/*
 * 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.jms.sasl;

import java.nio.charset.StandardCharsets;
import java.security.Principal;
import java.util.regex.Pattern;

/**
 * Implements the SASL XOAUTH2 authentication Mechanism .
 *
 * User name and Password values are sent without being encrypted.
 */
public class XOauth2Mechanism extends AbstractMechanism {

    private static final Pattern ACCESS_TOKEN_PATTERN = Pattern.compile("^[\\x20-\\x7F]+$");
    private String additionalFailureInformation;

    @Override
    public int getPriority() {
        return PRIORITY.LOWER_STILL.getValue();
    }

    @Override
    public String getName() {
        return "XOAUTH2";
    }

    @Override
    public byte[] getInitialResponse() {

        String username = getUsername();
        String password = getPassword();

        if (username == null) {
            username = "";
        }

        if (password == null) {
            password = "";
        }

        byte[] usernameBytes = username.getBytes(StandardCharsets.UTF_8);
        byte[] passwordBytes = password.getBytes(StandardCharsets.UTF_8);
        byte[] data = new byte[usernameBytes.length + passwordBytes.length + 20];
        System.arraycopy("user=".getBytes(StandardCharsets.US_ASCII), 0, data, 0, 5);
        System.arraycopy(usernameBytes, 0, data, 5, usernameBytes.length);
        data[5+usernameBytes.length] = 1;
        System.arraycopy("auth=Bearer ".getBytes(StandardCharsets.US_ASCII), 0, data, 6+usernameBytes.length, 12);
        System.arraycopy(passwordBytes, 0, data, 18 + usernameBytes.length, passwordBytes.length);
        data[data.length-2] = 1;
        data[data.length-1] = 1;

        return data;
    }

    @Override
    public byte[] getChallengeResponse(byte[] challenge) {
        if(challenge != null && challenge.length > 0 && additionalFailureInformation == null) {
            additionalFailureInformation = new String(challenge, StandardCharsets.UTF_8);
        }
        return EMPTY;
    }

    @Override
    public boolean isApplicable(String username, String password, Principal localPrincipal) {
        if(username != null && username.length() > 0 && password != null && password.length() > 0) {
            return ACCESS_TOKEN_PATTERN.matcher(password).matches();
        } else {
            return false;
        }
    }

    @Override
    public String getAdditionalFailureInformation() {
        return additionalFailureInformation;
    }
}