/*
 * Created on 22-Sep-2004
 * Created by Paul Gardner
 * Copyright (C) 2004 Aelitis, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program 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 General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 * 
 * AELITIS, SARL au capital de 30,000 euros
 * 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
 *
 */

package org.gudy.azureus2.core3.util;

import java.util.*;

/**
 * @author parg
 *
 */

public abstract class 
AEMonSem 
{
	protected static boolean	DEBUG					= AEDiagnostics.DEBUG_MONITOR_SEM_USAGE;
	protected static boolean	DEBUG_CHECK_DUPLICATES	= false;
	
	protected static long		DEBUG_TIMER				= 30000;
	
	protected static AEDiagnosticsLogger				diag_logger;
	
	private static ThreadLocal		tls	= 
		new ThreadLocal()
		{
			public Object
			initialValue()
			{
				return( new Stack());
			}
		};
	
	private static long	monitor_id_next;
	private static long	semaphore_id_next;
	
	private static Map 	debug_traces		= new HashMap();
	private static List	debug_recursions	= new ArrayList();
	private static List	debug_reciprocals	= new ArrayList();
	//private static List	debug_sem_in_mon	= new ArrayList();
	
	
	
	private static Map	debug_name_mapping		= new WeakHashMap();
	private static Map	debug_monitors			= new WeakHashMap();
	private static Map	debug_semaphores		= new WeakHashMap();
	
	static{
		if ( DEBUG ){
			
				// add know and validated exceptions 
			
			debug_recursions.add( "ResourceDownloader" );		// known tree recursion
			debug_recursions.add( "ConnectionPool:CP" );		// known tree recursion
			debug_recursions.add( "(S)RDRretry" );				// RDretry sem left on stack after 1st d/l so appears recursive on subsequent
			
			diag_logger	= AEDiagnostics.getLogger( "monsem" );
		
			new Timer("AEMonSem").addPeriodicEvent(
					DEBUG_TIMER,
					new TimerEventPerformer()
					{
						public void
						perform(
							TimerEvent	event )
						{
							check();
						}
					});
		}
	}
	
	protected static void
	check()
	{
		List	active				= new ArrayList();
		List	waiting_monitors	= new ArrayList();
		List	busy_monitors		= new ArrayList();
		List	waiting_semaphores	= new ArrayList();
		
		synchronized( AEMonSem.class ){

			diag_logger.log( 
					"AEMonSem: mid = " + monitor_id_next +
					", sid = " + semaphore_id_next +
					", monitors = " + debug_monitors.size() + 
					", semaphores = " + debug_semaphores.size() + 
					", names = " + debug_name_mapping.size() + 
					", traces = " + debug_traces.size());

		
			Iterator 	it = debug_monitors.keySet().iterator();
			
			long	new_mon_entries	= 0;
			
			while (it.hasNext()){
				
				AEMonitor	monitor = (AEMonitor)it.next();
							
				long	diff = monitor.entry_count - monitor.last_entry_count;
				
				if (  diff != 0 ){
					
					active.add( monitor );
					
					new_mon_entries += diff;
				}
				
				if (monitor.waiting > 0 ){
					
					waiting_monitors.add( monitor );
					
				}else if ( monitor.owner != null ){
					
					busy_monitors.add( monitor );
				}
			}
			
			it = debug_semaphores.keySet().iterator();
			
			long	new_sem_entries	= 0;
			
			while (it.hasNext()){
				
				AEMonSem	semaphore = (AEMonSem)it.next();
							
				long	diff = semaphore.entry_count - semaphore.last_entry_count;
				
				if (  diff != 0 ){
					
					active.add( semaphore );

					new_sem_entries += diff;
				}
				
				if (semaphore.waiting > 0 ){
					
					waiting_semaphores.add( semaphore );
				}
			}		
			
			diag_logger.log( 
					"    activity: monitors = " + new_mon_entries + " - " + (new_mon_entries / (DEBUG_TIMER/1000)) + 
					"/sec, semaphores = " + new_sem_entries + " - " +
					(new_sem_entries / (DEBUG_TIMER/1000)) + "/sec ");
		}
		
