(function () {
  'use strict';

  window.HttpClient = (function() {

    var _responseInterceptors = [];

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

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

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

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

    function parseHTML(response, idPrefix) {
      if (!idPrefix) {
        idPrefix = Math.floor(Math.random() * 100000);
      }

      var contentType = response.headers.get("content-type");
      if (contentType.indexOf("text/html") === -1) {
        throw new Error('Server returned ' + contentType + ' when HTML was expected');
      }

      return response.text().then(function (responseText) {
        var docFrag = document.createRange().createContextualFragment(responseText);
        
        var idAttrs = ['id', 'for', 'data-conditional-input', 'data-modal-trigger'];
        idAttrs.forEach(function(attr) {
          Array.from(docFrag.querySelectorAll('[' + attr + ']')).forEach(function(input) {
            var value = idPrefix + '__' + input.getAttribute(attr);
            input.setAttribute(attr, value);
          });
        });

        return Promise.resolve(docFrag);
      },
      function (error) {
        return Promise.reject(error);
      }).catch(function (error) { console.error(error); });
    }

    return {
      get: function(url, headers) {
        return _fetch(url, 'GET', headers);
      },
      post: function(url, headers, body) {
        return _fetch(url, 'POST', headers, body);
      },
      addResponseInterceptor: addResponseInterceptor,
      parseHTML: parseHTML,
    }
  })();
})();