import PropTypes from '../_util/vue-types'
import ResizeObserver from 'resize-observer-polyfill'
import SubMenu from './SubMenu'
import BaseMixin from '../_util/BaseMixin'
import { getWidth, setStyle, menuAllProps } from './util'
import { cloneElement } from '../_util/vnode'
import { getClass, getPropsData, getEvents } from '../_util/props-util'

const canUseDOM = !!(
  typeof window !== 'undefined' &&
  window.document &&
  window.document.createElement
)

const MENUITEM_OVERFLOWED_CLASSNAME = 'menuitem-overflowed'

// Fix ssr
if (canUseDOM) {
  require('mutationobserver-shim')
}

const DOMWrap = {
  name: 'DOMWrap',
  mixins: [BaseMixin],
  data () {
    this.resizeObserver = null
    this.mutationObserver = null

    // original scroll size of the list
    this.originalTotalWidth = 0

    // copy of overflowed items
    this.overflowedItems = []

    // cache item of the original items (so we can track the size and order)
    this.menuItemSizes = []
    return {
      lastVisibleIndex: undefined,
    }
  },

  mounted () {
    this.$nextTick(() => {
      this.setChildrenWidthAndResize()
      if (this.level === 1 && this.mode === 'horizontal') {
        const menuUl = this.$el
        if (!menuUl) {
          return
        }
        this.resizeObserver = new ResizeObserver(entries => {
          entries.forEach(this.setChildrenWidthAndResize)
        });

        [].slice.call(menuUl.children).concat(menuUl).forEach(el => {
          this.resizeObserver.observe(el)
        })

        if (typeof MutationObserver !== 'undefined') {
          this.mutationObserver = new MutationObserver(() => {
            this.resizeObserver.disconnect();
            [].slice.call(menuUl.children).concat(menuUl).forEach(el => {
              this.resizeObserver.observe(el)
            })
            this.setChildrenWidthAndResize()
          })
          this.mutationObserver.observe(
            menuUl,
            { attributes: false, childList: true, subTree: false }
          )
        }
      }
    })
  },

  beforeDestroy () {
    if (this.resizeObserver) {
      this.resizeObserver.disconnect()
    }
    if (this.mutationObserver) {
      this.resizeObserver.disconnect()
    }
  },
  methods: {
    // get all valid menuItem nodes
    getMenuItemNodes () {
      const { prefixCls } = this.$props
      const ul = this.$el
      if (!ul) {
        return []
      }

      // filter out all overflowed indicator placeholder
      return [].slice.call(ul.children)
        .filter(node => {
          return node.className.split(' ').indexOf(`${prefixCls}-overflowed-submenu`) < 0
        })
    },

    getOverflowedSubMenuItem (keyPrefix, overflowedItems, renderPlaceholder) {
      const { overflowedIndicator, level, mode, prefixCls, theme } = this.$props
      if (level !== 1 || mode !== 'horizontal') {
        return null
      }
      // put all the overflowed item inside a submenu
      // with a title of overflow indicator ('...')
      const copy = this.$slots.default[0]
      const { title, eventKey, ...rest } = getPropsData(copy) // eslint-disable-line no-unused-vars

      let style = {}
      let key = `${keyPrefix}-overflowed-indicator`

      if (overflowedItems.length === 0 && renderPlaceholder !== true) {
        style = {
          display: 'none',
        }
      } else if (renderPlaceholder) {
        style = {
          visibility: 'hidden',
          // prevent from taking normal dom space
          position: 'absolute',
        }
        key = `${key}-placeholder`
      }

      const popupClassName = theme ? `${prefixCls}-${theme}` : ''
      const props = {}
      menuAllProps.props.forEach(k => {
        if (rest[k] !== undefined) {
          props[k] = rest[k]
        }
      })
      const subMenuProps = {
        props: {
          title: overflowedIndicator,
          popupClassName,
          ...props,
          eventKey: `${keyPrefix}-overflowed-indicator`,
          disabled: false,
        },
        class: `${prefixCls}-overflowed-submenu`,
        key,
        style,
        on: getEvents(copy),
      }

      return (
        <SubMenu
          {...subMenuProps}
        >
          {overflowedItems}
        </SubMenu>
      )
    },

