Copyright (c) 2000, 2010 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
/*******************************************************************************
 * Copyright (c) 2000, 2010 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
 *******************************************************************************/
package org.eclipse.ltk.internal.core.refactoring;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.NullProgressMonitor;

import org.eclipse.core.filebuffers.FileBuffers;
import org.eclipse.core.filebuffers.ITextFileBuffer;
import org.eclipse.core.filebuffers.ITextFileBufferManager;

import org.eclipse.text.edits.MalformedTreeException;
import org.eclipse.text.edits.TextEdit;
import org.eclipse.text.edits.UndoEdit;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;

import org.eclipse.ltk.core.refactoring.Change;
import org.eclipse.ltk.core.refactoring.RefactoringStatus;

public class UndoDocumentChange extends Change {

	private String fName;
	private UndoEdit fUndo;
	private IDocument fDocument;
	private int fLength;

	public UndoDocumentChange(String name, IDocument document, UndoEdit undo) {
		fName= name;
		fUndo= undo;
		fDocument= document;
	}

	@Override
	public String getName() {
		return fName;
	}

	@Override
	public Object getModifiedElement() {
		return null;
	}

	@Override
	public void initializeValidationData(IProgressMonitor pm) {
		fLength= fDocument.getLength();
	}

	@Override
	public RefactoringStatus isValid(IProgressMonitor pm) throws CoreException {
		if (pm == null)
			pm= new NullProgressMonitor();
		pm.beginTask("", 1); //$NON-NLS-1$
		RefactoringStatus result= TextChanges.isValid(fDocument, fLength);
		pm.worked(1);
		return result;
	}

	@Override
	public Change perform(IProgressMonitor pm) throws CoreException {
		try {
			UndoEdit redo= performEdits();
			Change result= new UndoDocumentChange(getName(), fDocument, redo);
			return result;
		} catch (MalformedTreeException e) {
			throw Changes.asCoreException(e);
		} catch (BadLocationException e) {
			throw Changes.asCoreException(e);
		}
	}

	private UndoEdit performEdits() throws BadLocationException, MalformedTreeException {
		ITextFileBufferManager fileBufferManager= FileBuffers.getTextFileBufferManager();
		
		ITextFileBuffer fileBuffer= fileBufferManager.getTextFileBuffer(fDocument);
		if (fileBuffer == null || ! fileBuffer.isSynchronizationContextRequested()) {
			return fUndo.apply(fDocument, TextEdit.CREATE_UNDO);
		}
		
		/** The lock for waiting for computation in the UI thread to complete. */
		final Lock completionLock= new Lock();
		final UndoEdit[] result= new UndoEdit[1];
		final BadLocationException[] exception= new BadLocationException[1];
		Runnable runnable= new Runnable() {
			@Override
			public void run() {
				synchronized (completionLock) {
					try {
						result[0]= fUndo.apply(fDocument, TextEdit.CREATE_UNDO);
					} catch (BadLocationException e) {
						exception[0]= e;
					} finally {
						completionLock.fDone= true;
						completionLock.notifyAll();
					}
				}
			}
		};
		
		synchronized (completionLock) {
			fileBufferManager.execute(runnable);
			while (! completionLock.fDone) {
				try {
					completionLock.wait(500);
				} catch (InterruptedException x) {
				}
			}
		}
		
		if (exception[0] != null) {
			throw exception[0];
		}
		
		return result[0];
	}

}