/////////////////////////////////////////////////////////////////////////////
// Name:        No names yet.
// Purpose:     Contrib. demo
// Author:      Aleksandras Gluchovas
// Modified by:
// Created:     18/10/98
// RCS-ID:      $Id$
// Copyright:   (c) Aleksandras Gluchovas
// Licence:   	wxWindows license
/////////////////////////////////////////////////////////////////////////////


#ifdef __GNUG__
#pragma implementation "garbagec.cpp"
#pragma interface "garbagec.cpp"
#endif

// For compilers that support precompilation, includes "wx/wx.h".
#include "wx/wxprec.h"

/*
#ifdef __BORLANDC__
#pragma hdrstop
#endif
*/

#ifndef WX_PRECOMP
#include "wx/wx.h"
#endif

#include "garbagec.h"

/***** Implementation for class GarbageCollector *****/

inline static GCItem& node_to_item( wxNode* pNode )
{
	return *( (GCItem*)(pNode->Data()) );
}

GarbageCollector::~GarbageCollector()
{
	Reset();
}

/*** GC alg. helpers ***/

void GarbageCollector::DestroyItemList( wxList& lst )
{
	wxNode* pNode = lst.First();

	while( pNode )
	{
		delete &node_to_item( pNode );

		pNode = pNode->Next();
	}

	lst.Clear();
}

wxNode* GarbageCollector::FindItemNode( void* pForObj )
{
	wxNode* pNode = mAllNodes.First();

	while( pNode )
	{
		if ( node_to_item( pNode ).mpObj == pForObj )

			return pNode;

		pNode = pNode->Next();
	}

	wxASSERT(0); // DBG:: item should be presnet

	return 0;
}

wxNode* GarbageCollector::FindRefernceFreeItemNode()
{
	wxNode* pNode = mAllNodes.First();

	while( pNode )
	{
		if ( node_to_item( pNode ).mRefs.Number() == 0 ) 

			return pNode;

		pNode = pNode->Next();
	}

	return 0;
}

void GarbageCollector::RemoveReferencesToNode( wxNode* pItemNode )
{
	wxNode* pNode = mAllNodes.First();

	while( pNode )
	{
		wxList& refLst   = node_to_item( pNode ).mRefs;
		wxNode* pRefNode = refLst.First();

		while( pRefNode )
		{
			if ( pRefNode->Data() == (wxObject*)pItemNode )
			{
				wxNode* pNext = pRefNode->Next();

				refLst.DeleteNode( pRefNode );

				pRefNode = pNext;

				continue;
			}
			else pRefNode = pRefNode->Next();
		}

		pNode = pNode->Next();
	}
}

void GarbageCollector::ResolveReferences()
{
	wxNode* pNode = mAllNodes.First();

	while( pNode )
	{
		GCItem& item = node_to_item( pNode );

		wxNode* pRefNode = item.mRefs.First();

		while( pRefNode )
		{
			pRefNode->SetData( (wxObject*) FindItemNode( (void*)pRefNode->Data() ) );

			pRefNode = pRefNode->Next();
		}

		pNode = pNode->Next();
	}
}

void GarbageCollector::AddObject( void* pObj, int refCnt )
{
	// FOR NOW:: inital ref-count is not used

	GCItem* pItem = new GCItem();

	pItem->mpObj  = pObj;

	mAllNodes.Append( (wxObject*) pItem );
}

void GarbageCollector::AddDependency( void* pObj, void* pDepnedsOnObj )
{
	node_to_item( FindItemNode( pObj ) ).mRefs.Append( (wxObject*)pDepnedsOnObj );
}

/*** GC alg. implementation ***/

void GarbageCollector::ArrangeCollection()
{
	ResolveReferences();

	do
	{
		// find node, which does not depend on anything

		wxNode* pItemNode = FindRefernceFreeItemNode();

		if ( pItemNode )
		{
			// append it to the list, where items are contained
			// in the increasing order of dependencies

			mRegularLst.Append( pItemNode->Data() );

			mAllNodes.DeleteNode( pItemNode );

			// remove references to this current "least-dependent" node
			// from reference lists of all the other nodes

			RemoveReferencesToNode( pItemNode );
		}
		else
		{
			// otherwise, what is left - all nodes, which
			// are involved into cycled chains (rings)

			wxNode* pNode = mAllNodes.First();

			while( pNode )
			{
				mCycledLst.Append( pNode->Data() );

				pNode = pNode->Next();
			}

			break;
		}

		// continue search for "least-dependent" nodes

	} while(1);
}

wxList& GarbageCollector::GetRegularObjects()
{
	return mRegularLst;
}

wxList& GarbageCollector::GetCycledObjects()
{
	return mCycledLst;
}

void GarbageCollector::Reset()
{
	DestroyItemList( mAllNodes   );

	mRegularLst.Clear();
	mCycledLst.Clear();
}