/*******************************************************************************
 * Copyright (c) 2007, 2008 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.swt.dnd;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.win32.*;
import org.eclipse.swt.widgets.*;

/**
 * This class provides a default drag under effect (eg. select, insert, scroll and expand) 
 * when a drag occurs over a <code>Tree</code>.
 * 
 * <p>Classes that wish to provide their own drag under effect for a <code>Tree</code>
 * can extend the <code>TreeDropTargetEffect</code> class and override any applicable methods 
 * in <code>TreeDropTargetEffect</code> to display their own drag under effect.</p>
 *
 * Subclasses that override any methods of this class must call the corresponding
 * <code>super</code> method to get the default drag under effect implementation.
 *
 * <p>The feedback value is either one of the FEEDBACK constants defined in 
 * class <code>DND</code> which is applicable to instances of this class, 
 * or it must be built by <em>bitwise OR</em>'ing together 
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>DND</code> effect constants. 
 * </p>
 * <p>
 * <dl>
 * <dt><b>Feedback:</b></dt>
 * <dd>FEEDBACK_SELECT, FEEDBACK_INSERT_BEFORE, FEEDBACK_INSERT_AFTER, FEEDBACK_EXPAND, FEEDBACK_SCROLL</dd>
 * </dl>
 * </p><p>
 * Note: Only one of the styles FEEDBACK_SELECT, FEEDBACK_INSERT_BEFORE or
 * FEEDBACK_INSERT_AFTER may be specified.
 * </p>
 * 
 * @see DropTargetAdapter
 * @see DropTargetEvent
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 * 
 * @since 3.3
 */
public class TreeDropTargetEffect extends DropTargetEffect {
	static final int SCROLL_HYSTERESIS = 200; // milli seconds
	static final int EXPAND_HYSTERESIS = 1000; // milli seconds

	int /*long*/ dropIndex;
	int /*long*/ scrollIndex;	
	long scrollBeginTime;
	int /*long*/ expandIndex;
	long expandBeginTime;
	TreeItem insertItem;
	boolean insertBefore;
	
	/**
	 * Creates a new <code>TreeDropTargetEffect</code> to handle the drag under effect on the specified 
	 * <code>Tree</code>.
	 * 
	 * @param tree the <code>Tree</code> over which the user positions the cursor to drop the data
	 */
	public TreeDropTargetEffect(Tree tree) {
		super(tree);
	}

	int checkEffect(int effect) {
		// Some effects are mutually exclusive.  Make sure that only one of the mutually exclusive effects has been specified.
		if ((effect & DND.FEEDBACK_SELECT) != 0) effect = effect & ~DND.FEEDBACK_INSERT_AFTER & ~DND.FEEDBACK_INSERT_BEFORE;
		if ((effect & DND.FEEDBACK_INSERT_BEFORE) != 0) effect = effect & ~DND.FEEDBACK_INSERT_AFTER;
		return effect;
	}

	/**
	 * This implementation of <code>dragEnter</code> provides a default drag under effect
	 * for the feedback specified in <code>event.feedback</code>.
	 * 
	 * For additional information see <code>DropTargetAdapter.dragEnter</code>.
	 * 
	 * Subclasses that override this method should call <code>super.dragEnter(event)</code>
	 * to get the default drag under effect implementation.
	 *
	 * @param event  the information associated with the drag enter event
	 * 
	 * @see DropTargetAdapter
	 * @see DropTargetEvent
	 */
	public void dragEnter(DropTargetEvent event) {
		dropIndex = -1;
		insertItem = null;
		expandBeginTime = 0;
		expandIndex = -1;	
		scrollBeginTime = 0;
		scrollIndex = -1;
	}
	
	/**
	 * This implementation of <code>dragLeave</code> provides a default drag under effect
	 * for the feedback specified in <code>event.feedback</code>.
	 * 
	 * For additional information see <code>DropTargetAdapter.dragLeave</code>.
	 * 
	 * Subclasses that override this method should call <code>super.dragLeave(event)</code>
	 * to get the default drag under effect implementation.
	 *
	 * @param event  the information associated with the drag leave event
	 * 
	 * @see DropTargetAdapter
	 * @see DropTargetEvent
	 */
	public void dragLeave(DropTargetEvent event) {
		Tree tree = (Tree) control;
		int /*long*/ handle = tree.handle;
		if (dropIndex != -1) {
			TVITEM tvItem = new TVITEM ();
			tvItem.hItem = dropIndex;
			tvItem.mask = OS.TVIF_STATE;
			tvItem.stateMask = OS.TVIS_DROPHILITED;
			tvItem.state = 0;
			OS.SendMessage (handle, OS.TVM_SETITEM, 0, tvItem);
			dropIndex = -1;
		}
		if (insertItem != null) {
			tree.setInsertMark(null, false);
			insertItem = null;
		}
		expandBeginTime = 0;
		expandIndex = -1;	
		scrollBeginTime = 0;
		scrollIndex = -1;
	}

