<template>
  <div
    v-show="data.ready"
    class="el-carousel__item"
    :class="{
      'is-active': data.active,
      'el-carousel__item--card': type === 'card',
      'is-in-stage': data.inStage,
      'is-hover': data.hover,
      'is-animating': data.animating,
    }"
    :style="itemStyle"
    @click="handleItemClick"
  >
    <div
      v-if="type === 'card'"
      v-show="!data.active"
      class="el-carousel__mask"
    ></div>
    <slot></slot>
  </div>
</template>
<script lang="ts">
import {
  defineComponent,
  reactive,
  onMounted,
  inject,
  computed,
  toRefs,
  getCurrentInstance,
  onUnmounted,
} from 'vue'
import {
  autoprefixer,
  PartialCSSStyleDeclaration,
} from '@element-plus/utils/util'
import { InjectCarouselScope, ICarouselItemProps } from './carousel'

const CARD_SCALE = 0.83
export default defineComponent({
  name: 'ElCarouselItem',
  props: {
    name: { type: String, default: '' },
    label: {
      type: [String, Number],
      default: '',
    },
  },
  setup(props: ICarouselItemProps) {
    // instance
    const instance = getCurrentInstance()
    instance.uid

    // data
    const data = reactive({
      hover: false,
      translate: 0,
      scale: 1,
      active: false,
      ready: false,
      inStage: false,
      animating: false,
    })

    // inject
    const injectCarouselScope: InjectCarouselScope = inject(
      'injectCarouselScope',
    )

    // computed
    const parentDirection = computed(() => {
      return injectCarouselScope.direction
    })

    const itemStyle = computed(() => {
      const translateType =
        parentDirection.value === 'vertical' ? 'translateY' : 'translateX'
      const value = `${translateType}(${data.translate}px) scale(${data.scale})`
      const style: PartialCSSStyleDeclaration = {
        transform: value,
      }
      return autoprefixer(style)
    })

    // methods

    function processIndex(index, activeIndex, length) {
      if (activeIndex === 0 && index === length - 1) {
        return -1
      } else if (activeIndex === length - 1 && index === 0) {
        return length
      } else if (index < activeIndex - 1 && activeIndex - index >= length / 2) {
        return length + 1
      } else if (index > activeIndex + 1 && index - activeIndex >= length / 2) {
        return -2
      }
      return index
    }

    function calcCardTranslate(index, activeIndex) {
      const parentWidth = injectCarouselScope.offsetWidth.value
      if (data.inStage) {
        return (
          (parentWidth * ((2 - CARD_SCALE) * (index - activeIndex) + 1)) / 4
        )
      } else if (index < activeIndex) {
        return (-(1 + CARD_SCALE) * parentWidth) / 4
      } else {
        return ((3 + CARD_SCALE) * parentWidth) / 4
      }
    }

    function calcTranslate(index, activeIndex, isVertical) {
      const distance =
        injectCarouselScope[isVertical ? 'offsetHeight' : 'offsetWidth'].value
      return distance * (index - activeIndex)
    }

    const translateItem = (
      index: number,
      activeIndex: number,
      oldIndex: number,
    ) => {
      const parentType = injectCarouselScope.type
      const length = injectCarouselScope.items.value.length
      if (parentType !== 'card' && oldIndex !== undefined) {
        data.animating = index === activeIndex || index === oldIndex
      }
      if (index !== activeIndex && length > 2 && injectCarouselScope.loop) {
        index = processIndex(index, activeIndex, length)
      }
      if (parentType === 'card') {
        if (parentDirection.value === 'vertical') {
          console.warn(
            '[Element Warn][Carousel]vertical direction is not supported in card mode',
          )
        }
        data.inStage = Math.round(Math.abs(index - activeIndex)) <= 1
        data.active = index === activeIndex
        data.translate = calcCardTranslate(index, activeIndex)
        data.scale = data.active ? 1 : CARD_SCALE
      } else {
        data.active = index === activeIndex
        const isVertical = parentDirection.value === 'vertical'
        data.translate = calcTranslate(index, activeIndex, isVertical)
      }
      data.ready = true
    }

    function handleItemClick() {
      if (injectCarouselScope && injectCarouselScope.type === 'card') {
        const index = injectCarouselScope.items.value
          .map(d => d.uid)
          .indexOf(instance.uid)
        injectCarouselScope.setActiveItem(index)
      }
    }

    // lifecycle
    onMounted(() => {
      if (injectCarouselScope.addItem) {
        injectCarouselScope.addItem({
          uid: instance.uid,
          ...props,
          ...toRefs(data),
          translateItem,
        })
      }
    })

    onUnmounted(() => {
      if (injectCarouselScope.removeItem) {
        injectCarouselScope.removeItem(instance.uid)
      }
    })

    return {
      data,
      itemStyle,
      translateItem,
      type: injectCarouselScope.type,
      handleItemClick,
    }
  },
})
</script>
