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<?php

/*

* This file is part of the API Platform project.

*

* (c) Kévin Dunglas <dunglas@gmail.com>

*

* For the full copyright and license information, please view the LICENSE

* file that was distributed with this source code.

*/

declare(strict_types=1);

namespace ApiPlatform\HttpCache;

use Symfony\Contracts\HttpClient\HttpClientInterface;

/**

* Purges Varnish.

*

* @author Kévin Dunglas <dunglas@gmail.com>

*/

final class VarnishPurger implements PurgerInterface

{

private const DEFAULT_VARNISH_MAX_HEADER_LENGTH = 8000;

private const REGEXP_PATTERN = '(%s)($|\,)';

private readonly int $maxHeaderLength;

/**

* @param HttpClientInterface[] $clients

*/

public function __construct(private readonly iterable $clients, int $maxHeaderLength = self::DEFAULT_VARNISH_MAX_HEADER_LENGTH)

{

$this->maxHeaderLength = $maxHeaderLength - mb_strlen(self::REGEXP_PATTERN) + 2; // 2 for %s

}

/**

* Calculate how many tags fit into the header.

*

* This assumes that the tags are separated by one character.

*

* From https://github.com/FriendsOfSymfony/FOSHttpCache/blob/2.8.0/src/ProxyClient/HttpProxyClient.php#L137

*

* @param string[] $escapedTags

* @param string $glue The concatenation string to use

*

* @return int Number of tags per tag invalidation request

*/

private function determineTagsPerHeader(array $escapedTags, string $glue): int

{

if (mb_strlen(implode($glue, $escapedTags)) < $this->maxHeaderLength) {

return \count($escapedTags);

}

/*

* estimate the amount of tags to invalidate by dividing the max

* header length by the largest tag (minus the glue length)

*/

$tagsize = max(array_map('mb_strlen', $escapedTags));

$gluesize = \strlen($glue);

return (int) floor(($this->maxHeaderLength + $gluesize) / ($tagsize + $gluesize)) ?: 1;

}

/**

* {@inheritdoc}

*/

public function purge(array $iris): void

{

if (!$iris) {

return;

}

$chunkSize = $this->determineTagsPerHeader($iris, '|');

$irisChunks = array_chunk($iris, $chunkSize);

foreach ($irisChunks as $irisChunk) {

$this->purgeRequest($irisChunk);

}

}

/**

* {@inheritdoc}

*/

public function getResponseHeaders(array $iris): array

{

return ['Cache-Tags' => implode(',', $iris)];

}

private function purgeRequest(array $iris): void

{

// Create the regex to purge all tags in just one request

$parts = array_map(static fn ($iri): string => // here we should remove the prefix as it's not discriminent and cost a lot to compute

preg_quote($iri), $iris);

foreach ($this->chunkRegexParts($parts) as $regex) {

$regex = sprintf(self::REGEXP_PATTERN, $regex);

$this->banRegex($regex);

}

}

private function banRegex(string $regex): void

{

foreach ($this->clients as $client) {

$client->request('BAN', '', ['headers' => ['ApiPlatform-Ban-Regex' => $regex]]);

}

}

private function chunkRegexParts(array $parts): iterable

{

if (1 === \count($parts)) {

yield $parts[0];

return;

}

$concatenatedParts = implode("\n", $parts);

if (\strlen($concatenatedParts) <= $this->maxHeaderLength) {

yield str_replace("\n", '|', $concatenatedParts);

return;

}

$lastSeparator = strrpos(substr($concatenatedParts, 0, $this->maxHeaderLength + 1), "\n");

$chunk = substr($concatenatedParts, 0, $lastSeparator);

yield str_replace("\n", '|', $chunk);

$nextParts = \array_slice($parts, substr_count($chunk, "\n") + 1);

yield from $this->chunkRegexParts($nextParts);

}

}