http.js

'use strict';

/**
 * Parse headers into key value object
 *
 * @param {string} headers Raw headers as a string
 * @returns {Object} Parsed headers as key value object
 */
function parseHeaders(headers) {
  var parsed = {}, key, val, i;

  if (!headers) return parsed;

  forEach(headers.split('\n'), function(line) {
    i = line.indexOf(':');
    key = lowercase(trim(line.substr(0, i)));
    val = trim(line.substr(i + 1));

    if (key) {
      if (parsed[key]) {
        parsed[key] += ', ' + val;
      } else {
        parsed[key] = val;
      }
    }
  });

  return parsed;
}


/**
 * Returns a function that provides access to parsed headers.
 *
 * Headers are lazy parsed when first requested.
 * @see parseHeaders
 *
 * @param {(string|Object)} headers Headers to provide access to.
 * @returns {function(string=)} Returns a getter function which if called with:
 *
 *   - if called with single an argument returns a single header value or null
 *   - if called with no arguments returns an object containing all headers.
 */
function headersGetter(headers) {
  var headersObj = isObject(headers) ? headers : undefined;

  return function(name) {
    if (!headersObj) headersObj =  parseHeaders(headers);

    if (name) {
      return headersObj[lowercase(name)] || null;
    }

    return headersObj;
  };
}


/**
 * Chain all given functions
 *
 * This function is used for both request and response transforming
 *
 * @param {*} data Data to transform.
 * @param {function(string=)} headers Http headers getter fn.
 * @param {(Function|Array.<Function>)} fns Function or an array of functions.
 * @returns {*} Transformed data.
 */
function transformData(data, headers, fns) {
  if (isFunction(fns))
    return fns(data, headers);

  forEach(fns, function(fn) {
    data = fn(data, headers);
  });

  return data;
}


function isSuccess(status) {
  return 200 <= status && status < 300;
}


function $HttpProvider() {
  var JSON_START = /^\s*(\[|\{[^\{])/,
      JSON_END = /[\}\]]\s*$/,
      PROTECTION_PREFIX = /^\)\]\}',?\n/,
      CONTENT_TYPE_APPLICATION_JSON = {'Content-Type': 'application/json;charset=utf-8'};

  var defaults = this.defaults = {
    // transform incoming response data
    transformResponse: [function(data) {
      if (isString(data)) {
        // strip json vulnerability protection prefix
        data = data.replace(PROTECTION_PREFIX, '');
        if (JSON_START.test(data) && JSON_END.test(data))
          data = fromJson(data);
      }
      return data;
    }],

    // transform outgoing request data
    transformRequest: [function(d) {
      return isObject(d) && !isFile(d) && !isBlob(d) ? toJson(d) : d;
    }],

    // default headers
    headers: {
      common: {
        'Accept': 'application/json, text/plain, */*'
      },
      post:   copy(CONTENT_TYPE_APPLICATION_JSON),
      put:    copy(CONTENT_TYPE_APPLICATION_JSON),
      patch:  copy(CONTENT_TYPE_APPLICATION_JSON)
    },

    xsrfCookieName: 'XSRF-TOKEN',
    xsrfHeaderName: 'X-XSRF-TOKEN',
    paramsSerializer: 'keyValue'
  };

  /**
   * Are ordered by request, i.e. they are applied in the same order as the
   * array, on request, but reverse order, on response.
   */
  var interceptorFactories = this.interceptors = [];

  /**
   * The URL parameters serializers
   */
  var paramsSerializers = this.paramsSerializers = {
    keyValue: keyValueParametersSerializer,
    JSON: jsonParametersSerializer,
    nonShallowJSON: nonShallowJSONParametersSerializer,
    _default: keyValueParametersSerializer
  };

  function keyValueParametersSerializer(params, callback) {
    forEachSorted(params, function(value, key) {
      if (value === null || isUndefined(value)) return;
      if (!isArray(value)) value = [value];

      forEach(value, function(v) {
        if (isObject(v)) {
          v = toJson(v);
        }
        callback(key, v);
        });
      });
  }

