<template>
  <transition leave-active-class="zui-code-collapse"
              enter-active-class="zui-code-collapse"
              @before-enter="beforeEnter"
              @enter="enter"
              @after-enter="afterEnter"
              @before-leave="beforeLeave"
              @leave="leave"
              @after-leave="afterLeave">
    <slot></slot>
  </transition>
</template>
<script>
export default {
  methods: {
    beforeEnter(el) {
      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) {
      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) {
        el.style.height = 0;
        el.style.paddingTop = 0;
        el.style.paddingBottom = 0;
      }
    },

    afterLeave(el) {
      el.style.height = '';
      el.style.overflow = el.dataset.oldOverflow;
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    }
  }

}
</script>
<style lang="scss">
.zui-code-collapse {
  transition: 0.3s height ease-in-out, 0.3s padding-top ease-in-out,
    0.3s padding-bottom ease-in-out;
}
</style>