//   Copyright 2012 Georg-August-Universität Göttingen, Germany
//
//   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 de.ugoe.cs.autoquest.httpmonitor;

import java.util.Timer;
import java.util.TimerTask;

import de.ugoe.cs.autoquest.httpmonitor.exchange.HttpExchange;
import de.ugoe.cs.util.console.Console;

/**
 * <p>
 * The log manager handles an {@link HttpMonitorOutputWriter} to perform the logging
 * of recorded exchanges. It initializes the writer if the first exchange is received and it
 * closes the writer if for a specific period of time no further exchange was received. The writer
 * themselves considers log rotation. For handling exchanges, the {@link HttpMonitorExchangeHandler}
 * mechanism is used.
 * </p>
 * 
 * @author Patrick Harms
 */
public class HttpMonitorLogManager implements HttpMonitorComponent, HttpMonitorExchangeHandler {
    
    /**
     * the timeout after which the writer is closed
     */
    private static final int SESSION_TIMEOUT = 10 * 60 * 1000;
    
    /**
     * the directory into which the log files shall be written
     */
    private String logFileBaseDir;

    /**
     * the writer for the log file
     */
    private HttpMonitorOutputWriter writer;

    /**
     * a timer used to detect timeouts
     */
    private Timer logFileMonitorTimer;

    /**
     * <p>
     * initializes the log manager with the directory into which the log files shall be stored
     * </p>
     *
     * @param logFileBaseDir the directory into which the log files shall be stored
     */
    public HttpMonitorLogManager(String logFileBaseDir) {
        this.logFileBaseDir = logFileBaseDir;
    }

    /* (non-Javadoc)
     * @see de.ugoe.cs.autoquest.htmlmonitor.HttpMonitorComponent#init()
     */
    @Override
    public synchronized void init() throws IllegalStateException, HttpMonitorException {
        if (logFileMonitorTimer != null) {
            throw new IllegalStateException("already initialized");
        }
        
        logFileMonitorTimer = new Timer();
    }

    /* (non-Javadoc)
     * @see de.ugoe.cs.autoquest.htmlmonitor.HttpMonitorComponent#start()
     */
    @Override
    public synchronized void start() throws IllegalStateException, HttpMonitorException {
        if (logFileMonitorTimer == null) {
            throw new IllegalStateException("not initialized");
        }
        
        logFileMonitorTimer.schedule
            (new LogFileMonitorTimerTask(), SESSION_TIMEOUT / 2, SESSION_TIMEOUT / 2);
    }

    /* (non-Javadoc)
     * @see de.ugoe.cs.autoquest.htmlmonitor.HttpMonitorComponent#stop()
     */
    @Override
    public synchronized void stop() {
        if (logFileMonitorTimer != null) {
            logFileMonitorTimer.cancel();
        }
            
        if (writer != null) {
            writer.stop();
        }
        
        writer = null;
    }

    /* (non-Javadoc)
     * @see HttpMonitoringListener#handleHttpMessage()
     */
    @Override
    public synchronized void handleHttpExchange(HttpExchange httpExchange) {
        try {
            if (writer == null) {
                writer = new HttpMonitorOutputWriter(logFileBaseDir);
                writer.init();
            }

            writer.handleHttpExchange(httpExchange);
        }
        catch (Exception e) {
            Console.printerrln("could not handle message: " + e);
            Console.logException(e);
            
            // determine, if the writer exists but is not able to log something. In this case,
            // destroy the writer (part of the message may be logged twice through this).
            if (writer != null) {
                try {
                    writer.handleHttpExchange(httpExchange);
                }
                catch (Exception e1) {
                    synchronized (this) {
                        writer.stop();
                        writer = null;
                    }
                }
            }
        }
    }

    /**
     * <p>
     * internal timer task used for detecting session timeouts of clients
     * </p>
     * 
     * @author Patrick Harms
     */
    public class LogFileMonitorTimerTask extends TimerTask {

        /* (non-Javadoc)
         * @see java.lang.Runnable#run()
         */
        @Override
        public void run() {
            synchronized (HttpMonitorLogManager.this) {
                if (System.currentTimeMillis() - writer.getLastUpdate() > SESSION_TIMEOUT) {
                    writer.stop();
                    writer = null;
                }
            }
        }

    }

}