		AEMonSem[]	x = new AEMonSem[active.size()];
		
		active.toArray(x);
		
			// sort by name and merge values
		
		Arrays.sort(
				x,
				new Comparator()
				{
					public int
					compare(
						Object	o1,
						Object	o2 )
					{
						AEMonSem	a1 = (AEMonSem)o1;
						AEMonSem	a2 = (AEMonSem)o2;
						
						return( a1.name.compareTo( a2.name ));
					}
					
				});
		
		AEMonSem	current 		= null;
		long		current_total	= 0;
		
		Object[][]	total_x = new Object[x.length][];
		
		int	total_pos	= 0;
		
		for (int i=0;i<x.length;i++){
		
			AEMonSem	ms = x[i];
			
			long	diff = ms.entry_count - ms.last_entry_count;
			
			if ( current == null ){
			
				current	= ms;
	
			}else{
				
				if( current.name.equals( ms.name )){
	
					current_total += diff;
					
				}else{
					total_x[total_pos++] = new Object[]{ current.name, new Long( current_total )};
					
					current 		= ms;
					current_total	= diff;
				}
			}
		}
		
		if (current != null ){
			
			total_x[total_pos++] = new Object[]{ current.name, new Long( current_total )};
		}
		
		Arrays.sort(
			total_x,
			new Comparator()
			{
				public int
				compare(
					Object	o1,
					Object	o2 )
				{
					Object[]	a1 = (Object[])o1;
					Object[]	a2 = (Object[])o2;
					
					if ( a1 == null && a2 == null){
						
						return(0);
						
					}else if ( a1 == null ){
						
						return( 1 );
						
					}else if ( a2 == null ){
						
						return( -1 );
					}
					
					long	a1_count = ((Long)a1[1]).longValue();
					long	a2_count = ((Long)a2[1]).longValue();
					
					return((int)(a2_count - a1_count ));
				}
				
			});
			
		

		
		String	top_act_str = "    top activity: ";
		
		for (int i=0;i<Math.min(10,total_x.length);i++){
			
			if ( total_x[i] != null ){
			
				top_act_str +=  (i==0?"":", ") + total_x[i][0] + " = " + (total_x[i][1]);
			}
		}
		
		diag_logger.log( top_act_str );
	
		if ( waiting_monitors.size() > 0 ){
			
			diag_logger.log( "    waiting monitors" );
			
			for (int i=0;i<waiting_monitors.size();i++){
				
				AEMonSem	ms = (AEMonSem)waiting_monitors.get(i);
				
				Thread last_waiter = ((AEMonitor)ms).last_waiter;

				diag_logger.log( "        [" + (last_waiter==null?"<waiter lost>":last_waiter.getName()) + "] " +  ms.name + " - " + ms.last_trace_key );
			}
		}
		
		if ( busy_monitors.size() > 0 ){
			
			diag_logger.log( "    busy monitors" );
			
			for (int i=0;i<busy_monitors.size();i++){
				
				AEMonSem	ms = (AEMonSem)busy_monitors.get(i);
				
				Thread owner = ((AEMonitor)ms).owner;
				
				diag_logger.log( "        [" + (owner==null?"<owner lost>":owner.getName()) + "] " + ms.name + " - " + ms.last_trace_key );
			}
		}
		
		if ( waiting_semaphores.size() > 0 ){
			
			diag_logger.log( "    waiting semaphores" );
			
			for (int i=0;i<waiting_semaphores.size();i++){
				
				AEMonSem	ms = (AEMonSem)waiting_semaphores.get(i);
				
				Thread last_waiter = ((AESemaphore)ms).latest_waiter;

				diag_logger.log( "        [" + (last_waiter==null?"<waiter lost>":last_waiter.getName()) + "] " +  ms.name + " - " + ms.last_trace_key );
			}
		}
		
		for (int i=0;i<x.length;i++){
			
			AEMonSem	ms = x[i];
			
			ms.last_entry_count = ms.entry_count;
		}
	}
	
	
	protected long			entry_count;
	protected long			last_entry_count;
	protected String		last_trace_key;
	
	
	protected String		name;
	protected boolean		is_monitor;
	protected int			waiting		= 0;

	
	protected
	AEMonSem(
		String	_name,
		boolean	_monitor )
	{
		is_monitor		= _monitor;
		
		if ( is_monitor) {
			
			name		= _name;
		}else{
			
			name		= "(S)" + _name;
		}
		
		if ( DEBUG ){
			
			synchronized( AEMonSem.class ){
				
				if ( is_monitor ){
					monitor_id_next++;
				}else{
					semaphore_id_next++;
				}
								
