Add diff as a language.

src/Highlighter.php

@@ -9,6 +9,7 @@
 use Tempest\Highlight\Languages\Base\Injections\GutterInjection;
 use Tempest\Highlight\Languages\Blade\BladeLanguage;
 use Tempest\Highlight\Languages\Css\CssLanguage;
+use Tempest\Highlight\Languages\Diff\DiffLanguage;
 use Tempest\Highlight\Languages\DocComment\DocCommentLanguage;
 use Tempest\Highlight\Languages\Gdscript\GdscriptLanguage;
 use Tempest\Highlight\Languages\Html\HtmlLanguage;
@@ -38,6 +39,7 @@ public function __construct(
         $this
             ->addLanguage(new BladeLanguage())
             ->addLanguage(new CssLanguage())
+            ->addLanguage(new DiffLanguage())
             ->addLanguage(new DocCommentLanguage())
             ->addLanguage(new GdscriptLanguage())
             ->addLanguage(new HtmlLanguage())

src/Languages/Diff/DiffLanguage.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Tempest\Highlight\Languages\Diff;
+
+use Tempest\Highlight\Languages\Base\BaseLanguage;
+use Tempest\Highlight\Languages\Diff\Injections\DiffAdditionInjection;
+use Tempest\Highlight\Languages\Diff\Injections\DiffDeletionInjection;
+
+class DiffLanguage extends BaseLanguage
+{
+    public function getName(): string
+    {
+        return 'diff';
+    }
+
+    public function getInjections(): array
+    {
+        return [
+            ...parent::getInjections(),
+            new DiffAdditionInjection(),
+            new DiffDeletionInjection(),
+        ];
+    }
+}

src/Languages/Diff/Injections/DiffAdditionInjection.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace Tempest\Highlight\Languages\Diff\Injections;
+
+use Tempest\Highlight\Escape;
+use Tempest\Highlight\Highlighter;
+use Tempest\Highlight\ParsedInjection;
+
+class DiffAdditionInjection
+{
+    public function parse(string $content, Highlighter $highlighter): ParsedInjection
+    {
+        $content = preg_replace_callback(
+            '/^\+(.*)$/m',
+            function ($matches) {
+                $open = Escape::tokens('<span class="hl-addition">+ ');
+                $close = Escape::tokens('</span>');
+
+                return $open . $matches[1] . $close;
+            },
+            $content
+        );
+
+        return new ParsedInjection($content);
+    }
+}

src/Languages/Diff/Injections/DiffDeletionInjection.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace Tempest\Highlight\Languages\Diff\Injections;
+
+use Tempest\Highlight\Escape;
+use Tempest\Highlight\Highlighter;
+use Tempest\Highlight\ParsedInjection;
+
+class DiffDeletionInjection
+{
+    public function parse(string $content, Highlighter $highlighter): ParsedInjection
+    {
+        $content = preg_replace_callback(
+            '/^\-(.*)$/m', // Matches lines starting with '+'
+            function ($matches) {
+                $open = Escape::tokens('<span class="hl-deletion">- ');
+                $close = Escape::tokens('</span>');
+
+                return $open . $matches[1] . $close; // Wraps the matched line with the span
+            },
+            $content
+        );
+
+        return new ParsedInjection($content);
+    }
+}

tests/Languages/Diff/DiffLanguageTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Languages\Diff;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use Tempest\Highlight\Highlighter;
+
+class DiffLanguageTest extends TestCase
+{
+    #[DataProvider('data')]
+    public function test_highlight(string $content, string $expected): void
+    {
+        $highlighter = new Highlighter();
+
+        $this->assertSame(
+            $expected,
+            $highlighter->parse($content, 'diff'),
+        );
+    }
+
+    public static function data(): array
+    {
+        return [
+            [<<<'TXT'
++ $this->newCode();
+- $this->oldCode();
+TXT,
+                <<<'TXT'
+<span class="hl-addition">+  $this-&gt;newCode();</span>
+<span class="hl-deletion">-  $this-&gt;oldCode();</span>
+TXT
+            ],
+        ];
+    }
+}