<template>
  <div class="drag-list-wrapper">
    <div class="drag-list-con con1">
      <slot name="left-title"></slot>
      <draggable class="drop-box1" :class="dropConClass.left" :options="options" :value="list1" @input="handleListChange($event, 'left')" @end="handleEnd($event, 'left')">
        <div class="drag-list-item" v-for="(itemLeft, index) in list1" :key="`drag_li1_${index}`">
          <slot name="left" :itemLeft="itemLeft">{{ itemLeft }}</slot>
        </div>
      </draggable>
    </div>
    <div class="drag-list-con con2">
      <slot name="right-title"></slot>
      <draggable class="drop-box2" :class="dropConClass.right" :options="options" :value="list2" @input="handleListChange($event, 'right')" @end="handleEnd($event, 'right')">
        <div class="drag-list-item" v-for="(itemRight, index) in list2" :key="`drag_li2_${index}`">
          <slot name="right" :itemRight="itemRight">{{ itemRight }}</slot>
        </div>
      </draggable>
    </div>
  </div>
</template>
<script>
import draggable from 'vuedraggable'
export default {
    name: 'DragList',
    components: {
        draggable
    },
    props: {
        list1: {
            type: Array,
            required: true
        },
        list2: {
            type: Array,
            default: () => []
        },
        dropConClass: {
            type: Object,
            default: () => ({})
        }
    },
    data () {
        return {
            options: { group: 'drag_list' }
        }
    },
    methods: {
        handleListChange (value, type) {
            if (type === 'left') this.$emit('update:list1', value)
            else this.$emit('update:list2', value)
        },
        handleEnd (event, type) {
            const srcClassName = (event.srcElement || event.target).classList[0]
            const targetClassName = event.to.classList[0]
            let src = ''
            let target = ''
            if (srcClassName === targetClassName) {
                if (type === 'left') {
                    src = 'left'
                    target = 'left'
                } else {
                    src = 'right'
                    target = 'right'
                }
            } else {
                if (type === 'left') {
                    src = 'left'
                    target = 'right'
                } else {
                    src = 'right'
                    target = 'left'
                }
            }
            this.$emit('on-change', {
                src: src,
                target: target,
                oldIndex: event.oldIndex,
                newIndex: event.newIndex
            })
        }
    }
}
</script>
<style lang="less">
.drag-list-wrapper{
  height: 100%;
  .drag-list-con{
    width: 50%;
    float: left;
  }
}
</style>
