/*******************************************************************************
 * Copyright (c) 2010, 2018 itemis and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v20.html
 *
 * Contributors:
 *    itemis AG - initial API and implementation
 *    E.D.Willink - integration of XTFO code uder CQ 4866
 *******************************************************************************/
package org.eclipse.ocl.examples.xtext.console.xtfo;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.jdt.annotation.Nullable;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextInputListener;
import org.eclipse.jface.text.TextAttribute;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.swt.widgets.Display;
import org.eclipse.xtext.ide.editor.syntaxcoloring.IHighlightedPositionAcceptor;
import org.eclipse.xtext.ide.editor.syntaxcoloring.ISemanticHighlightingCalculator;
import org.eclipse.xtext.ide.editor.syntaxcoloring.MergingHighlightedPositionAcceptor;
import org.eclipse.xtext.resource.XtextResource;
import org.eclipse.xtext.ui.editor.XtextSourceViewer;
import org.eclipse.xtext.ui.editor.model.IXtextDocument;
import org.eclipse.xtext.ui.editor.model.IXtextModelListener;
import org.eclipse.xtext.ui.editor.model.XtextDocument;
import org.eclipse.xtext.ui.editor.syntaxcoloring.AttributedPosition;
import org.eclipse.xtext.ui.editor.syntaxcoloring.HighlightingPresenter;
import org.eclipse.xtext.ui.editor.syntaxcoloring.ITextAttributeProvider;
import org.eclipse.xtext.util.CancelIndicator;
import org.eclipse.xtext.util.concurrent.IUnitOfWork;

import com.google.inject.Inject;

/**
 * @author Sebastian Zarnekow - Initial contribution and API
 */
public class HighlightingReconciler implements ITextInputListener, IXtextModelListener, IHighlightedPositionAcceptor {

	@Inject(optional=true)
	private ISemanticHighlightingCalculator calculator;

	@Inject
	private ITextAttributeProvider attributeProvider;

	/** The source viewer this highlighting reconciler is installed on */
	private XtextSourceViewer sourceViewer;
	/** The highlighting presenter */
	private HighlightingPresenter presenter;

	/** Background job's added highlighted positions */
	private final List<AttributedPosition> addedPositions = new ArrayList<AttributedPosition>();
	/** Background job's removed highlighted positions */
	private List<AttributedPosition> removedPositions = new ArrayList<AttributedPosition>();
	/** Number of removed positions */
	private int removedPositionCount;

	/**
	 * Reconcile operation lock.
	 */
	private final Object fReconcileLock = new Object();
	/**
	 * <code>true</code> if any thread is executing <code>reconcile</code>, <code>false</code> otherwise.
	 */
	private boolean reconciling = false;

	/**
	 * Start reconciling positions.
	 */
	private void startReconcilingPositions() {
		presenter.addAllPositions(removedPositions);
		removedPositionCount = removedPositions.size();
	}

	/**
	 * Reconcile positions based on the AST subtrees
	 *
	 * @param subtrees
	 *            the AST subtrees
	 */
	private void reconcilePositions(XtextResource resource) {
		//		for (int i= 0, n= subtrees.length; i < n; i++)
		//			subtrees[i].accept(fCollector);
		MergingHighlightedPositionAcceptor acceptor = new MergingHighlightedPositionAcceptor(calculator);
		acceptor.provideHighlightingFor(resource, this, CancelIndicator.NullImpl);
		//		calculator.provideHighlightingFor(resource, this);
		List<AttributedPosition> oldPositions = removedPositions;
		List<AttributedPosition> newPositions = new ArrayList<AttributedPosition>(removedPositionCount);
		for (int i = 0, n = oldPositions.size(); i < n; i++) {
			AttributedPosition current = oldPositions.get(i);
			if (current != null)
				newPositions.add(current);
		}
		removedPositions = newPositions;
	}

	/**
	 * Add a position with the given range and highlighting if it does not exist already.
	 * @param offset The range offset
	 * @param length The range length
	 */
	@Override
	public void addPosition(int offset, int length, String... ids) {
		TextAttribute highlighting = ids.length == 1 ?
			attributeProvider.getAttribute(ids[0])
			:	attributeProvider.getMergedAttributes(ids);
			boolean isExisting= false;
			// TODO: use binary search
			for (int i= 0, n= removedPositions.size(); i < n; i++) {
				AttributedPosition position= removedPositions.get(i);
				if (position == null)
					continue;
				if (position.isEqual(offset, length, highlighting)) {
					isExisting= true;
					removedPositions.set(i, null);
					removedPositionCount--;
					break;
				}
			}

			if (!isExisting) {
				AttributedPosition position= presenter.createHighlightedPosition(offset, length, highlighting);
				addedPositions.add(position);
			}
	}