  function jsonParametersSerializer(params, callback) {
    forEachSorted(params, function(value, key) {
      if (value === null || isUndefined(value)) return;
      if (isArray(value) || isObject(value)) {
        value = toJson(value);
      }
      callback(key, value);
    });
  }

  function nonShallowJSONParametersSerializer(params, callback) {
    function serialize(toSerialize, prefix, topLevel) {
      if (toSerialize === null || isUndefined(toSerialize)) return;
      if (isArray(toSerialize)) {
        forEach(toSerialize, function(value) {
          serialize(value, prefix + '[]');
        });
      } else if (isObject(toSerialize)) {
        forEachSorted(toSerialize, function(value, key) {
          serialize(value, prefix +
              (topLevel ? '' : '[') +
              key +
              (topLevel ? '' : ']'));
        });
      } else {
        callback(prefix, toSerialize);
      }
    }

    serialize(params, '', true);
  }

  this.$get = ['$httpBackend', '$browser', '$cacheFactory', '$rootScope', '$q', '$injector',
      function($httpBackend, $browser, $cacheFactory, $rootScope, $q, $injector) {

    var defaultCache = $cacheFactory('$http');

    /**
     * Interceptors stored in reverse order. Inner interceptors before outer interceptors.
     * The reversal is needed so that we can build up the interception chain around the
     * server request.
     */
    var reversedInterceptors = [];

    forEach(interceptorFactories, function(interceptorFactory) {
      reversedInterceptors.unshift(isString(interceptorFactory)
          ? $injector.get(interceptorFactory) : $injector.invoke(interceptorFactory));
    });

