/**
 * Wraps a buffered FileWriter for generation with Acceleo. Note that this can also be used to create a Writer
 * that will previously merge the content of an existing file with the new content through JMerge.
 * 
 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
 * @since 3.0
 */
public final class AcceleoFileWriter extends AbstractAcceleoWriter {

. . .

	/**
	 * Constructs a writer that will use JMerge to merge the content of the file existing at path
	 * <em>filePath</em> with its new content. Note that the file will be written with the default System
	 * encoding if using this.
	 * 
	 * @param filePath
	 *            Path of the file this writer will contain the content of.
	 * @param hasJMergeTags
 	 *            Indicates whether the code has some  parts to merge
	 */
	public GeneratorFileWriter(String filePath, boolean hasJMergeTags) {
		delegate = new StringWriter(DEFAULT_BUFFER_SIZE);
		targetPath = filePath;
		this.hasJMergeTags= hasJMergeTags;
		shouldMerge = true;
	}

	/**
	 * Constructs a writer that will use JMerge to merge the content of the file existing at path
	 * <em>filePath</em> with its new content.
	 * 
	 * @param filePath
	 *            Path of the file this writer will contain the content of.
	 * @param hasJMergeTags
 	 *            Indicates whether the code has some  parts to merge
	 * @param charset
	 *            Encoding that's to be used to create the file with the merged content.
	 */
	public GeneratorFileWriter(String filePath, boolean hasJMergeTags, String charset) {
	this(filePath);
		selectedCharset = charset;
	}

	
	@Override
	public void close() throws IOException {
		if (!shouldMerge || !EMFPlugin.IS_ECLIPSE_RUNNING) {
			delegate.close();
		} else {
			// The decorated writer is a StringWriter. Closing has no effect on it
			flush();
			try {
				String generatedText= delegateWriter.toString();
				String existingContent= null;
				File file= new File(targetPath);
				boolean fileExists= file.exists();
				if(fileExists) existingContent= readFileAsString(targetPath);
				String finalContent= fileExists&& hasJMergeTags?
					merge(file, generatedText, selectedCharset):
					generatedText;
				Writer writer = null;
				boolean writeOk= false;
				if(fileExists){
					if(! existingContent.equals(finalContent)){
						writeOk= true;
					}
				}else{
					writeOk= true;
				}
				try {
					if(writeOk) {
						if (selectedCharset == null) {
							writer = new BufferedWriter(new FileWriter(new File(targetPath)));
						} else {
							final OutputStream fileOutputStream = new FileOutputStream(new File(targetPath));
							final OutputStreamWriter fileWriter = new OutputStreamWriter(fileOutputStream,
									selectedCharset);
							writer = new BufferedWriter(fileWriter);
						}
						writer.append(finalContent);
					}
				} finally {
					if (writer != null) {
						writer.close();
					}
				}
			} catch (ClassNotFoundException e) {
				/*
				 * shouldn't happen. This would mean we are in eclipse yet org.eclipse.emf.codegen cannot be
				 * found as a dependency of the generator plugin. This shouldn't happen since it is a
				 * reexported dependency of the engine.
				 */
				AcceleoEnginePlugin.log(e, true);
			}
		}
	}

	private String merge(File file, String generatedText, String selectedCharset) 
			throws ClassNotFoundException, IOException {
		Class.forName("org.eclipse.emf.codegen.merge.java.JMerger"); //$NON-NLS-1$
		return JMergeUtil.mergeFileContent(file, generatedText,	selectedCharset);
	}

	private String readFileAsString(String targetPath) throws IOException {
		return new String(Files.readAllBytes(Paths.get(targetPath)));
	}

. . .
}