plugins/org.eclipse.acceleo.engine/src/org/eclipse/acceleo/engine/internal/evaluation/JMergeUtil.java

/*******************************************************************************
 * Copyright (c) 2009, 2011 Obeo.
 * 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:
 *     Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.acceleo.engine.internal.evaluation;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Calendar;

import org.eclipse.acceleo.common.IAcceleoConstants;
import org.eclipse.acceleo.engine.AcceleoEngineMessages;
import org.eclipse.acceleo.engine.AcceleoEnginePlugin;
import org.eclipse.emf.codegen.merge.java.JControlModel;
import org.eclipse.emf.codegen.merge.java.JMerger;
import org.eclipse.emf.codegen.merge.java.facade.ast.ASTFacadeHelper;
import org.eclipse.emf.common.EMFPlugin;
import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.common.util.WrappedException;

/**
 * This class will be used to provide JMerge support when generating MTL files. Keep this in a separate class
 * to avoid non-optional dependency on org.eclipse.emf.ecore.codegen.
 * 
 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
 */
public final class JMergeUtil {
	/** This will hold the system specific line separator ("\n" for unix, "\r\n" for dos, "\r" for mac, ...). */
	private static final String LINE_SEPARATOR = System.getProperty("line.separator"); //$NON-NLS-1$

	/**
	 * Utility classes don't need to be instantiated.
	 */
	private JMergeUtil() {
		// Prevents instantiation
	}

	/**
	 * This can be used to support JMerge for the merging of generated <code>content</code> with the old file
	 * content. Old content will be read from the <code>target</code> File, new content will be read from
	 * <code>content</code>. The merged content will be not be written to disk.
	 * <p>
	 * <b>Note</b> that JMerge will <u>not</u> be called if eclipse is not running.
	 * </p>
	 * 
	 * @param target
	 *            Target file of the generation.
	 * @param content
	 *            The new content with which we should merge the old.
	 * @param charset
	 *            Encoding that should be used to read the target file. Can be <code>null</code>.
	 * @return The merged content.
	 * @throws IOException
	 *             Throw if we couldn't append data to the target file.
	 */
	public static String mergeFileContent(File target, String content, String charset) throws IOException {
		if (!EMFPlugin.IS_ECLIPSE_RUNNING) {
			return content;
		}
		String newContent = content;
		if (target.getName().endsWith(".java")) { //$NON-NLS-1$
			// FIXME With this kind of URI, JMerge support is only accessible within Eclipse
			String jmergeFile = URI.createPlatformPluginURI(
					"org.eclipse.emf.codegen.ecore/templates/emf-merge.xml", false).toString(); //$NON-NLS-1$
			JControlModel model = new JControlModel();
			model.initialize(new ASTFacadeHelper(), jmergeFile);
			if (model.canMerge()) {
				try {
					JMerger jMerger = new JMerger(model);
					jMerger.setSourceCompilationUnit(jMerger.createCompilationUnitForContents(content));
					// JMerge takes care of buffering the input stream we feed it
					jMerger.setTargetCompilationUnit(jMerger.createCompilationUnitForInputStream(
							new FileInputStream(target), charset));
					jMerger.merge();
					newContent = jMerger.getTargetCompilationUnit().getContents();
				} catch (WrappedException e) {
					// The Java file contains errors. We'll copy the old file as a ".lost"
					try {
						createLostFile(target);
					} catch (IOException ee) {
						// FIXME log Couldn't create the lost file.
					}
					AcceleoEnginePlugin.log(AcceleoEngineMessages.getString(
							"JMergeUtilError", target.getName()), false); //$NON-NLS-1$
				}
			} else {
				// FIXME log, couldn't find emf-merge.xml
			}
		}
		return newContent;
	}

	/**
	 * This will copy the given file as a ".lost" file in the same folder with the same name.
	 * 
	 * @param file
	 *            The file we are to copy as a lost file.
	 * @throws IOException
	 *             Thrown if we couldn't read the source file or create its ".lost" sibling.
	 */
	private static void createLostFile(File file) throws IOException {
		FileChannel source = null;
		FileChannel destination = null;

		try {
			source = new FileInputStream(file).getChannel();
			destination = new FileOutputStream(file.toString().concat(
					IAcceleoConstants.ACCELEO_LOST_FILE_EXTENSION), true).getChannel();

			// Print a time stamp of the current copy
			StringBuilder timestamp = new StringBuilder();
			timestamp.append(LINE_SEPARATOR).append(Calendar.getInstance().getTime().toString()).append(
					LINE_SEPARATOR);
			timestamp
					.append("================================================================================"); //$NON-NLS-1$
			timestamp.append(LINE_SEPARATOR);

			destination.write(ByteBuffer.wrap(timestamp.toString().getBytes()));
			source.transferTo(0, source.size(), destination);
		} finally {
			if (destination != null) {
				destination.close();
			}
			if (source != null) {
				source.close();
			}
		}
	}

	/**
	 * This can be used to support JMerge for the merging of generated <code>content</code> with old generated
	 * content. Old content will be read from <code>oldContent</code> while new content will be read from
	 * <code>content</code>. The target file's only purpose is to check if we can merge such files (only
	 * *.java for now).
	 * <p>
	 * <b>Note</b> that JMerge will <u>not</u> be called if eclipse is not running.
	 * </p>
	 * 
	 * @param target
	 *            Target file of the generation.
	 * @param content
	 *            The new content with which we should merge the old.
	 * @param oldContent
	 *            Previous content of the generation. Can be <code>null</code> if we are not in preview mode.
	 * @return The merged content.
	 * @throws IOException
	 *             Throw if we couldn't append data to the target file.
	 */
	public static String mergeContent(File target, String content, String oldContent) throws IOException {
		if (!EMFPlugin.IS_ECLIPSE_RUNNING) {
			return content;
		}
		String newContent = content;
		if (target.getName().endsWith(".java")) { //$NON-NLS-1$
			// FIXME With this kind of URI, JMerge support is only accessible within Eclipse
			String jmergeFile = URI.createPlatformPluginURI(
					"org.eclipse.emf.codegen.ecore/templates/emf-merge.xml", false).toString(); //$NON-NLS-1$
			JControlModel model = new JControlModel();
			model.initialize(new ASTFacadeHelper(), jmergeFile);
			if (model.canMerge()) {
				try {
					JMerger jMerger = new JMerger(model);
					jMerger.setSourceCompilationUnit(jMerger.createCompilationUnitForContents(content));
					jMerger.setTargetCompilationUnit(jMerger.createCompilationUnitForContents(oldContent));
					jMerger.merge();
					newContent = jMerger.getTargetCompilationUnit().getContents();
				} catch (WrappedException e) {
					AcceleoEnginePlugin.log(AcceleoEngineMessages.getString(
							"JMergeUtilError", target.getName()), false); //$NON-NLS-1$
				}
			} else {
				// FIXME log, couldn't find emf-merge.xml
			}
		}
		return newContent;
	}
}