    /**
     * @ngdoc service
     * @kind function
     * @name $http
     * @requires ng.$httpBackend
     * @requires $cacheFactory
     * @requires $rootScope
     * @requires $q
     * @requires $injector
     *
     * @description
     * The `$http` service is a core Angular service that facilitates communication with the remote
     * HTTP servers via the browser's [XMLHttpRequest](https://developer.mozilla.org/en/xmlhttprequest)
     * object or via [JSONP](http://en.wikipedia.org/wiki/JSONP).
     *
     * For unit testing applications that use `$http` service, see
     * {@link ngMock.$httpBackend $httpBackend mock}.
     *
     * For a higher level of abstraction, please check out the {@link ngResource.$resource
     * $resource} service.
     *
     * The $http API is based on the {@link ng.$q deferred/promise APIs} exposed by
     * the $q service. While for simple usage patterns this doesn't matter much, for advanced usage
     * it is important to familiarize yourself with these APIs and the guarantees they provide.
     *
     *
     * # General usage
     * The `$http` service is a function which takes a single argument — a configuration object —
     * that is used to generate an HTTP request and returns  a {@link ng.$q promise}
     * with two $http specific methods: `success` and `error`.
     *
     * ```js
     *   $http({method: 'GET', url: '/someUrl'}).
     *     success(function(data, status, headers, config) {
     *       // this callback will be called asynchronously
     *       // when the response is available
     *     }).
     *     error(function(data, status, headers, config) {
     *       // called asynchronously if an error occurs
     *       // or server returns response with an error status.
     *     });
     * ```
     *
     * Since the returned value of calling the $http function is a `promise`, you can also use
     * the `then` method to register callbacks, and these callbacks will receive a single argument –
     * an object representing the response. See the API signature and type info below for more
     * details.
     *
     * A response status code between 200 and 299 is considered a success status and
     * will result in the success callback being called. Note that if the response is a redirect,
     * XMLHttpRequest will transparently follow it, meaning that the error callback will not be
     * called for such responses.
     *
     * # Writing Unit Tests that use $http
     * When unit testing (using {@link ngMock ngMock}), it is necessary to call
     * {@link ngMock.$httpBackend#flush $httpBackend.flush()} to flush each pending
     * request using trained responses.
     *
     * ```
     * $httpBackend.expectGET(...);
     * $http.get(...);
     * $httpBackend.flush();
     * ```
     *
     * # Shortcut methods
     *
     * Shortcut methods are also available. All shortcut methods require passing in the URL, and
     * request data must be passed in for POST/PUT requests.
     *
     * ```js
     *   $http.get('/someUrl').success(successCallback);
     *   $http.post('/someUrl', data).success(successCallback);
     * ```
     *
     * Complete list of shortcut methods:
     *
     * - {@link ng.$http#get $http.get}
     * - {@link ng.$http#head $http.head}
     * - {@link ng.$http#post $http.post}
     * - {@link ng.$http#put $http.put}
     * - {@link ng.$http#delete $http.delete}
     * - {@link ng.$http#jsonp $http.jsonp}
     *
     *
     * # Setting HTTP Headers
     *
     * The $http service will automatically add certain HTTP headers to all requests. These defaults
     * can be fully configured by accessing the `$httpProvider.defaults.headers` configuration
     * object, which currently contains this default configuration:
     *
     * - `$httpProvider.defaults.headers.common` (headers that are common for all requests):
     *   - `Accept: application/json, text/plain, * / *`
     * - `$httpProvider.defaults.headers.post`: (header defaults for POST requests)
     *   - `Content-Type: application/json`
     * - `$httpProvider.defaults.headers.put` (header defaults for PUT requests)
     *   - `Content-Type: application/json`
     *
     * To add or overwrite these defaults, simply add or remove a property from these configuration
     * objects. To add headers for an HTTP method other than POST or PUT, simply add a new object
     * with the lowercased HTTP method name as the key, e.g.
     * `$httpProvider.defaults.headers.get = { 'My-Header' : 'value' }.
     *
     * The defaults can also be set at runtime via the `$http.defaults` object in the same
     * fashion. For example:
     *
     * ```
     * module.run(function($http) {
     *   $http.defaults.headers.common.Authorization = 'Basic YmVlcDpib29w'
     * });
     * ```
     *
     * In addition, you can supply a `headers` property in the config object passed when
     * calling `$http(config)`, which overrides the defaults without changing them globally.
     *
     *
     * # Transforming Requests and Responses
     *
     * Both requests and responses can be transformed using transform functions. By default, Angular
     * applies these transformations:
     *
     * Request transformations:
     *
     * - If the `data` property of the request configuration object contains an object, serialize it
     *   into JSON format.
     *
     * Response transformations:
     *
     *  - If XSRF prefix is detected, strip it (see Security Considerations section below).
     *  - If JSON response is detected, deserialize it using a JSON parser.
     *
     * To globally augment or override the default transforms, modify the
     * `$httpProvider.defaults.transformRequest` and `$httpProvider.defaults.transformResponse`
     * properties. These properties are by default an array of transform functions, which allows you
     * to `push` or `unshift` a new transformation function into the transformation chain. You can
     * also decide to completely override any default transformations by assigning your
     * transformation functions to these properties directly without the array wrapper.  These defaults
     * are again available on the $http factory at run-time, which may be useful if you have run-time
     * services you wish to be involved in your transformations.
     *
     * Similarly, to locally override the request/response transforms, augment the
