const delay = require('delay');

const callAwsPaginatedMethod = (service, method, methodParams, maxRPS = 0) => {
  const getPagingToken = ({
    PaginationToken, position, NextToken, NextContinuationToken,
  }) => (
    (PaginationToken && { PaginationToken })
    || (position && { position })
    || (NextToken && { NextToken })
    || (NextContinuationToken && { ContinuationToken: NextContinuationToken })
  );

  const retrievedData = [];
  const getResults = async (params) => {
    try {
      const preRunTime = Date.now();
      const data = await service[method](params).promise();
      retrievedData.push(data);

      // don't submit too many requests - put in a delay if passed as a param and more results to fetch.
      if (maxRPS && getPagingToken(data)) {
        await delay((preRunTime - Date.now() + 1000 / maxRPS));
      }

      if (getPagingToken(data)) {
        return getResults(Object.assign(params, getPagingToken(data)));
      }
    } catch (e) {
      console.log(`Error: calling AWS cli ${JSON.stringify(e)}`);
      return Promise.reject(e);
    }

    return Promise.resolve(retrievedData);
  };

  return getResults(methodParams);
};

const flattenAwsMethodResults = (dataArr, element) => [].concat(...dataArr.map(data => data[element]));

module.exports = {
  callAwsPaginatedMethod,
  flattenAwsMethodResults,
};