/*
* Copyright (c) 2013 TMate Software Ltd
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* For information on how to redistribute this software under
* the terms of a license other than GNU General Public License
* contact TMate Software at support@hg4j.com
*/
package org.tmatesoft.hg.internal;
import java.io.File;
import java.io.IOException;
import org.tmatesoft.hg.core.HgIOException;
import org.tmatesoft.hg.core.SessionContext;
import org.tmatesoft.hg.repo.HgInvalidStateException;
/**
* Implementation strategies possible:<ul>
* <li> Get a copy, write changes to origin, keep copy as backup till #commit
* <p>(-) doesn't break hard links
* <li> Get a copy, write changes to a copy, on commit rename copy to origin.
* <p>(-) What if we read newly written data (won't find it);
* <p>(-) complex #commit
* <p>(+) simple rollback
* <li> Get a copy, rename origin to backup (breaks hard links), rename copy to origin, write changes
* <p>(+) Modified file is in place right away;
* <p>(+) easy #commit
* <li> Do not copy, just record file size, truncate to that size on rollback
* <li> ...?
* </ul>
* @author Artem Tikhomirov
* @author TMate Software Ltd.
*/
public abstract class Transaction {
/**
* Record the file is going to be modified during this transaction, obtain actual
* destination to write to.
* The file to be modified not necessarily exists, might be just a name of an added file
*/
public abstract File prepare(File f) throws HgIOException;
/**
* overwrites backup if exists, backup is kept after successful {@link #commit()}
*/
public abstract File prepare(File origin, File backup) throws HgIOException;
/**
* Tell that file was successfully processed
*/
public abstract void done(File f) throws HgIOException;
/**
* optional?
*/
public abstract void failure(File f, IOException ex);
/**
* Complete the transaction
*/
public abstract void commit() throws HgIOException;
/**
* Undo all the changes
*/
public abstract void rollback() throws HgIOException;
public interface Factory {
public Transaction create(SessionContext.Source ctxSource);
}
public static class NoRollback extends Transaction {
@Override
public File prepare(File f) throws HgIOException {
return f;
}
@Override
public File prepare(File origin, File backup) throws HgIOException {
return origin;
}
@Override
public void done(File f) throws HgIOException {
// no-op
}
@Override
public void failure(File f, IOException ex) {
// no-op
}
@Override
public void commit() throws HgIOException {
// no-op
}
@Override
public void rollback() throws HgIOException {
throw new HgInvalidStateException("This transaction doesn't support rollback");
}
}
}