tikhomirov@617: /*
tikhomirov@617:  * Copyright (c) 2013 TMate Software Ltd
tikhomirov@617:  *  
tikhomirov@617:  * This program is free software; you can redistribute it and/or modify
tikhomirov@617:  * it under the terms of the GNU General Public License as published by
tikhomirov@617:  * the Free Software Foundation; version 2 of the License.
tikhomirov@617:  *
tikhomirov@617:  * This program is distributed in the hope that it will be useful,
tikhomirov@617:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
tikhomirov@617:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tikhomirov@617:  * GNU General Public License for more details.
tikhomirov@617:  *
tikhomirov@617:  * For information on how to redistribute this software under
tikhomirov@617:  * the terms of a license other than GNU General Public License
tikhomirov@617:  * contact TMate Software at support@hg4j.com
tikhomirov@617:  */
tikhomirov@617: package org.tmatesoft.hg.internal;
tikhomirov@617: 
tikhomirov@617: import java.io.File;
tikhomirov@617: import java.io.IOException;
tikhomirov@617: import java.util.Iterator;
tikhomirov@617: import java.util.LinkedList;
tikhomirov@617: import java.util.List;
tikhomirov@617: 
tikhomirov@617: import org.tmatesoft.hg.core.HgIOException;
tikhomirov@617: import org.tmatesoft.hg.core.SessionContext;
tikhomirov@617: 
tikhomirov@617: /**
tikhomirov@617:  * This transaction strategy makes a copy of original file and breaks origin hard links, if any.
tikhomirov@617:  * Changes are directed to actual repository files.
tikhomirov@617:  * 
tikhomirov@617:  * On commit, remove all backup copies
tikhomirov@617:  * On rollback, move all backup files in place of original
tikhomirov@617:  * 
tikhomirov@617:  * @author Artem Tikhomirov
tikhomirov@617:  * @author TMate Software Ltd.
tikhomirov@617:  */
tikhomirov@617: public final class COWTransaction extends Transaction {
tikhomirov@617: 	
tikhomirov@617: 	private final FileUtils fileHelper;
tikhomirov@617: 	private final List<RollbackEntry> entries = new LinkedList<RollbackEntry>();
tikhomirov@617: 	
tikhomirov@617: 	public COWTransaction(SessionContext.Source ctxSource) {
tikhomirov@617: 		fileHelper = new FileUtils(ctxSource.getSessionContext().getLog());
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	@Override
tikhomirov@617: 	public File prepare(File f) throws HgIOException {
tikhomirov@617: 		if (known(f)) {
tikhomirov@617: 			return f;
tikhomirov@617: 		}
tikhomirov@635: 		if (!f.exists()) {
tikhomirov@635: 			return recordNonExistent(f);
tikhomirov@635: 		}
tikhomirov@617: 		final File parentDir = f.getParentFile();
tikhomirov@617: 		assert parentDir.canWrite();
tikhomirov@617: 		File copy = new File(parentDir, f.getName() + ".hg4j.copy");
tikhomirov@617: 		fileHelper.copy(f, copy);
tikhomirov@617: 		final long lm = f.lastModified();
tikhomirov@617: 		copy.setLastModified(lm);
tikhomirov@617: 		File backup = new File(parentDir, f.getName() + ".hg4j.orig");
tikhomirov@617: 		if (backup.exists()) {
tikhomirov@617: 			backup.delete();
tikhomirov@617: 		}
tikhomirov@617: 		if (!f.renameTo(backup)) {
tikhomirov@617: 			throw new HgIOException(String.format("Failed to backup %s to %s", f.getName(), backup.getName()), backup);
tikhomirov@617: 		}
tikhomirov@617: 		if (!copy.renameTo(f)) {
tikhomirov@617: 			throw new HgIOException(String.format("Failed to bring on-write copy in place (%s to %s)", copy.getName(), f.getName()), copy);
tikhomirov@617: 		}
tikhomirov@617: 		f.setLastModified(lm);
tikhomirov@617: 		record(f, backup);
tikhomirov@617: 		return f;
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	@Override
tikhomirov@617: 	public File prepare(File origin, File backup) throws HgIOException {
tikhomirov@617: 		if (known(origin)) {
tikhomirov@617: 			return origin;
tikhomirov@617: 		}
tikhomirov@635: 		if (!origin.exists()) {
tikhomirov@635: 			return recordNonExistent(origin);
tikhomirov@635: 		}
tikhomirov@617: 		fileHelper.copy(origin, backup);
