feat: Release v3.0.0 - PHPStan-style analysis, configuration, baseline, and advanced WCAG rules

src/Rules/LanguageSubtag.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace YakNet\AccessibilityConsole\Rules;
+
+use DOMElement;
+use YakNet\AccessibilityConsole\Core\Severity;
+use YakNet\AccessibilityConsole\Core\Violation;
+use YakNet\AccessibilityConsole\Core\WCAGStandard;
+
+class LanguageSubtag extends AbstractRule
+{
+    public function getId(): string { return 'WCAG_3_1_2_LANG'; }
+    public function getDescription(): string { return 'Language attributes (lang) must use a valid language code format.'; }
+    public function getStandard(): WCAGStandard { return WCAGStandard::A; }
+    public function getSeverity(): Severity { return Severity::ERROR; }
+    public function getLevel(): int { return 3; }
+
+    public function check(DOMElement $element): ?Violation
+    {
+        if (!$element->hasAttribute('lang')) {
+            return null;
+        }
+
+        $lang = trim($element->getAttribute('lang'));
+        
+        // Simple IETF language tag format check (e.g. "en", "tr", "en-US", "zh-Hant")
+        $isValid = preg_match('/^[a-zA-Z]{2,3}(-[a-zA-Z0-9]{2,8})*$/', $lang);
+
+        if (!$isValid || $lang === '') {
+            return $this->createViolation(
+                $element,
+                $this->getDescription(),
+                'Use a valid IETF language code format for the lang attribute (e.g., "tr", "en", "en-US").'
+            );
+        }
+
+        return null;
+    }
+}