<template>
  <transition mode="out-in" v-on="on">
    <slot></slot>
  </transition>
</template>
<script lang="ts">
  import { defineComponent } from 'vue';
  import { addClass, removeClass } from '/@/utils/domUtils';

  export default defineComponent({
    name: 'MenuCollapseTransition',
    setup() {
      return {
        on: {
          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) {
            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) {
              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;
          },
        },
      };
    },
  });
</script>
