Ironhead

NodeJS Framework over express based on functional and declarative programming.

Motivation

In typical fast pace dev environment, code review is a challenge and simply causes more and more tech debt. Functional Programming enables developers to refactor a simple program or function. Taking control over execution reduces repetitive work to be done by programmer and eventually help in reducing number of lines of code to be written.

Key features

1. Code decoupling.
2. Functional programming.
3. Clear boundries between presentation and business logic.
4. Declarative program.
5. Refactoring smaller functions are much more easy.

MVC

MVC pattern has severed us exceptionally well over the period and still does. But it's no more fit for our next generation UI framework.

Contents

1. Routes
2. Middleware
3. Views
4. Userhooks
5. Configuration
6. Custom Path Configuration for components

Router

Route is plain javascript object. It defines how a particular http request will be handled by the web application.

And here's sample route!

// routes/foo.js
const requestSchema = require('../schema/request/foo');
const responseSchema = require('../schema/response/foo');
const gateway = require('../gateway/foo.js');
const { fn1, fn2 } = require('../dekorators');
const prehandler = require('../prehandler/foo');

module.exports = {
    domain: 'index',
    method: 'GET',
    url: '/',
    template: 'index',
    responseType: 'html',
    allowRedirect: false,
    isReqValidation: true,
    schema: {
        ...requestSchema,
        ...responseSchema
    },
    prehandlers: [
       prehandler
    ],
    gateway,
    dekorators: [  
    	fn1,
        fn2
    ]
};

// sample url - https://www.example.com/?cid=foo&pos=0
// request schema
// schema/request/foo.js
module.exports = {
    query: {
        type: 'object',
        properties: {
            cid: { type: 'string' },
            pos: { type: 'integer' },
        },
        required: ['cid']
    },
    cookies: {
        type: 'object',
        properties: {
            sid: { type: 'string' }
        },
        required: ['sid']
    },
    config: {
        type: 'object',
        properties: {
            showWelComeMessage: { type: 'boolean' }
        }
    }
}

// response schema
// schema/response/foo.js
module.exports = {
	response: {
        ok: { // A successful response
            type: 'array',
            items: {
                type: 'object',
                properties: {
                    id: { type: 'integer' },
                    fkc: { type: 'integer' }
                }
            }
        },
        notOk: { // Unsuccessful response
        	badReq: { // Bad request 
            	success: false,
                error: {
                	statusCode: 1001,
                    message: ''
                },
                data: {}
            },
            badRes: { // Api failed or some other exception
            	success: false,
                error: {
                	statusCode: 400, // 4xx, 5xx
                    message: ''
                },
                data: {}
            }
        }
    }
};

Route Schema

• domain -: You may want to group your application into different pages or modules. You can define these logical grouping in the route.

• method -: An HTTP verb i.e. GET or POST

• url -: External url to be handled by the application

• responseType -: Http Response format

  ResponseType Options: html|json
  Default Value: json

  Note -: If it is set to json, template will be ignored and json response will be sent to client

• allowRedirect -: Allow http redirect 301|302. If the flag is set true framework attach redirect middleware which expect a redirect node in the decorators output.

  {
      ... // other props
      redirect: {
          code: 302, // Default value 302, other option 301
          path: '/' // if path is not provided it will redirect to referrer
      }
  }
  

• isReqValidation -: It enables request validation. If validation fails it will respond with schema.response.notOk.badReq defined in response schema.

• template -: A template file path. The template will be used to prepare html response when responseType is set to html

• schema -: A request and response validator. Also it filters the data and send only those defined in the shcema. Please refer AJV documentations for further details. Refer above route definition for more details.

• prehandlers -: A pre handler is a plain JavaScript function. It has access to request parameters such as query params, path params, cookies, request body, headers etc. Developer can use these parameters and modify them for future use during request lifecycle. A prehandler gets access to properties defined in the request schema.

