// 只列举常用的函数，复杂的推荐使用第三方类库。
import _forIn from '@antv/util/lib/for-in';
import sum from './sum';
import warn from 'warning';

import partition from './partition';


/**
 * 百分比计算, 不支持重复数据统计
 * @param data object[] 数据源
 * @param field string 被统计的值 
 * @param as string 生成的百分比字段名
 * @param groupBy : string | string[] 将数据分组后再计算百分比
 */
export default (data: object[], field: string, as: string, groupBy?: string | string[]) => {
  const result: any[] = [];
  const groups = groupBy? partition(data, groupBy) : { _data: data };
  _forIn(groups, (group) => {
    const totalSum = sum(group.map((row: any) => row[field]));
    warn(totalSum !== 0, `Invalid data: total sum of field ${field} is 0!`);
    _forIn(group, (item) => {
      const resultRow = {...item};
      if (totalSum === 0) {
        resultRow[as] = 0;
      } else {
        resultRow[as] = item[field] / totalSum;
      }
      result.push(resultRow);
    });
  });
  return result;
}