<?php

namespace RoosterLMS\CourseBuilder;

use RoosterLMS\Content\Course;

defined( 'ABSPATH' ) || exit;

final class Rev {

	public const STALE = 'rooster_lms_stale';

	public const PATTERN = '/^[0-9a-f]{16}$/';

	public const ANY = '/^[0-9a-f]{16,64}$/';

	public static function of( $data ): string {
		return substr( md5( (string) wp_json_encode( self::canonical( $data ) ) ), 0, 16 );
	}

	public static function course( Course $course, ?\WP_Post $post ): string {
		$row = array();
		foreach ( get_object_vars( $course ) as $key => $value ) {
			$row[ $key ] = $value instanceof \BackedEnum ? $value->value : $value;
		}
		return self::of(
			array(
				'course' => $row,
				'post'   => null === $post ? null : array( $post->post_status, $post->post_title, $post->post_name, $post->post_modified_gmt ),
			)
		);
	}

	public static function is_stale( string $sent, string $current ): bool {
		return '' !== $sent && ! hash_equals( $current, $sent );
	}

	public static function stale( string $current, $value = null ): \WP_Error {
		$data = array(
			'status' => 409,
			'rev'    => $current,
		);
		if ( null !== $value ) {
			$data['value'] = $value;
		}
		return new \WP_Error( self::STALE, __( 'Someone else changed this since you opened it.', 'rooster-lms' ), $data );
	}

	private static function canonical( $data ) {
		if ( ! is_array( $data ) ) {
			return $data;
		}
		if ( ! array_is_list( $data ) ) {
			ksort( $data );
		}
		return array_map( array( self::class, 'canonical' ), $data );
	}
}