/*******************************************************************************
 * Copyright (c) 2006, 2007 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.debug.internal.ui.views.memory.renderings;

import java.math.BigInteger;
import java.util.ArrayList;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.ISafeRunnable;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.ListenerList;
import org.eclipse.core.runtime.SafeRunner;
import org.eclipse.core.runtime.Status;
import org.eclipse.debug.internal.ui.DebugUIPlugin;
import org.eclipse.debug.internal.ui.viewers.AsynchronousModel;
import org.eclipse.debug.internal.ui.viewers.AsynchronousTableViewer;
import org.eclipse.debug.internal.ui.viewers.model.provisional.IStatusMonitor;
import org.eclipse.debug.internal.ui.viewers.provisional.ILabelRequestMonitor;
import org.eclipse.debug.internal.ui.views.memory.MemoryViewUtil;
import org.eclipse.jface.viewers.CellEditor;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableColumn;
import org.eclipse.swt.widgets.TableItem;
import org.eclipse.ui.progress.UIJob;

abstract public class AsyncVirtualContentTableViewer extends AsynchronousTableViewer {

	private Object fPendingTopIndexKey;
	private ArrayList fTopIndexQueue = new ArrayList();
	
	private boolean fPendingResizeColumns;
	private ListenerList fVirtualContentListeners;
	private SelectionListener fScrollSelectionListener;
	private ListenerList fPresentationErrorListeners;
	private Object fTopIndexKey;

	public static boolean DEBUG_DYNAMIC_LOADING = false;
	
	public AsyncVirtualContentTableViewer(Composite parent, int style) {
		super(parent, style);
		fVirtualContentListeners = new ListenerList();
		fPresentationErrorListeners = new ListenerList();
		initScrollBarListener();
	}
	
	private void initScrollBarListener()
	{
		ScrollBar scroll = getTable().getVerticalBar();
		fScrollSelectionListener = new SelectionAdapter() {
			public void widgetSelected(SelectionEvent e) {
				handleScrollBarSelection();
			}};
		scroll.addSelectionListener(fScrollSelectionListener);
	}

	public void setTopIndex(Object key)
	{
		fPendingTopIndexKey = key;
		attemptSetTopIndex();
	}
	
	protected Object getPendingSetTopIndexKey()
	{
		return fPendingTopIndexKey;
	}
	
	protected void handlePresentationFailure(IStatusMonitor monitor, IStatus status) {
		notifyPresentationError(monitor, status);
	}
	
	public void disposeColumns()
	{
		// clean up old columns
		TableColumn[] oldColumns = getTable().getColumns();
		
		for (int i=0; i<oldColumns.length; i++)
		{
			oldColumns[i].dispose();
		}
	}
	
	public void disposeCellEditors()
	{
		// clean up old cell editors
		CellEditor[] oldCellEditors = getCellEditors();
		
		if (oldCellEditors != null)
		{
			for (int i=0; i<oldCellEditors.length; i++)
			{
				oldCellEditors[i].dispose();
			}
		}
	}
    
	/**
	 * Resize column to the preferred size.
	 */
	public void resizeColumnsToPreferredSize() {
		fPendingResizeColumns = true;
		fPendingResizeColumns = attemptResizeColumnsToPreferredSize();
	}
	
	private boolean attemptResizeColumnsToPreferredSize()
	{
		if (fPendingResizeColumns)
		{
			if(!hasPendingUpdates()) {
				UIJob job = new UIJob("packcolumns"){ //$NON-NLS-1$

					public IStatus runInUIThread(IProgressMonitor monitor) {
						Table table = getTable();
						
						if (!table.isDisposed())
						{
							// if table size is zero, the rendering has not been made visible
							// cannot pack until the rendering is visible
							if (table.getSize().x > 0)
							{
								TableColumn[] columns = table.getColumns();
								for (int i=0 ;i<columns.length-1; i++)
								{	
									columns[i].pack();
								}	
							}
							else
							{
								fPendingResizeColumns = true;
							}
						}
						return Status.OK_STATUS;
					}};
				job.setSystem(true);
				job.schedule();	
				return false;
			}
		}
		return fPendingResizeColumns;
	}
	