    // memorize rendered menuSize
    setChildrenWidthAndResize () {
      if (this.mode !== 'horizontal') {
        return
      }
      const ul = this.$el

      if (!ul) {
        return
      }

      const ulChildrenNodes = ul.children

      if (!ulChildrenNodes || ulChildrenNodes.length === 0) {
        return
      }

      const lastOverflowedIndicatorPlaceholder = ul.children[ulChildrenNodes.length - 1]

      // need last overflowed indicator for calculating length;
      setStyle(lastOverflowedIndicatorPlaceholder, 'display', 'inline-block')

      const menuItemNodes = this.getMenuItemNodes()

      // reset display attribute for all hidden elements caused by overflow to calculate updated width
      // and then reset to original state after width calculation

      const overflowedItems = menuItemNodes
        .filter(c => c.className.split(' ').indexOf(MENUITEM_OVERFLOWED_CLASSNAME) >= 0)

      overflowedItems.forEach(c => {
        setStyle(c, 'display', 'inline-block')
      })

      this.menuItemSizes = menuItemNodes.map(c => getWidth(c))

      overflowedItems.forEach(c => {
        setStyle(c, 'display', 'none')
      })
      this.overflowedIndicatorWidth = getWidth(ul.children[ul.children.length - 1])
      this.originalTotalWidth = this.menuItemSizes.reduce((acc, cur) => acc + cur, 0)
      this.handleResize()
      // prevent the overflowed indicator from taking space;
      setStyle(lastOverflowedIndicatorPlaceholder, 'display', 'none')
    },

    handleResize () {
      if (this.mode !== 'horizontal') {
        return
      }

      const ul = this.$el
      if (!ul) {
        return
      }
      const width = getWidth(ul)

      this.overflowedItems = []
      let currentSumWidth = 0

      // index for last visible child in horizontal mode
      let lastVisibleIndex

      if (this.originalTotalWidth > width) {
        lastVisibleIndex = -1

        this.menuItemSizes.forEach(liWidth => {
          currentSumWidth += liWidth
          if (currentSumWidth + this.overflowedIndicatorWidth <= width) {
            lastVisibleIndex++
          }
        })
      }

      this.setState({ lastVisibleIndex })
    },

    renderChildren (children) {
      // need to take care of overflowed items in horizontal mode
      const { lastVisibleIndex } = this.$data
      const className = getClass(this)
      return (children || []).reduce((acc, childNode, index) => {
        let item = childNode
        const eventKey = getPropsData(childNode).eventKey
        if (this.mode === 'horizontal') {
          let overflowed = this.getOverflowedSubMenuItem(eventKey, [])
          if (lastVisibleIndex !== undefined &&
          className[`${this.prefixCls}-root`] !== -1
          ) {
            if (index > lastVisibleIndex) {
              item = cloneElement(
                childNode,
                // 这里修改 eventKey 是为了防止隐藏状态下还会触发 openkeys 事件
                {
                  style: { display: 'none' },
                  props: { eventKey: `${eventKey}-hidden` },
                  class: { ...getClass(childNode), [MENUITEM_OVERFLOWED_CLASSNAME]: true },
                },
              )
            }
            if (index === lastVisibleIndex + 1) {
              this.overflowedItems = children.slice(lastVisibleIndex + 1).map(c => {
                return cloneElement(
                  c,
                  // children[index].key will become '.$key' in clone by default,
                  // we have to overwrite with the correct key explicitly
                  { key: getPropsData(c).eventKey, props: { mode: 'vertical-left' }},
                )
              })

              overflowed = this.getOverflowedSubMenuItem(
                eventKey,
                this.overflowedItems,
              )
            }
          }

          const ret = [...acc, overflowed, item]

          if (index === children.length - 1) {
            // need a placeholder for calculating overflowed indicator width
            ret.push(this.getOverflowedSubMenuItem(eventKey, [], true))
          }
          return ret
        }
        return [...acc, item]
      }, [])
    },
  },

  render () {
    const Tag = this.$props.tag
    const tagProps = {
      on: this.$listeners,
    }
    return <Tag {...tagProps}>{this.renderChildren(this.$slots.default)}</Tag>
  },
}

DOMWrap.props = {
  mode: PropTypes.oneOf(['horizontal', 'vertical', 'vertical-left', 'vertical-right', 'inline']),
  prefixCls: PropTypes.string,
  level: PropTypes.number,
  theme: PropTypes.string,
  overflowedIndicator: PropTypes.node,
  visible: PropTypes.bool,
  hiddenClassName: PropTypes.string,
  tag: PropTypes.string.def('div'),
}

export default DOMWrap