public String combine()

in common/src/main/java/com/alibaba/nacos/common/packagescan/resource/AntPathMatcher.java [556:603]
36 lines of code
20 McCabe index (conditional complexity)

    public String combine(String pattern1, String pattern2) {
        if (!StringUtils.hasText(pattern1) && !StringUtils.hasText(pattern2)) {
            return "";
        }
        if (!StringUtils.hasText(pattern1)) {
            return pattern2;
        }
        if (!StringUtils.hasText(pattern2)) {
            return pattern1;
        }

        boolean pattern1ContainsUriVar = (pattern1.indexOf('{') != -1);
        if (!pattern1.equals(pattern2) && !pattern1ContainsUriVar && match(pattern1, pattern2)) {
            // /* + /hotel -> /hotel ; "/*.*" + "/*.html" -> /*.html
            // However /user + /user -> /usr/user ; /{foo} + /bar -> /{foo}/bar
            return pattern2;
        }

        // /hotels/* + /booking -> /hotels/booking
        // /hotels/* + booking -> /hotels/booking
        if (pattern1.endsWith(this.pathSeparatorPatternCache.getEndsOnWildCard())) {
            return concat(pattern1.substring(0, pattern1.length() - 2), pattern2);
        }

        // /hotels/** + /booking -> /hotels/**/booking
        // /hotels/** + booking -> /hotels/**/booking
        if (pattern1.endsWith(this.pathSeparatorPatternCache.getEndsOnDoubleWildCard())) {
            return concat(pattern1, pattern2);
        }

        int starDotPos1 = pattern1.indexOf("*.");
        if (pattern1ContainsUriVar || starDotPos1 == -1 || this.pathSeparator.equals(".")) {
            // simply concatenate the two patterns
            return concat(pattern1, pattern2);
        }

        String ext1 = pattern1.substring(starDotPos1 + 1);
        int dotPos2 = pattern2.indexOf('.');
        String file2 = (dotPos2 == -1 ? pattern2 : pattern2.substring(0, dotPos2));
        String ext2 = (dotPos2 == -1 ? "" : pattern2.substring(dotPos2));
        boolean ext1All = (ext1.equals(".*") || ext1.isEmpty());
        boolean ext2All = (ext2.equals(".*") || ext2.isEmpty());
        if (!ext1All && !ext2All) {
            throw new IllegalArgumentException("Cannot combine patterns: " + pattern1 + " vs " + pattern2);
        }
        String ext = (ext1All ? ext2 : ext1);
        return file2 + ext;
    }