csblogs/feed-downloader

import request from 'request';
import check from 'check-types';
import log from '../log';
import getLastModifiedDate from './get-last-modified-date';

export default function httpRequestIfModifiedSince(uri, dateTime) {
  return new Promise((resolve, reject) => {
    if (!dateTime || check.instance(dateTime, Date.prototype)) {
      reject(new Error('Valid DateTime required'));
    }

    if (!check.nonEmptyString(uri)) {
      reject(new Error('Valid URI required'));
    }

    const requestOptions = {
      uri,
      timeout: process.env.CSBLOGS_HTTP_TIMEOUT,
      headers: {
        'If-Modified-Since': dateTime.toUTCString(),
        'User-Agent': 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36'
      }
    };

    request(requestOptions, (error, response, data) => {
      if (error) {
        log.error({ uri, error },
                  'HTTP Request for resource resulted in error');
        reject(new Error('HTTP request unsuccessful'));
      } else if ((response.statusCode !== 200 && response.statusCode !== 304)) {
        log.info({ uri, response }, 'HTTP Request returned non-success status code');
        reject(new Error('Non-success status code'));
      } else if (response.statusCode === 304) {
        log.info({ uri, lastModified: dateTime.toUTCString() },
                    'Requested resource has not been modified since lastModified date');
        resolve({ modified: false });
      } else {
        const newLastModifiedDateTime = getLastModifiedDate(response.headers);

        log.info({ uri,
          oldLastModified: dateTime.toUTCString(),
          newLastModified: newLastModifiedDateTime.toUTCString()
        }, 'Requested resource has been modified since oldLastModified date');

        resolve({ lastModified: newLastModifiedDateTime, data });
      }
    });
  });
}