/**
 * 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';

  /**
   * Get the application principal
   * @callback {Function} callback
   * @param {Error} err
   * @param {Application} application
   */
  RoleMapping.prototype.application = function (callback) {
    if (this.principalType === RoleMapping.APPLICATION) {
      var applicationModel = this.constructor.Application
        || loopback.getModelByType(loopback.Application);
      applicationModel.findById(this.principalId, callback);
    } else {
      process.nextTick(function () {
        callback && callback(null, null);
      });
    }
  };

  /**
   * Get the user principal
   * @callback {Function} callback
   * @param {Error} err
   * @param {User} user
   */
  RoleMapping.prototype.user = function (callback) {
    if (this.principalType === RoleMapping.USER) {
      var userModel = this.constructor.User
        || loopback.getModelByType(loopback.User);
      userModel.findById(this.principalId, callback);
    } else {
      process.nextTick(function () {
        callback && callback(null, null);
      });
    }
  };

  /**
   * Get the child role principal
   * @callback {Function} callback
   * @param {Error} err
   * @param {User} childUser
   */
  RoleMapping.prototype.childRole = function (callback) {
    if (this.principalType === RoleMapping.ROLE) {
      var roleModel = this.constructor.Role || loopback.getModelByType(Role);
      roleModel.findById(this.principalId, callback);
    } else {
      process.nextTick(function () {
        callback && callback(null, null);
      });
    }
  };
};