<?php
declare(strict_types=1);

namespace Shlinkio\Shlink\Core\Action;

use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Shlinkio\Shlink\Common\Exception\PreviewGenerationException;
use Shlinkio\Shlink\Common\Service\PreviewGeneratorInterface;
use Shlinkio\Shlink\Common\Util\ResponseUtilsTrait;
use Shlinkio\Shlink\Core\Action\Util\ErrorResponseBuilderTrait;
use Shlinkio\Shlink\Core\Exception\EntityDoesNotExistException;
use Shlinkio\Shlink\Core\Exception\InvalidShortCodeException;
use Shlinkio\Shlink\Core\Service\UrlShortenerInterface;

class PreviewAction implements MiddlewareInterface
{
    use ResponseUtilsTrait;
    use ErrorResponseBuilderTrait;

    /**
     * @var PreviewGeneratorInterface
     */
    private $previewGenerator;
    /**
     * @var UrlShortenerInterface
     */
    private $urlShortener;
    /**
     * @var LoggerInterface
     */
    private $logger;

    public function __construct(
        PreviewGeneratorInterface $previewGenerator,
        UrlShortenerInterface $urlShortener,
        LoggerInterface $logger = null
    ) {
        $this->previewGenerator = $previewGenerator;
        $this->urlShortener = $urlShortener;
        $this->logger = $logger ?: new NullLogger();
    }

    /**
     * Process an incoming server request and return a response, optionally delegating
     * to the next middleware component to create the response.
     *
     * @param Request $request
     * @param RequestHandlerInterface $handler
     *
     * @return Response
     */
    public function process(Request $request, RequestHandlerInterface $handler): Response
    {
        $shortCode = $request->getAttribute('shortCode');

        try {
            $url = $this->urlShortener->shortCodeToUrl($shortCode);
            $imagePath = $this->previewGenerator->generatePreview($url->getLongUrl());
            return $this->generateImageResponse($imagePath);
        } catch (InvalidShortCodeException | EntityDoesNotExistException | PreviewGenerationException $e) {
            $this->logger->warning('An error occurred while generating preview image.' . PHP_EOL . $e);
            return $this->buildErrorResponse($request, $handler);
        }
    }
}