// Helpers to keep heavy WebGL scene setup off the page's critical path.

// Runs fn once the main thread is idle (falling back to a short timeout),
// returning a cancel handle so an early unmount never leaks a scheduled init.
export const scheduleIdle = (fn: () => void, timeout = 1500): (() => void) => {
  const ric = (window as any).requestIdleCallback as
    | ((cb: () => void, opts?: { timeout: number }) => number)
    | undefined
  if (typeof ric === 'function') {
    const id = ric(fn, { timeout })
    return () => (window as any).cancelIdleCallback?.(id)
  }
  const id = setTimeout(fn, 200)
  return () => clearTimeout(id)
}

// Calls cb whenever tab visibility changes, returning an unsubscribe function.
export const onVisibility = (cb: (hidden: boolean) => void): (() => void) => {
  const handler = () => cb(document.hidden)
  document.addEventListener('visibilitychange', handler)
  return () => document.removeEventListener('visibilitychange', handler)
}