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# EasyLib

[![Build Status](https://travis-ci.org/2020-unitn-SE2/EasyLib.svg?branch=master)](https://travis-ci.org/2020-unitn-SE2/EasyLib)

Application deployed on Heroku:
https://easy-lib.herokuapp.com/

To start locally, use the npm script start_local, which loads environment variables from the `.env` file. Ideally, passwords in the `.env` file should not be reveled publicly, therefore the file should not be put in the repository. However, people should be able to easily re-create it starting from the `.env.example` file.

```shell
> npm run start_local
```

## Authentication

https://medium.com/@technospace/understanding-json-web-tokens-jwt-a9064621f2ca

![Simple procedure on JWT token generation and validation at the same server](https://miro.medium.com/max/700/1*7T41R0dSLEzssIXPHpvimQ.png)

Use this to manually encode and decode a token:
- https://jwt.io/

Implementation in EasyLib:

```javascript
app.post('/api/v1/authentications', async function(req, res) {
	
	// find the user
	let user = await Student.findOne({ email: req.body.email }).exec();
	
	// user not found
	if (!user)
        res.json({ success: false, message: 'Authentication failed. User not found.' });
	
	// check if password matches
	if (user.password != req.body.password)
		res.json({ success: false, message: 'Authentication failed. Wrong password.' });
	
	// if user is found and password is right create a token
	var token = jwt.sign({ email: user.email }, process.env.SUPER_SECRET, { expiresIn: 86400 });

res.json({
		success: true,
		message: 'Enjoy your token!',
		token: token
	});

});
}
```

File tokenChecker.js:
```javascript
const tokenChecker = function(req, res, next) {
	
	// check header or url parameters or post parameters for token
	var token = req.body.token || req.query.token || req.headers['x-access-token'];

// if there is no token
	if (!token) {
		return res.status(401).send({ 
			success: false,
			message: 'No token provided.'
		});
	}

// decode token, verifies secret and checks exp
	jwt.verify(token, process.env.SUPER_SECRET, function(err, decoded) {			
		if (err) {
			return res.status(403).send({
				success: false,
				message: 'Failed to authenticate token.'
			});		
		} else {
			// if everything is good, save to request for use in other routes
			req.loggedUser = decoded;
			next();
		}
	});
	
};

module.exports = tokenChecker
```

To protect endpoints, we can put the tockenChecker.js middelware before all route handlers that we want to protect:
```javascript
app.use('/api/v1/authentications', authentication);
...
// requests handled until here are not authenticated
app.use('', tokenChecker);
// request with no valid token stop here
// requests that goes through the tokenChecker have the field `req.loggedUser` set to the decoded token
```
Or we can protect specific endpoints, by associating the tockenChecker with specific url:
```javascript
app.use('/api/v1/booklendings', tokenChecker);
...
// only requests matching '/api/v1/booklendings' have been authenticated by the tokenChecker
app.use('/api/v1/booklendings', booklendings);
// Requests on '/api/v1/students' are not authenticated
app.use('/api/v1/students', books);
```

https://livecodestream.dev/post/2020-08-11-a-practical-guide-to-jwt-authentication-with-nodejs/

## MongoDb

https://mongoosejs.com/docs/

# Environment Variables

Environment variables are used to:
- Remove password and private configurations from the code;
- Manage different configurations for different execution environments.

## Local Environment Variables

https://medium.com/the-node-js-collection/making-your-node-js-work-everywhere-with-environment-variables-2da8cdf6e786

Locally, environment variables can be set at system level or passed in the command line:

```shell
> PORT=8626 node server.js
```

Alternatively, environment variables can be managed in a `.env` file, which ideally should not be put under version control. However, it is useful to provide a `.env.example` file with the list of all variables.

The .env file can be pre-loaded using the `dotenv` module.

```shell
> npm install dotenv
> node -r dotenv/config server.js
```

A script can be defined in the package.json:

```javascript
scripts: {
    "test": "jest",
    "start": "node index.js",
    "start_local": "node -r dotenv/config server.js"
}
```

It can be run by:

```shell
> npm run start_local
```

### Loading .env when using Jest

https://stackoverflow.com/questions/48033841/test-process-env-with-jest

When using Jest locally, a setup file can be used to load variablem from `.env` file with `dotenv`.

Jest configuration file `setEnvVars.js`:
```javascript
require("dotenv").config()
```

The `setupFiles` option can be specified in `jest.config.js` or directly in the `package.json`.

https://jestjs.io/docs/en/configuration#setupfiles-array

## Cloud services Environment Variables

On Heroku, TravisCI, or other cloud services, it is possible to manually set env variables.

- Heroku https://devcenter.heroku.com/articles/config-vars
- TravisCI https://docs.travis-ci.com/user/environment-variables/

When HerokuCLI is used to run the app locally, it automatically load env variables from .env file.

https://devcenter.heroku.com/articles/heroku-local#copy-heroku-config-vars-to-your-local-env-file

```shell
> heroku local web
```

EasyLib

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