/*=============================================================================#
 # Copyright (c) 2005, 2021 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.ltk.ui.sourceediting;

import java.util.Map;

import org.eclipse.core.runtime.NullProgressMonitor;
import org.eclipse.jface.text.AbstractDocument;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.BadPartitioningException;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.Position;
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.viewers.ISelection;
import org.eclipse.swt.graphics.Point;
import org.eclipse.ui.texteditor.IDocumentProvider;

import org.eclipse.statet.ecommons.text.core.PartitionConstraint;

import org.eclipse.statet.ltk.ast.core.util.AstSelection;
import org.eclipse.statet.ltk.core.SourceModelStamp;
import org.eclipse.statet.ltk.model.core.ModelManager;
import org.eclipse.statet.ltk.model.core.element.SourceUnit;
import org.eclipse.statet.ltk.model.core.element.SourceUnitModelInfo;
import org.eclipse.statet.ltk.ui.ISelectionWithElementInfoListener;
import org.eclipse.statet.ltk.ui.LTKInputData;


public abstract class AbstractMarkOccurrencesProvider implements ISourceEditorAddon,
		ISelectionWithElementInfoListener {
	
	
	private static final int CLEAR= -1;
	private static final int KEEP= 1;
	private static final int UPDATE= 2;
	
	
	public final class RunData {
		
		public final AbstractDocument doc;
		public SourceModelStamp stamp;
		
		private Annotation[] annotations;
		private Point range;
		
		private int set= 0;
		private Map<Annotation, Position> todo;
		
		
		RunData(final AbstractDocument doc, final SourceModelStamp stamp) {
			this.doc= doc;
			this.stamp= stamp;
		}
		
		
		public boolean isValid() {
			final Point currentSelection= AbstractMarkOccurrencesProvider.this.editor.currentSelection;
			return (this.range != null && currentSelection.x >= this.range.x
					&& currentSelection.x+currentSelection.y <= this.range.y
					&& this.doc.getModificationStamp() == this.stamp.getContentStamp() );
		}
		
		public boolean accept(final Point range) {
			this.range= range;
			if (isValid()) {
				return true;
			}
			this.range= null;
			return false;
		}
		
		public void set(final Map<Annotation, Position> annotations) {
			this.set= UPDATE;
			this.todo= annotations;
		}
		
		public void keep() {
			this.set= KEEP;
		}
		
		public void clear() {
			this.set= CLEAR;
		}
		
	}
	
	
	private final SourceEditor1 editor;
	
	private final String partitioning;
	private final PartitionConstraint toleratePartitions;
	
	private boolean isMarkEnabled;
	private RunData lastRun;
	
	
	public AbstractMarkOccurrencesProvider(final SourceEditor1 editor,
			final PartitionConstraint toleratePartitions) {
		if (editor == null) {
			throw new NullPointerException("editor");
		}
		if (toleratePartitions == null) {
			throw new NullPointerException("validPartitions");
		}
		this.editor= editor;
		this.partitioning= this.editor.getDocumentContentInfo().getPartitioning();
		this.toleratePartitions= toleratePartitions;
	}
	
	@Override
	public void install(final ISourceEditor editor) {
		this.isMarkEnabled= true;
		this.editor.addPostSelectionWithElementInfoListener(this);
	}
	
	@Override
	public void uninstall() {
		this.isMarkEnabled= false;
		this.editor.removePostSelectionWithElementInfoListener(this);
		removeAnnotations();
	}
	
	
	@Override
	public void inputChanged() {
		this.lastRun= null;
	}
	
	@Override
	public void stateChanged(final LTKInputData state) {
		final ISelection selection= state.getSelection();
		final boolean ok= update((SourceUnit) state.getInputElement(), state.getAstSelection(),
				(selection instanceof ITextSelection) ? (ITextSelection) selection : null );
		if (!ok && state.isStillValid()) {
			removeAnnotations();
		}
	}
	
