import { VantComponent } from '../common/component';
var ITEM_HEIGHT = 44;
VantComponent({
  props: {
    items: Array,
    mainActiveIndex: {
      type: Number,
      value: 0
    },
    activeId: {
      type: Number,
      value: 0
    },
    maxHeight: {
      type: Number,
      value: 300
    }
  },
  data: {
    subItems: [],
    mainHeight: 0,
    itemHeight: 0
  },
  watch: {
    items: function items() {
      this.updateSubItems();
      this.updateMainHeight();
    },
    maxHeight: function maxHeight() {
      this.updateItemHeight();
      this.updateMainHeight();
    },
    mainActiveIndex: 'updateSubItems'
  },
  methods: {
    // 当一个子项被选择时
    onSelectItem: function onSelectItem(event) {
      this.$emit('click-item', event.currentTarget.dataset.item);
    },
    // 当一个导航被点击时
    onClickNav: function onClickNav(event) {
      var index = event.currentTarget.dataset.index;
      this.$emit('click-nav', {
        index: index
      });
    },
    // 更新子项列表
    updateSubItems: function updateSubItems() {
      var selectedItem = this.data.items[this.data.mainActiveIndex] || {};
      this.setData({
        subItems: selectedItem.children || []
      });
      this.updateItemHeight();
    },
    // 更新组件整体高度，根据最大高度和当前组件需要展示的高度来决定
    updateMainHeight: function updateMainHeight() {
      var maxHeight = Math.max(this.data.items.length * ITEM_HEIGHT, this.data.subItems.length * ITEM_HEIGHT);
      this.setData({
        mainHeight: Math.min(maxHeight, this.data.maxHeight)
      });
    },
    // 更新子项列表高度，根据可展示的最大高度和当前子项列表的高度决定
    updateItemHeight: function updateItemHeight() {
      this.setData({
        itemHeight: Math.min(this.data.subItems.length * ITEM_HEIGHT, this.data.maxHeight)
      });
    }
  }
});