<?php

declare(strict_types=1);

namespace LinkCheckup\Shared\Rest;

use WP_REST_Request;

use function intdiv;
use function is_numeric;
use function max;
use function min;

final class PageRequest {

	public const MAXIMUM_PER_PAGE = 100;
	private const FIRST_PAGE      = 1;

	public function __construct(
		public readonly int $page,
		public readonly int $per_page
	) {
	}

	/** @param WP_REST_Request<array<string, mixed>> $request */
	public static function from_request(
		WP_REST_Request $request,
		int $default_per_page
	): self {
		$last_page = intdiv( PHP_INT_MAX, self::MAXIMUM_PER_PAGE );

		return new self(
			self::bounded(
				$request->get_param( 'page' ),
				self::FIRST_PAGE,
				$last_page
			),
			self::bounded(
				$request->get_param( 'per_page' ),
				$default_per_page,
				self::MAXIMUM_PER_PAGE
			)
		);
	}

	public function offset(): int {
		return ( $this->page - 1 ) * $this->per_page;
	}

	private static function bounded(
		mixed $parameter,
		int $fallback,
		int $maximum
	): int {
		$number = is_numeric( $parameter ) ? (float) $parameter : $fallback;

		return (int) max( self::FIRST_PAGE, min( $maximum, $number ) );
	}
}