//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util.component;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An AggregateLifeCycle is an {@link LifeCycle} implementation for a collection of contained beans.
 * <p>
 * Beans can be added the AggregateLifeCycle either as managed beans or as unmanaged beans.  A managed bean is started, stopped and destroyed with the aggregate.  
 * An unmanaged bean is associated with the aggregate for the purposes of {@link #dump()}, but it's lifecycle must be managed externally.
 * <p>
 * When a bean is added, if it is a {@link LifeCycle} and it is already started, then it is assumed to be an unmanaged bean.  
 * Otherwise the methods {@link #addBean(Object, boolean)}, {@link #manage(Object)} and {@link #unmanage(Object)} can be used to 
 * explicitly control the life cycle relationship.
 * <p>
 * If adding a bean that is shared between multiple {@link AggregateLifeCycle} instances, then it should be started before being added, so it is unmanaged, or 
 * the API must be used to explicitly set it as unmanaged.
 * <p>
 */
public class AggregateLifeCycle extends AbstractLifeCycle implements Destroyable, Dumpable
{
	private static final Logger LOG = LoggerFactory.getLogger(AggregateLifeCycle.class);
	private final List<Bean> _beans=new CopyOnWriteArrayList<Bean>();
	private boolean _started=false;

	private class Bean
	{
		Bean(Object b) 
		{
			_bean=b;
		}
		final Object _bean;
		volatile boolean _managed=true;
		
		public String toString()
		{
			return "{"+_bean+","+_managed+"}";
		}
	}

	/* ------------------------------------------------------------ */
	/**
	 * Start the managed lifecycle beans in the order they were added.
	 * @see org.eclipse.jetty.util.component.AbstractLifeCycle#doStart()
	 */
	@Override
	protected void doStart() throws Exception
	{
		for (Bean b:_beans)
		{
			if (b._managed && b._bean instanceof LifeCycle)
			{
				LifeCycle l=(LifeCycle)b._bean;
				if (!l.isRunning())
					l.start();
			}
		}
		// indicate that we are started, so that addBean will start other beans added.
		_started=true;
		super.doStart();
	}
	
	/* ------------------------------------------------------------ */
	/**
	 * Stop the joined lifecycle beans in the reverse order they were added.
	 * @see org.eclipse.jetty.util.component.AbstractLifeCycle#doStart()
	 */
	@Override
	protected void doStop() throws Exception
	{
		_started=false;
		super.doStop();
		List<Bean> reverse = new ArrayList<Bean>(_beans);
		Collections.reverse(reverse);
		for (Bean b:reverse)
		{
			if (b._managed && b._bean instanceof LifeCycle)
			{
				LifeCycle l=(LifeCycle)b._bean;
				if (l.isRunning())
					l.stop();
			}
		}
	}


	/* ------------------------------------------------------------ */
	/**
	 * Destroy the joined Destroyable beans in the reverse order they were added.
	 * @see org.eclipse.jetty.util.component.Destroyable#destroy()
	 */
	public void destroy()
	{
		List<Bean> reverse = new ArrayList<Bean>(_beans);
		Collections.reverse(reverse);
		for (Bean b:reverse)
		{
			if (b._bean instanceof Destroyable && b._managed)
			{
				Destroyable d=(Destroyable)b._bean;
				d.destroy();
			}
		}
		_beans.clear();
	}


	/* ------------------------------------------------------------ */
	/** Is the bean contained in the aggregate.
	 * @param bean
	 * @return True if the aggregate contains the bean
	 */
	public boolean contains(Object bean)
	{
		for (Bean b:_beans)
			if (b._bean==bean)
				return true;
		return false;
	}
	
	/* ------------------------------------------------------------ */
	/** Is the bean joined to the aggregate.
	 * @param bean
	 * @return True if the aggregate contains the bean and it is joined
	 */
	public boolean isManaged(Object bean)
	{
		for (Bean b:_beans)
			if (b._bean==bean)
				return b._managed;
		return false;
	}
	
	/* ------------------------------------------------------------ */
	/**
	 * Add an associated bean.
	 * If the bean is a {@link LifeCycle}, then it will be managed if it is not 
	 * already started and umanaged if it is already started. The {@link #addBean(Object, boolean)}
	 * method should be used if this is not correct, or the {@link #manage(Object)} and {@link #unmanage(Object)}
	 * methods may be used after an add to change the status.
	 * @param o the bean object to add
	 * @return true if the bean was added or false if it has already been added.
	 */
	public boolean addBean(Object o)
	{
		// beans are joined unless they are started lifecycles
		return addBean(o,!((o instanceof LifeCycle)&&((LifeCycle)o).isStarted()));
	}
	
	/* ------------------------------------------------------------ */
	/** Add an associated lifecycle.
	 * @param o The lifecycle to add
	 * @param managed True if the LifeCycle is to be joined, otherwise it will be disjoint.
	 * @return true if bean was added, false if already present.
	 */
	public boolean addBean(Object o, boolean managed)
	{
		if (contains(o))
			return false;
		
