@onehilltech/blueprint/lib/middleware/check-policy.js

lightweight, simple, elegant framework for building mean applications

/*
 * Copyright (c) 2018 One Hill Technologies, LLC
 *
 * 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.
 */

const InternalServerError = require ('../internal-server-error');
const ForbiddenError = require ('../forbidden-error');

const {
  isObjectLike,
} = require ('lodash');

/**
 * Factory method for creating a policy middleware for a request.
 *
 * @param policy          A Policy object
 * @returns {Function}
 */
module.exports = function (policy) {
  return function __blueprint_check_policy (req, res, next) {
    let result = policy.runCheck (req, res);

    return Promise.resolve (result).then (result => {
      if (result === true)
        return next ();

      if (result === false) {
        // The policy result was a boolean value. This means that we are to use
        // the default failure code and message as the policy error.
        const {failureCode, failureMessage} = policy;
        return next (new ForbiddenError (failureCode, failureMessage));
      }
      else if (isObjectLike (result)) {
        // The result is an object. This means we are to use the result
        // as-is for the policy error.
        const {failureCode, failureMessage} = result;
        return next (new ForbiddenError (failureCode, failureMessage));
      }
      else {
        console.error (`Policy ${policy.name} returned a bad result.`);
        return next (new InternalServerError ('bad_result', 'The policy returned a bad result.'));
      }
    }).catch (next);
  };
};