<?php

declare(strict_types=1);

namespace KTXF\Event;

use Psr\Container\ContainerInterface;
use Psr\Log\LoggerInterface;

final class EventDispatcher implements EventDispatcherInterface, DeferredEventProcessorInterface
{
    /** @var array<string, list<Event>> */
    private array $deferred = [];
    private ?string $activeExecution = null;
    private int $dispatchDepth = 0;

    public function __construct(
        private readonly EventListenerRegistry $registry,
        private readonly ContainerInterface $container,
        private readonly LoggerInterface $logger,
    ) {
    }

    public function dispatch(Event $event): void
    {
        if (++$this->dispatchDepth > 32) {
            --$this->dispatchDepth;
            throw new \RuntimeException('Event dispatch recursion limit exceeded.');
        }

        try {
            $this->invoke($event, DeliveryMode::Immediate);
            if ($this->registry->listeners($event->getName(), DeliveryMode::Deferred) !== []) {
                if ($this->activeExecution === null) {
                    throw new \LogicException('Deferred events require an active execution scope.');
                }
                $this->deferred[$this->activeExecution][] = $event;
            }
        } finally {
            --$this->dispatchDepth;
        }
    }

    public function beginExecution(string $executionId): void
    {
        if ($this->activeExecution !== null) {
            throw new \LogicException('An event execution scope is already active.');
        }
        $this->activeExecution = $executionId;
        $this->deferred[$executionId] = [];
    }

    public function processDeferred(string $executionId): DeferredProcessingResult
    {
        if ($this->activeExecution !== $executionId) {
            throw new \LogicException('Cannot process deferred events for an inactive execution.');
        }

        $processed = 0;
        $deadline = microtime(true) + 1.0;
        $deadlineExceeded = false;
        $limitExceeded = false;
        while (($event = array_shift($this->deferred[$executionId])) !== null) {
            if ($processed >= 1000) {
                $limitExceeded = true;
                array_unshift($this->deferred[$executionId], $event);
                break;
            }
            if (microtime(true) >= $deadline) {
                $deadlineExceeded = true;
                array_unshift($this->deferred[$executionId], $event);
                break;
            }
            $processed += $this->invoke($event, DeliveryMode::Deferred);
        }

        $remaining = count($this->deferred[$executionId]);
        unset($this->deferred[$executionId]);
        $this->activeExecution = null;

        return new DeferredProcessingResult(
            $processed,
            $remaining,
            $deadlineExceeded,
            $limitExceeded,
        );
    }

    public function discardDeferred(string $executionId): void
    {
        unset($this->deferred[$executionId]);
        if ($this->activeExecution === $executionId) {
            $this->activeExecution = null;
        }
    }

    private function invoke(Event $event, DeliveryMode $delivery): int
    {
        $processed = 0;
        foreach ($this->registry->listeners($event->getName(), $delivery) as $listener) {
            if ($event->isPropagationStopped()) {
                break;
            }

            try {
                $service = $this->container->get($listener->service);
                $service->{$listener->method}($event);
                $processed++;
            } catch (\Throwable $error) {
                $this->logger->error('Event listener failed.', [
                    'event' => $event->getName(),
                    'module' => $listener->module,
                    'listener' => $listener->service . '::' . $listener->method,
                    'exception' => $error,
                ]);
                if ($listener->failurePolicy === FailurePolicy::Propagate) {
                    throw $error;
                }
            }
        }

        return $processed;
    }
}