<template>
  <div class="container">
    <div class="node-container">
      <div v-for="(item, index) in nodeList"
           :key="index"
           class="source-node"
           draggable="true"
           @dragstart="dragStart(item)">
        {{ item }}
      </div>
    </div>
    <div class="tree-container"
         @dragover="allowDrop"
         @drop="handleDrop">
      <tree-node v-if="nodeData"
                 ref="node"
                 :nodeData="nodeData"
                 @delete-node="deleteTree" />
    </div>
  </div>
</template>
<script>
import TreeNode from './treeNode.vue'
import { Node } from './config.js'
export default {
  name: 'vue-tree',
  components: {
    TreeNode
  },
  // 后代節(jié)點無法獲取節(jié)點數據，即無法獨立創(chuàng)建節(jié)點，所以將祖先節(jié)點的創(chuàng)建節(jié)點方法暴露給后代節(jié)點
  provide () {
    return {
      createNode: this.createNode
    }
  },
  data () {
    return {
      nodeList: ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'],
      currNode: null,
      nodeData: null
    }
  },
  methods: {
    // 開始拖拽，獲取節(jié)點數據
    dragStart (item) {
      this.currNode = item
    },
    // 若未生成跟節(jié)點，則允許拖拽
    allowDrop (event) {
      if (!this.nodeData) {
        event.preventDefault()
      }
    },
    // 拖拽結束，生成節(jié)點
    handleDrop () {
      if (!this.nodeData) {
        this.nodeData = this.createNode()
      }
    },
    createNode () {
      let node = new Node(this.currNode)
      return node
    },
    // 根節(jié)點刪除，刪除整個樹
    deleteTree () {
      this.nodeData = null
    }
  }
}
</script>
<style lang="scss" scoped>
.container {
  padding: 20px;
  width: calc(100% - 40px);
  height: calc(100% - 40px);
  .node-container {
    height: 100px;
    border: 1px dashed red;
    display: flex;
    .source-node {
      width: 50px;
      height: 30px;
      background: #fff;
      border: 1px solid blue;
      text-align: center;
      line-height: 30px;
      margin: 10px;
      cursor: pointer;
    }
  }
  .tree-container {
    height: calc(100% - 122px);
    margin-top: 20px;
  }
}
</style>

export class Node{
  constructor(name){
    this.name = name,
    this.children = []
  }
}

<template>
  <!-- 
    結構：最外層是node-inner，每個node-inner中有一個node與node-box，node存放當前節(jié)點，node-box存放當前節(jié)點的全部子節(jié)點，當前節(jié)點有幾個子節(jié)點則node-box中就會有幾個node-inner，以此循環(huán)
      <node-inner>
        <node></node>
        <node-box>
          <node-inner>
            <node></node>
            <node-box>...</node-box>
          </node-inner>
          <node-inner>
            <node></node>
            <node-box>...</node-box>
          </node-inner>
          ...
        </node-box>
      </node-inner>
   -->
  <div class="node-inner">
    <div class="node"
         :class="{ 'drag-over-node': isDragover }"
         @dragover="dragOver"
         @dragleave="dragLeave"
         @drop="nodeDrop">
      <span class="name">{{nodeData.name}}</span>
      <span class="del"
            @click="deleteNode">刪除</span>
    </div>
    <div v-show="nodeData.children.length > 0"
         class="node-box">
      <tree-node v-for="(item,index) in nodeData.children"
                 :key="index"
                 :nodeData="item"
                 @delete-node="deleteChild(index)" />
    </div>
  </div>
</template>
<script>
export default {
  name: 'tree-node',
  props: {
    nodeData: {
      type: Object,
      default: () => { }
    }
  },
  // 獲取祖先節(jié)點傳遞的數據
  inject: ['createNode'],
  data () {
    return {
      isDragover: false
    }
  },
  methods: {
    // 節(jié)點允許拖拽添加子節(jié)點
    dragOver (event) {
      event.preventDefault()
      if (!this.isDragover) {
        this.isDragover = true
      }
    },
    dragLeave () {
      if (this.isDragover) {
        this.isDragover = false
      }
    },
    // 為節(jié)點添加子節(jié)點
    nodeDrop () {
      let node = this.createNode()
      this.nodeData.children.push(node)
      this.isDragover = false
    },
    // 刪除當前節(jié)點，本質是交給父級刪除子節(jié)點
    deleteNode () {
      this.$emit("delete-node")
    },
    // 接收刪除子節(jié)點的指令并執(zhí)行刪除功能
    deleteChild (index) {
      this.nodeData.children.splice(index, 1)
    }
  }
}
</script>
<style lang="scss" scoped>
.node {
  border: 1px solid orange;
  border-radius: 4px;
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: space-between;
  background-color: #fff;
  height: 36px;
  padding: 0 12px 0 16px;
  line-height: 36px;
  margin-bottom: 10px;
  .name {
    font-size: 16px;
    margin-right: 12px;
  }
  .del {
    color: red;
    font-size: 12px;
    cursor: pointer;
  }
  &.drag-over-node {
    box-shadow: 6px 6px 12px rgba(106, 20, 134, 0.15);
  }
}
.node-box {
  display: inline-flex;
  flex-direction: column;
  .node-inner {
    margin-left: 80px;
    // 連接豎條
    &:not(:last-child):before {
      position: absolute;
      left: -70px;
      top: 22px;
      border: 1px solid orange;
      content: "";
      width: 8px;
      background-color: #fff;
      border-bottom-color: #fff;
      height: 100%;
      border-top-color: #fff;
      z-index: 3;
    }
    // 連接橫條
    &:after {
      left: -61px;
      width: 60px;
      content: "";
      position: absolute;
      top: 14px;
      height: 8px;
      border: 1px solid orange;
      content: "";
      background-color: #fff;
      border-right-color: #fff;
      border-left-color: #fff;
      z-index: 3;
    }
    // 最后一個豎條圓滑拐角
    &:nth-last-child(2):before {
      border-bottom-left-radius: 6px;
      border-bottom-color: orange;
    }
    // 第一個橫條拉長
    &:first-child:after {
      left: -81px;
      width: 80px;
      z-index: 2;
    }
  }
}
.node-inner {
  position: relative;
}
</style>