/*
 * 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.logging.log4j.core.net;

import java.io.IOException;
import java.io.OutputStream;
import java.io.Serializable;
import java.net.ConnectException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;

import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.appender.AppenderLoggingException;
import org.apache.logging.log4j.core.appender.ManagerFactory;
import org.apache.logging.log4j.core.appender.OutputStreamManager;
import org.apache.logging.log4j.core.util.Log4jThread;
import org.apache.logging.log4j.core.util.NullOutputStream;
import org.apache.logging.log4j.util.Strings;

/**
 * Manager of TCP Socket connections.
 */
public class TcpSocketManager extends AbstractSocketManager {
    /**
      The default reconnection delay (30000 milliseconds or 30 seconds).
     */
    public static final int DEFAULT_RECONNECTION_DELAY_MILLIS   = 30000;
    /**
      The default port number of remote logging server (4560).
     */
    private static final int DEFAULT_PORT = 4560;

    private static final TcpSocketManagerFactory FACTORY = new TcpSocketManagerFactory();

    private final int reconnectionDelay;

    private Reconnector reconnector;

    private Socket socket;

    private final boolean retry;

    private final boolean immediateFail;
    
    private final int connectTimeoutMillis;

    /**
     * The Constructor.
     * @param name The unique name of this connection.
     * @param os The OutputStream.
     * @param socket The Socket.
     * @param inetAddress The Internet address of the host.
     * @param host The name of the host.
     * @param port The port number on the host.
     * @param connectTimeoutMillis the connect timeout in milliseconds.
     * @param delay Reconnection interval.
     * @param immediateFail True if the write should fail if no socket is immediately available.
     * @param layout The Layout.
     * @param bufferSize The buffer size.
     */
    public TcpSocketManager(final String name, final OutputStream os, final Socket socket, final InetAddress inetAddress,
                            final String host, final int port, final int connectTimeoutMillis, final int delay,
                            final boolean immediateFail, final Layout<? extends Serializable> layout, final int bufferSize) {
        super(name, os, inetAddress, host, port, layout, true, bufferSize);
        this.connectTimeoutMillis = connectTimeoutMillis;
        this.reconnectionDelay = delay;
        this.socket = socket;
        this.immediateFail = immediateFail;
        retry = delay > 0;
        if (socket == null) {
            reconnector = createReconnector();
            reconnector.start();
        }
    }

    /**
     * Obtain a TcpSocketManager.
     * @param host The host to connect to.
     * @param port The port on the host.
     * @param connectTimeoutMillis the connect timeout in milliseconds
     * @param reconnectDelayMillis The interval to pause between retries.
     * @param bufferSize The buffer size.
     * @return A TcpSocketManager.
     */
    public static TcpSocketManager getSocketManager(final String host, int port, final int connectTimeoutMillis,
            int reconnectDelayMillis, final boolean immediateFail, final Layout<? extends Serializable> layout, final int bufferSize) {
        if (Strings.isEmpty(host)) {
            throw new IllegalArgumentException("A host name is required");
        }
        if (port <= 0) {
            port = DEFAULT_PORT;
        }
        if (reconnectDelayMillis == 0) {
            reconnectDelayMillis = DEFAULT_RECONNECTION_DELAY_MILLIS;
        }
        return (TcpSocketManager) getManager("TCP:" + host + ':' + port, new FactoryData(
                host, port, connectTimeoutMillis, reconnectDelayMillis, immediateFail, layout, bufferSize), FACTORY);
    }

    @Override
    protected void write(final byte[] bytes, final int offset, final int length, final boolean immediateFlush)  {
        if (socket == null) {
            if (reconnector != null && !immediateFail) {
                reconnector.latch();
            }
            if (socket == null) {
                final String msg = "Error writing to " + getName() + " socket not available";
                throw new AppenderLoggingException(msg);
            }
        }
        synchronized (this) {
            try {
                final OutputStream outputStream = getOutputStream();
                outputStream.write(bytes, offset, length);
                if (immediateFlush) {
                    outputStream.flush();
                }
            } catch (final IOException ex) {
                if (retry && reconnector == null) {
                    reconnector = createReconnector();
                    reconnector.start();
                }
                final String msg = "Error writing to " + getName();
                throw new AppenderLoggingException(msg, ex);
            }
        }
    }

    @Override
    protected synchronized boolean closeOutputStream() {
        final boolean closed = super.closeOutputStream();
        if (reconnector != null) {
            reconnector.shutdown();
            reconnector.interrupt();
            reconnector = null;
        }
        final Socket oldSocket = socket;
        socket = null;
        if (oldSocket != null) {
            try {
                oldSocket.close();
            } catch (final IOException e) {
                LOGGER.error("Could not close socket {}", socket);
                return false;
            }
        }
        return closed;
    }

    public int getConnectTimeoutMillis() {
        return connectTimeoutMillis;
    }