				StackTraceElement	elt = new Exception().getStackTrace()[2];
				
				String	class_name 	= elt.getClassName();
				int		line_number	= elt.getLineNumber(); 
			
				monSemData new_entry	= new monSemData( class_name, line_number);

				if ( is_monitor ){
					
					debug_monitors.put( this, new_entry );
					
				}else{
					
					debug_semaphores.put( this, new_entry );
				}
				
				if ( DEBUG_CHECK_DUPLICATES ){
					
					monSemData		existing_name_entry	= (monSemData)debug_name_mapping.get( name );
					
					if ( existing_name_entry == null ){
						
						debug_name_mapping.put( name, new_entry );
						
					}else{
						
						if ( 	( !existing_name_entry.owning_class.getName().equals( class_name )) ||
								existing_name_entry.line_number != line_number ){
							
							Debug.out( new Exception("Duplicate AEMonSem name '" + name + "'"));
						}
					}
				}
			}	
		}
	}
	
	protected void
	debugEntry()
	{
		try{
				// bad things are:
				// A->B and somewhere else B->A
				// or
				// A(inst1) -> A(inst2)
			
			Stack	stack = (Stack)tls.get();
				
			if ( stack.size() > 64 ){
				
				Debug.out( "**** Whoaaaaaa, AEMonSem debug stack is getting too large!!!! ****" );
			}
			
			if ( !stack.isEmpty()){
				
				String	recursion_trace = "";
				
				/* not very useful 
				if (	(!is_monitor) &&
						((AEMonSem)stack.peek()).is_monitor ){
					
					if ( !debug_sem_in_mon.contains( name )){
						
						recursion_trace += ( recursion_trace.length()==0?"":"\r\n" ) +
											"Semaphore reservation while holding a monitor: sem = " + name+ ", mon = " + ((AEMonSem)stack.peek()).name;
									
						debug_sem_in_mon.add( name );
					}
				}
				*/
				
				StringBuffer	sb = new StringBuffer();
		
					// not very interesting for semaphores as these tend to get left on stack traces when
					// asymetric usage (which is often)
				
				boolean	check_recursion = is_monitor && !debug_recursions.contains( name );
				
				String	prev_name	= null;
				
				for (int i=0;i<stack.size();i++){
				
					AEMonSem	mon = (AEMonSem)stack.get(i);
					
					if ( check_recursion ){
						if ( 	mon.name.equals( name ) &&
								mon != this ){
							
							recursion_trace += 
								( recursion_trace.length()==0?"":"\r\n" ) +
								"Recursive locks on different instances: " + name;
							
							debug_recursions.add( name );
						}
					}
		
						// remove consecutive duplicates
					
					if ( prev_name == null || !mon.name.equals( prev_name )){
						
						sb.append("$");
						sb.append(mon.name);
					}
					
					prev_name	= mon.name;
				}
				
				sb.append( "$" );
				sb.append( name );
				sb.append( "$" );
				
				String trace_key = sb.toString();
				
				if ( recursion_trace.length() > 0 ){
					
					Debug.outNoStack( recursion_trace + "\r\n    " + trace_key );
				}
				
				last_trace_key	= trace_key;
				
				if ( !is_monitor ){
					
						// only add semaphores to the stack if they aren't already present.
						// This is because we can reserve a semaphore on one thread and
						// release it on another. This will grow the stack indefinitely
					
					boolean	match 	= false;
					
					for (int i=0;i<stack.size();i++){
						
						AEMonSem	ms = (AEMonSem)stack.get(i);
						
						if ( ms.name.equals( name )){
							
							match	= true;
							
							break;
						}
					}
					
					if ( !match ){
						
						stack.push( this );
					}
				}else{
					
					stack.push( this );
				}
		
				synchronized( debug_traces ){
								
					if ( debug_traces.get(trace_key) == null ){
					
						String	thread_name	= Thread.currentThread().getName();
						String	stack_trace	= Debug.getCompressedStackTrace(3);
						
