feat: add support for new OS regular expressions that use backreferen…

…ces for major, minor, patch properties

restores passing unit tests
fixes #27

src/main/java/ua_parser/OSParser.java

@@ -105,17 +105,17 @@ public OS match(String agentString) {
       }
 
       if (v1Replacement != null) {
-        v1 = v1Replacement;
+        v1 = getReplacement(matcher, v1Replacement);
       } else if (groupCount >= 2) {
         v1 = matcher.group(2);
       }
       if (v2Replacement != null) {
-        v2 = v2Replacement;
+        v2 = getReplacement(matcher, v2Replacement);
       } else if (groupCount >= 3) {
         v2 = matcher.group(3);
       }
       if (v3Replacement != null) {
-        v3 = v3Replacement;
+        v3 = getReplacement(matcher, v3Replacement);
       } else if (groupCount >= 4) {
         v3 = matcher.group(4);
       }
@@ -125,5 +125,28 @@ public OS match(String agentString) {
 
       return family == null ? null : new OS(family, v1, v2, v3, v4);
     }
+
+    private String getReplacement(Matcher matcher, String replacement) {
+    	if (isBackReference(replacement)) {
+    		int group = getGroup(replacement);
+    		return matcher.group(group);
+    	} else {
+    		return replacement;
+    	}
+    }
+
+    /**
+     * Checks if the replacement is a backreference (i.e. $1, $2, $3, etc) to a capturing group in the regular expression.
+     */
+    private boolean isBackReference(String replacement) {
+    	return replacement.startsWith("$");
+    }
+
+    /**
+     * Extracts the group number from a backreference like $1, $2, $3, etc.
+     */
+    private int getGroup(String backReference) {
+    	return Integer.valueOf(backReference.substring(1));
+    }
   }
 }