     * `transformRequest` and/or `transformResponse` properties of the configuration object passed
     * into `$http`.
     *
     *
     * # Caching
     *
     * To enable caching, set the request configuration `cache` property to `true` (to use default
     * cache) or to a custom cache object (built with {@link ng.$cacheFactory `$cacheFactory`}).
     * When the cache is enabled, `$http` stores the response from the server in the specified
     * cache. The next time the same request is made, the response is served from the cache without
     * sending a request to the server.
     *
     * Note that even if the response is served from cache, delivery of the data is asynchronous in
     * the same way that real requests are.
     *
     * If there are multiple GET requests for the same URL that should be cached using the same
     * cache, but the cache is not populated yet, only one request to the server will be made and
     * the remaining requests will be fulfilled using the response from the first request.
     *
     * You can change the default cache to a new object (built with
     * {@link ng.$cacheFactory `$cacheFactory`}) by updating the
     * {@link ng.$http#properties_defaults `$http.defaults.cache`} property. All requests who set
     * their `cache` property to `true` will now use this cache object.
     *
     * If you set the default cache to `false` then only requests that specify their own custom
     * cache object will be cached.
     *
     * # Interceptors
     *
     * Before you start creating interceptors, be sure to understand the
     * {@link ng.$q $q and deferred/promise APIs}.
     *
     * For purposes of global error handling, authentication, or any kind of synchronous or
     * asynchronous pre-processing of request or postprocessing of responses, it is desirable to be
     * able to intercept requests before they are handed to the server and
     * responses before they are handed over to the application code that
     * initiated these requests. The interceptors leverage the {@link ng.$q
     * promise APIs} to fulfill this need for both synchronous and asynchronous pre-processing.
     *
     * The interceptors are service factories that are registered with the `$httpProvider` by
     * adding them to the `$httpProvider.interceptors` array. The factory is called and
     * injected with dependencies (if specified) and returns the interceptor.
     *
     * There are two kinds of interceptors (and two kinds of rejection interceptors):
     *
     *   * `request`: interceptors get called with http `config` object. The function is free to
     *     modify the `config` or create a new one. The function needs to return the `config`
     *     directly or as a promise.
     *   * `requestError`: interceptor gets called when a previous interceptor threw an error or
     *     resolved with a rejection.
     *   * `response`: interceptors get called with http `response` object. The function is free to
     *     modify the `response` or create a new one. The function needs to return the `response`
     *     directly or as a promise.
     *   * `responseError`: interceptor gets called when a previous interceptor threw an error or
     *     resolved with a rejection.
     *
     *
     * ```js
     *   // register the interceptor as a service
     *   $provide.factory('myHttpInterceptor', function($q, dependency1, dependency2) {
     *     return {
     *       // optional method
     *       'request': function(config) {
     *         // do something on success
     *         return config || $q.when(config);
     *       },
     *
     *       // optional method
     *      'requestError': function(rejection) {
     *         // do something on error
     *         if (canRecover(rejection)) {
     *           return responseOrNewPromise
     *         }
     *         return $q.reject(rejection);
     *       },
     *
     *
     *
     *       // optional method
     *       'response': function(response) {
     *         // do something on success
     *         return response || $q.when(response);
     *       },
     *
     *       // optional method
     *      'responseError': function(rejection) {
     *         // do something on error
     *         if (canRecover(rejection)) {
     *           return responseOrNewPromise
     *         }
     *         return $q.reject(rejection);
     *       }
     *     };
     *   });
     *
     *   $httpProvider.interceptors.push('myHttpInterceptor');
     *
     *
     *   // alternatively, register the interceptor via an anonymous factory
     *   $httpProvider.interceptors.push(function($q, dependency1, dependency2) {
     *     return {
     *      'request': function(config) {
     *          // same as above
     *       },
     *
     *       'response': function(response) {
     *          // same as above
     *       }
     *     };
     *   });
     * ```
     *
     * # Security Considerations
     *
     * When designing web applications, consider security threats from:
     *
     * - [JSON vulnerability](http://haacked.com/archive/2008/11/20/anatomy-of-a-subtle-json-vulnerability.aspx)
     * - [XSRF](http://en.wikipedia.org/wiki/Cross-site_request_forgery)
     *
     * Both server and the client must cooperate in order to eliminate these threats. Angular comes
     * pre-configured with strategies that address these issues, but for this to work backend server
     * cooperation is required.
     *
     * ## JSON Vulnerability Protection
     *
     * A [JSON vulnerability](http://haacked.com/archive/2008/11/20/anatomy-of-a-subtle-json-vulnerability.aspx)
     * allows third party website to turn your JSON resource URL into
     * [JSONP](http://en.wikipedia.org/wiki/JSONP) request under some conditions. To
     * counter this your server can prefix all JSON requests with following string `")]}',\n"`.
     * Angular will automatically strip the prefix before processing it as JSON.
     *
     * For example if your server needs to return:
     * ```js
     * ['one','two']
     * ```
     *
     * which is vulnerable to attack, your server can return:
     * ```js
     * )]}',
     * ['one','two']
     * ```
     *
     * Angular will strip the prefix, before processing the JSON.
     *
     *
     * ## Cross Site Request Forgery (XSRF) Protection