• gateway -: A gateway is bridge between your application and external systems i.e. rest apis, databases etc. gateway attaches final response into response. Your application response module can access it calling `res.props('data');

// express middleware
// sendToClinet.js

const sendToClinet = (req, res) => {
    const data = res.props('data');
    // application logic ...
    // application logic ...
    if(sendJson) {
        return res.json(data);
    }
    return res.render('templateName', data);
}

• dekorators -: A dekorator is a pure javascript function that can bind to certain properties of bigger response, it can modify the data. A dekorator must return an object. Having dekorator in place offers you to define functions with single responsibility.

// Simple dekorator

// title.js

const title = (props) => {
    const { name, brand, done } = props; // dispatch is injected by connect.
    const newName = name.replace(brand.name, '');

    return done({
        name: newName   // name is propery in initial state
    });
  };

  module.exports = connect(['name', 'brand'], title);

Middleware

Middlewares are the functions which are executed in the middle of request response cycle.

Custom Middlewares definition is similar to middlewares

And here's how you define the custom middlewares and its execution chain!!

// Defining middleware chain


// Custom Middlewares definition
const {
	responseFactory,
    notFound,
    defaultErrorHandler
} = require('./app/middleware');

{
    order: [
        'cookieParser',
        ....
        ....
        .....
        'router',
        'responseFactory',
        'notFound',
        'defaultErrorHandler'
    ],
    {
        responseFactory,
        notFound,
        defaultErrorHandler
    }
}

// Default Error handler
const defaultErrorHandler = (err, req, res, next) => {
};

// Custom Middleware Definition
const customMiddleware = (req, res, next) => {};

Order

It is an array in which we can define the execution order of the middlewares. One can specify the custom middlewares and some are given to the application by the framework like:

1. Cookie Parser - cookieParser key to be used in order.
2. Router - router key to be used in order.

Cookie Parser

It is a middleware which is offered by the framework and it internally uses Cookie-Parser by express.

NOTE: For signing the cookies with a secret, one should use cookies configuration.

Router

It is also a middleware, which needs to be plugged in order list and the routes declared by the application will be executed at that particular point in the request response lifecycle .

Views - templaing engine

A templating engine/view engine enables the application to use static templates files to genarate HTML which is rendered at the client side.

And here's the example of configuring the Template/View Engine!!

 // config/views.js
 
 module.exports = {
 	engine: <engine>
 };

Templates path can be configured using rc configuration

Framework Supports express-compliant template engines. More about it can be explored at Express Template Engines

Userhooks

Hooks are an array of functions that are executed prior to application binding. Only after successfull execution of all the hooks, Application binds to the specified port.

And here's the sample hook!!

// Custom Hook definition
function customHook(app, cb) {
    try {
        app.setLocals('key', 'value');
    } catch (err) {
        console.log('\n---------------------------------------------------\n');
        console.error('Error.');
        console.log('\n---------------------------------------------------\n');
    }
    cb();
}

Custom Hook receives two arguments:

1. app - Application Instance
2. cb - Callback function

NOTE: cb function must be called otherwise your application won't start.

Configuration

Framework supports the default and environment configs.

Config - config/*

config/config.js It should contain the default configuration of the application.

And here's the sample to define the configuration, to set the secret value of the cookies for sigining and port!!

// secret will be used by cookie parser for signing the cookies
module.exports = {
    cookie: {
        secret: '123123123'
    },
    port: 1447
};

Environment Config - /config/env/*

NODE_ENV defines the environment of the application and depending on that environment config is loaded.

If no environment is set, it will try to load the development.js

NOTE: Environment configs overrides the default configuration.

Custom path configuration

One can specify the custom path for components.

{
    "cluster": true,
    "paths": {
        "config": '/config',
        "routes": '/app/routes',
        "middleware": '/app/middleware',
        "hooks": "/app/hooks",
        "views": "/public/templates"

    }
}

Concept and Fundamentals

Prehandlers, gateway, dekorators must follow functional programming fundamentals. Please refer below resources for more details

Learning Functional Programming with JavaScript - JSUnconf 2016 Master Functional Programming

License

MIT