import { isDef, isUndef } from 'shared/util'
import type { KNodeData } from 'types/knode'

import { concat, stringifyClass, genClassForKnode } from 'web/util/index'

function updateClass(oldKnode: any, knode: any) {
  const el = knode.elm
  const data: KNodeData = knode.data
  const oldData: KNodeData = oldKnode.data
  if (
    isUndef(data.staticClass) &&
    isUndef(data.class) &&
    (isUndef(oldData) ||
      (isUndef(oldData.staticClass) && isUndef(oldData.class)))
  ) {
    return
  }

  let cls = genClassForKnode(knode)

  // handle transition classes
  const transitionClass = el._transitionClasses
  if (isDef(transitionClass)) {
    cls = concat(cls, stringifyClass(transitionClass))
  }

  // set the class
  if (cls !== el._prevClass) {
    el.setAttribute('class', cls)
    el._prevClass = cls
  }
}

export default {
  create: updateClass,
  update: updateClass
}