spaghiajoeojo / express-beans

import { pinoHttp, startTime } from 'pino-http';

import { ServerResponse, IncomingMessage } from 'http';

import EventEmitter from 'events';

import { ExpressBeansOptions, ExpressRouterBean } from '@/ExpressBeansTypes';

import { logger } from '@/core';

import { Executor } from '@/core/Executor';

type ExpressBeanEventMap = {

  error: [Error];

  initialized: [];

}

export default class ExpressBeans extends EventEmitter<ExpressBeanEventMap> {

  private readonly app: Express;

  private readonly router: Router;

  /**

   * Constructor of ExpressBeans application

   * @constructor

   * @param options {ExpressBeansOptions}

   */

  constructor(options?: Partial<ExpressBeansOptions>) {

    super();

    this.router = express.Router();

    this.app = express();

    this.app.disable('x-powered-by');

    this.app.use(options?.baseURL ?? '/', this.router);

    if (options?.logRequests === undefined || options.logRequests) {

      this.router.use(pinoHttp(

        {

          logger,

          customSuccessMessage: this.serializeRequest.bind(this),

          customErrorMessage: this.serializeRequest.bind(this),

        },

      ));

    }

    Executor.setExecution('init', async () => this.initialize(options ?? {}));

    Executor.eventEmitter.on('error', () => {

      process.exit(1);

    });

    Executor.startLifecycle();

  }

  private serializeRequest(req: IncomingMessage, res: ServerResponse) {

    const request: Request = req as Request;

    const remoteAddress = request.headers['x-forwarded-for'] ?? request.socket.remoteAddress;

    const { method, originalUrl, httpVersion } = request;

    const responseTime = Date.now() - res[startTime];

    const optionals = [

      res.statusCode,

      res.getHeader('content-length'),

      res.getHeader('content-type'),

      request.headers.referer,

      request.headers['user-agent'],

    ]

      .filter((i) => !!i)

      .join(' ');

    return `${remoteAddress} - "${method} ${originalUrl} HTTP/${httpVersion}" ${optionals} - ${responseTime}ms`;

  }

  /**

   * Initializes the application and checks

   * if all beans are valid

   * @param listen {boolean}

   * @param port {number}

   * @param beans {Object[]}

   * @param onInitialized {Function}

   * @private

   */

  private async initialize({

    listen = true,

    port = 8080,

    routerBeans = [],

  }: Partial<ExpressBeansOptions>) {

    return Promise.resolve(routerBeans as Array<ExpressRouterBean>)

      .then(this.checkRouterBeans.bind(this))

      .then(this.registerRouters.bind(this))

      .then(() => {

        if (listen) {

          return new Promise<void>(

            (resolve, reject) => {

              this.listen(port, (err) => (err ? reject(err) : resolve()));

            },

          ).catch((err) => Promise.reject(err));

        }

        return Promise.resolve();

      });

  }

  /**

   * Starts the server and emits the initialized event

   * @param {number} port

   */

  listen(port: number, callback?: (error?: Error) => void) {

    return this.app.listen(port, (error) => {

      callback?.(error);

      if (error) {

        this.emit('error', error);

        return;

      }

      logger.info(`Server listening on port ${port}`);

      this.emit('initialized');

    });

  }

  /**

   * Registers all routers

   * @param routers {Array<ExpressRouterBean>}

   * @private

   */

  private async registerRouters(routers: Array<ExpressRouterBean>) {

    return new Promise((resolve, reject) => {

      Array.from(routers)

        .map((bean) => bean._instance)

        .forEach((instance) => {

          try {

            const {

              path,

              router,

            } = instance._routerConfig;

            logger.debug(`Registering router ${instance._className}`);

            this.router.use(path, router);

          } catch (e) {

            logger.error(e);

            reject(new Error(`Router ${instance._className} not initialized correctly`, { cause: e }));

          }

        });

      resolve(true);

    });

  }

  /**

   * Checks if all beans are valid

   * @param routerBeans {Array<ExpressRouterBean>}

   * @returns {Array<ExpressRouterBean>}

   * @throws {Error}

   * @private

   */

  private async checkRouterBeans(routerBeans: Array<ExpressRouterBean>):

  Promise<ExpressRouterBean[]> {

    const invalidBeans = routerBeans

      .filter(((bean) => !bean._beanUUID))

      .map((object: any) => object.prototype.constructor.name);

    if (invalidBeans.length > 0) {

      return Promise.reject(new Error(`Trying to use something that is not an ExpressBean: ${invalidBeans.join(', ')}`));

    }

    return routerBeans;

  }

  /**

   * Gets Express application

   * @returns {Express}

   */

  getApp() {

    return this.app;

  }

  /**

   * Exposes use function of Express application

   * @param handlers

   */

  use(...handlers: any) {

    this.app.use(...handlers);

  }

}