add regexp_capture

extensions/regexp/src/lib.rs

@@ -82,3 +82,36 @@ fn regexp_replace(&self, args: &[Value]) -> Value {
         _ => Value::from_text("".to_string()), // Return an empty string for invalid value types
     }
 }
+
+
+#[scalar(name = "regexp_capture")]
+fn regexp_capture(args: &[Value]) -> Value {
+    match (args.get(0), args.get(1)) {
+        (Some(source), Some(pattern)) if source.value_type() == ValueType::Text && pattern.value_type() == ValueType::Text => {
+            let Some(source_text) = source.to_text() else {
+                return Value::null();
+            };
+
+            let Some(pattern_text) = pattern.to_text() else {
+                return Value::null();
+            };
+
+            let group_index: usize = args.get(2).and_then(|v| v.to_integer()).map(|n| n as usize).unwrap_or(1);
+
+
+            let re = match Regex::new(pattern_text) {
+                Ok(re) => re,
+                Err(_) => return Value::null()
+            };
+
+            if let Some(caps) = re.captures(source_text) {
+                if let Some(m) = caps.get(group_index) {
+                    return Value::from_text(m.as_str().to_string());
+                }
+            }
+
+            Value::null()
+        }
+        _ => Value::null()
+    }
+}