import { VantComponent } from '../common/component'
import { touch } from '../mixins/touch'
import { getAllRect, getRect, isDef } from '../common/utils'
VantComponent({
  mixins: [touch],
  classes: ['nav-class', 'tab-class', 'tab-active-class', 'line-class'],
  relation: {
    name: 'tab',
    type: 'descendant',
    current: 'tabs',
    linked(target) {
      target.index = this.children.length - 1
      this.updateTabs()
    },
    unlinked() {
      this.children = this.children.map((child, index) => {
        child.index = index
        return child
      })
      this.updateTabs()
    },
  },
  props: {
    sticky: Boolean,
    border: Boolean,
    swipeable: Boolean,
    titleActiveColor: String,
    titleInactiveColor: String,
    color: String,
    animated: {
      type: Boolean,
      observer() {
        wx.nextTick(() => {
          this.children.forEach((child, index) =>
            child.updateRender(index === this.data.currentIndex, this)
          )
        })
      },
    },
    lineWidth: {
      type: [String, Number],
      value: 40,
      observer: 'resize',
    },
    lineHeight: {
      type: [String, Number],
      value: -1,
    },
    active: {
      type: [String, Number],
      value: 0,
      observer(name) {
        wx.nextTick(() => {
          if (name !== this.getCurrentName()) {
            this.setCurrentIndexByName(name)
          }
        })
      },
    },
    type: {
      type: String,
      value: 'line',
    },
    ellipsis: {
      type: Boolean,
      value: true,
    },
    duration: {
      type: Number,
      value: 0.3,
    },
    zIndex: {
      type: Number,
      value: 1,
    },
    swipeThreshold: {
      type: Number,
      value: 5,
      observer(value) {
        this.setData({
          scrollable: this.children.length > value || !this.data.ellipsis,
        })
      },
    },
    offsetTop: {
      type: Number,
      value: 0,
    },
    lazyRender: {
      type: Boolean,
      value: true,
    },
  },
  data: {
    tabs: [],
    lineStyle: '',
    scrollLeft: 0,
    scrollable: false,
    trackStyle: '',
    currentIndex: 0,
    container: null,
    skipTransition: true,
    lineOffsetLeft: 0,
  },
  mounted() {
    wx.nextTick(() => {
      this.resize(true)
      this.scrollIntoView()
    }, 200)
  },
  methods: {
    updateContainer() {
      this.setData({
        container: () => this.createSelectorQuery().select('.van-tabs'),
      })
    },
    updateTabs() {
      const { children = [], data } = this
      this.setData({
        tabs: children.map((child) => child.data),
        scrollable:
          this.children.length > data.swipeThreshold || !data.ellipsis,
      })
      this.setCurrentIndexByName(this.getCurrentName() || data.active)
    },
    trigger(eventName, child) {
      const { currentIndex } = this.data
      const currentChild = child || this.children[currentIndex]
      if (!isDef(currentChild)) {
        return
      }
      this.$emit(eventName, {
        index: currentChild.index,
        name: currentChild.getComputedName(),
        title: currentChild.data.title,
      })
    },
    onTap(event) {
      const { index } = event.currentTarget.dataset
      const child = this.children[index]
      if (child.data.disabled) {
        this.trigger('disabled', child)
      } else {
        this.setCurrentIndex(index)
        wx.nextTick(() => {
          this.trigger('click')
        })
      }
    },
    // correct the index of active tab
    setCurrentIndexByName(name) {
      const { children = [] } = this
      const matched = children.filter(
        (child) => child.getComputedName() === name
      )
      if (matched.length) {
        this.setCurrentIndex(matched[0].index)
      }
    },
    setCurrentIndex(currentIndex) {
      const { data, children = [] } = this
      if (
        !isDef(currentIndex) ||
        currentIndex >= children.length ||
        currentIndex < 0
      ) {
        return
      }
      children.forEach((item, index) => {
        const active = index === currentIndex
        if (active !== item.data.active || !item.inited) {
          item.updateRender(active, this)
        }
      })
      if (currentIndex === data.currentIndex) {
        return
      }
      const shouldEmitChange = data.currentIndex !== null
      this.setData({ currentIndex })
      wx.nextTick(() => {
        this.resize()
        this.scrollIntoView()
        this.updateContainer()
        this.trigger('input')
        if (shouldEmitChange) {
          this.trigger('change')
        }
      })
    },
    getCurrentName() {
      const activeTab = this.children[this.data.currentIndex]
      if (activeTab) {
        return activeTab.getComputedName()
      }
    },
    resize(skipTransition = false) {
      if (this.data.type !== 'line') {
        return
      }
      const { currentIndex, ellipsis } = this.data
      Promise.all([
        getAllRect.call(this, '.van-tab'),
        getRect.call(this, '.van-tabs__line'),
      ]).then(([rects = [], lineRect]) => {
        const rect = rects[currentIndex]
        if (rect == null) {
          return
        }
        let lineOffsetLeft = rects
          .slice(0, currentIndex)
          .reduce((prev, curr) => prev + curr.width, 0)
        lineOffsetLeft += (rect.width - lineRect.width) / 2 + (ellipsis ? 0 : 8)
        this.setData({
          lineOffsetLeft,
          skipTransition,
        })
      })
    },
    // scroll active tab into view
    scrollIntoView() {
      const { currentIndex, scrollable } = this.data
      if (!scrollable) {
        return
      }
      Promise.all([
        getAllRect.call(this, '.van-tab'),
        getRect.call(this, '.van-tabs__nav'),
      ]).then(([tabRects, navRect]) => {
        const tabRect = tabRects[currentIndex]
        const offsetLeft = tabRects
          .slice(0, currentIndex)
          .reduce((prev, curr) => prev + curr.width, 0)
        this.setData({
          scrollLeft: offsetLeft - (navRect.width - tabRect.width) / 2,
        })
      })
    },
    onTouchScroll(event) {
      this.$emit('scroll', event.detail)
    },
    onTouchStart(event) {
      if (!this.data.swipeable) return
      this.touchStart(event)
    },
    onTouchMove(event) {
      if (!this.data.swipeable) return
      this.touchMove(event)
    },
    // watch swipe touch end
    onTouchEnd() {
      if (!this.data.swipeable) return
      const { direction, deltaX, offsetX } = this
      const minSwipeDistance = 50
      if (direction === 'horizontal' && offsetX >= minSwipeDistance) {
        const index = this.getAvaiableTab(deltaX)
        if (index !== -1) {
          this.setCurrentIndex(index)
        }
      }
    },
    getAvaiableTab(direction) {
      const { tabs, currentIndex } = this.data
      const step = direction > 0 ? -1 : 1
      for (
        let i = step;
        currentIndex + i < tabs.length && currentIndex + i >= 0;
        i += step
      ) {
        const index = currentIndex + i
        if (
          index >= 0 &&
          index < tabs.length &&
          tabs[index] &&
          !tabs[index].disabled
        ) {
          return index
        }
      }
      return -1
    },
  },
})
