'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/;

  var $config = 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, true);
      }
      return data;
    },

    // transform outgoing request data
    transformRequest: function(d) {
      return isObject(d) ? toJson(d) : d;
    },

    // default headers
    headers: {
      common: {
        'Accept': 'application/json, text/plain, */*',
        'X-Requested-With': 'XMLHttpRequest'
      },
      post: {'Content-Type': 'application/json'},
      put:  {'Content-Type': 'application/json'}
    }
  };

  var providerResponseInterceptors = this.responseInterceptors = [];

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

    var defaultCache = $cacheFactory('$http'),
        responseInterceptors = [];

    forEach(providerResponseInterceptors, function(interceptor) {
      responseInterceptors.push(isString(interceptor) ? $injector.get(interceptor) : interceptor);
    });


    /**
     * @ngdoc function
     * @name angular.module.ng.$http
     * @requires $httpBacked
     * @requires $browser
     * @requires $cacheFactory
     * @requires $rootScope
     * @requires $q
     * @requires $injector
     *
     * @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.
     *    - **data** – `{string|Object}` – Data to be sent as the request message data.
     *    - **headers** – `{Object}` – Map of strings representing HTTP headers to send to the server.
     *    - **cache** – `{boolean|Cache}` – If true, a default $http cache will be used to cache the
     *      GET request, otherwise if a cache instance built with $cacheFactory, this cache will be
     *      used for caching.
     *
     * @returns {HttpPromise} Returns a 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.
     *
     * @property {Array.<Object>} pendingRequests Array of config objects for pending requests.
     *   This is primarily meant to be used for debugging purposes.
     *
     * @description
     * $http is a service through which XHR and JSONP requests can be made.
     */
    function $http(config) {
      config.method = uppercase(config.method);

      var reqTransformFn = config.transformRequest || $config.transformRequest,
          respTransformFn = config.transformResponse || $config.transformResponse,
          defHeaders = $config.headers,
          reqHeaders = extend({'X-XSRF-TOKEN': $browser.cookies()['XSRF-TOKEN']},
              defHeaders.common, defHeaders[lowercase(config.method)], config.headers),
          reqData = transformData(config.data, headersGetter(reqHeaders), reqTransformFn),
          promise;


      // send request
      promise = sendReq(config, reqData, reqHeaders);


      // transform future response
      promise = promise.then(transformResponse, transformResponse);

      // apply interceptors
      forEach(responseInterceptors, function(interceptor) {
        promise = interceptor(promise);
      });

      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, respTransformFn)
        });
        return (isSuccess(response.status))
          ? resp
          : $q.reject(resp);
      }
    }

    $http.pendingRequests = [];

    /**
     * @ngdoc method
     * @name angular.module.ng.$http#get
     * @methodOf angular.module.ng.$http
     *
     * @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 angular.module.ng.$http#delete
     * @methodOf angular.module.ng.$http
     *
     * @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 angular.module.ng.$http#head
     * @methodOf angular.module.ng.$http
     *
     * @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 {XhrFuture} Future object
     */

    /**
     * @ngdoc method
     * @name angular.module.ng.$http#patch
     * @methodOf angular.module.ng.$http
     *
     * @description
     * Shortcut method to perform `PATCH` 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 angular.module.ng.$http#jsonp
     * @methodOf angular.module.ng.$http
     *
     * @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 {XhrFuture} Future object
     */
    createShortMethods('get', 'delete', 'head', 'patch', 'jsonp');

    /**
     * @ngdoc method
     * @name angular.module.ng.$http#post
     * @methodOf angular.module.ng.$http
     *
     * @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 angular.module.ng.$http#put
     * @methodOf angular.module.ng.$http
     *
     * @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 {XhrFuture} Future object
     */
    createShortMethodsWithData('post', 'put');


    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, $config, $log, $rootScope, defaultCache, $http.pendingRequests
     */
    function sendReq(config, reqData, reqHeaders) {
      var deferred = $q.defer(),
          promise = deferred.promise,
          cache,
          cachedResp;

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


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

      if (cache) {
        cachedResp = cache.get(config.url);
        if (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]));
            } else {
              resolvePromise(cachedResp, 200, {});
            }
          }
        } else {
          // put the promise for the non-transformed response into cache as a placeholder
          cache.put(config.url, promise);
        }
      }

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

      return promise;


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

        resolvePromise(response, status, headersString);
        $rootScope.$apply();
      }


      /**
       * Resolves the raw $http promise.
       */
      function resolvePromise(response, status, headers) {
        // 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
        });
      }


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