	/**
	 * Attempts to update any pending setTopIndex
	 * 
	 * @param reveal whether to reveal the selection
	 */
	protected synchronized void attemptSetTopIndex() {
		if (fPendingTopIndexKey != null) {
            Object remaining = doAttemptSetTopIndex(fPendingTopIndexKey);
            if (remaining == null)
            {
            	fPendingTopIndexKey = remaining;
            }
		}
	}
	
	private synchronized Object doAttemptSetTopIndex(final Object topIndexKey)
	{
		final int i = getVirtualContentModel().indexOfKey(topIndexKey);
		if (i >= 0)
		{
			UIJob job = new UIJob("set top index"){ //$NON-NLS-1$

				public IStatus runInUIThread(IProgressMonitor monitor)  {
						if (getTable().isDisposed())
						{
							fTopIndexQueue.clear();
							return Status.OK_STATUS;
						}
						
						int idx = getVirtualContentModel().indexOfKey(topIndexKey);
						if (idx >= 0)
						{
							if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
								System.out.println("actual set top index: " + ((BigInteger)topIndexKey).toString(16)); //$NON-NLS-1$
							fPendingTopIndexKey = null;
							setTopIndexKey(topIndexKey);
							getTable().setTopIndex(idx);							
							tableTopIndexSetComplete();		
							
							if (getTable().getTopIndex() != idx  )
							{
								if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
									System.out.println(">>> FAILED set top index : " + ((BigInteger)topIndexKey).toString(16)); //$NON-NLS-1$

								// only retry if we have pending updates
								if (hasPendingUpdates())
								{
									if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
										System.out.println(">>> Retry top index: " + ((BigInteger)topIndexKey).toString(16)); //$NON-NLS-1$

									fPendingTopIndexKey = topIndexKey;
								}
							}														
						}
						else
						{
							if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
								System.out.println("cannot find key, put it back to the queue: " + topIndexKey); //$NON-NLS-1$
							fPendingTopIndexKey = topIndexKey;
						}
						
						// remove the top index key from queue when it is processed
						removeKeyFromQueue(topIndexKey);
						
					return Status.OK_STATUS;
				}};
				
			// set top index does not happen immediately, keep track of
			// all pending set top index
			addKeyToQueue(topIndexKey);
			
			job.setSystem(true);
			job.schedule();
			return topIndexKey;
		}
		return topIndexKey;
	}
	
	protected void tableTopIndexSetComplete()
	{
		
	}
	 
	 public void addVirtualContentListener(IVirtualContentListener listener)
	 {
		 fVirtualContentListeners.add(listener);
	 }
	 
	 public void removeVirtualContentListener(IVirtualContentListener listener)
	 {
		 fVirtualContentListeners.remove(listener);
	 }
	 
	 protected void notifyListenersAtBufferStart()
	 {
		 int topIdx = getTable().getTopIndex();
		 Object[] listeners = fVirtualContentListeners.getListeners();
	 
		for (int i = 0; i < listeners.length; i++) {
			final IVirtualContentListener listener = (IVirtualContentListener) listeners[i];
			if (topIdx < listener.getThreshold(IVirtualContentListener.BUFFER_START))
			{
				SafeRunner.run(new ISafeRunnable() {
					public void run() throws Exception {	
						listener.handledAtBufferStart();
					}
					public void handleException(Throwable exception) {
						DebugUIPlugin.log(exception);
					}
				});
			}
		}
	 }
	 
	 protected void notifyListenersAtBufferEnd()
	 {
		Object[] listeners = fVirtualContentListeners.getListeners();
		int topIdx = getTable().getTopIndex();
		int bottomIdx = topIdx + getNumberOfVisibleLines();
		int elementsCnt = getVirtualContentModel().getElements().length;
		int numLinesLeft = elementsCnt - bottomIdx;
	 
		for (int i = 0; i < listeners.length; i++) {
			final IVirtualContentListener listener = (IVirtualContentListener) listeners[i];
			if (numLinesLeft <= listener.getThreshold(IVirtualContentListener.BUFFER_END))
			{
				SafeRunner.run(new ISafeRunnable() {
					public void run() throws Exception {
						listener.handleAtBufferEnd();
					}
					public void handleException(Throwable exception) {
						DebugUIPlugin.log(exception);
					}
				});
			}
		}
	 }
	 
	protected void  handleScrollBarSelection()
	{
//		 ignore event if there is pending set top index in the queue
		if (!fTopIndexQueue.isEmpty())
			return;
		topIndexChanged();
	}
	
	public void topIndexChanged()
	{
		if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
		{
			MemorySegment a = (MemorySegment)getTable().getItem(getTable().getTopIndex()).getData();
			System.out.println(Thread.currentThread().getName() + " " + this + " handle scroll bar moved:  top index: " + a.getAddress().toString(16)); //$NON-NLS-1$ //$NON-NLS-2$
		}

		setTopIndexKey(getVirtualContentModel().getKey(getTable().getTopIndex()));

		notifyListenersAtBufferStart();
		notifyListenersAtBufferEnd();
	}
	
	protected void setTopIndexKey(Object key)
	{
		fTopIndexKey = key;
	}
	
	protected Object getTopIndexKey()
	{
		return fTopIndexKey;
	}

	protected synchronized void preservingSelection(Runnable updateCode) {
		Object oldTopIndexKey = null;
		if (fPendingTopIndexKey == null) {
			// preserve selection
			oldTopIndexKey = getTopIndexKey();
		}
		else
		{
			oldTopIndexKey = fPendingTopIndexKey;
		}
		
		try {

			// perform the update
			updateCode.run();
		} finally {			
			if (oldTopIndexKey != null)
			{
				setTopIndex(oldTopIndexKey);
			}
		}

