/*******************************************************************************
 * Copyright (c) 2007, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Michael Krkoska - initial API and implementation (bug 188333)
 *     Pawel Piech - Bug 291245 - [Viewers] StyledCellLabelProvider.paint(...) does not respect column alignment
 *******************************************************************************/
package org.eclipse.jface.viewers;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.viewers.StyledString.Styler;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyleRange;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.TextLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;

/**
 * A {@link StyledCellLabelProvider} supports styled labels by using owner
 * draw.
 * Besides the styles in labels, the label provider preserves native viewer behavior:
 * <ul>
 * <li>similar image and label positioning</li>
 * <li>native drawing of focus and selection</li>
 * </ul>
 * <p>
 * For providing the label's styles, create a subclass and overwrite
 * {@link StyledCellLabelProvider#update(ViewerCell)} to
 * return set all information needed to render a element. Use
 * {@link ViewerCell#setStyleRanges(StyleRange[])} to set style ranges
 * on the label.
 * </p>
 *
 * @since 3.4
 */
public abstract class StyledCellLabelProvider extends OwnerDrawLabelProvider {

	/**
	 * Style constant for indicating that the styled colors are to be applied
	 * even it the viewer's item is selected. Default is not to apply colors.
	 */
	public static final int COLORS_ON_SELECTION = 1 << 0;

	/**
	 * Style constant for indicating to draw the focus if requested by the owner
	 * draw event. Default is to draw the focus.
	 */
	public static final int NO_FOCUS = 1 << 1;

	/**
	 * Private constant to indicate if owner draw is enabled for the
	 * label provider's column.
	 */
	private static final int OWNER_DRAW_ENABLED = 1 << 4;

	private int style;

	// reused text layout
	private TextLayout cachedTextLayout;

	private ColumnViewer viewer;
	private ViewerColumn column;

	private int deltaOfLastMeasure;

	/**
	 * Creates a new StyledCellLabelProvider. By default, owner draw is enabled, focus is drawn and no
	 * colors are painted on selected elements.
	 */
	public StyledCellLabelProvider() {
		this(0);
	}

	/**
	 * Creates a new StyledCellLabelProvider. By default, owner draw is enabled.
	 *
	 * @param style
	 *            the style bits
	 * @see StyledCellLabelProvider#COLORS_ON_SELECTION
	 * @see StyledCellLabelProvider#NO_FOCUS
	 */
	public StyledCellLabelProvider(int style) {
		this.style = style & (COLORS_ON_SELECTION | NO_FOCUS)
							| OWNER_DRAW_ENABLED;
	}

	/**
	 * Returns <code>true</code> is the owner draw rendering is enabled for this label provider.
	 * By default owner draw rendering is enabled. If owner draw rendering is disabled, rending is
	 * done by the viewer and no styled ranges (see {@link ViewerCell#getStyleRanges()})
	 * are drawn.
	 *
	 * @return <code>true</code> is the rendering of styles is enabled.
	 */
	public boolean isOwnerDrawEnabled() {
		return (this.style & OWNER_DRAW_ENABLED) != 0;
	}

	/**
	 * Specifies whether owner draw rendering is enabled for this label
	 * provider. By default owner draw rendering is enabled. If owner draw
	 * rendering is disabled, rendering is done by the viewer and no styled
	 * ranges (see {@link ViewerCell#getStyleRanges()}) are drawn.
	 * It is the caller's responsibility to also call
	 * {@link StructuredViewer#refresh()} or similar methods to update the
	 * underlying widget.
	 *
	 * @param enabled
	 *            specifies if owner draw rendering is enabled
	 */
	public void setOwnerDrawEnabled(boolean enabled) {
		boolean isEnabled= isOwnerDrawEnabled();
		if (isEnabled != enabled) {
			if (enabled) {
				this.style |= OWNER_DRAW_ENABLED;
			} else {
				this.style &= ~OWNER_DRAW_ENABLED;
			}
			if (this.viewer != null) {
				setOwnerDrawEnabled(this.viewer, this.column, enabled);
			}
		}
	}

	/**
	 * Returns the viewer on which this label provider is installed on or <code>null</code> if the
	 * label provider is not installed.
	 *
	 * @return the viewer on which this label provider is installed on or <code>null</code> if the
	 * label provider is not installed.
	 */
	protected final ColumnViewer getViewer() {
		return this.viewer;
	}

