/*
 *
 * 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.client.handler;

import org.apache.qpid.AMQException;
import org.apache.qpid.client.protocol.AMQProtocolSession;
import org.apache.qpid.client.security.AMQCallbackHandler;
import org.apache.qpid.client.security.CallbackHandlerRegistry;
import org.apache.qpid.client.state.AMQState;
import org.apache.qpid.client.state.AMQStateManager;
import org.apache.qpid.client.state.StateAwareMethodListener;
import org.apache.qpid.common.ClientProperties;
import org.apache.qpid.common.QpidProperties;
import org.apache.qpid.framing.AMQShortString;
import org.apache.qpid.framing.ConnectionStartBody;
import org.apache.qpid.framing.ConnectionStartOkBody;
import org.apache.qpid.framing.FieldTable;
import org.apache.qpid.framing.FieldTableFactory;
import org.apache.qpid.framing.ProtocolVersion;
import org.apache.qpid.protocol.AMQMethodEvent;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.security.sasl.Sasl;
import javax.security.sasl.SaslClient;
import javax.security.sasl.SaslException;

import java.io.UnsupportedEncodingException;
import java.util.HashSet;
import java.util.StringTokenizer;

public class ConnectionStartMethodHandler implements StateAwareMethodListener
{
    private static final Logger _log = LoggerFactory.getLogger(ConnectionStartMethodHandler.class);

    private static final ConnectionStartMethodHandler _instance = new ConnectionStartMethodHandler();

    public static ConnectionStartMethodHandler getInstance()
    {
        return _instance;
    }

    private ConnectionStartMethodHandler()
    { }

    public void methodReceived(AMQStateManager stateManager, AMQProtocolSession protocolSession, AMQMethodEvent evt)
        throws AMQException
    {
        _log.debug("public void methodReceived(AMQStateManager stateManager, AMQProtocolSession protocolSession, "
            + "AMQMethodEvent evt): called");

        ConnectionStartBody body = (ConnectionStartBody) evt.getMethod();

        ProtocolVersion pv = new ProtocolVersion((byte) body.versionMajor, (byte) body.versionMinor);

        // For the purposes of interop, we can make the client accept the broker's version string.
        // If it does, it then internally records the version as being the latest one that it understands.
        // It needs to do this since frame lookup is done by version.
        if (Boolean.getBoolean("qpid.accept.broker.version") && !pv.isSupported())
        {

            pv = ProtocolVersion.getLatestSupportedVersion();
        }

        if (pv.isSupported())
        {
            protocolSession.setProtocolVersion(pv.getMajorVersion(), pv.getMinorVersion());

            try
            {
                // Used to hold the SASL mechanism to authenticate with.
                String mechanism;

                if (body.mechanisms == null)
                {
                    throw new AMQException(null, "mechanism not specified in ConnectionStart method frame", null);
                }
                else
                {
                    mechanism = chooseMechanism(body.mechanisms);
                    _log.debug("mechanism = " + mechanism);
                }

                if (mechanism == null)
                {
                    throw new AMQException(null, "No supported security mechanism found, passed: " + new String(body.mechanisms), null);
                }

                byte[] saslResponse;
                try
                {
                    SaslClient sc =
                        Sasl.createSaslClient(new String[] { mechanism }, null, "AMQP", "localhost", null,
                            createCallbackHandler(mechanism, protocolSession));
                    if (sc == null)
                    {
                        throw new AMQException(null, "Client SASL configuration error: no SaslClient could be created for mechanism " + mechanism
                            + ". Please ensure all factories are registered. See DynamicSaslRegistrar for "
                            + " details of how to register non-standard SASL client providers.", null);
                    }

                    protocolSession.setSaslClient(sc);
                    saslResponse = (sc.hasInitialResponse() ? sc.evaluateChallenge(new byte[0]) : null);
                }
                catch (SaslException e)
                {
                    protocolSession.setSaslClient(null);
                    throw new AMQException(null, "Unable to create SASL client: " + e, e);
                }

                if (body.locales == null)
                {
                    throw new AMQException(null, "Locales is not defined in Connection Start method", null);
                }

