AMP_Cart_Controller

class AMP_Cart_Controller extends Proxy_Controller {
	/**
	 * Init endpoint.
	 *
	 * @return void
	 */
	public function register_routes() {
		$public_args = [
			'methods'             => WP_REST_Server::READABLE,
			'callback'            => [ $this, 'get_items' ],
			'permission_callback' => '__return_true',
		];

		register_rest_route( $this->proxy_base, '/amp-cart/', $public_args );
	}

	/**
	 * Adds additional data to a single item.
	 *
	 * @param array $item Cart item.
	 * @return array Updated data.
	 */
	private function build_item( $item ) {
		$query = new WP_Query(
			[
				'post_type'      => Product::NAME,
				'posts_per_page' => 1,
				'meta_key'       => 'bigcommerce_id',
				'meta_value'     => $item['product_id'],
			]
		);

		if ( is_wp_error( $query ) || ! $query->have_posts() ) {
			return $item;
		}

		$post = reset( $query->posts );

		$product           = new Product( $post->ID );
		$item['permalink'] = amp_get_permalink( $post->ID );
		$thumbnail_id      = get_post_thumbnail_id( $post->ID );

		$thumbnail = get_the_post_thumbnail( $post->ID, Image_Sizes::BC_SMALL );
		if ( $thumbnail_id ) {
			$image                    = wp_get_attachment_image_src( $thumbnail_id, Image_Sizes::BC_SMALL );
			$item['thumbnail_src']    = str_replace( home_url(), '', $image[0] );
			$item['thumbnail_height'] = $image[2];
			$item['thumbnail_width']  = $image[1];
			$item['thumbnail_srcset'] = wp_get_attachment_image_srcset( $thumbnail_id, Image_Sizes::BC_SMALL );
		}

		$brand = $product->brand();

		if ( $brand ) {
			$item['brand'] = $brand;
		}

		$item['price'] = apply_filters(
			'bigcommerce/currency/format',
			sprintf( '¤%0.2f', $item['sale_price'] ),
			$item['sale_price']
		);

		return $item;
	}

	/**
	 * Adds additional data to items.
	 *
	 * @param array $data Array of items.
	 * @return array Modified array.
	 */
	private function build_items( $data ) {
		// Extract items from physical_items, digital_items, etc.
		$items = array_reduce(
			array_keys( $data['line_items'] ),
			function( $list, $key ) use ( $data ) {
				return $list + (array) $data['line_items'][ $key ];
			},
			[]
		);

		$items = array_map( [ $this, 'build_item' ], $items );

		return $items;
	}

	/**
	 * Returns cart data.
	 *
	 * @param \WP_REST_Request $request Request instance.
	 *
	 * @return \WP_REST_Response|\WP_Error
	 */
	public function get_items( $request ) {
		$cart_id = $request->get_param( 'cart_id' );

		if ( empty( $cart_id ) ) {
			return rest_ensure_response( null );
		}

		$request = new WP_REST_Request(
			'GET',
			sprintf( '/%scarts/%s', trailingslashit( $this->proxy_base ), $cart_id )
		);

		$response = rest_do_request( $request );

		if ( 200 !== $response->status || is_wp_error( $response ) || ! isset( $response->data['data'] ) ) {
			return rest_ensure_response( null );
		}

		$data                = $response->data['data'];
		$data['items']       = $this->build_items( $data );
		$data['items_count'] = count( $data['items'] );
		$data['total']       = apply_filters(
			'bigcommerce/currency/format',
			sprintf( '¤%0.2f', $data['cart_amount'] ),
			$data['cart_amount']
		);

		return rest_ensure_response( $data );
	}
}