CraftCMS API Wrapper class

Api.php

<?php

namespace Craft;

use Closure;
use function array_merge;

/**
 * API endpoints wrapper
 *
 * @package config\api
 */
class Api {

    /**
     * current API version. will be false if there's no version.
     *
     * @var int|bool
     */
    protected $version;

    /**
     * API URI prefix
     *
     * @var string
     */
    protected $baseURI;

    /**
     * API endpoints
     *
     * @var array
     */
    protected $endpoints = [];

    /**
     * holds the endpoint defaults
     *
     * @var array
     */
    protected $defaults = [];

    /**
     * Api constructor
     *
     * @param string   $baseURI API base URI prefix
     * @param int|null $version Current API version. Omit to skip versioning.
     */
    public function __construct( string $baseURI = 'api', int $version = null ) {
        $this->baseURI = $baseURI;

        $this->version = $version ?? false;
    }

    /**
     * adds an endpoint to the API
     *
     * @param string  $uri     relative endpoint URI to add
     * @param Closure $handler handler this endpoint will call
     *
     * @return void
     */
    public function addEndpoint( string $uri, Closure $handler ) {
        $this->endpoints[ $this->buildEndpointURI( $uri ) ] = $handler;
    }

    /**
     * builds an endpoint URI
     *
     * @param string $uri relative URI to prepend the base URI prefix and version, if set
     *
     * @return string
     */
    protected function buildEndpointURI( string $uri ): string {
        $uri = ltrim($uri, '/');

        if ( $this->version ) {
            return "{$this->baseURI}/v{$this->version}/$uri";
        }

        return "{$this->baseURI}/$uri";
    }

    /**
     * Adds a collection. This will call a callback with a new Api instance as its call context
     * and merged with the existing endpoints later on.
     * Collections can be nested, too.
     *
     * @param string   $uri               URI for all members of the group
     * @param \Closure $endpointsCallback callback which makes changes to the collection
     *
     * @return void
     */
    public function addCollection( string $uri, Closure $endpointsCallback ) {

        // create a new Api instance with the given URI as its base URI
        $collection = new self( $this->buildEndpointURI( $uri ) );

        // call the endpoints callback with the collection passed as context.
        // this means all methods need to be called on "$this" or use the arguments
        $endpointsCallback->call( $collection, $collection, $this );

        // merge the resulting endpoints
        $this->endpoints = array_merge( $this->getEndpoints(), $collection->getEndpoints() );
    }

    /**
     * retrieves the API endpoints
     *
     * @return array
     */
    public function getEndpoints(): array {
        return $this->endpoints;
    }

    /**
     * removes an endpoint
     *
     * @param string $uri relative endpoint URI to remove. Will be run through buildEndpointURI
     *
     * @return void
     */
    public function removeEndpoint( string $uri ) {
        unset( $this->endpoints[ $this->buildEndpointURI( $uri ) ] );
    }

    /**
     * retrieves the Api version
     *
     * @return int
     */
    public function getVersion(): int {
        return $this->version;
    }

    /**
     * retrieves the API URI prefix
     *
     * @return string
     */
    public function getBaseURI(): string {
        return $this->baseURI;
    }

    /**
     * converts the API definitions into an array consumable by the elementAPI plugin
     *
     * @return array
     */
    public function toArray() {
        return [
            'defaults'  => $this->getDefaults(),
            'endpoints' => $this->getEndpoints()
        ];
    }

    /**
     * retrieves the default endpoint settings
     *
     * @return array
     */
    public function getDefaults(): array {
        return $this->defaults;
    }

    /**
     * sets the default endpoint settings
     *
     * @param array $defaults default settings to apply for this configuration. Will be ignored if set
     *                        on a collection.
     */
    public function setDefaults( array $defaults ) {
        $this->defaults = $defaults;
    }
}

endpoints.php

<?php
namespace Craft;

$myApi = new Api('api', 1);

// endpoint for /api/v1/news
$myApi->addEndpoint( 'news.json', function() {
  return [
    'elementType' => Entry::class,
    'criteria' =>    ['section' => 'news'],
    'transformer' => function(Entry $entry) {
      return [
        'title' =>   $entry->title,
        'url' =>     $entry->url,
        'jsonUrl' => UrlHelper::url("news/{$entry->id}.json"),
        'summary' => $entry->summary,
      ];
    },
  ];
} );

// collection for /api/v1/receipts/
$myApi->addCollection( 'receipts', function( Api $collection, Api $api ) {
  
  // endpoint for /api/v1/receipts/:id.json
  $this->addEndpoint( '<entryId:\d+>.json', function() { /* ... */ } );
  
  // collection for /api/v1/receipts/ingredients/
  $this->addCollection( 'ingredients', function() {
    
    // endpoint for /api/v1/receipts/ingredients/:id.json
    $this->addEndpoint( '<entryId:\d+.json', function() { /* ... */ } );
  } );
} );