Mediator pattern - Part 1

CreateUserCommand.js

import handler from './handler'

type ICommand = {
    username: string;
    password: string;
    email: string;
}

@handler('./createUserCommandHandler')
export default class CreateUserCommand {
  constructor(o : ICommand) {
    Object.assign(this, o);
  }
  
  username: string;
  password: string;
  email: string;
}

createUserCommandHandler.js

import Command from './CreateUserCommand';

export default async handler(command : Command) {
  await somewhatCreateAUser(command.username, command.password, command.email);
}

handler.js

import { resolve, dirname } from 'path';
import parentModule from 'parent-module';

export default function (handlerPath: string) {
  return function (command) {
    handlerPath = resolve(dirname(parentModule()), handlerPath);
    
    // eslint-disable-next-line import/no-dynamic-require
    const handler = require(handlerPath).default;
    command.handler = handler;
  };
};

mediator.js

import winston from 'winston';

export async function exec(command) {
    const commandHandler = command.constructor.handler;
  
    try {
        return await commandHandler(command, context);
    } catch (err) {
        throw err;
    }
}