(function () {
  'use strict';

  window.HttpClient = (function() {

    var _responseInterceptors = [];

    function addResponseInterceptor(interceptor) {
      if (typeof interceptor === 'function') {
        _responseInterceptors.push(interceptor);
      }
    }

    function _fetch(options) {
      var requestOptions = {
        credentials: 'same-origin',
        headers: { },
        method: options.method,
        body: options.body,
      };

      Object.keys(options.headers).forEach(function(headerKey) {
        requestOptions.headers[headerKey] = options.headers[headerKey];
      });

      return fetch(options.url, requestOptions).then(
        function(response) {
          _responseInterceptors.forEach(function(interceptor) {
            interceptor(response, options);
          });
          return Promise.resolve(response);
        },
        function(error) {
          return Promise.reject(error);
        }
      ).catch(function(error) {
        console.error(error);
      });
    }

    return {
      get: function(args) {
        args.method = 'GET';
        return _fetch(args);
      },
      post: function(args) {
        args.method = 'POST';
        return _fetch(args);
      },
      addResponseInterceptor: addResponseInterceptor,
      ACCEPT: {
        TEXT_HTML: 'text/html',
        JSON: 'application/json',
      },
    }
  })();

  // HttpClient ships with its own little interceptor to throw an error
  // if the response does not match the expected content-type
  function contentTypeInterceptor(response, options) {
    if (!options || !options.accept) {
      return;
    }

    var contentType = response.headers.get("content-type");
    if (!contentType.match(options.accept)) {
      throw new Error('Server returned with "' + contentType + '" when "' + options.accept + '" was expected');
    }
  }

  HttpClient.addResponseInterceptor(contentTypeInterceptor);
})();