  }, [])

  /**
   * Reset the hover-expanded flag whenever the stack empties. The hover wrapper
   * unmounts without firing mouse-leave when the last toast goes (dismiss / clear
   * / navigation), so without this `expanded` could stay `true` and stop the next
   * toasts from auto-dismissing.
   */
  useEffect(() => {
    if (toasts.length === 0) setExpanded(false)
  }, [toasts.length])

  /**
   * Adds a toast. Actionable toasts persist (`duration: 0`) unless an explicit
   * `duration` is given. When the stack exceeds `STACK_LIMIT` the oldest
   * auto-dismissable toast is evicted first, so a persistent (actionable) toast
   * isn't silently dropped — only an all-persistent overflow evicts the oldest.
   */
  const addToast = useCallback((input: ToastInput): string => {
    const id = generateId()
    const data: ToastData = {
      id,
      message: input.message,
      description: input.description,
      variant: input.variant ?? 'default',
      action: input.action,
      duration: input.duration ?? (input.action ? 0 : AUTO_DISMISS_MS),
      persistAcrossRoutes: input.persistAcrossRoutes ?? false,
    }
    setToasts((prev) => {
      const next = [...prev, data]
      if (next.length <= STACK_LIMIT) return next
      const evictIndex = next.findIndex((t) => t.duration > 0)
      next.splice(evictIndex === -1 ? 0 : evictIndex, 1)
      return next
    })
    return id
  }, [])

  const dismissToast = useCallback((id: string) => {
    const timer = timersRef.current.get(id)
    if (timer) {
      clearTimeout(timer)
      timersRef.current.delete(id)