/*
 * Copyright DataStax, Inc.
 *
 * 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 com.datastax.driver.core;

import com.google.common.base.Charsets;
import com.google.common.collect.ImmutableMap;

import java.net.InetSocketAddress;
import java.util.Map;

/**
 * A simple {@code AuthProvider} implementation.
 * <p/>
 * This provider allows to programmatically define authentication
 * information that will then apply to all hosts. The
 * PlainTextAuthenticator instances it returns support SASL
 * authentication using the PLAIN mechanism for version 2 (or above) of the
 * CQL native protocol.
 */
public class PlainTextAuthProvider implements AuthProvider {

    private volatile String username;
    private volatile String password;

    /**
     * Creates a new simple authentication information provider with the
     * supplied credentials.
     *
     * @param username to use for authentication requests
     * @param password to use for authentication requests
     */
    public PlainTextAuthProvider(String username, String password) {
        this.username = username;
        this.password = password;
    }

    /**
     * Changes the user name.
     * <p/>
     * The new credentials will be used for all connections initiated after this method was called.
     *
     * @param username the new name.
     */
    public void setUsername(String username) {
        this.username = username;
    }

    /**
     * Changes the password.
     * <p/>
     * The new credentials will be used for all connections initiated after this method was called.
     *
     * @param password the new password.
     */
    public void setPassword(String password) {
        this.password = password;
    }

    /**
     * Uses the supplied credentials and the SASL PLAIN mechanism to login
     * to the server.
     *
     * @param host          the Cassandra host with which we want to authenticate
     * @param authenticator the configured authenticator on the host
     * @return an Authenticator instance which can be used to perform
     * authentication negotiations on behalf of the client
     */
    @Override
    public Authenticator newAuthenticator(InetSocketAddress host, String authenticator) {
        return new PlainTextAuthenticator(username, password);
    }

    /**
     * Simple implementation of {@link Authenticator} which can
     * perform authentication against Cassandra servers configured
     * with PasswordAuthenticator.
     */
    private static class PlainTextAuthenticator extends ProtocolV1Authenticator implements Authenticator {

        private final byte[] username;
        private final byte[] password;

        public PlainTextAuthenticator(String username, String password) {
            this.username = username.getBytes(Charsets.UTF_8);
            this.password = password.getBytes(Charsets.UTF_8);
        }

        @Override
        public byte[] initialResponse() {
            byte[] initialToken = new byte[username.length + password.length + 2];
            initialToken[0] = 0;
            System.arraycopy(username, 0, initialToken, 1, username.length);
            initialToken[username.length + 1] = 0;
            System.arraycopy(password, 0, initialToken, username.length + 2, password.length);
            return initialToken;
        }

        @Override
        public byte[] evaluateChallenge(byte[] challenge) {
            return null;
        }

        @Override
        public void onAuthenticationSuccess(byte[] token) {
            // no-op, the server should send nothing anyway
        }

        @Override
        Map<String, String> getCredentials() {
            return ImmutableMap.of("username", new String(username, Charsets.UTF_8),
                    "password", new String(password, Charsets.UTF_8));
        }
    }
}
