import ResizeObserver from 'resize-observer-polyfill'
import { isServer } from './is$'

export type ResizableElement = CustomizedHTMLElement<{
  __resizeListeners__: Array<(...args: unknown[]) => unknown>
  __ro__: ResizeObserver
}>

export const resizeHandler = (entries: ResizeObserverEntry[]) => {
  for (const entry of entries) {
    const listeners = (entry.target as ResizableElement).__resizeListeners__ || []
    if (listeners.length) {
      listeners.forEach(fn => {
        fn()
      })
    }
  }
}

export const addResizeListener = (element: ResizableElement, fn: (...args: unknown[]) => unknown): void => {
  if (isServer) return
  if (!element.__resizeListeners__) {
    element.__resizeListeners__ = []
    element.__ro__ = new ResizeObserver(resizeHandler)
    element.__ro__.observe(element)
  }
  element.__resizeListeners__.push(fn)
}

export const removeResizeListener = (element: ResizableElement, fn: (...args: unknown[]) => unknown) => {
  if (!element || !element.__resizeListeners__) return
  element.__resizeListeners__.splice(element.__resizeListeners__.indexOf(fn), 1)
  if (!element.__resizeListeners__.length) {
    element.__ro__.disconnect()
  }
}