/*******************************************************************************
 * Copyright (c) 2000, 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
 *     dinko.ivanov@sap.com - patch #70790
 *******************************************************************************/
package org.eclipse.ui.forms.widgets;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Layout;
/**
 * This layout manager arranges children of the composite parent in vertical
 * columns. All the columns are identical size and children are stretched
 * horizontally to fill the column width. The goal is to give layout some
 * reasonable range of column numbers to allow it to handle various parent
 * widths. That way, column number will drop to the lowest number in the range
 * when width decreases, and grow up to the highest number in the range when
 * allowed by the parent width.
 * <p>
 * In addition, the layout attempts to 'fill the space' equally i.e. to avoid
 * large gaps at the and of the last column.
 * <p>
 * Child controls are layed out according to their 'natural' (preferred) size.
 * For 'stretchy' controls that do not have natural preferred size, it is
 * possible to set width and/or height hints using ColumnLayoutData objects.
 * 
 * @see ColumnLayoutData
 * @since 3.0
 */
public final class ColumnLayout extends Layout implements ILayoutExtension {
	/**
	 * Minimum number of columns (default is 1).
	 */
	public int minNumColumns = 1;
	/**
	 * Maximum number of columns (default is 3).
	 */
	public int maxNumColumns = 3;
	/**
	 * Horizontal spacing between columns (default is 5).
	 */
	public int horizontalSpacing = 5;
	/**
	 * Vertical spacing between controls (default is 5).
	 */
	public int verticalSpacing = 5;
	/**
	 * Top margin (default is 5).
	 */
	public int topMargin = 5;
	/**
	 * Left margin (default is 5).
	 */
	public int leftMargin = 5;
	/**
	 * Bottom margin (default is 5).
	 */
	public int bottomMargin = 5;
	/**
	 * Right margin (default is 5).
	 */
	public int rightMargin = 5;

	/**
	 * Creates a new instance of the column layout.
	 */
	public ColumnLayout() {
	}

	protected Point computeSize(Composite composite, int wHint, int hHint, boolean flushCache) {
		if (wHint == 0)
			return computeSize(composite, wHint, hHint, minNumColumns);
		else if (wHint == SWT.DEFAULT)
			return computeSize(composite, wHint, hHint, maxNumColumns);
		else
			return computeSize(composite, wHint, hHint, -1);
	}

	private Point computeSize(Composite parent, int wHint, int hHint, int ncolumns) {
		Control[] children = parent.getChildren();
		int cwidth = 0;
		int cheight = 0;
		Point[] sizes = new Point[children.length];

		int cwHint = SWT.DEFAULT;
		if (ncolumns != -1) {
			cwHint = wHint - leftMargin - rightMargin - (ncolumns - 1) * horizontalSpacing;
			if (cwHint <= 0)
				cwHint = 0;
			else
				cwHint /= ncolumns;
		}

		for (int i = 0; i < children.length; i++) {
			sizes[i] = computeControlSize(children[i], cwHint);
			cwidth = Math.max(cwidth, sizes[i].x);
			cheight += sizes[i].y;
		}
		if (ncolumns == -1) {
			// must compute
			ncolumns = (wHint - leftMargin - rightMargin - horizontalSpacing) / (cwidth + horizontalSpacing);
			ncolumns = Math.min(ncolumns, children.length);
			ncolumns = Math.max(ncolumns, minNumColumns);
			ncolumns = Math.min(ncolumns, maxNumColumns);
		}
		int perColHeight = cheight / ncolumns;
		if (cheight % ncolumns != 0)
			perColHeight++;
		int colHeight = 0;
		int[] heights = new int[ncolumns];
		int ncol = 0;
		
		boolean fillIn = false;
		
		for (int i = 0; i < sizes.length; i++) {
			int childHeight = sizes[i].y;
			if (i>0 && colHeight + childHeight > perColHeight) {
				heights[ncol] = colHeight;
				ncol++;
				if (ncol == ncolumns || fillIn) {
					// overflow - start filling in
					fillIn = true;
					ncol = findShortestColumn(heights);
				}
				colHeight = heights[ncol];
			}
			if (colHeight > 0)
				colHeight += verticalSpacing;
			colHeight += childHeight;
		}
		heights[ncol] = Math.max(heights[ncol],colHeight);
		
