interface TreeHelperConfig {
  id: string
  children: string
  pid: string
}

// 默认配置
const DEFAULT_CONFIG: TreeHelperConfig = {
  id: 'id',
  children: 'children',
  pid: 'pid',
}

// 获取配置。  Object.assign 从一个或多个源对象复制到目标对象
const getConfig = (config: Partial<TreeHelperConfig>) => Object.assign({}, DEFAULT_CONFIG, config)

// tree from list
// 列表中的树
export function listToTree<T = any>(list: any[], config: Partial<TreeHelperConfig> = {}): T[] {
  const conf = getConfig(config) as TreeHelperConfig
  const nodeMap = new Map()
  const result: T[] = []
  const { id, children, pid } = conf

  for (const node of list) {
    node[children] = node[children] || []
    nodeMap.set(node[id], node)
  }
  for (const node of list) {
    const parent = nodeMap.get(node[pid]);
    (parent ? parent[children] : result).push(node)
  }
  return result
}

export function treeToList<T = any>(tree: any, config: Partial<TreeHelperConfig> = {}): T {
  config = getConfig(config)
  const { children } = config
  const result: any = [...tree]
  for (let i = 0; i < result.length; i++) {
    if (!result[i][children!]) continue
    result.splice(i + 1, 0, ...result[i][children!])
  }
  return result
}

export function findNode<T = any>(
  tree: any,
  func: Fn,
  config: Partial<TreeHelperConfig> = {},
): T | null {
  config = getConfig(config)
  const { children } = config
  const list = [...tree]
  for (const node of list) {
    if (func(node)) return node
    node[children!] && list.push(...node[children!])
  }
  return null
}

export function findNodeAll<T = any>(
  tree: any,
  func: Fn,
  config: Partial<TreeHelperConfig> = {},
): T[] {
  config = getConfig(config)
  const { children } = config
  const list = [...tree]
  const result: T[] = []
  for (const node of list) {
    func(node) && result.push(node)
    node[children!] && list.push(...node[children!])
  }
  return result
}

export function findPath<T = any>(
  tree: any,
  func: Fn,
  config: Partial<TreeHelperConfig> = {},
): T | T[] | null {
  config = getConfig(config)
  const path: T[] = []
  const list = [...tree]
  const visitedSet = new Set()
  const { children } = config
  while (list.length) {
    const node = list[0]
    if (visitedSet.has(node)) {
      path.pop()
      list.shift()
    }
    else {
      visitedSet.add(node)
      node[children!] && list.unshift(...node[children!])
      path.push(node)
      if (func(node))
        return path
    }
  }
  return null
}

export function findPathAll(tree: any, func: Fn, config: Partial<TreeHelperConfig> = {}) {
  config = getConfig(config)
  const path: any[] = []
  const list = [...tree]
  const result: any[] = []
  const visitedSet = new Set()
  const { children } = config
  while (list.length) {
    const node = list[0]
    if (visitedSet.has(node)) {
      path.pop()
      list.shift()
    }
    else {
      visitedSet.add(node)
      node[children!] && list.unshift(...node[children!])
      path.push(node)
      func(node) && result.push([...path])
    }
  }
  return result
}

export function filter<T = any>(
  tree: T[],
  func: (n: T) => boolean,
  // Partial 将 T 中的所有属性设为可选
  config: Partial<TreeHelperConfig> = {},
): T[] {
  // 获取配置
  config = getConfig(config)
  const children = config.children as string

  function listFilter(list: T[]) {
    return list
      .map((node: any) => ({ ...node }))
      .filter((node) => {
        // 递归调用 对含有children项  进行再次调用自身函数 listFilter
        node[children] = node[children] && listFilter(node[children])
        // 执行传入的回调 func 进行过滤
        return func(node) || (node[children] && node[children].length)
      })
  }

  return listFilter(tree)
}

export function forEach<T = any>(
  tree: T[],
  func: (n: T) => any,
  config: Partial<TreeHelperConfig> = {},
): void {
  config = getConfig(config)
  const list: any[] = [...tree]
  const { children } = config
  for (let i = 0; i < list.length; i++) {
    // func 返回true就终止遍历，避免大量节点场景下无意义循环，引起浏览器卡顿
    if (func(list[i]))
      return

    children && list[i][children] && list.splice(i + 1, 0, ...list[i][children])
  }
}

/**
 * @description: Extract tree specified structure
 * @description: 提取树指定结构
 */
export function treeMap<T = any>(treeData: T[], opt: { children?: string; conversion: Fn }): T[] {
  return treeData.map(item => treeMapEach(item, opt))
}

/**
 * @description: Extract tree specified structure
 * @description: 提取树指定结构
 */
export function treeMapEach(
  data: any,
  { children = 'children', conversion }: { children?: string; conversion: Fn },
) {
  const haveChildren = Array.isArray(data[children]) && data[children].length > 0
  const conversionData = conversion(data) || {}
  if (haveChildren) {
    return {
      ...conversionData,
      [children]: data[children].map((i: number) =>
        treeMapEach(i, {
          children,
          conversion,
        }),
      ),
    }
  }
  else {
    return {
      ...conversionData,
    }
  }
}

/**
 * 递归遍历树结构
 * @param treeDatas 树
 * @param callBack 回调
 * @param parentNode 父节点
 */
export function eachTree(treeDatas: any[], callBack: Fn, parentNode = {}) {
  treeDatas.forEach((element) => {
    const newNode = callBack(element, parentNode) || element
    if (element.children)
      eachTree(element.children, callBack, newNode)
  })
}