Ensure language redirect conditions do not match for too low quality accepted languages

CHANGELOG.md

@@ -6,7 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com), and this
 
 ## [Unreleased]
 ### Added
-* [#2041](https://github.com/shlinkio/shlink/issues/2041) Document `color` and `bgColor` params for the QR code route in the OAS docs.
+* *Nothing*
 
 ### Changed
 * *Nothing*
@@ -18,7 +18,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com), and this
 * *Nothing*
 
 ### Fixed
-* *Nothing*
+* [#2041](https://github.com/shlinkio/shlink/issues/2041) Document missing `color` and `bgColor` params for the QR code route in the OAS docs.
+* [#2043](https://github.com/shlinkio/shlink/issues/2043) Fix language redirect conditions matching too low quality accepted languages.
 
 
 ## [4.0.0] - 2024-03-03

module/Core/functions/functions.php

@@ -8,6 +8,7 @@ use BackedEnum;
 use Cake\Chronos\Chronos;
 use DateTimeInterface;
 use Doctrine\ORM\Mapping\Builder\FieldBuilder;
+use GuzzleHttp\Psr7\Query;
 use Jaybizzle\CrawlerDetect\CrawlerDetect;
 use Laminas\Filter\Word\CamelCaseToSeparator;
 use Laminas\Filter\Word\CamelCaseToUnderscore;
@@ -16,7 +17,6 @@ use PUGX\Shortid\Factory as ShortIdFactory;
 use Shlinkio\Shlink\Common\Util\DateRange;
 use Shlinkio\Shlink\Core\ShortUrl\Model\ShortUrlMode;
 
-use function array_filter;
 use function array_keys;
 use function array_map;
 use function array_pad;
@@ -27,6 +27,7 @@ use function implode;
 use function is_array;
 use function print_r;
 use function Shlinkio\Shlink\Common\buildDateRange;
+use function Shlinkio\Shlink\Core\ArrayUtils\map;
 use function sprintf;
 use function str_repeat;
 use function str_replace;
@@ -85,16 +86,30 @@ function normalizeLocale(string $locale): string
 }
 
 /**
+ * Parse an accept-language-like pattern into a list of locales, optionally filtering out those which do not match a
+ * minimum quality
+ *
  * @param non-empty-string $acceptLanguage
- * @return string[];
+ * @param float<0, 1> $minQuality
+ * @return iterable<string>;
  */
-function acceptLanguageToLocales(string $acceptLanguage): array
+function acceptLanguageToLocales(string $acceptLanguage, float $minQuality = 0): iterable
 {
-    $acceptLanguagesList = array_map(function (string $lang): string {
+    /** @var array{string, float|null}[] $acceptLanguagesList */
-        [$lang] = explode(';', $lang); // Discard everything after the semicolon (en-US;q=0.7)
+    $acceptLanguagesList = map(explode(',', $acceptLanguage), static function (string $lang): array {
-        return normalizeLocale($lang);
+        // Split locale/language and quality (en-US;q=0.7) -> [en-US, q=0.7]
-    }, explode(',', $acceptLanguage));
+        [$lang, $qualityString] = array_pad(explode(';', $lang), length: 2, value: '');
-    return array_filter($acceptLanguagesList, static fn (string $lang) => $lang !== '*');
+        $normalizedLang = normalizeLocale($lang);
+        $quality = Query::parse(trim($qualityString))['q'] ?? 1;
+
+        return [$normalizedLang, (float) $quality];
+    });
+
+    foreach ($acceptLanguagesList as [$lang, $quality]) {
+        if ($lang !== '*' && $quality >= $minQuality) {
+            yield $lang;
+        }
+    }
 }
 
 /**
@@ -108,7 +123,7 @@ function acceptLanguageToLocales(string $acceptLanguage): array
  */
 function splitLocale(string $locale): array
 {
-    return array_pad(explode('-', $locale), 2, null);
+    return array_pad(explode('-', $locale), length: 2, value: null);
 }
 
 function getOptionalIntFromInputFilter(InputFilter $inputFilter, string $fieldName): ?int

module/Core/src/RedirectRule/Entity/RedirectCondition.php

@@ -77,7 +77,7 @@ class RedirectCondition extends AbstractEntity implements JsonSerializable
             return false;
         }
 
-        $acceptedLanguages = acceptLanguageToLocales($acceptLanguage);
+        $acceptedLanguages = acceptLanguageToLocales($acceptLanguage, minQuality: 0.9);
         [$matchLanguage, $matchCountryCode] = splitLocale(normalizeLocale($this->matchValue));
 
         return some(

module/Core/test-api/Action/RedirectTest.php

@@ -75,9 +75,15 @@ class RedirectTest extends ApiTestCase
         ];
         yield 'rule: complex matching accept language' => [
             [
-                RequestOptions::HEADERS => ['Accept-Language' => 'fr-FR, es;q=08, en;q=0.5, *;q=0.2'],
+                RequestOptions::HEADERS => ['Accept-Language' => 'fr-FR, es;q=0.9, en;q=0.9, *;q=0.2'],
             ],
             'https://example.com/only-english',
         ];
+        yield 'rule: too low quality accept language' => [
+            [
+                RequestOptions::HEADERS => ['Accept-Language' => 'fr-FR, es;q=0.8, en;q=0.5, *;q=0.2'],
+            ],
+            'https://blog.alejandrocelaya.com/2017/12/09/acmailer-7-0-the-most-important-release-in-a-long-time/',
+        ];
     }
 }

module/Core/test/RedirectRule/Entity/RedirectConditionTest.php

@@ -35,6 +35,8 @@ class RedirectConditionTest extends TestCase
     #[TestWith(['es, en,fr', 'en', true])] // multiple languages match
     #[TestWith(['es, en-US,fr', 'EN', true])] // multiple locales match
     #[TestWith(['es_ES', 'es-ES', true])] // single locale match
+    #[TestWith(['en-US,es-ES;q=0.6', 'es-ES', false])] // too low quality
+    #[TestWith(['en-US,es-ES;q=0.9', 'es-ES', true])] // quality high enough
     #[TestWith(['en-UK', 'en-uk', true])] // different casing match
     #[TestWith(['en-UK', 'en', true])] // only lang
     #[TestWith(['es-AR', 'en', false])] // different only lang