<?php
/**
 * REST route for the load more pagination.
 *
 * @package MM_Post_Grid
 */

namespace MM_Post_Grid;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Serves the next page of cards for a load more grid.
 *
 * The route is public because it returns nothing that is not already on the
 * page: published posts of publicly viewable post types, rendered with the same
 * renderer as the shortcode. Every value in the payload is re-validated by
 * `Args::from_request()` before it reaches a query, so the client cannot widen
 * the query to private content.
 *
 * @since 0.1
 */
final class REST_Controller {

	/**
	 * Route namespace.
	 *
	 * @since 0.1
	 * @var string
	 */
	const REST_NAMESPACE = 'mm-post-grid/v1';

	/**
	 * Maximum accepted payload size in bytes.
	 *
	 * @since 0.1
	 * @var int
	 */
	const MAX_PAYLOAD = 4000;

	/**
	 * Hooks the route registration.
	 *
	 * @since 0.1
	 * @return void
	 */
	public function register() {
		add_action( 'rest_api_init', array( $this, 'register_routes' ) );
	}

	/**
	 * Registers the grid route.
	 *
	 * @since 0.1
	 * @return void
	 */
	public function register_routes() {
		register_rest_route(
			self::REST_NAMESPACE,
			'/grid',
			array(
				'methods'             => \WP_REST_Server::READABLE,
				'callback'            => array( $this, 'get_grid' ),
				'permission_callback' => array( $this, 'permissions_check' ),
				'args'                => array(
					'page' => array(
						'description'       => __( 'Page of posts to return.', 'mm-post-grid' ),
						'type'              => 'integer',
						'default'           => 2,
						'minimum'           => 1,
						'maximum'           => 500,
						'sanitize_callback' => 'absint',
					),
					'grid' => array(
						'description'       => __( 'JSON encoded grid arguments.', 'mm-post-grid' ),
						'type'              => 'string',
						'required'          => true,
						'validate_callback' => array( $this, 'validate_payload' ),
					),
				),
			)
		);
	}

	/**
	 * Read only route for public, published content.
	 *
	 * @since 0.1
	 * @return bool
	 */
	public function permissions_check() {
		return true;
	}

	/**
	 * Rejects payloads that are too large to be a grid.
	 *
	 * @since 0.1
	 *
	 * @param mixed $value Raw parameter value.
	 * @return bool
	 */
	public function validate_payload( $value ) {
		return is_string( $value ) && '' !== $value && strlen( $value ) <= self::MAX_PAYLOAD;
	}

	/**
	 * Returns the cards of the requested page.
	 *
	 * @since 0.1
	 *
	 * @param \WP_REST_Request $request Request object.
	 * @return \WP_REST_Response|\WP_Error
	 */
	public function get_grid( \WP_REST_Request $request ) {
		$payload = json_decode( (string) $request->get_param( 'grid' ), true, 8 );

		if ( ! is_array( $payload ) ) {
			return new \WP_Error(
				'mmpg_invalid_payload',
				__( 'The grid arguments could not be read.', 'mm-post-grid' ),
				array( 'status' => 400 )
			);
		}

		$args = Args::from_request( $payload );
		$page = max( 1, (int) $request->get_param( 'page' ) );

		$query     = Query_Builder::query( $args, $page );
		$max_pages = Query_Builder::max_pages( $query, $args );

		if ( $page > $max_pages ) {
			return new \WP_REST_Response(
				array(
					'html'      => '',
					'page'      => $page,
					'max_pages' => $max_pages,
					'has_more'  => false,
					'count'     => 0,
				),
				200
			);
		}

		return new \WP_REST_Response(
			array(
				'html'      => wp_kses( Renderer::cards( $query, $args ), Renderer::allowed_html() ),
				'page'      => $page,
				'max_pages' => $max_pages,
				'has_more'  => $page < $max_pages,
				'count'     => (int) $query->post_count,
			),
			200
		);
	}
}