     *
     * [XSRF](http://en.wikipedia.org/wiki/Cross-site_request_forgery) is a technique by which
     * an unauthorized site can gain your user's private data. Angular provides a mechanism
     * to counter XSRF. When performing XHR requests, the $http service reads a token from a cookie
     * (by default, `XSRF-TOKEN`) and sets it as an HTTP header (`X-XSRF-TOKEN`). Since only
     * JavaScript that runs on your domain could read the cookie, your server can be assured that
     * the XHR came from JavaScript running on your domain. The header will not be set for
     * cross-domain requests.
     *
     * To take advantage of this, your server needs to set a token in a JavaScript readable session
     * cookie called `XSRF-TOKEN` on the first HTTP GET request. On subsequent XHR requests the
     * server can verify that the cookie matches `X-XSRF-TOKEN` HTTP header, and therefore be sure
     * that only JavaScript running on your domain could have sent the request. The token must be
     * unique for each user and must be verifiable by the server (to prevent the JavaScript from
     * making up its own tokens). We recommend that the token is a digest of your site's
     * authentication cookie with a [salt](https://en.wikipedia.org/wiki/Salt_(cryptography))
     * for added security.
     *
     * The name of the headers can be specified using the xsrfHeaderName and xsrfCookieName
     * properties of either $httpProvider.defaults at config-time, $http.defaults at run-time,
     * or the per-request config object.
     *
     *
     * @param {object} config Object describing the request to be made and how it should be
     *    processed. The object has following properties:
     *
     *    - **method** – `{string}` – HTTP method (e.g. 'GET', 'POST', etc)
     *    - **url** – `{string}` – Absolute or relative URL of the resource that is being requested.
     *    - **params** – `{Object.<string|Object>}` – Map of strings or objects which will be turned
     *      to `?key1=value1&key2=value2` after the url. If the value is not a string, it will be
     *      JSONified.
     *    - **data** – `{string|Object}` – Data to be sent as the request message data.
     *    - **headers** – `{Object}` – Map of strings or functions which return strings representing
     *      HTTP headers to send to the server. If the return value of a function is null, the
     *      header will not be sent.
     *    - **xsrfHeaderName** – `{string}` – Name of HTTP header to populate with the XSRF token.
     *    - **xsrfCookieName** – `{string}` – Name of cookie containing the XSRF token.
     *    - **transformRequest** –
     *      `{function(data, headersGetter)|Array.<function(data, headersGetter)>}` –
     *      transform function or an array of such functions. The transform function takes the http
     *      request body and headers and returns its transformed (typically serialized) version.
     *    - **transformResponse** –
     *      `{function(data, headersGetter)|Array.<function(data, headersGetter)>}` –
     *      transform function or an array of such functions. The transform function takes the http
     *      response body and headers and returns its transformed (typically deserialized) version.
     *    - **cache** – `{boolean|Cache}` – If true, a default $http cache will be used to cache the
     *      GET request, otherwise if a cache instance built with
     *      {@link ng.$cacheFactory $cacheFactory}, this cache will be used for
     *      caching.
     *    - **timeout** – `{number|Promise}` – timeout in milliseconds, or {@link ng.$q promise}
     *      that should abort the request when resolved.
     *    - **withCredentials** - `{boolean}` - whether to to set the `withCredentials` flag on the
     *      XHR object. See [requests with credentials]https://developer.mozilla.org/en/http_access_control#section_5
     *      for more information.
     *    - **responseType** - `{string}` - see
     *      [requestType](https://developer.mozilla.org/en-US/docs/DOM/XMLHttpRequest#responseType).
     *
     * @returns {HttpPromise} Returns a {@link ng.$q promise} object with the
     *   standard `then` method and two http specific methods: `success` and `error`. The `then`
     *   method takes two arguments a success and an error callback which will be called with a
     *   response object. The `success` and `error` methods take a single argument - a function that
     *   will be called when the request succeeds or fails respectively. The arguments passed into
     *   these functions are destructured representation of the response object passed into the
     *   `then` method. The response object has these properties:
     *
     *   - **data** – `{string|Object}` – The response body transformed with the transform
     *     functions.
     *   - **status** – `{number}` – HTTP status code of the response.
     *   - **headers** – `{function([headerName])}` – Header getter function.
     *   - **config** – `{Object}` – The configuration object that was used to generate the request.
     *   - **statusText** – `{string}` – HTTP status text of the response.
     *
     * @property {Array.<Object>} pendingRequests Array of config objects for currently pending
     *   requests. This is primarily meant to be used for debugging purposes.
     *
     *
     * @example
<example>
<file name="index.html">
  <div ng-controller="FetchCtrl">
    <select ng-model="method">
      <option>GET</option>
      <option>JSONP</option>
    </select>
    <input type="text" ng-model="url" size="80"/>
    <button id="fetchbtn" ng-click="fetch()">fetch</button><br>
    <button id="samplegetbtn" ng-click="updateModel('GET', 'http-hello.html')">Sample GET</button>
    <button id="samplejsonpbtn"
      ng-click="updateModel('JSONP',
                    'http://angularjs.org/greet.php?callback=JSON_CALLBACK&name=Super%20Hero')">
      Sample JSONP
    </button>
    <button id="invalidjsonpbtn"
      ng-click="updateModel('JSONP', 'http://angularjs.org/doesntexist&callback=JSON_CALLBACK')">
        Invalid JSONP
      </button>
    <pre>http status code: {{status}}</pre>
    <pre>http response data: {{data}}</pre>
  </div>
</file>
<file name="script.js">
  function FetchCtrl($scope, $http, $templateCache) {
    $scope.method = 'GET';
    $scope.url = 'http-hello.html';