	/**
	 * This implementation of <code>dragOver</code> provides a default drag under effect
	 * for the feedback specified in <code>event.feedback</code>.
	 * 
	 * For additional information see <code>DropTargetAdapter.dragOver</code>.
	 * 
	 * Subclasses that override this method should call <code>super.dragOver(event)</code>
	 * to get the default drag under effect implementation.
	 *
	 * @param event  the information associated with the drag over event
	 * 
	 * @see DropTargetAdapter
	 * @see DropTargetEvent
	 * @see DND#FEEDBACK_SELECT
	 * @see DND#FEEDBACK_INSERT_BEFORE
	 * @see DND#FEEDBACK_INSERT_AFTER
	 * @see DND#FEEDBACK_SCROLL
	 */
	public void dragOver(DropTargetEvent event) {
		Tree tree = (Tree) getControl();
		int effect = checkEffect(event.feedback);
		int /*long*/ handle = tree.handle;
		Point coordinates = new Point(event.x, event.y);
		coordinates = tree.toControl(coordinates);
		TVHITTESTINFO lpht = new TVHITTESTINFO ();
		lpht.x = coordinates.x;
		lpht.y = coordinates.y;
		OS.SendMessage (handle, OS.TVM_HITTEST, 0, lpht);
		int /*long*/ hItem = lpht.hItem;
		if ((effect & DND.FEEDBACK_SCROLL) == 0) {
			scrollBeginTime = 0;
			scrollIndex = -1;
		} else {
			if (hItem != -1 && scrollIndex == hItem && scrollBeginTime != 0) {
				if (System.currentTimeMillis() >= scrollBeginTime) {
					int /*long*/ topItem = OS.SendMessage(handle, OS.TVM_GETNEXTITEM, OS.TVGN_FIRSTVISIBLE, 0);
					int /*long*/ nextItem = OS.SendMessage(handle, OS.TVM_GETNEXTITEM, hItem == topItem ? OS.TVGN_PREVIOUSVISIBLE : OS.TVGN_NEXTVISIBLE, hItem);
					boolean scroll = true;
					if (hItem == topItem) {
						scroll = nextItem != 0;
					} else {
						RECT itemRect = new RECT ();
						if (OS.TreeView_GetItemRect (handle, nextItem, itemRect, true)) {
							RECT rect = new RECT ();
							OS.GetClientRect (handle, rect);
							POINT pt = new POINT ();
							pt.x = itemRect.left;
							pt.y = itemRect.top;
							if (OS.PtInRect (rect, pt)) {
								pt.y = itemRect.bottom;
								if (OS.PtInRect (rect, pt)) scroll = false;
							}
						}
					}
					if (scroll) {
						OS.SendMessage (handle, OS.TVM_ENSUREVISIBLE, 0, nextItem);
						tree.redraw();
					}
					scrollBeginTime = 0;
					scrollIndex = -1;
				}
			} else {
				scrollBeginTime = System.currentTimeMillis() + SCROLL_HYSTERESIS;
				scrollIndex = hItem;
			}
		}
		if ((effect & DND.FEEDBACK_EXPAND) == 0) {
			expandBeginTime = 0;
			expandIndex = -1;
		} else {
			if (hItem != -1 && expandIndex == hItem && expandBeginTime != 0) {
				if (System.currentTimeMillis() >= expandBeginTime) {
					if (OS.SendMessage (handle, OS.TVM_GETNEXTITEM, OS.TVGN_CHILD, hItem) != 0) {
						TreeItem item = (TreeItem)tree.getDisplay().findWidget(tree.handle, hItem);
						if (item != null && !item.getExpanded()) {
							item.setExpanded(true);
							tree.redraw();
							Event expandEvent = new Event ();
							expandEvent.item = item;
							tree.notifyListeners(SWT.Expand, expandEvent);
						}
					}
					expandBeginTime = 0;
					expandIndex = -1;
				}
			} else {
				expandBeginTime = System.currentTimeMillis() + EXPAND_HYSTERESIS;
				expandIndex = hItem;
			}
		}
		if (dropIndex != -1 && (dropIndex != hItem || (effect & DND.FEEDBACK_SELECT) == 0)) {
			TVITEM tvItem = new TVITEM ();
			tvItem.hItem = dropIndex;
			tvItem.mask = OS.TVIF_STATE;
			tvItem.stateMask = OS.TVIS_DROPHILITED;
			tvItem.state = 0;
			OS.SendMessage (handle, OS.TVM_SETITEM, 0, tvItem);
			dropIndex = -1;
		}
		if (hItem != -1 && hItem != dropIndex && (effect & DND.FEEDBACK_SELECT) != 0) {
			TVITEM tvItem = new TVITEM ();
			tvItem.hItem = hItem;
			tvItem.mask = OS.TVIF_STATE;
			tvItem.stateMask = OS.TVIS_DROPHILITED;
			tvItem.state = OS.TVIS_DROPHILITED;
			OS.SendMessage (handle, OS.TVM_SETITEM, 0, tvItem);
			dropIndex = hItem;
		}
		if ((effect & DND.FEEDBACK_INSERT_BEFORE) != 0 || (effect & DND.FEEDBACK_INSERT_AFTER) != 0) {
			boolean before = (effect & DND.FEEDBACK_INSERT_BEFORE) != 0;
			/*
			* Bug in Windows.  When TVM_SETINSERTMARK is used to set
			* an insert mark for a tree and an item is expanded or
			* collapsed near the insert mark, the tree does not redraw
			* the insert mark properly.  The fix is to hide and show
			* the insert mark whenever an item is expanded or collapsed.
			* Since the insert mark can not be queried from the tree,
			* use the Tree API rather than calling the OS directly.
			*/
			TreeItem item = (TreeItem)tree.getDisplay().findWidget(tree.handle, hItem);
			if (item != null) {
				if (item != insertItem || before != insertBefore) {
					tree.setInsertMark(item, before);
				}
				insertItem = item;
				insertBefore = before;
			} else {
				if (insertItem != null) {
					tree.setInsertMark(null, false);
				}
				insertItem = null;
			}
		} else {
			if (insertItem != null) {
				tree.setInsertMark(null, false);
			}
			insertItem = null;
		}
	}
}
