<?php
/**
 * Processes queued jobs until the queue is empty or time runs out.
 *
 * @package Akantio\Cache
 */

declare(strict_types=1);

namespace Akantio\Cache\Application\Queue;

use Akantio\Cache\Domain\Queue\RetryPolicy;

/**
 * Pulls one job at a time so several workers can share the queue safely.
 */
final class QueueWorker {

	/**
	 * @param JobQueue                  $queue    Queue.
	 * @param array<string, JobHandler> $handlers Handler per job type.
	 * @param RetryPolicy               $retry    Retry policy.
	 */
	public function __construct(
		private readonly JobQueue $queue,
		private readonly array $handlers,
		private readonly RetryPolicy $retry,
	) {
	}

	/**
	 * Runs jobs until the queue is empty, $should_stop says so, or a job is postponed (the
	 * reason, such as a busy server, applies to the jobs behind it too).
	 *
	 * @param callable(): bool $should_stop Checked before each job (deadline, memory).
	 */
	public function run( callable $should_stop ): WorkerReport {
		$processed = 0;
		while ( ! $should_stop() ) {
			$job = $this->queue->claim();
			if ( null === $job ) {
				break;
			}
			try {
				$this->process( $job );
			} catch ( Postponed $wait ) {
				$this->queue->postpone( $job, $wait->seconds );
				return new WorkerReport( $processed, true );
			}
			++$processed;
		}

		return new WorkerReport( $processed, false );
	}

	/**
	 * Runs one job and records the outcome.
	 *
	 * @param Job $job Job.
	 * @throws Postponed When the job asks to wait.
	 */
	private function process( Job $job ): void {
		$handler = $this->handlers[ $job->type ] ?? null;
		if ( null === $handler ) {
			$this->queue->fail( $job, "No handler for job type {$job->type}." );
			return;
		}

		try {
			$handler->handle( $job );
			$this->queue->complete( $job );
		} catch ( Postponed $wait ) {
			throw $wait;
		} catch ( PermanentFailure $error ) {
			$this->queue->fail( $job, $error->getMessage() );
		} catch ( \Throwable $error ) {
			if ( $this->retry->shouldRetry( $job->attempts ) ) {
				$this->queue->retry( $job, $error->getMessage(), $this->retry->delayAfter( $job->attempts ) );
			} else {
				$this->queue->fail( $job, $error->getMessage() );
			}
		}
	}
}