	/**
	 * Returns the column on which this label provider is installed on or <code>null</code> if the
	 * label provider is not installed.
	 *
	 * @return the column on which this label provider is installed on or <code>null</code> if the
	 * label provider is not installed.
	 */
	protected final ViewerColumn getColumn() {
		return this.column;
	}

	@Override
	public void initialize(ColumnViewer viewer, ViewerColumn column) {
		Assert.isTrue(this.viewer == null && this.column == null, "Label provider instance already in use"); //$NON-NLS-1$

		this.viewer= viewer;
		this.column= column;
		super.initialize(viewer, column, isOwnerDrawEnabled());
	}

	@Override
	public void dispose() {
		if (this.cachedTextLayout != null) {
			cachedTextLayout.dispose();
			cachedTextLayout = null;
		}

		this.viewer= null;
		this.column= null;

		super.dispose();
	}

	@Override
	public void update(ViewerCell cell) {
		// clients must override and configure the cell and call super
		super.update(cell); // calls 'repaint' to trigger the paint listener
	}

	private TextLayout getSharedTextLayout(Display display) {
		if (cachedTextLayout == null) {
			int orientation = viewer.getControl().getStyle() & (SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT);
			cachedTextLayout = new TextLayout(display);
			cachedTextLayout.setOrientation(orientation);
		}
		return cachedTextLayout;
	}

	private boolean useColors(Event event) {
		return (event.detail & SWT.SELECTED) == 0
				|| (this.style & COLORS_ON_SELECTION) != 0;
	}

	private boolean drawFocus(Event event) {
		return (event.detail & SWT.FOCUSED) != 0
				&& (this.style & NO_FOCUS) == 0;
	}

	/**
	 * Prepares the given style range before it is applied to the label. This method makes sure that
	 * no colors are drawn when the element is selected.
	 * The current version of the {@link StyledCellLabelProvider} will also ignore all font settings on the
	 * style range. Clients can override.
	 *
	 * @param styleRange
	 *               the style range to prepare. the style range element must not be modified
	 * @param applyColors
	 *               specifies if colors should be applied.
	 * @return
	 *               returns the style range to use on the label
	 */
	protected StyleRange prepareStyleRange(StyleRange styleRange, boolean applyColors) {
		// if no colors apply or font is set, create a clone and clear the
		// colors and font
		if (!applyColors && (styleRange.foreground != null || styleRange.background != null)) {
			styleRange = (StyleRange) styleRange.clone();
			if (!applyColors) {
				styleRange.foreground = null;
				styleRange.background = null;
			}
		}
		return styleRange;
	}

	private ViewerCell getViewerCell(Event event, Object element) {
		ViewerRow row= viewer.getViewerRowFromItem(event.item);
		return new ViewerCell(row, event.index, element);
	}

	/**
	 * Handle the erase event. The default implementation does nothing to ensure
	 * keep native selection highlighting working.
	 *
	 * @param event
	 *            the erase event
	 * @param element
	 *            the model object
	 * @see SWT#EraseItem
	 */
	@Override
	protected void erase(Event event, Object element) {
		// use native erase
		if (isOwnerDrawEnabled()) {
			// info has been set by 'update': announce that we paint ourselves
			event.detail &= ~SWT.FOREGROUND;
		}
	}

	@Override
	protected void measure(Event event, Object element) {
		if (!isOwnerDrawEnabled())
			return;

		ViewerCell cell= getViewerCell(event, element);
		boolean applyColors = useColors(event);

		TextLayout layout = getSharedTextLayout(event.display);

		int textWidthDelta = deltaOfLastMeasure = updateTextLayout(layout, cell, applyColors);

		event.width += textWidthDelta;
	}

	/**
	 * @param layout
	 * @param cell
	 * @param applyColors
	 * @return the text width delta (0 if the text layout contains no other font)
	 */
	private int updateTextLayout(TextLayout layout, ViewerCell cell,
			boolean applyColors) {
		layout.setStyle(null, 0, Integer.MAX_VALUE); // clear old styles

		layout.setText(cell.getText());
		layout.setFont(cell.getFont()); // set also if null to clear previous usages

		int originalTextWidth = layout.getBounds().width; // text width without any styles
		boolean containsOtherFont= false;

		StyleRange[] styleRanges = cell.getStyleRanges();
		if (styleRanges != null) { // user didn't fill styled ranges
			for (StyleRange styleRange : styleRanges) {
				StyleRange curr = prepareStyleRange(styleRange, applyColors);
				layout.setStyle(curr, curr.start, curr.start + curr.length - 1);
				if (curr.font != null) {
					containsOtherFont= true;
				}
			}
		}
		int textWidthDelta = 0;
		if (containsOtherFont) {
			textWidthDelta = layout.getBounds().width - originalTextWidth;
		}
		return textWidthDelta;
	}

