<template>
  <div
    class="dropdown-wrapper"
    :class="{ open }"
  >
    <button
      class="dropdown-title"
      type="button"
      :aria-label="dropdownAriaLabel"
      @click="handleDropdown"
    >
      <span class="title">{{ item.text }}</span>
      <span
        class="arrow down"
      />
    </button>
    <button
      class="mobile-dropdown-title"
      type="button"
      :aria-label="dropdownAriaLabel"
      @click="setOpen(!open)"
    >
      <span class="title">{{ item.text }}</span>
      <span
        class="arrow"
        :class="open ? 'down' : 'right'"
      />
    </button>

    <DropdownTransition>
      <ul
        v-show="open"
        class="nav-dropdown"
      >
        <li
          v-for="(subItem, index) in item.items"
          :key="subItem.link || index"
          class="dropdown-item"
        >
          <h4 v-if="subItem.type === 'links'">
            {{ subItem.text }}
          </h4>

          <ul
            v-if="subItem.type === 'links'"
            class="dropdown-subitem-wrapper"
          >
            <li
              v-for="childSubItem in subItem.items"
              :key="childSubItem.link"
              class="dropdown-subitem"
            >
              <NavLink
                :item="childSubItem"
                @focusout="
                  isLastItemOfArray(childSubItem, subItem.items) &&
                    isLastItemOfArray(subItem, item.items) &&
                    setOpen(false)
                "
              />
            </li>
          </ul>

          <NavLink
            v-else
            :item="subItem"
            @focusout="isLastItemOfArray(subItem, item.items) && setOpen(false)"
          />
        </li>
      </ul>
    </DropdownTransition>
  </div>
</template>

<script>
import NavLink from '@theme/components/NavLink.vue'
import DropdownTransition from '@theme/components/DropdownTransition.vue'
import last from 'lodash/last'

export default {
  name: 'DropdownLink',

  components: {
    NavLink,
    DropdownTransition
  },

  props: {
    item: {
      required: true
    }
  },

  data () {
    return {
      open: false
    }
  },

  computed: {
    dropdownAriaLabel () {
      return this.item.ariaLabel || this.item.text
    }
  },

  watch: {
    $route () {
      this.open = false
    }
  },

  methods: {
    setOpen (value) {
      this.open = value
    },

    isLastItemOfArray (item, array) {
      return last(array) === item
    },

    /**
     * Open the dropdown when user tab and click from keyboard.
     *
     * Use event.detail to detect tab and click from keyboard. Ref: https://developer.mozilla.org/en-US/docs/Web/API/UIEvent/detail
     * The Tab + Click is UIEvent > KeyboardEvent, so the detail is 0.
     */
    handleDropdown () {
      const isTriggerByTab = event.detail === 0
      if (isTriggerByTab) this.setOpen(!this.open)
    }
  }
}
</script>

<style lang="stylus">
.dropdown-wrapper
  cursor pointer
  .dropdown-title
    display block
    font-size 0.9rem
    font-family inherit
    cursor inherit
    padding inherit
    line-height 1.4rem
    background transparent
    border none
    font-weight 500
    color $textColor
    &:hover
      border-color transparent
    .arrow
      vertical-align middle
      margin-top -1px
      margin-left 0.4rem
  .mobile-dropdown-title
    @extends .dropdown-title
    display none
    font-weight 600
    font-size inherit
      &:hover
        color $accentColor
  .nav-dropdown
    .dropdown-item
      color inherit
      line-height 1.7rem
      h4
        margin 0.45rem 0 0
        border-top 1px solid #eee
        padding 1rem 1.5rem 0.45rem 1.25rem
      .dropdown-subitem-wrapper
        padding 0
        list-style none
        .dropdown-subitem
          font-size 0.9em
      a
        display block
        line-height 1.7rem
        position relative
        border-bottom none
        font-weight 400
        margin-bottom 0
        padding 0 1.5rem 0 1.25rem
        &:hover
          color $accentColor
        &.router-link-active
          color $accentColor
          &::after
            content ""
            width 0
            height 0
            border-left 5px solid $accentColor
            border-top 3px solid transparent
            border-bottom 3px solid transparent
            position absolute
            top calc(50% - 2px)
            left 9px
      &:first-child h4
        margin-top 0
        padding-top 0
        border-top 0

@media (max-width: $MQMobile)
  .dropdown-wrapper
    &.open .dropdown-title
      margin-bottom 0.5rem
    .dropdown-title
      display: none
    .mobile-dropdown-title
      display: block
    .nav-dropdown
      transition height .1s ease-out
      overflow hidden
      .dropdown-item
        h4
          border-top 0
          margin-top 0
          padding-top 0
        h4, & > a
          font-size 15px
          line-height 2rem
        .dropdown-subitem
          font-size 14px
          padding-left 1rem

@media (min-width: $MQMobile)
  .dropdown-wrapper
    height 1.8rem
    &:hover .nav-dropdown,
    &.open .nav-dropdown
      // override the inline style.
      display block !important
    .nav-dropdown
      display none
      // Avoid height shaked by clicking
      height auto !important
      box-sizing border-box;
      max-height calc(100vh - 2.7rem)
      overflow-y auto
      position absolute
      top 100%
      right 0
      background-color #fff
      padding 0.6rem 0
      border 1px solid #ddd
      border-bottom-color #ccc
      text-align left
      border-radius 0.25rem
      white-space nowrap
      margin 0
</style>
