'use strict';

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

  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;
}

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

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

  return data;
}


/**
 * @ngdoc object
 * @name angular.module.ng.$http
 * @requires $browser
 * @requires $exceptionHandler
 * @requires $cacheFactory
 *
 * @description
 */
function $HttpProvider() {
  var $config = this.defaults = {
    // transform in-coming reponse data
    transformResponse: function(data) {
      if (isString(data)) {
        if (/^\)\]\}',\n/.test(data)) data = data.substr(6);
        if (/^\s*[\[\{]/.test(data) && /[\}\]]\s*$/.test(data))
          data = fromJson(data, true);
      }
      return data;
    },

    // transform out-going 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'}
    }
  };

  this.$get = ['$browser', '$exceptionHandler', '$cacheFactory', '$rootScope',
      function($browser, $exceptionHandler, $cacheFactory, $rootScope) {

  var cache = $cacheFactory('$http'),
      pendingRequestsCount = 0;

  // the actual service
  function $http(config) {
    return new XhrFuture().retry(config);
  }

  /**
   * @workInProgress
   * @ngdoc method
   * @name angular.service.$http#pendingCount
   * @methodOf angular.service.$http
   *
   * @description
   * Return number of pending requests
   *
   * @returns {number} Number of pending requests
   */
  $http.pendingCount = function() {
    return pendingRequestsCount;
  };

  /**
   * @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 {XhrFuture} 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 {XhrFuture} 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 {XhrFuture} 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 {XhrFuture} 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
        }));
      };
    });
  }

  /**
   * Represents Request object, returned by $http()
   *
   * !!! ACCESS CLOSURE VARS: $browser, $config, $log, $rootScope, cache, pendingRequestsCount
   */
  function XhrFuture() {
    var rawRequest, cfg = {}, callbacks = [],
        defHeaders = $config.headers,
        parsedHeaders;

    /**
     * Callback registered to $browser.xhr:
     *  - caches the response if desired
     *  - calls fireCallbacks()
     *  - clears the reference to raw request object
     */
    function done(status, response) {
      // aborted request or jsonp
      if (!rawRequest) parsedHeaders = {};

      if (cfg.cache && cfg.method == 'GET' && 200 <= status && status < 300) {
        parsedHeaders = parsedHeaders || parseHeaders(rawRequest.getAllResponseHeaders());
        cache.put(cfg.url, [status, response, parsedHeaders]);
      }

      fireCallbacks(response, status);
      rawRequest = null;
    }

    /**
     * Fire all registered callbacks for given status code
     *
     * This method when:
     *  - serving response from real request ($browser.xhr callback)
     *  - serving response from cache
     *
     * It does:
     *  - transform the response
     *  - call proper callbacks
     *  - log errors
     *  - apply the $scope
     *  - clear parsed headers
     */
    function fireCallbacks(response, status) {
      // transform the response
      response = transform(response, cfg.transformResponse || $config.transformResponse, rawRequest);

      var regexp = statusToRegexp(status),
          pattern, callback;

      pendingRequestsCount--;

      // normalize internal statuses to 0
      status = Math.max(status, 0);
      for (var i = 0; i < callbacks.length; i += 2) {
        pattern = callbacks[i];
        callback = callbacks[i + 1];
        if (regexp.test(pattern)) {
          try {
            callback(response, status, headers);
          } catch(e) {
            $exceptionHandler(e);
          }
        }
      }

      $rootScope.$apply();
      parsedHeaders = null;
    }

    /**
     * Convert given status code number into regexp
     *
     * It would be much easier to convert registered statuses (e.g. "2xx") into regexps,
     * but this has an advantage of creating just one regexp, instead of one regexp per
     * registered callback. Anyway, probably not big deal.
     *
     * @param status
     * @returns {RegExp}
     */
    function statusToRegexp(status) {
      var strStatus = status + '',
          regexp = '';

      for (var i = Math.min(0, strStatus.length - 3); i < strStatus.length; i++) {
        regexp += '(' + (strStatus.charAt(i) || 0) + '|x)';
      }

      return new RegExp(regexp);
    }

    /**
     * This is the third argument in any user callback
     * @see parseHeaders
     *
     * Return single header value or all headers parsed as object.
     * Headers all lazy parsed when first requested.
     *
     * @param {string=} name Name of header
     * @returns {string|Object}
     */
    function headers(name) {
      if (name) {
        return parsedHeaders
          ? parsedHeaders[lowercase(name)] || null
          : rawRequest.getResponseHeader(name);
      }

      parsedHeaders = parsedHeaders || parseHeaders(rawRequest.getAllResponseHeaders());

      return parsedHeaders;
    }

    /**
     * Retry the request
     *
     * @param {Object=} config Optional config object to extend the original configuration
     * @returns {XhrFuture}
     */
    this.retry = function(config) {
      if (rawRequest) throw 'Can not retry request. Abort pending request first.';

      extend(cfg, config);
      cfg.method = uppercase(cfg.method);

      var data = transform(cfg.data, cfg.transformRequest || $config.transformRequest),
          headers = extend({'X-XSRF-TOKEN': $browser.cookies()['XSRF-TOKEN']},
                           defHeaders.common, defHeaders[lowercase(cfg.method)], cfg.headers);

      var fromCache;
      if (cfg.cache && cfg.method == 'GET' && (fromCache = cache.get(cfg.url))) {
        $browser.defer(function() {
          parsedHeaders = fromCache[2];
          fireCallbacks(fromCache[1], fromCache[0]);
        });
      } else {
        rawRequest = $browser.xhr(cfg.method, cfg.url, data, done, headers, cfg.timeout);
      }

      pendingRequestsCount++;
      return this;
    };

    /**
     * Abort the request
     */
    this.abort = function() {
      if (rawRequest) {
        rawRequest.abort();
      }
      return this;
    };

    /**
     * Register a callback function based on status code
     * Note: all matched callbacks will be called, preserving registered order !
     *
     * Internal statuses:
     *  `-2` = jsonp error
     *  `-1` = timeout
     *   `0` = aborted
     *
     * @example
     *   .on('2xx', function(){});
     *   .on('2x1', function(){});
     *   .on('404', function(){});
     *   .on('xxx', function(){});
     *   .on('20x,3xx', function(){});
     *   .on('success', function(){});
     *   .on('error', function(){});
     *   .on('always', function(){});
     *
     * @param {string} pattern Status code pattern with "x" for any number
     * @param {function(*, number, Object)} callback Function to be called when response arrives
     * @returns {XhrFuture}
     */
    this.on = function(pattern, callback) {
      var alias = {
        success: '2xx',
        error: '0-2,0-1,000,4xx,5xx',
        always: 'xxx',
        timeout: '0-1',
        abort: '000'
      };

      callbacks.push(alias[pattern] || pattern);
      callbacks.push(callback);

      return this;
    };
  }
}];
}