[6.x] Fix Comb returning 500 when matched search token is longer than the configured snippet_length

src/Search/Comb/Comb.php

@@ -1077,13 +1077,13 @@ private function extractSnippets($value, $chunks)
             [, $before, $chunk, $after] = $match;
             $before = $surplus.$before;
             $surplus = '';
-            $half = floor(($length - Str::length($chunk)) / 2);
+            $half = max(0, floor(($length - Str::length($chunk)) / 2));
             if (Str::length($after) < $half) {
                 $snippet = $chunk.$after;
-                $snippet = Str::safeTruncateReverse($before, $length - Str::length($snippet)).$snippet;
+                $snippet = Str::safeTruncateReverse($before, max(0, $length - Str::length($snippet))).$snippet;
             } else {
                 $snippet = Str::safeTruncateReverse($before, $half).$chunk;
-                $trimmed = Str::safeTruncate($after, $length - Str::length($snippet));
+                $trimmed = Str::safeTruncate($after, max(0, $length - Str::length($snippet)));
                 $surplus = Str::substr($after, Str::length($trimmed));
                 $snippet = $snippet.$trimmed;
             }

tests/Search/CombTest.php

@@ -202,6 +202,36 @@ public function it_extracts_snippets_from_a_bard_field()
         $this->assertEquals($expected, collect($results['data'] ?? [])->pluck('snippets.content')->all());
     }
 
+    #[Test]
+    public function it_extracts_snippets_when_the_term_is_longer_than_the_snippet_length()
+    {
+        // https://github.com/statamic/cms/issues/12951
+        $content = <<<'EOT'
+        We know, it was a long wait, but now we finally have it, support for OpenID
+        Connect front and back-channel logout. The backchannel_logout_session_required
+        flag can be set on a client. See backchannel_logout_uri too. The
+        frontchannel_logout_session_required flag is the front-channel equivalent, and
+        backchannel_logout_session_required appears once more right here.
+        EOT;
+
+        $comb = new Comb([
+            ['content' => $content],
+        ], ['snippet_length' => 30]);
+
+        try {
+            $results = $comb->lookUp('backchannel_logout_session_required');
+        } catch (NoResultsFound $e) {
+            $results = [];
+        }
+
+        $expected = [[
+            'backchannel_logout_session_required',
+            'backchannel_logout_session_required',
+        ]];
+
+        $this->assertEquals($expected, collect($results['data'] ?? [])->pluck('snippets.content')->all());
+    }
+
     #[Test]
     public function it_can_search_for_plus_signs()
     {