Random MySQL Mixin for Loopback

random.ts

/// <reference path='../../typings/tsd.d.ts' />
/// <reference path='../../local_modules/tsd.d.ts' />

import path = require('path');
import async = require('async');
import _ = require('lodash');

import IRemoteMethodCallbackFunction = loopback.IRemoteMethodCallbackFunction;
import IMySQLTableDefinition = loopback.IMySQLTableDefinition;
import IPersistenceModelItem = loopback.IPersistenceModelItem;

function Mixin(Model:loopback.IPersistenceModel):void {

  Model['random'] = function (callback:IRemoteMethodCallbackFunction):void {

    async.waterfall([

        function (stepCallback:Function):void {

          switch (Model.dataSource.connector.name) {

            case 'mysql':
              var tableDefinition:IMySQLTableDefinition = <IMySQLTableDefinition>Model.definition.settings['mysql'];
              var query:string = 'SELECT T.id FROM `' + tableDefinition.table + '` T ORDER BY RAND() LIMIT 1';
              Model.dataSource.connector.query(query, function (err:Error, result:Array<any>):void {
                if (err) {
                  return stepCallback(err);
                }
                if (result.length > 0) {
                  result = result.pop();
                }

                var value:string|number = _.get(result, 'id');
                stepCallback(null, value);
              })
              break

            default:
              return callback({'Only MySQL connectors are supported at the moment.'})
              break;
          }
        }
        ,
        function (id:string|number, stepCallback:Function):void {

          Model.findById(id, function (err:Error, result:IPersistenceModelItem):void {
            stepCallback(err, result);
          })
        }
      ],
      function (err:Error, result:IPersistenceModelItem):void {
        callback(err, result);
      }
    )
  }

  Model.remoteMethod(
    'random',
    {
      accepts: [],
      returns: {arg: 'document', type: 'object', root: true},
      http: {path: '/random', verb: 'get'}
    }
  )
}

export = Mixin;