const _ = require('lodash');

const searchService = require('../service/search');
const logger = require('pelias-logger').get('api');
const logging = require( '../helper/logging' );
const retry = require('retry');

function isRequestTimeout(err) {
  return _.get(err, 'status') === 408;
}

function setup( apiConfig, esclient, query, should_execute ){
  function controller( req, res, next ){
    if (!should_execute(req, res)) {
      return next();
    }

    const cleanOutput = _.cloneDeep(req.clean);
    if (logging.isDNT(req)) {
      logging.removeFields(cleanOutput);
    }
    // log clean parameters for stats
    logger.info('[req]', `endpoint=${req.path}`, cleanOutput);

    const renderedQuery = query(req.clean, res);

    // if there's no query to call ES with, skip the service
    if (_.isUndefined(renderedQuery)) {
      return next();
    }

    // options for retry
    // maxRetries is from the API config with default of 3
    // factor of 1 means that each retry attempt will esclient requestTimeout
    const operationOptions = {
      retries: _.get(apiConfig, 'requestRetries', 3),
      factor: 1,
      minTimeout: _.get(esclient, 'transport.requestTimeout')
    };

    // setup a new operation
    const operation = retry.operation(operationOptions);

    // elasticsearch command
    const cmd = {
      index: apiConfig.indexName,
      searchType: 'dfs_query_then_fetch',
      body: renderedQuery.body
    };

    logger.debug( '[ES req]', cmd );

    operation.attempt((currentAttempt) => {
      // query elasticsearch
      searchService( esclient, cmd, function( err, docs, meta ){
        // returns true if the operation should be attempted again
        // (handles bookkeeping of maxRetries)
        // only consider for status 408 (request timeout)
        if (isRequestTimeout(err) && operation.retry(err)) {
          logger.info(`request timed out on attempt ${currentAttempt}, retrying`);
          return;
        }

        // if execution has gotten this far then one of three things happened:
        // - the request didn't time out
        // - maxRetries has been hit so we're giving up
        // - another error occurred
        // in either case, handle the error or results

        // error handler
        if( err ){
          // push err.message or err onto req.errors
          req.errors.push( _.get(err, 'message', err));
        }
        else {
          // log that a retry was successful
          // most requests succeed on first attempt so this declutters log files
          if (currentAttempt > 1) {
            logger.info(`succeeded on retry ${currentAttempt-1}`);
          }

          // because this is used in response to placeholder, there may already
          // be results.  if there are no results from this ES call, don't overwrite
          // what's already there from placeholder.
          if (!_.isEmpty(docs)) {
            res.data = docs;
            res.meta = meta || {};
            // store the query_type for subsequent middleware
            res.meta.query_type = renderedQuery.type;

            const messageParts = [
              '[controller:search]',
              `[queryType:${renderedQuery.type}]`,
              `[es_result_count:${docs.length}]`
            ];

            logger.info(messageParts.join(' '));

          }

        }
        logger.debug('[ES response]', docs);
        next();
      });

    });

  }

  return controller;
}

module.exports = setup;