	/**
	 * Updates the occurrences annotations based on the current selection.
	 * 
	 * @return <code>true</code> if the annotation is ok (still valid or updated), 
	 *     otherwise <code>false</code>
	 */
	protected boolean update(final SourceUnit inputElement, final AstSelection astSelection,
			final ITextSelection orgSelection) {
		if (!this.isMarkEnabled) {
			return false;
		}
		try {
			final SourceUnitModelInfo info= inputElement.getModelInfo(this.editor.getModelTypeId(),
					ModelManager.NONE, new NullProgressMonitor() );
			if (this.editor.getSourceUnit() != inputElement || info == null || astSelection == null) {
				return false;
			}
			final RunData run= new RunData(inputElement.getDocument(null), info.getStamp());
			if (run.doc == null) {
				return false;
			}
			if (this.lastRun != null && this.lastRun.isValid() && this.lastRun.stamp.equals(run.stamp)) {
				return true;
			}
			
			doUpdate(run, info, astSelection, orgSelection);
			if (!this.isMarkEnabled) {
				return false;
			}
			
			if (run.set == 0) {
				checkKeep(run, orgSelection);
			}
			switch (run.set) {
			case KEEP:
				return true;
			case UPDATE:
				updateAnnotations(run);
				return true;
			default:
				removeAnnotations();
				return true;
			}
		}
		catch (final BadLocationException e) {
		}
		catch (final BadPartitioningException e) {
		}
		catch (final UnsupportedOperationException e) {
		}
		return false;
	}
	
	protected abstract void doUpdate(RunData run, SourceUnitModelInfo info,
			AstSelection astSelection, ITextSelection orgSelection) 
			throws BadLocationException, BadPartitioningException, UnsupportedOperationException;
	
	
	protected void checkKeep(final RunData run, final ITextSelection selection)
			throws BadLocationException, BadPartitioningException {
		if (this.lastRun == null || !this.lastRun.stamp.equals(run.stamp)) {
			run.clear();
			return;
		}
		if (selection instanceof ITextSelection) {
			final ITextSelection textSelection= selection;
			final Point currentSelection= this.editor.currentSelection;
			final int offset= textSelection.getOffset();
			final int docLength= run.doc.getLength();
			final ITypedRegion partition= run.doc.getPartition(this.partitioning, offset, false);
			if (docLength > 0 &&
					(	(currentSelection.y > 0)
					||	(offset != currentSelection.x)
					||	(textSelection.getLength() == 0
						&& partition != null && this.toleratePartitions.matches(partition.getType())
						&& (offset <= 0 || !Character.isLetterOrDigit(run.doc.getChar(offset-1)) )
						&& (offset >= docLength || Character.isWhitespace(run.doc.getChar(offset)) ) )
					)) {
				run.keep();
				return;
			}
		}
		return;
	}
	
	protected IAnnotationModel getAnnotationModel() {
		final IDocumentProvider documentProvider= this.editor.getDocumentProvider();
		if (documentProvider == null) {
			throw new UnsupportedOperationException();
		}
		final IAnnotationModel annotationModel= documentProvider.getAnnotationModel(
				this.editor.getEditorInput());
		if (annotationModel == null || !(annotationModel instanceof IAnnotationModelExtension)) {
			throw new UnsupportedOperationException();
		}
		return annotationModel;
	}
	
	protected void updateAnnotations(final RunData run) throws BadLocationException {
		if (!run.isValid()) {
			return;
		}
		
		// Add occurrence annotations
		final IAnnotationModel annotationModel= getAnnotationModel();
//			create diff ?
//			if (this.lastRun != null && Arrays.equals(run.name, this.lastRun.name)) {
//			}
		final Annotation[] lastAnnotations= (this.lastRun != null) ? this.lastRun.annotations : null;
		synchronized (SourceEditor1.getLockObject(annotationModel)) {
			if (!run.isValid()) {
				return;
			}
			((IAnnotationModelExtension) annotationModel).replaceAnnotations(lastAnnotations, run.todo);
			run.annotations= run.todo.keySet().toArray(new Annotation[run.todo.keySet().size()]);
			run.todo= null;
			this.lastRun= run;
		}
	}
	
	protected void removeAnnotations() {
		final IAnnotationModel annotationModel= getAnnotationModel();
		synchronized (SourceEditor1.getLockObject(annotationModel)) {
			if (this.lastRun == null) {
				return;
			}
			((IAnnotationModelExtension) annotationModel).replaceAnnotations(this.lastRun.annotations, null);
			this.lastRun= null;
		}
	}
	
}