    $scope.fetch = function() {
      $scope.code = null;
      $scope.response = null;

      $http({method: $scope.method, url: $scope.url, cache: $templateCache}).
        success(function(data, status) {
          $scope.status = status;
          $scope.data = data;
        }).
        error(function(data, status) {
          $scope.data = data || "Request failed";
          $scope.status = status;
      });
    };

    $scope.updateModel = function(method, url) {
      $scope.method = method;
      $scope.url = url;
    };
  }
</file>
<file name="http-hello.html">
  Hello, $http!
</file>
<file name="protractor.js" type="protractor">
  var status = element(by.binding('status'));
  var data = element(by.binding('data'));
  var fetchBtn = element(by.id('fetchbtn'));
  var sampleGetBtn = element(by.id('samplegetbtn'));
  var sampleJsonpBtn = element(by.id('samplejsonpbtn'));
  var invalidJsonpBtn = element(by.id('invalidjsonpbtn'));

  it('should make an xhr GET request', function() {
    sampleGetBtn.click();
    fetchBtn.click();
    expect(status.getText()).toMatch('200');
    expect(data.getText()).toMatch(/Hello, \$http!/);
  });

  it('should make a JSONP request to angularjs.org', function() {
    sampleJsonpBtn.click();
    fetchBtn.click();
    expect(status.getText()).toMatch('200');
    expect(data.getText()).toMatch(/Super Hero!/);
  });

  it('should make JSONP request to invalid URL and invoke the error handler',
      function() {
    invalidJsonpBtn.click();
    fetchBtn.click();
    expect(status.getText()).toMatch('0');
    expect(data.getText()).toMatch('Request failed');
  });
</file>
</example>
     */
    function $http(requestConfig) {
      var config = {
        method: 'get',
        transformRequest: defaults.transformRequest,
        transformResponse: defaults.transformResponse,
        paramsSerializer: defaults.paramsSerializer
      };
      var headers = mergeHeaders(requestConfig);

      extend(config, requestConfig);
      config.headers = headers;
      config.method = uppercase(config.method);

      var xsrfValue = urlIsSameOrigin(config.url)
          ? $browser.cookies()[config.xsrfCookieName || defaults.xsrfCookieName]
          : undefined;
      if (xsrfValue) {
        headers[(config.xsrfHeaderName || defaults.xsrfHeaderName)] = xsrfValue;
      }


      var serverRequest = function(config) {
        headers = config.headers;
        var reqData = transformData(config.data, headersGetter(headers), config.transformRequest);

