/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.qpid.tests.protocol;

import java.nio.charset.StandardCharsets;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class SaslUtils
{
    private static final char[] HEX = "0123456789abcdef".toCharArray();

    private static String toHex(byte[] bin)
    {
        StringBuilder result = new StringBuilder(2 * bin.length);
        for (byte b : bin) {
            result.append(HEX[(b >> 4) & 0xF]);
            result.append(HEX[(b & 0xF)]);
        }
        return result.toString();
    }
    public static byte[] generateCramMD5ClientResponse(String userName, String userPassword, byte[] challengeBytes)
            throws Exception
    {
        String macAlgorithm = "HmacMD5";
        Mac mac = Mac.getInstance(macAlgorithm);
        mac.init(new SecretKeySpec(userPassword.getBytes(StandardCharsets.UTF_8), macAlgorithm));
        final byte[] messageAuthenticationCode = mac.doFinal(challengeBytes);
        String responseAsString = userName + " " + toHex(messageAuthenticationCode);
        return responseAsString.getBytes();
    }
}