						Iterator	it = debug_traces.keySet().iterator();
					
						while( it.hasNext()){
							
							String	old_key = (String)it.next();
							
							String[]	data = (String[])debug_traces.get(old_key);
							
							String	old_thread_name	= data[0];
							String	old_trace		= data[1];
							
								// find the earliest occurrence of a common monitor - no point in searching
								// beyond it
								//    e.g.  a -> b -> c -> g
							    //          x -> y -> b -> z
								// stop at b because beyond this things are "protected"
							
							
							int	earliest_common = stack.size();
							int	common_count	= 0;
							
							for (int i=0;i<stack.size();i++){
					
								String	n1 = ((AEMonSem)stack.get(i)).name;
							
								int	p1 = old_key.indexOf( "$" + n1 + "$");
		
								if ( p1 != -1 ){
							
									common_count++;
									
									earliest_common = Math.min( earliest_common, i+1 );
								}
							}
							
								// need at least 2 common monitors for chance of deadlock
							
							if ( common_count >= 2 ){
								
								for (int i=0;i<earliest_common;i++){
									
									AEMonSem	ms1 = (AEMonSem)stack.get(i);
									
									if ( !ms1.is_monitor ){
										
										continue;
									}
									
									String	n1 = ms1.name;
		
									for (int j=i+1;j<stack.size();j++){
										
										AEMonSem	ms2 = (AEMonSem)stack.get(j);
										
										if ( !ms2.is_monitor ){
											
											continue;
										}
										
										String	n2 = ms2.name;
										
											// same object recursion already tested above
										
										if ( !n1.equals( n2 )){
										
											int	p1 = old_key.indexOf( "$" + n1 + "$");
											int p2 = old_key.indexOf( "$" + n2 + "$");
											
											if ( p1 != -1 && p2 != -1 && p1 > p2 ){
												
												String	reciprocal_log = trace_key + " / " + old_key;
												
												if ( !debug_reciprocals.contains( reciprocal_log )){
													
													debug_reciprocals.add( reciprocal_log );
													
													Debug.outNoStack(
															"AEMonSem: Reciprocal usage:\r\n" +
															"    " + trace_key + "\r\n" + 
															"        [" + thread_name + "] " + stack_trace + "\r\n" +
															"    " + old_key + "\r\n" +
															"        [" + old_thread_name + "] " + old_trace );
												}
											}
										}
									}
								}
							}
						}
						
						debug_traces.put( trace_key, new String[]{ thread_name, stack_trace });
				
							// look through all the traces for an A->B and B->A
					}
				}
				
			}else{
				
				last_trace_key	= "$" + name + "$";
				
				stack.push( this );
				
			}
		}catch( Throwable e ){
			
			try{
				Debug.printStackTrace(e);
				
			}catch( Throwable f ){
				
			}
		}
	}
	
	protected void
	debugExit()
	{
		try{
			Stack	stack = (Stack)tls.get();
			
			if ( is_monitor ){
		
					// skip over any sem reserves within a sync block
				
				while( stack.peek() != this ){
					
					stack.pop();
				}
				
				stack.pop();
				
			}else{
				
					// for semaphores we can release stuff without a matching reserve if
					// the semaphore has an initial value or if we have one thread releasing
					// a semaphore and another reserving it
						
				if ( !stack.isEmpty()){
				
					if ( stack.peek() == this ){
										
						stack.pop();
					}
				}
			}
		}catch( Throwable e ){
			
			try{
				Debug.printStackTrace(e);
				
			}catch( Throwable f ){
				
			}
		}
	}
	
	protected static class
	monSemData
	{
		protected Class			owning_class;
		protected int			line_number;
		
		
		protected
		monSemData(
			String			_class_name,
			int				_line_number )
		{			
			try{
				owning_class	= Class.forName( _class_name );
				
			}catch( Throwable e ){
				
				Debug.printStackTrace( e );
			}
			
			line_number		= _line_number;
		}
	}
}
