core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/editor/highlighting/AbstractSemanticHighlighter.java

/*******************************************************************************
 * Copyright (c) 2008, 2017 xored software, Inc. 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:
 *     xored software, Inc. - initial API and Implementation (Alex Panchenko)
 *******************************************************************************/
package org.eclipse.dltk.ui.editor.highlighting;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.eclipse.dltk.compiler.env.IModuleSource;
import org.eclipse.dltk.core.DLTKCore;
import org.eclipse.jface.text.Position;

/**
 * Abstract implementation of the {@link ISemanticHighlightingUpdater}.
 *
 * Descendant classes should override
 * {@link #doHighlighting(org.eclipse.dltk.compiler.env.ISourceModule)} and call
 * {@link #addPosition(int, int, int)} to highlight specified regions.
 *
 * Comparing old and new positions is performed in this class and calculated
 * "delta" is returned from the
 * {@link #reconcile(org.eclipse.dltk.compiler.env.ISourceModule, HighlightedPosition[])}
 * method.
 */
public abstract class AbstractSemanticHighlighter implements
		ISemanticHighlightingUpdater, ISemanticHighlightingRequestor {

	private IHighlightedPositionFactory positionFactory;
	private Map<String, HighlightingStyle> highlightingStyles = new HashMap<>();

	@Override
	public void initialize(IHighlightedPositionFactory factory,
			HighlightingStyle[] styles) {
		this.positionFactory = factory;
		this.highlightingStyles.clear();
		if (styles != null) {
			for (HighlightingStyle style : styles) {
				this.highlightingStyles.put(
						style.getSemaHighlighting().getPreferenceKey(), style);
			}
		}
	}

	private final List<HighlightedPosition> newPositions = new ArrayList<>();
	private int oldPositionCount = 0;
	private final List<HighlightedPosition> oldPositions = new ArrayList<>();

	@Override
	public UpdateResult reconcile(IModuleSource code,
			List<HighlightedPosition> currentPositions) {
		try {
			newPositions.clear();
			this.oldPositionCount = currentPositions.size();
			this.oldPositions.clear();
			this.oldPositions.addAll(currentPositions);
			if (doHighlighting(code)) {
				checkNewPositionOrdering();
				final HighlightedPosition[] removed = getRemovedPositions();
				if (DEBUG) {
					System.out.println(
							"Add:" + newPositions.size() + " " + newPositions); //$NON-NLS-1$ //$NON-NLS-2$
					System.out.println("Remove:" + removed.length + " " //$NON-NLS-1$ //$NON-NLS-2$
							+ Arrays.asList(removed));
				}
				return new UpdateResult(getAddedPositions(), removed);
			}
		} catch (Exception e) {
			DLTKCore.error("Error in SemanticPositionUpdater", e); //$NON-NLS-1$
		}
		return new UpdateResult(HighlightedPosition.NO_POSITIONS,
				HighlightedPosition.NO_POSITIONS);
	}

	/**
	 * This method should do all of the semantic highlighting. When something
	 * should be highlighted
	 *
	 * @param code
	 * @return
	 * @throws Exception
	 */
	protected abstract boolean doHighlighting(IModuleSource code)
			throws Exception;

	@Override
	public void addPosition(int start, int end, String highlightingKey) {
		final int len = end - start;
		if (len <= 0) {
			return;
		}
		final HighlightingStyle hl = highlightingStyles.get(highlightingKey);
		if (hl == null) {
			return;
		}
		for (int i = 0, size = oldPositions.size(); i < size; ++i) {
			final HighlightedPosition p = oldPositions.get(i);
			if (p != null && p.isEqual(start, len, hl)) {
				oldPositions.set(i, null);
				--oldPositionCount;
				return;
			}
		}
		if (!newPositions.isEmpty()) {
			final int lowBound = Math.max(newPositions.size() - 2, 0);
			for (int i = newPositions.size(); --i >= lowBound;) {
				final HighlightedPosition p = newPositions.get(i);
				if (p.isEqual(start, len, hl)) {
					if (DEBUG) {
						System.err.println("WARN: duplicate in new positions [" //$NON-NLS-1$
								+ start + "+" + len + "]"); //$NON-NLS-1$ //$NON-NLS-2$
					}
					return;
				}
			}
		}
		final HighlightedPosition hp = positionFactory
				.createHighlightedPosition(start, len, hl);
		newPositions.add(hp);
		if (DEBUG) {
			checkNewPositionOrdering();
		}
	}

	/**
	 * @return
	 */
	protected HighlightedPosition[] getAddedPositions() {
		final HighlightedPosition[] result = new HighlightedPosition[newPositions
				.size()];
		newPositions.toArray(result);
		return result;
	}

	protected HighlightedPosition[] getRemovedPositions() {
		final HighlightedPosition[] result = new HighlightedPosition[oldPositionCount];
		int index = 0;
		for (int i = 0, size = oldPositions.size(); i < size; ++i) {
			final HighlightedPosition p = oldPositions.get(i);
			if (p != null) {
				result[index++] = p;
			}
		}
		return result;
	}

	protected void checkNewPositionOrdering() {
		if (newPositions.isEmpty())
			return;
		Collections.sort(newPositions,
				(p1, p2) -> p1.getOffset() - p2.getOffset());
		Position previous = null;
		for (Iterator<HighlightedPosition> i = newPositions.iterator(); i
				.hasNext();) {
			final Position current = i.next();
			if (previous != null && previous.getOffset()
					+ previous.getLength() > current.getOffset()) {
				if (DEBUG) {
					System.err.println("ERROR: unordered position " + current); //$NON-NLS-1$
				}
				i.remove();
			} else {
				previous = current;
			}
		}
	}

	private static final boolean DEBUG = false;

}