import decode from './decode';

interface Query {
  [key: string]: unknown;
}

/**
 * 解析query字符串到query对象
 * @param qs query字符串
 */
export default function querystring(qs = ''): Query {
  if (typeof qs !== 'string') return {};
  const index = qs.indexOf('?');
  if (index > 0) {
    qs = qs.substring(index);
  }

  const parser = /([^=?&]+)=?([^&]*)/g;
  const result: Query = {};

  let part = parser.exec(qs);
  while (part) {
    const key = decode(part[1]);
    const value = decode(part[2]);
    if (!(key === null || value == null)) {
      result[key] = key in result ? ([] as unknown[]).concat(result[key], value) : value;
      part = parser.exec(qs);
    }
  }

  return result;
}