/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License (the "License").

 * You may not use this file except in compliance with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright (c) 2009, 2012, Oracle and/or its affiliates. All rights reserved.

 */

package com.oracle.solaris.vp.util.misc;

import java.io.*;

/**

 * A generic configuration writing class, used for adding, removing, or

 * updating lines in a #-commented line-based configuration file while

 * maintaining existing comments.

 */

public abstract class ConfigWriter

{

    /**

     * Called for each existing non-comment line if the default

     * {@link #processFile} implementation is used.  Should be overridden by

     * subclasses that don't override {@link #processFile}.

     *

     * @param writer the writer to which new configuration should be emitted

     * @param line the input line being processed

     * @return {@code true} if the line was processed, {@code false} if the

     * caller should emit the line

     * @throws java.io.IOException

     */

    protected boolean processLine(BufferedWriter writer, String line)

	throws IOException

    {

	return (false);

    }

    /**

     * Called when the end of the configuration file is reached if the

     * default {@link #processFile} implementation is used.  Default

     * implementation does nothing.

     *

     * @param writer the writer to which new configuration should be emitted

     * @throws java.io.IOException

     */

    protected void processEOF(BufferedWriter writer)

	throws IOException

    {

    }

    /**

     * Reads the configuration found in the old configuration file and writes

     * the updated configuration to the new configuration file.  The default

     * implementation copies each comment line and line for which

     * {@link #processLine} returns {@code false}, and calls {@link #processEOF}

     * when the end of the input file is reached.

     *

     * @param reader the old configuration file

     * @param writer the new configuration file

     * @throws java.io.IOException

     */

    protected void processFile(BufferedReader reader, BufferedWriter writer)

	throws IOException

    {

	String line;

	while ((line = reader.readLine()) != null) {

	    if (line.startsWith("#") || !processLine(writer, line)) {

		writer.write(line);

		writer.newLine();

	    }

	}

	processEOF(writer);

    }

    /**

     * Transforms the configuration of the specified file.  Creates a

     * temporary file, passes it and the original to {@link #processFile},

     * and renames it over the original.

     *

     * @param filename the file to transform

     * @throws java.io.IOException

     */

    protected void writeConfig(String filename) throws IOException

    {

	/*

	 * Assume we're dealing with a trusted location.

	 */

	String tmpfile = filename + ".tmp";

	BufferedReader reader = new BufferedReader(new FileReader(filename));

	BufferedWriter writer = new BufferedWriter(new FileWriter(tmpfile));

	try {

	    processFile(reader, writer);

	} finally {

	    /*

	     * Close files and move temporary file over the original.

	     */

	    reader.close();

	    writer.close();

	    (new File(tmpfile)).renameTo(new File(filename));

	}

    }

}