/*
 * 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.log4j.varia;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.ServerSocket;
import java.net.Socket;

import org.apache.log4j.RollingFileAppender;
import org.apache.log4j.helpers.LogLog;

/**
 * This appender listens on a socket on the port specified by the <b>Port</b>
 * property for a "RollOver" message. When such a message is received, the
 * underlying log file is rolled over and an acknowledgment message is sent back
 * to the process initiating the roll over.
 * 
 * <p>
 * This method of triggering roll over has the advantage of being operating
 * system independent, fast and reliable.
 * 
 * <p>
 * A simple application {@link Roller} is provided to initiate the roll over.
 * 
 * <p>
 * Note that the initiator is not authenticated. Anyone can trigger a rollover.
 * In production environments, it is recommended that you add some form of
 * protection to prevent undesired rollovers.
 * 
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @since version 0.9.0
 */
public class ExternallyRolledFileAppender extends RollingFileAppender {

    /**
     * The string constant sent to initiate a roll over. Current value of this
     * string constant is <b>RollOver</b>.
     */
    static final public String ROLL_OVER = "RollOver";

    /**
     * The string constant sent to acknowledge a roll over. Current value of this
     * string constant is <b>OK</b>.
     */
    static final public String OK = "OK";

    int port = 0;
    HUP hup;

    /**
     * The default constructor does nothing but calls its super-class constructor.
     */
    public ExternallyRolledFileAppender() {
    }

    /**
     * The <b>Port</b> [roperty is used for setting the port for listening to
     * external roll over messages.
     */
    public void setPort(int port) {
	this.port = port;
    }

    /**
     * Returns value of the <b>Port</b> option.
     */
    public int getPort() {
	return port;
    }

    /**
     * Start listening on the port specified by a preceding call to
     * {@link #setPort}.
     */
    public void activateOptions() {
	super.activateOptions();
	if (port != 0) {
	    if (hup != null) {
		hup.interrupt();
	    }
	    hup = new HUP(this, port);
	    hup.setDaemon(true);
	    hup.start();
	}
    }
}

class HUP extends Thread {

    int port;
    ExternallyRolledFileAppender er;

    HUP(ExternallyRolledFileAppender er, int port) {
	this.er = er;
	this.port = port;
    }

    public void run() {
	while (!isInterrupted()) {
	    try {
		ServerSocket serverSocket = new ServerSocket(port);
		while (true) {
		    Socket socket = serverSocket.accept();
		    LogLog.debug("Connected to client at " + socket.getInetAddress());
		    new Thread(new HUPNode(socket, er), "ExternallyRolledFileAppender-HUP").start();
		}
	    } catch (InterruptedIOException e) {
		Thread.currentThread().interrupt();
		e.printStackTrace();
	    } catch (IOException e) {
		e.printStackTrace();
	    } catch (RuntimeException e) {
		e.printStackTrace();
	    }
	}
    }
}

class HUPNode implements Runnable {

    Socket socket;
    DataInputStream dis;
    DataOutputStream dos;
    ExternallyRolledFileAppender er;

    public HUPNode(Socket socket, ExternallyRolledFileAppender er) {
	this.socket = socket;
	this.er = er;
	try {
	    dis = new DataInputStream(socket.getInputStream());
	    dos = new DataOutputStream(socket.getOutputStream());
	} catch (InterruptedIOException e) {
	    Thread.currentThread().interrupt();
	    e.printStackTrace();
	} catch (IOException e) {
	    e.printStackTrace();
	} catch (RuntimeException e) {
	    e.printStackTrace();
	}
    }

    public void run() {
	try {
	    String line = dis.readUTF();
	    LogLog.debug("Got external roll over signal.");
	    if (ExternallyRolledFileAppender.ROLL_OVER.equals(line)) {
		synchronized (er) {
		    er.rollOver();
		}
		dos.writeUTF(ExternallyRolledFileAppender.OK);
	    } else {
		dos.writeUTF("Expecting [RollOver] string.");
	    }
	    dos.close();
	} catch (InterruptedIOException e) {
	    Thread.currentThread().interrupt();
	    LogLog.error("Unexpected exception. Exiting HUPNode.", e);
	} catch (IOException e) {
	    LogLog.error("Unexpected exception. Exiting HUPNode.", e);
	} catch (RuntimeException e) {
	    LogLog.error("Unexpected exception. Exiting HUPNode.", e);
	}
    }
}