    /**
     * Gets this TcpSocketManager's content format. Specified by:
     * <ul>
     * <li>Key: "protocol" Value: "tcp"</li>
     * <li>Key: "direction" Value: "out"</li>
     * </ul>
     * 
     * @return Map of content format keys supporting TcpSocketManager
     */
    @Override
    public Map<String, String> getContentFormat() {
        final Map<String, String> result = new HashMap<>(super.getContentFormat());
        result.put("protocol", "tcp");
        result.put("direction", "out");
        return result;
    }

    /**
     * Handles reconnecting to a Thread.
     */
    private class Reconnector extends Log4jThread {

        private final CountDownLatch latch = new CountDownLatch(1);

        private boolean shutdown = false;

        private final Object owner;

        public Reconnector(final OutputStreamManager owner) {
            super("TcpSocketManager-Reconnector");
            this.owner = owner;
        }

        public void latch()  {
            try {
                latch.await();
            } catch (final InterruptedException ex) {
                // Ignore the exception.
            }
        }

        public void shutdown() {
            shutdown = true;
        }

        @Override
        public void run() {
            while (!shutdown) {
                try {
                    sleep(reconnectionDelay);
                    final Socket sock = createSocket(inetAddress, port);
                    final OutputStream newOS = sock.getOutputStream();
                    synchronized (owner) {
                        try {
                            getOutputStream().close();
                        } catch (final IOException ioe) {
                            // Ignore this.
                        }

                        setOutputStream(newOS);
                        socket = sock;
                        reconnector = null;
                        shutdown = true;
                    }
                    LOGGER.debug("Connection to " + host + ':' + port + " reestablished.");
                } catch (final InterruptedException ie) {
                    LOGGER.debug("Reconnection interrupted.");
                } catch (final ConnectException ex) {
                    LOGGER.debug(host + ':' + port + " refused connection");
                } catch (final IOException ioe) {
                    LOGGER.debug("Unable to reconnect to " + host + ':' + port);
                } finally {
                    latch.countDown();
                }
            }
        }
    }

    private Reconnector createReconnector() {
        final Reconnector recon = new Reconnector(this);
        recon.setDaemon(true);
        recon.setPriority(Thread.MIN_PRIORITY);
        return recon;
    }

    protected Socket createSocket(final InetAddress host, final int port) throws IOException {
        return createSocket(host.getHostName(), port);
    }

    protected Socket createSocket(final String host, final int port) throws IOException {
        final InetSocketAddress address = new InetSocketAddress(host, port);
        final Socket newSocket = new Socket();
        newSocket.connect(address, connectTimeoutMillis);
        return newSocket;
    }

    /**
     * Data for the factory.
     */
    private static class FactoryData {
        private final String host;
        private final int port;
        private final int connectTimeoutMillis;
        private final int reconnectDelayMillis;
        private final boolean immediateFail;
        private final Layout<? extends Serializable> layout;
        private final int bufferSize;

        public FactoryData(final String host, final int port, final int connectTimeoutMillis, final int reconnectDelayMillis,
                           final boolean immediateFail, final Layout<? extends Serializable> layout, final int bufferSize) {
            this.host = host;
            this.port = port;
            this.connectTimeoutMillis = connectTimeoutMillis;
            this.reconnectDelayMillis = reconnectDelayMillis;
            this.immediateFail = immediateFail;
            this.layout = layout;
            this.bufferSize = bufferSize;
        }
    }

    /**
     * Factory to create a TcpSocketManager.
     */
    protected static class TcpSocketManagerFactory implements ManagerFactory<TcpSocketManager, FactoryData> {
        @Override
        public TcpSocketManager createManager(final String name, final FactoryData data) {

            InetAddress inetAddress;
            OutputStream os;
            try {
                inetAddress = InetAddress.getByName(data.host);
            } catch (final UnknownHostException ex) {
                LOGGER.error("Could not find address of " + data.host, ex, ex);
                return null;
            }
            try {
                // LOG4J2-1042
                final Socket socket = new Socket();
                socket.connect(new InetSocketAddress(data.host, data.port), data.connectTimeoutMillis);
                os = socket.getOutputStream();
                return new TcpSocketManager(name, os, socket, inetAddress, data.host, data.port,
                        data.connectTimeoutMillis, data.reconnectDelayMillis, data.immediateFail, data.layout, data.bufferSize);
            } catch (final IOException ex) {
                LOGGER.error("TcpSocketManager (" + name + ") " + ex, ex);
                os = NullOutputStream.getInstance();
            }
            if (data.reconnectDelayMillis == 0) {
                return null;
            }
            return new TcpSocketManager(name, os, null, inetAddress, data.host, data.port, data.connectTimeoutMillis,
                    data.reconnectDelayMillis, data.immediateFail, data.layout, data.bufferSize);
        }
    }

}