                final String locales = new String(body.locales, "utf8");
                final StringTokenizer tokenizer = new StringTokenizer(locales, " ");
                String selectedLocale = null;
                if (tokenizer.hasMoreTokens())
                {
                    selectedLocale = tokenizer.nextToken();
                }
                else
                {
                    throw new AMQException(null, "No locales sent from server, passed: " + locales, null);
                }

                stateManager.changeState(AMQState.CONNECTION_NOT_TUNED);
                FieldTable clientProperties = FieldTableFactory.newFieldTable();

                clientProperties.setString(new AMQShortString(ClientProperties.instance.toString()),
                    protocolSession.getClientID());
                clientProperties.setString(new AMQShortString(ClientProperties.product.toString()),
                    QpidProperties.getProductName());
                clientProperties.setString(new AMQShortString(ClientProperties.version.toString()),
                    QpidProperties.getReleaseVersion());
                clientProperties.setString(new AMQShortString(ClientProperties.platform.toString()), getFullSystemInfo());

                // AMQP version change: Hardwire the version to 0-8 (major=8, minor=0)
                // TODO: Connect this to the session version obtained from ProtocolInitiation for this session.
                // Be aware of possible changes to parameter order as versions change.
                protocolSession.writeFrame(ConnectionStartOkBody.createAMQFrame(evt.getChannelId(),
                        protocolSession.getProtocolMajorVersion(), protocolSession.getProtocolMinorVersion(),
                        clientProperties, // clientProperties
                        new AMQShortString(selectedLocale), // locale
                        new AMQShortString(mechanism), // mechanism
                        saslResponse)); // response

            }
            catch (UnsupportedEncodingException e)
            {
                throw new AMQException(null, "Unable to decode data: " + e, e);
            }
        }
        else
        {
            _log.error("Broker requested Protocol [" + body.versionMajor + "-" + body.versionMinor
                + "] which is not supported by this version of the client library");

            protocolSession.closeProtocolSession();
        }
    }

    private String getFullSystemInfo()
    {
        StringBuffer fullSystemInfo = new StringBuffer();
        fullSystemInfo.append(System.getProperty("java.runtime.name"));
        fullSystemInfo.append(", " + System.getProperty("java.runtime.version"));
        fullSystemInfo.append(", " + System.getProperty("java.vendor"));
        fullSystemInfo.append(", " + System.getProperty("os.arch"));
        fullSystemInfo.append(", " + System.getProperty("os.name"));
        fullSystemInfo.append(", " + System.getProperty("os.version"));
        fullSystemInfo.append(", " + System.getProperty("sun.os.patch.level"));

        return fullSystemInfo.toString();
    }

    private String chooseMechanism(byte[] availableMechanisms) throws UnsupportedEncodingException
    {
        final String mechanisms = new String(availableMechanisms, "utf8");
        StringTokenizer tokenizer = new StringTokenizer(mechanisms, " ");
        HashSet mechanismSet = new HashSet();
        while (tokenizer.hasMoreTokens())
        {
            mechanismSet.add(tokenizer.nextToken());
        }

        String preferredMechanisms = CallbackHandlerRegistry.getInstance().getMechanisms();
        StringTokenizer prefTokenizer = new StringTokenizer(preferredMechanisms, " ");
        while (prefTokenizer.hasMoreTokens())
        {
            String mech = prefTokenizer.nextToken();
            if (mechanismSet.contains(mech))
            {
                return mech;
            }
        }

        return null;
    }

    private AMQCallbackHandler createCallbackHandler(String mechanism, AMQProtocolSession protocolSession)
        throws AMQException
    {
        Class mechanismClass = CallbackHandlerRegistry.getInstance().getCallbackHandlerClass(mechanism);
        try
        {
            Object instance = mechanismClass.newInstance();
            AMQCallbackHandler cbh = (AMQCallbackHandler) instance;
            cbh.initialise(protocolSession);

            return cbh;
        }
        catch (Exception e)
        {
            throw new AMQException(null, "Unable to create callback handler: " + e, e);
        }
    }
}
