java source code of PunycodeURLNormalizer

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.commoncrawl.stormcrawler.news;

import java.net.IDN;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Map;

import com.digitalpebble.stormcrawler.Metadata;
import com.digitalpebble.stormcrawler.filtering.URLFilter;
import com.fasterxml.jackson.databind.JsonNode;

public class PunycodeURLNormalizer implements URLFilter {

    @Override
    public void configure(Map stormConf, JsonNode filterParams) {
    }

    private boolean isAscii(String str) {
        char[] chars = str.toCharArray();
        for (char c : chars) {
            if (c > 127) {
                return false;
            }
        }
        return true;
    }

    @Override
    public String filter(URL sourceUrl, Metadata sourceMetadata,
            String urlToFilter) {
        try {
            URL url = new URL(urlToFilter);
            String hostName = url.getHost();
            if (isAscii(hostName)) {
                return urlToFilter;
            }
            hostName = IDN.toASCII(url.getHost());
            if (hostName.equals(url.getHost())) {
                return urlToFilter;
            }
            urlToFilter = new URL(url.getProtocol(), hostName, url.getPort(),
                    url.getFile()).toString();
        } catch (MalformedURLException e) {
            return null;
        }
        return urlToFilter;
    }

}