<?php
/**
 * Hourly check budget.
 *
 * @package Unbreak
 */

namespace Unbreak\Check;

use Unbreak\Data\LinkRepository;
use Unbreak\Support\Clock;
use Unbreak\Support\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Never more than N checks in any trailing hour (default 600). The count is derived from
 * links.last_checked_at, so there is no counter that can drift or race.
 */
final class RateLimiter {

	/**
	 * Repository.
	 *
	 * @var LinkRepository
	 */
	private $links;

	/**
	 * Constructor.
	 *
	 * @param LinkRepository|null $links Repository.
	 */
	public function __construct( ?LinkRepository $links = null ) {
		$this->links = $links ?? new LinkRepository();
	}

	/**
	 * Checks still allowed in the trailing hour.
	 */
	public function remaining(): int {
		$limit = (int) Settings::get( 'rate_limit_per_hour' );
		return max( 0, $limit - $this->links->checked_since( Clock::now() - HOUR_IN_SECONDS ) );
	}

	/**
	 * Budget for one lane batch. The remaining hourly budget is split between lanes so that even
	 * concurrently running lanes can never exceed the limit together.
	 *
	 * @param int $lane      Lane index.
	 * @param int $lanes     Number of lanes.
	 * @param int $batch_max Max URLs per batch.
	 */
	public function lane_budget( int $lane, int $lanes, int $batch_max ): int {
		$remaining = $this->remaining();
		$lanes     = max( 1, $lanes );
		$share     = intdiv( $remaining, $lanes ) + ( $lane < $remaining % $lanes ? 1 : 0 );
		return max( 0, min( $batch_max, $share ) );
	}
}