Creating an API can be a tedious task, and if you need to filter your data in specific ways, things are bound to get nasty. Epi comes with a controller that handles your basic CRUD tasks for an Eloquent model, but the index / "read all" method it where Epi really shines.

Imagine that you have a Page model that has got a relationship with a PageTranslation model. Perhaps you would want to retrieve a page by it's slug that lives in the PageTranslation model. With Epi, it would be a simple as requesting the following URL: api/pages?filter[translation.slug]=some-slug.

To add Epi to your Laravel application, follow these steps:

Add the following to your composer.json file:

"vespakoen/epi" : "dev-master"

Then, run composer update or composer install if you have not already installed packages.

Add the line below to the providers array (at the end) in the app/config/app.php configuration file:

'Vespakoen\Epi\EpiServiceProvider',

Optionally, if you don't want to add "use" statements to your controller, add the line below to the aliases array (at the end) in the app/config/app.php configuration file:

'EpiController' => 'Vespakoen\Epi\Controllers\EpiController',

You will want to run the following command to publish the config to your application, otherwise it will be overwritten when the package is updated.

php artisan config:publish vespakoen/epi

To build an Api using Epi we will need to create a controller that extends from the EpiController and is then registered with the router. First we need to create a controller, preferrably, this controller is seperated from the rest of your controllers by putting the controllers for the Api in a new folder. This folder could be app/controllers/api (make sure you add this path to the autoloader in app/start/global.php !) or /src/Somevendor/SomePackage/Controllers/Api depending on your situation.

Here is an example:

<?php

class ApiUsersController extends Controller {

	/**
	 * Create a new ApiUsersController instance.
	 *
	 * @param  Illuminate\Database\Eloquent\Model  $model
	 * @return void
	 */
	public function __construct(User $model)
	{
		// Epi will look for $this->model, so make sure it is set like this.
		$this->model = $model;
	}

	/**
	 * $eagerLoad Relations to eagerload by default
	 *
	 * @var array
	 */
	public $eagerLoad = array();

	/**
	 * $indexRules Validation rules used when getting a list of resources
	 *
	 * @var array
	 */
	public $indexRules = array();

	/**
	 * $storeRules Validation rules used when storing a resource
	 *
	 * @var array
	 */
	public $storeRules = array(
		'email' => 'required|email'
	);

	/**
	 * $updateRules Validation rules used when updating a resource
	 *
	 * @var array
	 */
	public $updateRules = array(
		'email' => 'required|email'
	);

}

Now we need to register this controller with the router, which is as easy as adding the following lines to your app/routes.php file.

Route::resource('api/users', 'ApiUsersController');

Done!

Under the hood Epi works it's magic to make all the good stuff happen, I can imagine you got curious how it works, to understand this, let's first take a look at the objects that live in the Epi codebase.

A manipulator is an object that modifies the query that will be made. Manipulators will also add and use aliases to avoid any conficts with self-referencing relationships. Epi comes with the following manipulators built-in.

Calls ->where() on the query and aliases tables

Calls ->join() on the query and aliases tables

Calls ->take() and optionally ->skip() on the query and aliases tables

Calls ->orderBy() on the query and aliases tables

Extractors get all the input, and have to make sure to extract the correct manipulators from them. Epi comes with the following extractors built-in.

...

...

...

...

Epi has it's own Relation object for every Laravel relation, these objects have a ->getJoins() method that will returns Join manipulators that are needed for filtering or sorting on a related table.

More soon...