class Tree {
  constructor(list = [], config) {
    this.config = {
      key: 'id', parent: 'parentId', children: 'children',
      ...config
    }
    this.list = list
    if (Array.isArray(list)) this.tree = this.arr2tree(list)
  }

  arr2tree(list) {
    const {key, parent, children} = this.config
    const result = []
    this.map = {}
    const ids = list?.map(e => `#${e[key]}#`)?.toString()
    for (const e of list) {
      const id = e[key], pid = e[parent]
      this.map[id] = {...e, [children]: [this.map[id]?.[children]].flat().filter(Boolean)}
      const treeItem = this.map[id]
      if (!!pid && ids.indexOf(`#${pid}#`) > -1) {
        if (!this.map[pid]) {
          this.map[pid] = {
            children: []
          }
        }
        this.map[pid].children.push(treeItem)
      } else result.push(treeItem)
    }
    const removeNullChildren = node => {
      if (node[children] && node[children].length > 0) {
        node[children].map(c => removeNullChildren(c))
      } else delete node[children]
    }
    result.forEach(removeNullChildren)
    return result
  }

  root(id) {
    return this.map[id]
  }

  find(id) {
    return this.map[id]
  }

  every(cb) {
    const iterate = list => {
      list?.map(e => {
        cb(e)
        iterate(e.children)
      })
    }
    iterate(this.tree)
  }
}

export default Tree