        // strip content-type if data is undefined
        if (isUndefined(config.data)) {
          forEach(headers, function(value, header) {
            if (lowercase(header) === 'content-type') {
                delete headers[header];
            }
          });
        }

        if (isUndefined(config.withCredentials) && !isUndefined(defaults.withCredentials)) {
          config.withCredentials = defaults.withCredentials;
        }

        // send request
        return sendReq(config, reqData, headers).then(transformResponse, transformResponse);
      };

      var chain = [serverRequest, undefined];
      var promise = $q.when(config);

      // apply interceptors
      forEach(reversedInterceptors, function(interceptor) {
        if (interceptor.request || interceptor.requestError) {
          chain.unshift(interceptor.request, interceptor.requestError);
        }
        if (interceptor.response || interceptor.responseError) {
          chain.push(interceptor.response, interceptor.responseError);
        }
      });

      while(chain.length) {
        var thenFn = chain.shift();
        var rejectFn = chain.shift();

        promise = promise.then(thenFn, rejectFn);
      }

      promise.success = function(fn) {
        promise.then(function(response) {
          fn(response.data, response.status, response.headers, config);
        });
        return promise;
      };

      promise.error = function(fn) {
        promise.then(null, function(response) {
          fn(response.data, response.status, response.headers, config);
        });
        return promise;
      };

      return promise;

      function transformResponse(response) {
        // make a copy since the response must be cacheable
        var resp = extend({}, response, {
          data: transformData(response.data, response.headers, config.transformResponse)
        });
        return (isSuccess(response.status))
          ? resp
          : $q.reject(resp);
      }

      function mergeHeaders(config) {
        var defHeaders = defaults.headers,
            reqHeaders = extend({}, config.headers),
            defHeaderName, lowercaseDefHeaderName, reqHeaderName;

        defHeaders = extend({}, defHeaders.common, defHeaders[lowercase(config.method)]);

        // execute if header value is function
        execHeaders(defHeaders);
        execHeaders(reqHeaders);

        // using for-in instead of forEach to avoid unecessary iteration after header has been found
        defaultHeadersIteration:
        for (defHeaderName in defHeaders) {
          lowercaseDefHeaderName = lowercase(defHeaderName);

          for (reqHeaderName in reqHeaders) {
            if (lowercase(reqHeaderName) === lowercaseDefHeaderName) {
              continue defaultHeadersIteration;
            }
          }

          reqHeaders[defHeaderName] = defHeaders[defHeaderName];
        }

        return reqHeaders;

        function execHeaders(headers) {
          var headerContent;

          forEach(headers, function(headerFn, header) {
            if (isFunction(headerFn)) {
              headerContent = headerFn();
              if (headerContent != null) {
                headers[header] = headerContent;
              } else {
                delete headers[header];
              }
            }
          });
        }
      }
    }

    $http.pendingRequests = [];

    /**
     * @ngdoc method
     * @name $http#get
     *
     * @description
     * Shortcut method to perform `GET` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */

    /**
     * @ngdoc method
     * @name $http#delete
     *
     * @description
     * Shortcut method to perform `DELETE` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */

    /**
     * @ngdoc method
     * @name $http#head
     *
     * @description
     * Shortcut method to perform `HEAD` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */

    /**
     * @ngdoc method
     * @name $http#jsonp
     *
     * @description
     * Shortcut method to perform `JSONP` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request.
     *                     Should contain `JSON_CALLBACK` string.
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */
    createShortMethods('get', 'delete', 'head', 'jsonp');

    /**
     * @ngdoc method
     * @name $http#post
     *
     * @description
     * Shortcut method to perform `POST` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request
     * @param {*} data Request content
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */

    /**
     * @ngdoc method
     * @name $http#put
     *
     * @description
     * Shortcut method to perform `PUT` request.
     *
     * @param {string} url Relative or absolute URL specifying the destination of the request
     * @param {*} data Request content
     * @param {Object=} config Optional configuration object
     * @returns {HttpPromise} Future object
     */
    createShortMethodsWithData('post', 'put');

