/**
 * https://github.com/ElemeFE/element/blob/dev/src/transitions/collapse-transition.js
 */
import { addClass, removeClass } from './util'

const Transition = {
  beforeEnter (el) {
    addClass(el, 'collapse-transition')
    if (!el.dataset) el.dataset = {}

    // // el.dataset.oldPaddingTop = el.style.paddingTop
    // // el.dataset.oldPaddingBottom = el.style.paddingBottom

    el.style.height = '0'
    // el.style.paddingTop = 0
    // el.style.paddingBottom = 0
  },

  enter (el) {
    el.dataset.oldOverflow = el.style.overflow
    if (el.scrollHeight !== 0) {
      el.style.height = `${el.scrollHeight}px`
      // // el.style.paddingTop = el.dataset.oldPaddingTop
      // // el.style.paddingBottom = el.dataset.oldPaddingBottom
    } else {
      el.style.height = ''
      // // el.style.paddingTop = el.dataset.oldPaddingTop
      // // el.style.paddingBottom = el.dataset.oldPaddingBottom
    }

    el.style.overflow = 'hidden'
  },

  afterEnter (el) {
    // for safari: remove class then reset height is necessary
    removeClass(el, 'collapse-transition')
    el.style.height = ''
    el.style.overflow = el.dataset.oldOverflow
  },

  beforeLeave (el) {
    if (!el.dataset) el.dataset = {}
    // // el.dataset.oldPaddingTop = el.style.paddingTop
    // // el.dataset.oldPaddingBottom = el.style.paddingBottom
    el.dataset.oldOverflow = el.style.overflow

    el.style.height = `${el.scrollHeight}px`
    el.style.overflow = 'hidden'
  },

  leave (el) {
    if (el.scrollHeight !== 0) {
      // for safari: add class after set height, or it will jump to zero height suddenly, weired
      addClass(el, 'collapse-transition')
      el.style.height = 0
      // el.style.paddingTop = 0
      // el.style.paddingBottom = 0
    }
  },

  afterLeave (el) {
    removeClass(el, 'collapse-transition')
    el.style.height = ''
    el.style.overflow = el.dataset.oldOverflow
    // // el.style.paddingTop = el.dataset.oldPaddingTop
    // // el.style.paddingBottom = el.dataset.oldPaddingBottom
  }
}

export default {
  name: 'CollapseTransition',
  functional: true,
  render (h, { children }) {
    const data = {
      on: Transition
    }

    return h('transition', data, children)
  }
}
