middleware-chainer

middleware-chainer-1.0.0

Simplifies Node.js express middlewares modularization.

Best for those currently stuck with swagger-node or alike; those that have limited means of middleware "chaining".

Basically behaves similarly to express middlewares (including error handling).

Make your code much more readable!
        ... and small enough to ease unit-testing!

Contents:

1. How-To?
   1. Basic Usage
      1. Basic Arguments/Parameters
   2. Simple Usage
   3. Factory Usage
      1. Factory Arguments/Parameters
2. Principles/Inspiration
3. 100% Code Coverage
4. License

Basic Usage : require('middleware-chainer')

Here we have a simple authentication API endpoints:

# ---------------------------------------------
# $BASEDIR/api/swagger/swagger.yaml
# ---------------------------------------------
paths:
  /auth:
    x-swagger-router-controller: auth
    post:
      operationId: login
      description: User Authentication/Authorization (Generate Token)
      # ...
    delete:
      operationId: logout
      description: Invalidate User Token/s
      # ...

Here's the controller:

/**
 * $BASEDIR/api/controllers/auth.js
 */
const chain = require('middleware-chainer');

const loginHitCounter = require('./auth/login-hit-counter');
const loginErrorHandler = require('./auth/login-error-handler');

const login = require('./auth/login');
const logout = require('./auth/logout');

module.exports = {
  login: chain({ middlewares: [loginHitCounter, login, loginErrorHandler] }),
  logout: logout
};

In the example above, login has a "special 'pre' step (middleware)" prior to actual login, plus a special error handler.

Here's the would-be structure of the sample modularized swagger-generated project above:

/swagger-project
|-- /controllers
|   |-- /auth
|   |   |-- login.js
|   |   |-- login.spec.js
|   |   |-- login-error-handler.js
|   |   |-- login-error-handler.spec.js
|   |   |-- login-hit-counter.js
|   |   |-- login-hit-counter.spec.js
|   |   |-- logout.js
|   |   |-- logout.spec.js
|   |-- auth.js
|   |-- auth.spec.js
|-- /swagger
|   |-- swagger.yaml

Note: *.spec.js being unit tests.

The chain Arguments

chain, pertaining to the variable where require('middleware-chainer') was assigned in the example above.

The chain function takes a single object literal {} as argument. Keys are as follows:

Key	Type/Format	Description	Default	Example
name	string	middleware name; shows in "debug"	'mw-chain'	'lol'
loggers	object literal (ie: {})	see next two entries (loggers.*)	-	-
loggers.debug	function	receives "message" string as argument	() => undefined	console.log
loggers.error	function	receives "message" string as argument	console.error	console.log
middlewares	array of functions	array of middlewares (req, res[, next]) or (err, req, res, next)	-	-

Sample "full" configuration:

const debug = require('debug'); // https://www.npmjs.com/package/debug
const chain = require('middleware-chainer');

const chainedMiddleware = chain({
  name: 'lol',
  loggers: {
    debug: debug,
    error: debug
  },
  middlewares: [...]
});

Sample output from one of the unit tests with configured loggers.debug w/ console.log:

Hint: Given the loggers.error has a default (console.error); you may opt to "mute" it by setting the value to: () => undefined.

Simple Usage : require('middleware-chainer/simple')

/**
 * $BASEDIR/api/controllers/auth.js
 */
const chain = require('middleware-chainer/simple');

const loginHitCounter = require('./auth/login-hit-counter');
const loginErrorHandler = require('./auth/login-error-handler');

const login = require('./auth/login');
const logout = require('./auth/logout');

module.exports = {
  login: chain(loginHitCounter, login, loginErrorHandler),
  logout: logout
};

No fuss. Simple... Just middlewares.

Factory Usage : require('middleware-chainer/factory')

/**
 * $BASEDIR/api/controllers/auth.js
 */
const ChainFactory = require('middleware-chainer/factory');

const loginHitCounter = require('./auth/login-hit-counter');
const loginErrorHandler = require('./auth/login-error-handler');

const loginChain = new ChainFactory({ // or `ChainFactory({})`
  name: 'login-chain',
  loggers: { debug: console.log },
  before: [loginHitCounter],
  after: [loginErrorHandler]
});

const login = require('./auth/login');
const refresh = require('./auth/refresh-token');
const logout = require('./auth/logout');

module.exports = {
  login: loginChain(login), // chain(loginHitCounter, login, loginErrorHandler)
  refresh: loginChain(refresh), // chain(loginHitCounter, refresh, loginErrorHandler)
  logout: logout
};

Constructor arguments are very much the same as the "basic", apart from one omission and two additions:

Key	Type/Format	Description	Default	Example
middlewares	array of functions	array of middlewares (req, res[, next]) or (err, req, res, next)	-	-
before	array of functions	middlewares to be put at the beggining of the "chain"	-	-
after	array of functions	middlewares to be put at the end of the "chain"	-	-

Principles/Inspiration

As described in this Wikipedia page, UNIT TESTING is described: "Intuitively, one can view a unit as the smallest testable part of an application". Therefore, being able to break-apart your application into smallest possible (sensible) modules is BEST!

If you employ/enforce the ideals of "single responsibility" per-class/file/module; middleware-chainer is an easy go-to.

100% Code Coverage

See for yourself!

1. Clone:

   git clone https://github.com/jpbaking/middleware-chainer.git

2. ...of course go into folder:

   cd middleware-chainer

3. Download/install dependencies:

   npm install

4. Test!!!

   npm test

5. Expected output:
   

License

MIT License

Copyright (c) 2018 Joseph Baking

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.