/**
 * 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.storm.security.auth.sasl;

import java.io.Closeable;
import java.io.IOException;
import java.net.Socket;
import java.security.Principal;
import java.util.Map;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import javax.security.auth.Subject;
import javax.security.auth.login.Configuration;
import javax.security.sasl.SaslServer;
import org.apache.storm.security.auth.ITransportPlugin;
import org.apache.storm.security.auth.ReqContext;
import org.apache.storm.security.auth.ThriftConnectionType;
import org.apache.storm.security.auth.kerberos.NoOpTTrasport;
import org.apache.storm.thrift.TException;
import org.apache.storm.thrift.TProcessor;
import org.apache.storm.thrift.protocol.TBinaryProtocol;
import org.apache.storm.thrift.protocol.TProtocol;
import org.apache.storm.thrift.server.TServer;
import org.apache.storm.thrift.server.TThreadPoolServer;
import org.apache.storm.thrift.transport.TSaslServerTransport;
import org.apache.storm.thrift.transport.TServerSocket;
import org.apache.storm.thrift.transport.TSocket;
import org.apache.storm.thrift.transport.TTransport;
import org.apache.storm.thrift.transport.TTransportException;
import org.apache.storm.thrift.transport.TTransportFactory;
import org.apache.storm.utils.ExtendedThreadPoolExecutor;

/**
 * Base class for SASL authentication plugin.
 */
public abstract class SaslTransportPlugin implements ITransportPlugin, Closeable {
    protected ThriftConnectionType type;
    protected Map<String, Object> conf;
    private int port;

    @Override
    public void prepare(ThriftConnectionType type, Map<String, Object> conf) {
        this.type = type;
        this.conf = conf;
    }

    @Override
    public TServer getServer(TProcessor processor) throws IOException, TTransportException {
        int configuredPort = type.getPort(conf);
        Integer socketTimeout = type.getSocketTimeOut(conf);
        TTransportFactory serverTransportFactory = getServerTransportFactory(type.isImpersonationAllowed());
        TServerSocket serverTransport = null;
        if (socketTimeout != null) {
            serverTransport = new TServerSocket(configuredPort, socketTimeout);
        } else {
            serverTransport = new TServerSocket(configuredPort);
        }
        this.port = serverTransport.getServerSocket().getLocalPort();
        int numWorkerThreads = type.getNumThreads(conf);
        Integer queueSize = type.getQueueSize(conf);

        TThreadPoolServer.Args serverArgs = new TThreadPoolServer.Args(serverTransport)
            .processor(new TUGIWrapProcessor(processor))
            .minWorkerThreads(numWorkerThreads)
            .maxWorkerThreads(numWorkerThreads)
            .protocolFactory(new TBinaryProtocol.Factory(false, true));

        if (serverTransportFactory != null) {
            serverArgs.transportFactory(serverTransportFactory);
        }
        BlockingQueue<Runnable> workQueue = new SynchronousQueue<>();
        if (queueSize != null) {
            workQueue = new ArrayBlockingQueue<>(queueSize);
        }
        ThreadPoolExecutor executorService = new ExtendedThreadPoolExecutor(numWorkerThreads, numWorkerThreads,
                                                                            60, TimeUnit.SECONDS, workQueue);
        serverArgs.executorService(executorService);
        return new TThreadPoolServer(serverArgs);
    }

    @Override
    public void close() {
    }

    /**
     * Create the transport factory needed for serving.  All subclass must implement this method.
     *
     * @param impersonationAllowed true if SASL impersonation should be allowed, else false.
     * @return server transport factory
     *
     * @throws IOException on any error.
     */
    protected abstract TTransportFactory getServerTransportFactory(boolean impersonationAllowed) throws IOException;

    @Override
    public int getPort() {
        return this.port;
    }


    /**
     * Processor that pulls the SaslServer object out of the transport, and assumes the remote user's UGI before calling through to the
     * original processor. This is used on the server side to set the UGI for each specific call.
     */
    @SuppressWarnings("checkstyle:AbbreviationAsWordInName")
    private static class TUGIWrapProcessor implements TProcessor {
        final TProcessor wrapped;

        TUGIWrapProcessor(TProcessor wrapped) {
            this.wrapped = wrapped;
        }

        @Override
        public boolean process(final TProtocol inProt, final TProtocol outProt) throws TException {
            //populating request context
            ReqContext reqContext = ReqContext.context();

            TTransport trans = inProt.getTransport();
            //Sasl transport
            TSaslServerTransport saslTrans = (TSaslServerTransport) trans;

            if (trans instanceof NoOpTTrasport) {
                return false;
            }

            //remote address
            TSocket tsocket = (TSocket) saslTrans.getUnderlyingTransport();
            Socket socket = tsocket.getSocket();
            reqContext.setRemoteAddress(socket.getInetAddress());

            //remote subject
            SaslServer saslServer = saslTrans.getSaslServer();
            String authId = saslServer.getAuthorizationID();
            Subject remoteUser = new Subject();
            remoteUser.getPrincipals().add(new User(authId));
            reqContext.setSubject(remoteUser);

            //invoke service handler
            return wrapped.process(inProt, outProt);
        }
    }

    public static class User implements Principal {
        private final String name;

        public User(String name) {
            this.name = name;
        }

        /**
         * Get the full name of the user.
         */
        @Override
        public String getName() {
            return name;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            return !(o == null || getClass() != o.getClass()) && (name.equals(((User) o).name));
        }

        @Override
        public int hashCode() {
            return name.hashCode();
        }

        @Override
        public String toString() {
            return name;
        }
    }
}