        /**
         * @ngdoc property
         * @name $http#defaults
         *
         * @description
         * Runtime equivalent of the `$httpProvider.defaults` property. Allows configuration of
         * default headers, withCredentials as well as request and response transformations.
         *
         * See "Setting HTTP Headers" and "Transforming Requests and Responses" sections above.
         */
    $http.defaults = defaults;


    return $http;


    function createShortMethods(names) {
      forEach(arguments, function(name) {
        $http[name] = function(url, config) {
          return $http(extend(config || {}, {
            method: name,
            url: url
          }));
        };
      });
    }


    function createShortMethodsWithData(name) {
      forEach(arguments, function(name) {
        $http[name] = function(url, data, config) {
          return $http(extend(config || {}, {
            method: name,
            url: url,
            data: data
          }));
        };
      });
    }


    /**
     * Makes the request.
     *
     * !!! ACCESSES CLOSURE VARS:
     * $httpBackend, defaults, $log, $rootScope, defaultCache, $http.pendingRequests
     */
    function sendReq(config, reqData, reqHeaders) {
      var deferred = $q.defer(),
          promise = deferred.promise,
          cache,
          cachedResp,
          url = buildUrl(config.url, config.params, config.paramsSerializer);

      $http.pendingRequests.push(config);
      promise.then(removePendingReq, removePendingReq);


      if ((config.cache || defaults.cache) && config.cache !== false && config.method == 'GET') {
        cache = isObject(config.cache) ? config.cache
              : isObject(defaults.cache) ? defaults.cache
              : defaultCache;
      }

      if (cache) {
        cachedResp = cache.get(url);
        if (isDefined(cachedResp)) {
          if (cachedResp.then) {
            // cached request has already been sent, but there is no response yet
            cachedResp.then(removePendingReq, removePendingReq);
            return cachedResp;
          } else {
            // serving from cache
            if (isArray(cachedResp)) {
              resolvePromise(cachedResp[1], cachedResp[0], copy(cachedResp[2]), cachedResp[3]);
            } else {
              resolvePromise(cachedResp, 200, {}, 'OK');
            }
          }
        } else {
          // put the promise for the non-transformed response into cache as a placeholder
          cache.put(url, promise);
        }
      }

      // if we won't have the response in cache, send the request to the backend
      if (isUndefined(cachedResp)) {
        $httpBackend(config.method, url, reqData, done, reqHeaders, config.timeout,
            config.withCredentials, config.responseType);
      }

      return promise;


      /**
       * Callback registered to $httpBackend():
       *  - caches the response if desired
       *  - resolves the raw $http promise
       *  - calls $apply
       */
      function done(status, response, headersString, statusText) {
        if (cache) {
          if (isSuccess(status)) {
            cache.put(url, [status, response, parseHeaders(headersString), statusText]);
          } else {
            // remove promise from the cache
            cache.remove(url);
          }
        }

        resolvePromise(response, status, headersString, statusText);
        if (!$rootScope.$$phase) $rootScope.$apply();
      }


      /**
       * Resolves the raw $http promise.
       */
      function resolvePromise(response, status, headers, statusText) {
        // normalize internal statuses to 0
        status = Math.max(status, 0);

        (isSuccess(status) ? deferred.resolve : deferred.reject)({
          data: response,
          status: status,
          headers: headersGetter(headers),
          config: config,
          statusText : statusText
        });
      }


      function removePendingReq() {
        var idx = indexOf($http.pendingRequests, config);
        if (idx !== -1) $http.pendingRequests.splice(idx, 1);
      }
    }


    function buildUrl(url, params, paramsSerializer) {
      if (!params) return url;

      var parts = [];
      if (!isFunction(paramsSerializer)) {
        paramsSerializer = paramsSerializers[paramsSerializer] ||
            paramsSerializers._default;
      }

      paramsSerializer(params, function(key, value) {
        parts.push(encodeUriQuery(key) + '=' + encodeUriQuery(value));
      });
      if(parts.length > 0) {
        url += ((url.indexOf('?') == -1) ? '?' : '&') + parts.join('&');
      }
      return url;
    }


  }];
}