		Bean b = new Bean(o);
		b._managed=managed;
		_beans.add(b);
		
		if (o instanceof LifeCycle)
		{
			LifeCycle l=(LifeCycle)o;

			// Start the bean if we are started
			if (managed && _started)
			{
				try
				{
					l.start();
				}
				catch(Exception e)
				{
					throw new RuntimeException (e);
				}
			}
		}
		return true;
	}
	
	/* ------------------------------------------------------------ */
	/** Get dependent beans 
	 * @return List of beans.
	 */
	public Collection<Object> getBeans()
	{
		return getBeans(Object.class);
	}
	
	/* ------------------------------------------------------------ */
	/** Get dependent beans of a specific class
	 * @see #addBean(Object)
	 * @param clazz
	 * @return List of beans.
	 */
	public <T> List<T> getBeans(Class<T> clazz)
	{
		ArrayList<T> beans = new ArrayList<T>();
		for (Bean b:_beans)
		{
			if (clazz.isInstance(b._bean))
				beans.add((T)(b._bean));
		}
		return beans;
	}

	
	/* ------------------------------------------------------------ */
	/** Get dependent beans of a specific class.
	 * If more than one bean of the type exist, the first is returned.
	 * @see #addBean(Object)
	 * @param clazz
	 * @return bean or null
	 */
	public <T> T getBean(Class<T> clazz)
	{
		for (Bean b:_beans)
		{
			if (clazz.isInstance(b._bean))
				return (T)b._bean;
		}
		
		return null;
	}
	
	/* ------------------------------------------------------------ */
	/**
	 * Remove all associated bean.
	 */
	public void removeBeans ()
	{
		_beans.clear();
	}

	/* ------------------------------------------------------------ */
	/**
	 * Remove an associated bean.
	 */
	public boolean removeBean (Object o)
	{
		Iterator<Bean> i = _beans.iterator();
		while(i.hasNext())
		{
			Bean b=i.next();
			if (b._bean==o)
			{
				_beans.remove(b);
				return true;
			}
		}
		return false;
	}

	/* ------------------------------------------------------------ */
	public void dumpStdErr()
	{
		try
		{
			dump(System.err,"");
		}
		catch (IOException e)
		{
			LOG.warn("",e);
		}
	}
	
	/* ------------------------------------------------------------ */
	public String dump()
	{
		return dump(this);
	}    
	
	/* ------------------------------------------------------------ */
	public static String dump(Dumpable dumpable)
	{
		StringBuilder b = new StringBuilder();
		try
		{
			dumpable.dump(b,"");
		}
		catch (IOException e)
		{
			LOG.warn("",e);
		}
		return b.toString();
	}    

	/* ------------------------------------------------------------ */
	public void dump(Appendable out) throws IOException
	{
		dump(out,"");
	}

	/* ------------------------------------------------------------ */
	protected void dumpThis(Appendable out) throws IOException
	{
		out.append(String.valueOf(this)).append(" - ").append(getState()).append("\n");
	}

	/* ------------------------------------------------------------ */
	public static void dumpObject(Appendable out,Object o) throws IOException
	{
		try
		{
			if (o instanceof LifeCycle)
				out.append(String.valueOf(o)).append(" - ").append((AbstractLifeCycle.getState((LifeCycle)o))).append("\n");
			else
				out.append(String.valueOf(o)).append("\n");
		}
		catch(Throwable th)
		{
			out.append(" => ").append(th.toString()).append('\n');
		}
	}
	
	/* ------------------------------------------------------------ */
	public void dump(Appendable out,String indent) throws IOException
	{
		dumpThis(out);
		int size=_beans.size();
		if (size==0)
			return;
		int i=0;
		for (Bean b : _beans)
		{
			i++;

			out.append(indent).append(" +- ");
			if (b._managed)
			{
				if (b._bean instanceof Dumpable)
					((Dumpable)b._bean).dump(out,indent+(i==size?"    ":" |  "));
				else 
					dumpObject(out,b._bean);
			}
			else 
				dumpObject(out,b._bean);
		}

		if (i!=size)
			out.append(indent).append(" |\n");
	}
	
	/* ------------------------------------------------------------ */
	public static void dump(Appendable out,String indent,Collection<?>... collections) throws IOException
	{
		if (collections.length==0)
			return;
		int size=0;
		for (Collection<?> c : collections)
			size+=c.size();    
		if (size==0)
			return;

		int i=0;
		for (Collection<?> c : collections)
		{
			for (Object o : c)
			{
				i++;
				out.append(indent).append(" +- ");

				if (o instanceof Dumpable)
					((Dumpable)o).dump(out,indent+(i==size?"    ":" |  "));
				else 
					dumpObject(out,o);
			}
			
			if (i!=size)
				out.append(indent).append(" |\n");          
		}
	}
}