<?php
/**
 * Warms one URL.
 *
 * @package Akantio\Cache
 */

declare(strict_types=1);

namespace Akantio\Cache\Application\Preload;

use Akantio\Cache\Application\PageCache\PageStore;
use Akantio\Cache\Application\Queue\Job;
use Akantio\Cache\Application\Queue\JobHandler;
use Akantio\Cache\Application\Queue\PermanentFailure;
use Akantio\Cache\Application\Queue\Postponed;
use Akantio\Cache\Domain\PageCache\CacheKey;
use Akantio\Cache\Domain\Purge\PurgeTargets;
use Akantio\Cache\Domain\Url;

/**
 * Pages a visitor already cached are skipped: rendering them again would only cost CPU.
 */
final class PreloadUrlHandler implements JobHandler {

	/**
	 * @param PreloadClient $client  HTTP client.
	 * @param PurgeTargets  $targets Own-URL check; prevents SSRF through queued payloads.
	 * @param PageStore     $store   Cached pages.
	 * @param PreloadPacer  $pacer   Load guard and pause between pages.
	 */
	public function __construct(
		private readonly PreloadClient $client,
		private readonly PurgeTargets $targets,
		private readonly PageStore $store,
		private readonly PreloadPacer $pacer,
	) {
	}

	/**
	 * {@inheritDoc}
	 *
	 * @param Job $job Job.
	 * @throws PermanentFailure For foreign URLs and client errors.
	 * @throws Postponed When the server is busy.
	 */
	public function handle( Job $job ): void {
		$url    = (string) ( $job->payload['url'] ?? '' );
		$mobile = true === ( $job->payload['mobile'] ?? false );
		if ( ! $this->targets->isOwnUrl( $url ) ) {
			throw new PermanentFailure( 'Refusing to preload a URL outside this site.' );
		}
		if ( $this->isCached( $url, $mobile ) ) {
			return;
		}

		$this->pacer->beforeFetch();
		$status = $this->client->fetch( $url, $mobile );
		$this->pacer->afterFetch();

		if ( $status >= 400 && $status < 500 && 429 !== $status ) {
			PermanentFailure::raise( 'Preload got HTTP %d.', (int) $status );
		}
		if ( $status < 200 || $status >= 400 ) {
			throw new \RuntimeException( 'Preload got HTTP ' . (int) $status . '.' );
		}
	}

	/**
	 * Whether the page is already in the cache for this device.
	 *
	 * @param string $url    URL.
	 * @param bool   $mobile Mobile variant.
	 */
	private function isCached( string $url, bool $mobile ): bool {
		$parts = Url::parse( $url );
		if ( ! is_array( $parts ) || ! isset( $parts['host'] ) ) {
			return false;
		}
		// Same host[:port] as the request that stored the page (see PurgeService::purgeUrls).
		$host = $parts['host'] . ( isset( $parts['port'] ) ? ':' . $parts['port'] : '' );
		$key  = CacheKey::forUrl( $host, (string) ( $parts['path'] ?? '/' ), $mobile );

		return null !== $key && null !== $this->store->fetch( $key, '' );
	}
}