	}
	
	public void addPresentationErrorListener(IPresentationErrorListener errorListener)
	{
		fPresentationErrorListeners.add(errorListener);
	}
	
	public void removePresentationErrorListener(IPresentationErrorListener errorListener)
	{
		fPresentationErrorListeners.remove(errorListener);
	}
	
	private void notifyPresentationError(final IStatusMonitor monitor, final IStatus status)
	{
		Object[] listeners = fPresentationErrorListeners.getListeners();
	 
		for (int i = 0; i < listeners.length; i++) {
			
			if (listeners[i] instanceof IPresentationErrorListener)
			{
				final IPresentationErrorListener listener = (IPresentationErrorListener)listeners[i];
				SafeRunner.run(new ISafeRunnable() {
					public void run() throws Exception {
						listener.handlePresentationFailure(monitor, status);
					}
					public void handleException(Throwable exception) {
						DebugUIPlugin.log(exception);
					}
				});
			}
		}
	}

	protected AsynchronousModel createModel() {
		return createVirtualContentTableModel();
	}
	
	abstract protected AbstractVirtualContentTableModel createVirtualContentTableModel();
	
	private void addKeyToQueue(Object topIndexKey)
	{
		synchronized(fTopIndexQueue){
			if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
				System.out.println(" >>> add to top index queue: " + ((BigInteger)topIndexKey).toString(16)); //$NON-NLS-1$
			fTopIndexQueue.add(topIndexKey);
		}
	}
	
	private void removeKeyFromQueue(Object topIndexKey)
	{
		synchronized(fTopIndexQueue){
			if (AsyncVirtualContentTableViewer.DEBUG_DYNAMIC_LOADING)
				System.out.println(" >>> remove frome top index queue: " + ((BigInteger)topIndexKey).toString(16)); //$NON-NLS-1$
			fTopIndexQueue.remove(topIndexKey);
		}
	}
	
	public AbstractVirtualContentTableModel getVirtualContentModel()
	{
		if (getModel() instanceof AbstractVirtualContentTableModel)
			return (AbstractVirtualContentTableModel) getModel();
		return null;
	}
	
	private int getNumberOfVisibleLines()
	{	
		Table table = getTable();
		int height = table.getSize().y;
		
		// when table is not yet created, height is zero
		if (height == 0)
		{
			// make use of the table viewer to estimate table size
			height = table.getParent().getSize().y;
		}
		
		// height of border
		int border = table.getHeaderHeight();
		
		// height of scroll bar
		int scroll = table.getHorizontalBar().getSize().y;

		// height of table is table's area minus border and scroll bar height		
		height = height-border-scroll;

		// calculate number of visible lines
		int lineHeight = getMinTableItemHeight(table);
		
		int numberOfLines = height/lineHeight;
		
		if (numberOfLines <= 0)
			return 20;
	
		return numberOfLines;		
	}
	
	private int getMinTableItemHeight(Table table){
		
		// Hack to get around Linux GTK problem.
		// On Linux GTK, table items have variable item height as
		// carriage returns are actually shown in a cell.  Some rows will be
		// taller than others.  When calculating number of visible lines, we
		// need to find the smallest table item height.  Otherwise, the rendering
		// underestimates the number of visible lines.  As a result the rendering
		// will not be able to get more memory as needed.
		if (MemoryViewUtil.isLinuxGTK())
		{
			// check each of the items and find the minimum
			TableItem[] items = table.getItems();
			int minHeight = table.getItemHeight();
			for (int i=0; i<items.length; i++)
			{
				if (items[i].getData() != null)
					minHeight = Math.min(items[i].getBounds(0).height, minHeight);
			}
			
			return minHeight;
				
		}
		return table.getItemHeight();
	}

	protected void updateComplete(IStatusMonitor monitor) {
		super.updateComplete(monitor);
		attemptSetTopIndex();
		if (monitor instanceof ILabelRequestMonitor)
		{
			fPendingResizeColumns = attemptResizeColumnsToPreferredSize();
		}
	}
	
	protected boolean hasPendingSetTopIndex()
	{
		return !fTopIndexQueue.isEmpty();
	}

}
