/**
 * 数组 转 Tree
 * @param {*} arr
 * @param {*} parent
 * @param {*} key
 * @returns
 */
export function arr2Tree(arr = [], parent = "parentId", key = "key") {
  // 转换为字典
  const dict = arr.reduce((acc, item) => {
    return {
      ...acc,
      [item[key]]: {
        ...item,
        children: [],
      },
    };
  }, {});

  // // 查找顶级结点
  // const getRootNode = (node) => {
  //   const found = arr.filter((x) => node[parentId] === x[key])[0];

  //   return !found ? dict[node[key]] : getRootNode(found);
  // };

  // 挂载父子节点
  const tree = [];
  for (let item of arr) {
    const it = dict[item[key]];
    const parentNodeId = it[parent];
    const parentNode = dict[parentNodeId];

    if (!parentNode) {
      tree.push(it);
    } else {
      dict[parentNodeId].children.push(it);
    }
  }
  return [tree, dict];
}

/**
 * 深度展平数组
 * @param {*} arr
 * @returns
 */
export function flatten(arr = []) {
  return arr.reduce((acc, it) => {
    const list = Array.isArray(it) ? flatten(it) : it;
    return acc.concat(list);
  }, []);
}

/**
 * 深度数组去重
 * @param {*} arr
 */
export function uniq(arr = []) {
  const list = flatten(arr);
  return list.reduce((acc, it) => {
    return acc.indexOf(it) > -1 ? acc : acc.concat(it);
  }, []);
}