/**
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

(function() {
  'use strict';

  angular
    .module('horizon.app.core.openstack-service-api')
    .factory('horizon.app.core.openstack-service-api.policy', PolicyService);

  PolicyService.$inject = [
    '$q',
    'horizon.framework.util.filters.$memoize',
    'horizon.framework.util.http.service',
    'horizon.framework.widgets.toast.service'
  ];

  /**
   * @ngdoc service
   * @name PolicyService
   * @param {Object} $q
   * @param {Object} memoize
   * @param {Object} apiService
   * @param {Object} toastService
   * @description Provides a direct pass through to the policy engine in
   * Horizon.
   * @returns {Object} The service
   */
  function PolicyService($q, memoize, apiService, toastService) {

    var service = {
      check: memoize(check, memoizeHasher),
      ifAllowed: memoize(ifAllowed, memoizeHasher)
    };

    return service;

    //////////////

    /**
     * @name check
     * @param {Object} policyRules
     * @description
     * Check the passed in policy rule list to determine if the user has
     * permission to perform the actions specified by the rules. The service
     * APIs will ultimately reject actions that are not permitted. This is used
     * for Role Based Access Control in the UI only. The required parameter
     * should have the following structure:
     *
     *   {
     *     "rules": [
     *                [ "compute", "compute:get_all" ],
     *              ],
     *     "target": {
     *                 "project_id": "1"
     *               }
     *   }
     *
     * where "rules" is a list of rules (1 or greater in length) policy rules
     * which are composed of a
     *    * service name -- maps the policy rule to a service
     *    * rule -- the policy rule to check
     * and "target" key and value is optional. In some cases, policy rules
     * require specific details about the object that is to be acted on.
     * If added, it is merely a dictionary of keys and values.
     *
     *
     * The following is the response if the check passes:
     *   {
     *     "allowed": true
     *   }
     *
     * The following is the response if the check fails:
     *   {
     *     "allowed": false
     *   }
     * @returns {Object} The result of the API call
     */
    function check(policyRules) {
      // Return a deferred and map then to success since legacy angular http uses success.
      // The .error is already overriden in this function to just display toast, so this should
      // work the same as if only success was returned.
      var deferred = $q.defer();

      apiService.post('/api/policy/', policyRules)
        .success(function successPath(result) {
          deferred.resolve(result);
        })
        .error(function failurePath(result) {
          toastService.add('warning', gettext('Policy check failed.'));
          deferred.reject(result);
        });

      deferred.promise.success = deferred.promise.then;
      return deferred.promise;
    }

    /**
     * @name ifAllowed
     * @param {Object} policyRules
     * @description
     * Wrapper function for check that returns a deferred promise.
     * Resolves if the response is allowed, rejects otherwise.
     * The policyRules input is the same as the check function. Please
     * refer to it for more information on the input.
     *
     * @example
     * Assume if the users is not allowed to delete an object,
     * you will delete the object, otherwise, you will do something else.
     *
     ```js
     policyService.ifAllowed(myRules).then(deleteObject, doSomethingElse);
     ```
     * @returns {promise} A promise resolving if true, rejecting if not
     */
    function ifAllowed(policyRules) {
      var deferred = $q.defer();
      service.check(policyRules).then(success);
      return deferred.promise;

      function success(response) {
        if (response.allowed) {
          deferred.resolve();
        } else {
          deferred.reject();
        }
      }
    }

    function memoizeHasher(policyRules) {
      return angular.toJson(policyRules);
    }
  }
}());