	/**
	 * Update the presentation.
	 *
	 * @param textPresentation
	 *            the text presentation
	 * @param addedPositions
	 *            the added positions
	 * @param removedPositions
	 *            the removed positions
	 */
	private void updatePresentation(TextPresentation textPresentation, List<AttributedPosition> addedPositions,
			List<AttributedPosition> removedPositions) {
		Runnable runnable = presenter.createUpdateRunnable(textPresentation, addedPositions, removedPositions);
		if (runnable == null)
			return;

		Display display = getDisplay();
		display.asyncExec(runnable);
	}

	private Display getDisplay() {
		return this.sourceViewer.getControl().getDisplay();
	}

	/**
	 * Stop reconciling positions.
	 */
	private void stopReconcilingPositions() {
		removedPositions.clear();
		removedPositionCount = 0;
		addedPositions.clear();
	}

	/**
	 * Install this reconciler on the given editor and presenter.
	 *
	 * @param sourceViewer
	 *            the source viewer
	 * @param presenter
	 *            the highlighting presenter
	 */
	public void install(XtextSourceViewer sourceViewer, HighlightingPresenter presenter) {
		this.presenter = presenter;
		this.sourceViewer = sourceViewer;
		if (calculator != null) {
			((IXtextDocument) sourceViewer.getDocument()).addModelListener(this);
			sourceViewer.addTextInputListener(this);
		}
		refresh();
	}

	/**
	 * Uninstall this reconciler from the editor
	 */
	public void uninstall() {
		if (presenter != null)
			presenter.setCanceled(true);

		if (sourceViewer.getDocument() != null) {
			if (calculator != null) {
				XtextDocument document = (XtextDocument) sourceViewer.getDocument();
				document.removeModelListener(this);
				sourceViewer.removeTextInputListener(this);
			}
		}

		sourceViewer = null;
		presenter = null;
	}

	/*
	 * @see org.eclipse.jface.text.ITextInputListener#inputDocumentAboutToBeChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
	 */
	@Override
	public void inputDocumentAboutToBeChanged(IDocument oldInput, IDocument newInput) {
		if (oldInput != null)
			((IXtextDocument) oldInput).removeModelListener(this);
	}

	/*
	 * @see org.eclipse.jface.text.ITextInputListener#inputDocumentChanged(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.IDocument)
	 */
	@Override
	public void inputDocumentChanged(IDocument oldInput, IDocument newInput) {
		if (newInput != null) {
			refresh();
			((IXtextDocument) newInput).addModelListener(this);
		}
	}

	/**
	 * Refreshes the highlighting.
	 */
	public void refresh() {
		if (calculator != null) {
			((XtextDocument) sourceViewer.getDocument()).readOnly(new IUnitOfWork.Void<XtextResource>() {
				@Override
				public void process(@Nullable XtextResource state) throws Exception {
					modelChanged(state);
				}
			});
		} else {
			Display display = getDisplay();
			display.asyncExec(presenter.createSimpleUpdateRunnable());
		}
	}

	@Override
	public void modelChanged(XtextResource resource) {
		// ensure at most one thread can be reconciling at any time
		synchronized (fReconcileLock) {
			if (reconciling)
				return;
			reconciling = true;
		}
		final HighlightingPresenter highlightingPresenter = presenter;
		try {
			if (highlightingPresenter == null)
				return;

			highlightingPresenter.setCanceled(false);

			if (highlightingPresenter.isCanceled())
				return;

			startReconcilingPositions();

			if (!highlightingPresenter.isCanceled()) {
				reconcilePositions(resource);
			}

			final TextPresentation[] textPresentation = new TextPresentation[1];
			if (!highlightingPresenter.isCanceled()) {
				textPresentation[0] = highlightingPresenter.createPresentation(addedPositions, removedPositions);
			}

			if (!highlightingPresenter.isCanceled())
				updatePresentation(textPresentation[0], addedPositions, removedPositions);

			stopReconcilingPositions();
		}
		finally {
			synchronized (fReconcileLock) {
				reconciling = false;
			}
		}
	}

	public void setCalculator(ISemanticHighlightingCalculator calculator) {
		this.calculator = calculator;
	}

	public ISemanticHighlightingCalculator getCalculator() {
		return calculator;
	}
}