* <p>
     * Usage example:
     * </p>
     *
     * <pre>
     * StringUtil.defaultString(null, "NULL")  = "NULL"
     * StringUtil.defaultString("", "NULL")    = ""
     * StringUtil.defaultString("aaa", "NULL") = "aaa"
     * StringUtil.defaultString("aaa", null)   = "aaa"
     * StringUtil.defaultString(null, null)    = null
     * </pre>
     *
     * @param str

     * @return the host name, or empty string if URL is blank, or unknown hostname if parsing fails
     */
    default String getHost(final String u) {
        if (StringUtil.isBlank(u)) {
            return StringUtil.EMPTY; // empty
        }

        String url = u;
        final String originalUrl = url;

        int idx = url.indexOf("://");
        if (idx >= 0) {

        final String tokenPattern = getParameter(TOKEN_PATTERN);
        final List<Pair<String, String>> responseParams = new ArrayList<>();
        final String encoding = getParameter(ENCODING);
        if (StringUtil.isNotBlank(tokenUrl) && StringUtil.isNotBlank(tokenPattern)) {
            final String tokenHttpMethod = getParameter(TOKEN_METHOD);
            final String tokenReqParams = getParameter(TOKEN_PARAMTERS);

            credentials = new NTCredentials(username, password == null ? StringUtil.EMPTY : password,
                    workstation == null ? StringUtil.EMPTY : workstation, domain == null ? StringUtil.EMPTY : domain);
        } else {
            credentials = new UsernamePasswordCredentials(username, password == null ? StringUtil.EMPTY : password);
        }
        return credentials;
    }

                return pagingQueryList.stream()
                        .filter(s -> prefix == null || !s.startsWith(prefix))
                        .collect(Collectors.joining("&", "&", StringUtil.EMPTY));
            }
            return null;
        }).orElse(StringUtil.EMPTY);
    }

    /**
     * Generates URL query parameters for facet filtering.
     *
     * @return URL-encoded query string containing facet parameters

     */
    public static String getAppType() {
        final String appType = System.getenv(FESS_APP_TYPE);
        if (StringUtil.isNotBlank(appType)) {
            return appType;
        }
        return StringUtil.EMPTY;
    }

    /**
     * Gets the override configuration path from environment variable when running in Docker.

     */
    public static String decodePath(final String id) {
        final PathInfo pi = convertToItem(id);
        if (StringUtil.isEmpty(pi.getPath()) && StringUtil.isEmpty(pi.getName())) {
            return StringUtil.EMPTY;
        }
        if (StringUtil.isEmpty(pi.getPath())) {
            return pi.getName();
        }
        return pi.getPath() + "/" + pi.getName();
    }

    /**

        assertEquals("c", StringUtil.substringToLast("abc", "b"));
        assertEquals("c", StringUtil.substringToLast("abcbc", "b"));
        assertEquals("abc", StringUtil.substringToLast("abc", ""));
        assertEquals("abc", StringUtil.substringToLast("abc", null));
        assertEquals("abc", StringUtil.substringToLast("abc", "dddd"));
    }

    /**
     * @throws Exception
     */

        final StringBuilder queryBuf = new StringBuilder(255);

        final String query = buildBaseQuery();
        if (StringUtil.isNotBlank(query)) {
            queryBuf.append(escapeQuery(query));
        }

        stream(params.getExtraQueries())
                .of(stream -> stream.filter(q -> StringUtil.isNotBlank(q) && q.length() <= maxQueryLength).forEach(q -> {
                    appendQuery(queryBuf, q);
                }));

        form.storageEndpoint = fessConfig.getStorageEndpoint();
        form.storageAccessKey = StringUtil.isNotBlank(fessConfig.getStorageAccessKey()) ? DUMMY_PASSWORD : StringUtil.EMPTY;
        form.storageSecretKey = StringUtil.isNotBlank(fessConfig.getStorageSecretKey()) ? DUMMY_PASSWORD : StringUtil.EMPTY;
        form.storageBucket = fessConfig.getStorageBucket();