	@Override
	protected void paint(Event event, Object element) {
		if (!isOwnerDrawEnabled())
			return;

		ViewerCell cell= getViewerCell(event, element);

		boolean applyColors= useColors(event);

		GC gc = event.gc;
		// remember colors to restore the GC later
		Color oldForeground = gc.getForeground();
		Color oldBackground = gc.getBackground();

		if (applyColors) {
			Color foreground= cell.getForeground();
			if (foreground != null) {
				gc.setForeground(foreground);
			}

			Color background= cell.getBackground();
			if (background != null) {
				gc.setBackground(background);
			}
		}
		Image image = cell.getImage();
		if (image != null) {
			Rectangle imageBounds = cell.getImageBounds();
			if (imageBounds != null) {
				Rectangle bounds = image.getBounds();

				// center the image in the given space
				int x = imageBounds.x
						+ Math.max(0, (imageBounds.width - bounds.width) / 2);
				int y = imageBounds.y
						+ Math.max(0, (imageBounds.height - bounds.height) / 2);
				gc.drawImage(image, x, y);
			}
		}

		Rectangle textBounds = cell.getTextBounds();
		if (textBounds != null) {
			TextLayout textLayout= getSharedTextLayout(event.display);
			// text layout already configured in measure(Event, Object)

			Rectangle layoutBounds = textLayout.getBounds();

			int style = viewer.getColumnViewerOwner(cell.getColumnIndex()).getStyle();
			int x = textBounds.x;
			if ((style & SWT.RIGHT) != 0) {
				x = textBounds.x + textBounds.width - textLayout.getBounds().width;
			} else if ((style & SWT.CENTER) != 0) {
				x = textBounds.x + (textBounds.width - textLayout.getBounds().width)/2;
			}
			int y = textBounds.y
					+ Math.max(0, (textBounds.height - layoutBounds.height) / 2);

			if (gc.isClipped()) {
				Rectangle saveClipping = gc.getClipping();
				gc.setClipping(textBounds);
				textLayout.draw(gc, x, y);
				gc.setClipping(saveClipping);
			} else {
				// in the case of no clipping, a tooltip will be drawn and the horizontal
				// alignment for the tooltip should be LEFT, so x has to be set to textBounds.x
				// Because the other alignments are not working combined with the tooltip, since
				// these are aligned to the textBounds.width which depends on the cell
				// width which is wrong for the tooltip case.
				x = textBounds.x;
				textLayout.draw(gc, x, y);
			}
		}

		if (drawFocus(event)) {
			Rectangle focusBounds = cell.getViewerRow().getBounds();
			gc.drawFocus(focusBounds.x, focusBounds.y, focusBounds.width + deltaOfLastMeasure,
					focusBounds.height);
		}

		if (applyColors) {
			gc.setForeground(oldForeground);
			gc.setBackground(oldBackground);
		}
	}

	/**
	 * Applies decoration styles to the decorated string and adds the styles of the previously
	 * undecorated string.
	 * <p>
	 * If the <code>decoratedString</code> contains the <code>styledString</code>, then the result
	 * keeps the styles of the <code>styledString</code> and styles the decorations with the
	 * <code>decorationStyler</code>. Otherwise, the decorated string is returned without any
	 * styles.
	 *
	 * @param decoratedString the decorated string
	 * @param decorationStyler the styler to use for the decoration or <code>null</code> for no
	 *            styles
	 * @param styledString the original styled string
	 *
	 * @return the styled decorated string (can be the given <code>styledString</code>)
	 * @since 3.5
	 */
	public static StyledString styleDecoratedString(String decoratedString, Styler decorationStyler, StyledString styledString) {
		String label= styledString.getString();
		int originalStart= decoratedString.indexOf(label);
		if (originalStart == -1) {
			return new StyledString(decoratedString); // the decorator did something wild
		}

		if (decoratedString.length() == label.length())
			return styledString;

		if (originalStart > 0) {
			StyledString newString= new StyledString(decoratedString.substring(0, originalStart), decorationStyler);
			newString.append(styledString);
			styledString= newString;
		}
		if (decoratedString.length() > originalStart + label.length()) { // decorator appended something
			return styledString.append(decoratedString.substring(originalStart + label.length()), decorationStyler);
		}
		return styledString; // no change
	}

}