		Point size = new Point(0, 0);
		for (int i = 0; i < ncolumns; i++) {
			size.y = Math.max(size.y, heights[i]);
		}
		size.x = cwidth * ncolumns + (ncolumns - 1) * horizontalSpacing;
		size.x += leftMargin + rightMargin;
		//System.out.println("ColumnLayout: whint="+wHint+", size.x="+size.x);
		size.y += topMargin + bottomMargin;
		return size;
	}

	private Point computeControlSize(Control c, int wHint) {
		ColumnLayoutData cd = (ColumnLayoutData) c.getLayoutData();
		int widthHint = cd != null ? cd.widthHint : wHint;
		int heightHint = cd != null ? cd.heightHint : SWT.DEFAULT;
		return c.computeSize(widthHint, heightHint);
	}

	private int findShortestColumn(int[] heights) {
		int result = 0;
		int height = Integer.MAX_VALUE;
		for (int i = 0; i < heights.length; i++) {
			if (height > heights[i]) {
				height = heights[i];
				result = i;
			}
		}
		return result;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.swt.widgets.Layout#layout(org.eclipse.swt.widgets.Composite,
	 *      boolean)
	 */
	protected void layout(Composite parent, boolean flushCache) {
		Control[] children = parent.getChildren();
		Rectangle carea = parent.getClientArea();
		int cwidth = 0;
		int cheight = 0;
		Point[] sizes = new Point[children.length];
		for (int i = 0; i < children.length; i++) {
			sizes[i] = computeControlSize(children[i], SWT.DEFAULT);
			cwidth = Math.max(cwidth, sizes[i].x);
			cheight += sizes[i].y;
		}
		int ncolumns = (carea.width - leftMargin - rightMargin - horizontalSpacing) / (cwidth + horizontalSpacing);
		ncolumns = Math.min(ncolumns, children.length);		
		ncolumns = Math.max(ncolumns, minNumColumns);
		ncolumns = Math.min(ncolumns, maxNumColumns);
		int realWidth = (carea.width - leftMargin - rightMargin + horizontalSpacing) / ncolumns - horizontalSpacing;
//		int childrenPerColumn = children.length / ncolumns;
//		if (children.length % ncolumns != 0)
//			childrenPerColumn++;
//		int colWidth = 0;

		int fillWidth = Math.max(cwidth, realWidth);
		
		int perColHeight = cheight / ncolumns;
		if (cheight % ncolumns != 0)
			perColHeight++;
		
		int colHeight = 0;
		int[] heights = new int[ncolumns];
		int ncol = 0;
		int x = leftMargin;
		boolean fillIn = false;
		
		for (int i = 0; i < sizes.length; i++) {
			Control child = children[i];
			Point csize = sizes[i];
			ColumnLayoutData cd = (ColumnLayoutData) child.getLayoutData();
			int align = cd != null ? cd.horizontalAlignment : ColumnLayoutData.FILL;
			int childWidth = align == ColumnLayoutData.FILL ? fillWidth : csize.x;

			if (i>0 && colHeight + csize.y > perColHeight) {
				heights[ncol] = colHeight;
				if (fillIn || ncol == ncolumns-1) {
					// overflow - start filling in
					fillIn = true;
					ncol = findShortestColumn(heights);
					
					x = leftMargin + ncol * (fillWidth + horizontalSpacing);

				}
				else {
					ncol++;
					x += fillWidth + horizontalSpacing;
				}
				colHeight = heights[ncol];
			}
			if (colHeight > 0)
				colHeight += verticalSpacing;
			
			
			switch (align) {
				case ColumnLayoutData.LEFT :
				case ColumnLayoutData.FILL :
					child.setBounds(x, topMargin+colHeight, childWidth, csize.y);
					break;
				case ColumnLayoutData.RIGHT :
					child.setBounds(x + fillWidth - childWidth, topMargin+colHeight, childWidth, csize.y);
					break;
				case ColumnLayoutData.CENTER :
					child.setBounds(x + fillWidth / 2 - childWidth / 2, topMargin+colHeight, childWidth, csize.y);
					break;
			}
			
			colHeight += csize.y;
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.forms.widgets.ILayoutExtension#computeMaximumWidth(org.eclipse.swt.widgets.Composite,
	 *      boolean)
	 */
	public int computeMaximumWidth(Composite parent, boolean changed) {
		return computeSize(parent, SWT.DEFAULT, SWT.DEFAULT, changed).x;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.forms.widgets.ILayoutExtension#computeMinimumWidth(org.eclipse.swt.widgets.Composite,
	 *      boolean)
	 */
	public int computeMinimumWidth(Composite parent, boolean changed) {
		return computeSize(parent, 0, SWT.DEFAULT, changed).x;
	}
}