<template>
  <el-tree lazy :load="loadNode" :props="props" show-checkbox />
</template>

<script lang="ts" setup>
import type Node from 'element-plus/es/components/tree/src/model/node'

let count = 1

interface Tree {
  name: string
}

const props = {
  label: 'name',
  children: 'zones',
}

const loadNode = (node: Node, resolve: (data: Tree[]) => void) => {
  if (node.level === 0) {
    return resolve([{ name: 'Root1' }, { name: 'Root2' }])
  }
  if (node.level > 3) return resolve([])

  let hasChild = false
  if (node.data.name === 'region1') {
    hasChild = true
  } else if (node.data.name === 'region2') {
    hasChild = false
  } else {
    hasChild = Math.random() > 0.5
  }

  setTimeout(() => {
    let data: Tree[]
    if (hasChild) {
      data = [
        {
          name: `zone${count++}`,
        },
        {
          name: `zone${count++}`,
        },
      ]
    } else {
      data = []
    }

    resolve(data)
  }, 500)
}
</script>
