/**
 * Helios, OpenSource Monitoring
 * Brought to you by the Helios Development Group
 *
 * Copyright 2007, Helios Development Group and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 
 *
 */
package org.helios.apmrouter.monitor;

import org.helios.apmrouter.jmx.ConfigurationHelper;
import org.helios.apmrouter.jmx.ScheduledThreadPoolFactory;
import org.helios.apmrouter.trace.ITracer;
import org.helios.apmrouter.trace.TracerFactory;
import org.helios.apmrouter.util.SystemClock;
import org.helios.apmrouter.util.SystemClock.ElapsedTime;

import java.util.Properties;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * <p>Title: AbstractMonitor</p>
 * <p>Description: Base class for monitor implementations</p> 
 * <p>Company: Helios Development Group LLC</p>
 * @author Whitehead (nwhitehead AT heliosdev DOT org)
 * <p><code>org.helios.apmrouter.monitor.AbstractMonitor</code></p>
 */

public abstract class AbstractMonitor implements Monitor, Runnable, AbstractMonitorMXBean {
	/** The scheduler shared amongst all monitor instances */
	protected static final ScheduledThreadPoolExecutor scheduler = ScheduledThreadPoolFactory.newScheduler("Monitor");
	/** The tracer instance */
	protected final ITracer tracer = TracerFactory.getTracer();
	/** The scheduler handle for this monitor */
	protected ScheduledFuture<?> scheduleHandle = null;
	/** The collection period in ms. */
	protected long collectionPeriod = -1L;
	/** The collection sweep, starting at 0 and incrementing each period */
	protected long collectionSweep = 0;
	/** The properties set by XML config for this monitor */
	protected Properties configProps = new Properties();
	/** Indicates if the monitor is started */
	protected final AtomicBoolean started = new AtomicBoolean(false);
	/** Indicates if the monitor is scheduled for a start */
	protected final AtomicBoolean startScheduled = new AtomicBoolean(false);
	
	static {
		Runtime.getRuntime().addShutdownHook(new Thread(){
			@Override
			public void run() {
				scheduler.shutdownNow();
			}
		});
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.AbstractMonitorMXBean#collect()
	 */
	@Override
	public void collect() {
		SystemClock.startTimer();
		doCollect(collectionSweep);
		ElapsedTime et = SystemClock.endTimer();
		collectionSweep++;
		tracer.traceGauge(et.elapsedMs, "ElpasedTimeMs", "Monitors", getClass().getSimpleName());
	}
	
	/**
	 * Sets the configuration properties on this monitor
	 * @param p The configuration properties
	 */
	public void setProperties(Properties p) {
		if(p!=null) configProps.putAll(p);
	}
	
	/**
	 * {@inheritDoc}
	 * @see java.lang.Runnable#run()
	 */
	@Override
	public void run() {
		try { collect(); } catch (Throwable t) {}
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.AbstractMonitorMXBean#getCollectPeriod()
	 */
	@Override
	public long getCollectPeriod() {	
		if(collectionPeriod==-1L) {
			collectionPeriod = ConfigurationHelper.getLongSystemThenEnvProperty("org.helios.apmrouter." + getClass().getSimpleName().toLowerCase() + ".period", 15000L);
		}
		return collectionPeriod;
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.AbstractMonitorMXBean#setCollectPeriod(long)
	 */
	@Override
	public void setCollectPeriod(long period) {
		collectionPeriod = period;
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.AbstractMonitorMXBean#startMonitor()
	 */
	@Override
	public void startMonitor() {
		long collectPeriod = getCollectPeriod();
		scheduleHandle = scheduler.scheduleWithFixedDelay(this, 1, collectPeriod, TimeUnit.MILLISECONDS);
		log("Started collection schedule with frequency of ["+ collectPeriod + "] ms.");
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.Monitor#startMonitor(long)
	 */
	@Override
	public void startMonitor(long seconds) {
		log("Delaying start of [" + getClass().getSimpleName() + "] for [" + seconds + "] seconds");
		scheduler.schedule(new Runnable(){
			public void run() { startMonitor(); }
		}, seconds, TimeUnit.SECONDS);
	}
	
	/**
	 * {@inheritDoc}
	 * @see org.helios.apmrouter.monitor.AbstractMonitorMXBean#stopMonitor()
	 */
	@Override
	public void stopMonitor() {
		if(scheduleHandle!=null) {
			scheduleHandle.cancel(false);
			log("Stopped collection");
		}
	}
	
	/**
	 * Simple out logger
	 * @param msg the message
	 */
	public void log(Object msg) {
		System.out.println("[" + getClass().getSimpleName() + "]:" + msg);
	}
	
	/**
	 * Directs a concrete monitor to collect and trace
	 * @param collectionSweep The collection sweep, starting at 0 and incrementing each period
	 */
	protected abstract void doCollect(long collectionSweep);
}