/*******************************************************************************
 * Copyright (c) 2017 Red Hat Inc. 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:
 * - Lucas Bullen (Red Hat Inc.)
 *******************************************************************************/
package org.eclipse.ui.genericeditor.examples.dotproject;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.core.runtime.preferences.IEclipsePreferences.IPreferenceChangeListener;
import org.eclipse.core.runtime.preferences.IEclipsePreferences.PreferenceChangeEvent;
import org.eclipse.core.runtime.preferences.InstanceScope;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ISynchronizable;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.ITextViewerExtension5;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.reconciler.DirtyRegion;
import org.eclipse.jface.text.reconciler.IReconcilingStrategy;
import org.eclipse.jface.text.reconciler.IReconcilingStrategyExtension;
import org.eclipse.jface.text.source.Annotation;
import org.eclipse.jface.text.source.IAnnotationModel;
import org.eclipse.jface.text.source.IAnnotationModelExtension;
import org.eclipse.jface.text.source.ISourceViewer;
import org.eclipse.swt.custom.CaretEvent;
import org.eclipse.swt.custom.CaretListener;

/**
*
* This Reconciler Strategy is an example for how to override the default highlight strategy.
* It will highlight closing and opening tag names that match the current word the user is on.
*
*/
public class HighlightStrategy implements IReconcilingStrategy, IReconcilingStrategyExtension, CaretListener, IPreferenceChangeListener {

	private static final String ANNOTATION_TYPE = "org.eclipse.ui.genericeditor.text"; //$NON-NLS-1$
	public static final String TOGGLE_HIGHLIGHT_PREFERENCE = "org.eclipse.ui.genericeditor.togglehighlight"; //$NON-NLS-1$
	public static final String GENERIC_EDITOR_BUNDLE_ID = "org.eclipse.ui.genericeditor"; //$NON-NLS-1$

	private boolean enabled;
	private ISourceViewer sourceViewer;
	private IDocument document;

	private static final String TAG_NAME_REGEX = "<\\/?\\s*([a-zA-Z]+)"; //$NON-NLS-1$
	private static final Pattern TAG_NAME_PATTERN = Pattern.compile(TAG_NAME_REGEX);

	private Annotation[] fOccurrenceAnnotations = null;

	private void applyHighlights(int offset) {
		if (sourceViewer == null || !enabled) {
			return;
		}
		String text = document.get();
		offset = ((ITextViewerExtension5)sourceViewer).widgetOffset2ModelOffset(offset);

		int wordStartOffset = Math.max(text.lastIndexOf('/',offset),text.lastIndexOf('<',offset))+1;
		int wordEndOffset = findEndingOffset(text, offset);
		if(wordEndOffset <= wordStartOffset || wordEndOffset == -1 || wordStartOffset == -1)
			return;
		String word = text.substring(wordStartOffset, wordEndOffset);
		if(word.indexOf('>') != -1 || word.indexOf('<') != -1) {
			removeOccurrenceAnnotations();
			return;
		}

		Matcher m = TAG_NAME_PATTERN.matcher(text);
		Map<Annotation, Position> annotationMap = new HashMap<>();
		while(m.find()) {
			if(m.group(1).equals(word)) {
				annotationMap.put(new Annotation(ANNOTATION_TYPE, false, null),
						new Position(m.start(1), m.end(1) - m.start(1)));
			}
		}

		if(annotationMap.size() < 2) {
			removeOccurrenceAnnotations();
			return;
		}

		IAnnotationModel annotationModel = sourceViewer.getAnnotationModel();
		synchronized (getLockObject(annotationModel)) {
			if (annotationModel instanceof IAnnotationModelExtension) {
				((IAnnotationModelExtension) annotationModel).replaceAnnotations(fOccurrenceAnnotations, annotationMap);
			} else {
				removeOccurrenceAnnotations();
				Iterator<Entry<Annotation, Position>> iter = annotationMap.entrySet().iterator();
				while (iter.hasNext()) {
					Entry<Annotation, Position> mapEntry = iter.next();
					annotationModel.addAnnotation(mapEntry.getKey(), mapEntry.getValue());
				}
			}
			fOccurrenceAnnotations = annotationMap.keySet().toArray(new Annotation[annotationMap.size()]);
		}
	}

	private static int findEndingOffset(String text, int offset) {
		String substring = text.substring(offset);
		String[] split = substring.split("[^a-zA-Z0-9]+");//$NON-NLS-1$
		if(split.length == 0) {
			return -1;
		}
		return offset + split[0].length();
	}

	public void install(ITextViewer viewer) {
		if (!(viewer instanceof ISourceViewer)) {
			return;
		}
		IEclipsePreferences preferences = InstanceScope.INSTANCE.getNode(GENERIC_EDITOR_BUNDLE_ID);
		preferences.addPreferenceChangeListener(this);
		this.enabled = preferences.getBoolean(TOGGLE_HIGHLIGHT_PREFERENCE, true);
		this.sourceViewer = (ISourceViewer) viewer;
		this.sourceViewer.getTextWidget().addCaretListener(this);
	}

	public void uninstall() {
		if (sourceViewer != null) {
			sourceViewer.getTextWidget().removeCaretListener(this);
		}
		IEclipsePreferences preferences = InstanceScope.INSTANCE.getNode(GENERIC_EDITOR_BUNDLE_ID);
		preferences.removePreferenceChangeListener(this);
	}

	@Override
	public void preferenceChange(PreferenceChangeEvent event) {
		if (event.getKey().equals(TOGGLE_HIGHLIGHT_PREFERENCE)) {
			this.enabled = Boolean.parseBoolean(event.getNewValue().toString());
			if (enabled) {
				initialReconcile();
			} else {
				removeOccurrenceAnnotations();
			}
		}
	}

	@Override
	public void caretMoved(CaretEvent event) {
		applyHighlights(event.caretOffset);
	}

	@Override
	public void initialReconcile() {
		if (sourceViewer != null) {
			sourceViewer.getTextWidget().getDisplay().asyncExec(() -> {
				if (sourceViewer != null && sourceViewer.getTextWidget() != null) {
					applyHighlights(sourceViewer.getTextWidget().getCaretOffset());
				}
			});
		}
	}

	void removeOccurrenceAnnotations() {
		IAnnotationModel annotationModel = sourceViewer.getAnnotationModel();
		if (annotationModel == null || fOccurrenceAnnotations == null)
			return;

		synchronized (getLockObject(annotationModel)) {
			if (annotationModel instanceof IAnnotationModelExtension) {
				((IAnnotationModelExtension) annotationModel).replaceAnnotations(fOccurrenceAnnotations, null);
			} else {
				for (Annotation fOccurrenceAnnotation : fOccurrenceAnnotations)
					annotationModel.removeAnnotation(fOccurrenceAnnotation);
			}
			fOccurrenceAnnotations = null;
		}
	}

	private static Object getLockObject(IAnnotationModel annotationModel) {
		if (annotationModel instanceof ISynchronizable) {
			Object lock = ((ISynchronizable) annotationModel).getLockObject();
			if (lock != null)
				return lock;
		}
		return annotationModel;
	}

	@Override
	public void setDocument(IDocument document) {
		this.document = document;
	}

	@Override
	public void reconcile(DirtyRegion dirtyRegion, IRegion subRegion) {
		// Do nothing
	}

	@Override
	public void reconcile(IRegion partition) {
		// Do nothing
	}

	@Override
	public void setProgressMonitor(IProgressMonitor monitor) {
		// Not used
	}
}