// Copyright IBM Corp. 2014,2016. All Rights Reserved.
  // Node module: loopback
  // This file is licensed under the MIT License.
  // License text available at https://opensource.org/licenses/MIT
  
  var loopback = require('../../lib/loopback');
  
  /**
   * The `RoleMapping` model extends from the built in `loopback.Model` type.
   *
   * @property {String} id Generated ID.
   * @property {String} name Name of the role.
   * @property {String} Description Text description.
   *
   * @class RoleMapping
   * @inherits {PersistedModel}
   */
  
  module.exports = function(RoleMapping) {
    // Principal types
    RoleMapping.USER = 'USER';
    RoleMapping.APP = RoleMapping.APPLICATION = 'APP';
    RoleMapping.ROLE = 'ROLE';
  
    RoleMapping.resolveRelatedModels = function() {
      if (!this.userModel) {
        var reg = this.registry;
        this.roleModel = reg.getModelByType(loopback.Role);
        this.userModel = reg.getModelByType(loopback.User);
        this.applicationModel = reg.getModelByType(loopback.Application);
      }
    };
  
    /**
     * Get the application principal
     * @callback {Function} callback
     * @param {Error} err
     * @param {Application} application
     */
    RoleMapping.prototype.application = function(callback) {
      this.constructor.resolveRelatedModels();
  
      if (this.principalType === RoleMapping.APPLICATION) {
        var applicationModel = this.constructor.applicationModel;
        applicationModel.findById(this.principalId, callback);
      } else {
        process.nextTick(function() {
          if (callback) callback(null, null);
        });
      }
    };
  
    /**
     * Get the user principal
     * @callback {Function} callback
     * @param {Error} err
     * @param {User} user
     */
    RoleMapping.prototype.user = function(callback) {
      this.constructor.resolveRelatedModels();
      if (this.principalType === RoleMapping.USER) {
        var userModel = this.constructor.userModel;
        userModel.findById(this.principalId, callback);
      } else {
        process.nextTick(function() {
          if (callback) callback(null, null);
        });
      }
    };
  
    /**
     * Get the child role principal
     * @callback {Function} callback
     * @param {Error} err
     * @param {User} childUser
     */
    RoleMapping.prototype.childRole = function(callback) {
      this.constructor.resolveRelatedModels();
  
      if (this.principalType === RoleMapping.ROLE) {
        var roleModel = this.constructor.roleModel;
        roleModel.findById(this.principalId, callback);
      } else {
        process.nextTick(function() {
          if (callback) callback(null, null);
        });
      }
    };
  };