'use strict';

import utils from '../utils.js';

// RawAxiosHeaders whose duplicates are ignored by node
// c.f. https://nodejs.org/api/http.html#http_message_headers
const ignoreDuplicateOf = utils.toObjectSet([
  'age',
  'authorization',
  'content-length',
  'content-type',
  'etag',
  'expires',
  'from',
  'host',
  'if-modified-since',
  'if-unmodified-since',
  'last-modified',
  'location',
  'max-forwards',
  'proxy-authorization',
  'referer',
  'retry-after',
  'user-agent',
]);

/**
 * Parse headers into an object
 *
 * ```
 * Date: Wed, 27 Aug 2014 08:58:49 GMT
 * Content-Type: application/json
 * Connection: keep-alive
 * Transfer-Encoding: chunked
 * ```
 *
 * @param {String} rawHeaders Headers needing to be parsed
 *
 * @returns {Object} Headers parsed into an object
 */
export default (rawHeaders) => {
  const parsed = {};
  let key;
  let val;
  let i;

  rawHeaders &&
    rawHeaders.split('\n').forEach(function parser(line) {
      i = line.indexOf(':');
      key = line.substring(0, i).trim().toLowerCase();
      val = line.substring(i + 1).trim();

      if (!key || (parsed[key] && ignoreDuplicateOf[key])) {
        return;
      }

      if (key === 'set-cookie') {
        if (parsed[key]) {
          parsed[key].push(val);
        } else {
          parsed[key] = [val];
        }
      } else {
        parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
      }
    });

  return parsed;
};