Added support for IDN

module/Core/src/Util/UrlValidator.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Util;
+
+use Fig\Http\Message\RequestMethodInterface;
+use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Exception\GuzzleException;
+use GuzzleHttp\RequestOptions;
+use Shlinkio\Shlink\Core\Exception\InvalidUrlException;
+use Zend\Diactoros\Uri;
+
+use function idn_to_ascii;
+
+use const IDNA_DEFAULT;
+use const INTL_IDNA_VARIANT_UTS46;
+
+class UrlValidator implements UrlValidatorInterface
+{
+    private const MAX_REDIRECTS = 15;
+
+    /** @var ClientInterface */
+    private $httpClient;
+
+    public function __construct(ClientInterface $httpClient)
+    {
+        $this->httpClient = $httpClient;
+    }
+
+    /**
+     * @throws InvalidUrlException
+     */
+    public function validateUrl(string $url): void
+    {
+        // FIXME Guzzle is about to add support for this https://github.com/guzzle/guzzle/pull/2286
+        //       Remove custom implementation when Guzzle's PR is merged
+        $uri = new Uri($url);
+        $originalHost = $uri->getHost();
+        $normalizedHost = idn_to_ascii($originalHost, IDNA_DEFAULT, INTL_IDNA_VARIANT_UTS46);
+        if ($originalHost !== $normalizedHost) {
+            $uri = $uri->withHost($normalizedHost);
+        }
+
+        try {
+            $this->httpClient->request(RequestMethodInterface::METHOD_GET, (string) $uri, [
+                RequestOptions::ALLOW_REDIRECTS => ['max' => self::MAX_REDIRECTS],
+            ]);
+        } catch (GuzzleException $e) {
+            throw InvalidUrlException::fromUrl($url, $e);
+        }
+    }
+}

module/Core/src/Util/UrlValidatorInterface.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Util;
+
+use Shlinkio\Shlink\Core\Exception\InvalidUrlException;
+
+interface UrlValidatorInterface
+{
+    /**
+     * @throws InvalidUrlException
+     */
+    public function validateUrl(string $url): void;
+}