tikhomirov@617: 		final RollbackEntry e = record(origin, backup);
tikhomirov@617: 		e.keepBackup = true;
tikhomirov@617: 		return origin;
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	@Override
tikhomirov@617: 	public void done(File f) throws HgIOException {
tikhomirov@617: 		find(f).success = true;
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	@Override
tikhomirov@617: 	public void failure(File f, IOException ex) {
tikhomirov@617: 		find(f).failure = ex;
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	// XXX custom exception for commit and rollback to hold information about files rolled back
tikhomirov@617: 	
tikhomirov@617: 	@Override
tikhomirov@617: 	public void commit() throws HgIOException {
tikhomirov@617: 		for (Iterator<RollbackEntry> it = entries.iterator(); it.hasNext();) {
tikhomirov@617: 			RollbackEntry e = it.next();
tikhomirov@617: 			assert e.success;
tikhomirov@617: 			if (e.failure != null) {
tikhomirov@617: 				throw new HgIOException("Can't close transaction with a failure.", e.failure, e.origin);
tikhomirov@617: 			}
tikhomirov@617: 			if (!e.keepBackup && e.backup != null) {
tikhomirov@617: 				e.backup.delete();
tikhomirov@617: 			}
tikhomirov@617: 			it.remove();
tikhomirov@617: 		}
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	@Override
tikhomirov@617: 	public void rollback() throws HgIOException {
tikhomirov@617: 		LinkedList<RollbackEntry> success = new LinkedList<RollbackEntry>();
tikhomirov@617: 		for (Iterator<RollbackEntry> it = entries.iterator(); it.hasNext();) {
tikhomirov@617: 			RollbackEntry e = it.next();
tikhomirov@617: 			e.origin.delete();
tikhomirov@617: 			if (e.backup != null) {
tikhomirov@617: 				if (!e.backup.renameTo(e.origin)) {
tikhomirov@617: 					String msg = String.format("Transaction rollback failed, could not rename backup %s back to %s", e.backup.getName(), e.origin.getName());
tikhomirov@617: 					throw new HgIOException(msg, e.origin);
tikhomirov@617: 				}
tikhomirov@621: 				// renameTo() doesn't update timestamp, while the rest of the code relies
tikhomirov@621: 				// on file timestamp to detect revlog changes. Rollback *is* a change,
tikhomirov@621: 				// even if it brings the old state.
tikhomirov@621: 				e.origin.setLastModified(System.currentTimeMillis());
tikhomirov@617: 			}
tikhomirov@617: 			success.add(e);
tikhomirov@617: 			it.remove();
tikhomirov@617: 		}
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@635: 	private File recordNonExistent(File f) throws HgIOException {
tikhomirov@635: 		record(f, null);
tikhomirov@635: 		try {
tikhomirov@635: 			f.getParentFile().mkdirs();
tikhomirov@635: 			f.createNewFile();
tikhomirov@635: 			return f;
tikhomirov@635: 		} catch (IOException ex) {
tikhomirov@635: 			throw new HgIOException("Failed to create new file", ex, f);
tikhomirov@635: 		}
tikhomirov@635: 	}
tikhomirov@635: 	
tikhomirov@617: 	private RollbackEntry record(File origin, File backup) {
tikhomirov@617: 		final RollbackEntry e = new RollbackEntry(origin, backup);
tikhomirov@617: 		entries.add(e);
tikhomirov@617: 		return e;
tikhomirov@617: 	}
tikhomirov@617: 
tikhomirov@617: 	private boolean known(File f) {
tikhomirov@635: 		RollbackEntry e = lookup(f);
tikhomirov@635: 		return e != null;
tikhomirov@635: 	}
tikhomirov@635: 
tikhomirov@635: 	private RollbackEntry find(File f) {
tikhomirov@635: 		RollbackEntry e = lookup(f);
tikhomirov@635: 		if (e != null) {
tikhomirov@635: 			return e;
tikhomirov@617: 		}
tikhomirov@635: 		assert false;
tikhomirov@635: 		return new RollbackEntry(f,f);
tikhomirov@617: 	}
tikhomirov@635: 	
tikhomirov@635: 	private RollbackEntry lookup(File f) {
tikhomirov@617: 		for (RollbackEntry e : entries) {
tikhomirov@617: 			if (e.origin.equals(f)) {
tikhomirov@617: 				return e;
tikhomirov@617: 			}
tikhomirov@617: 		}
tikhomirov@635: 		return null;
tikhomirov@617: 	}
tikhomirov@635: 	
tikhomirov@617: 	private static class RollbackEntry {
tikhomirov@617: 		public final File origin;
tikhomirov@617: 		public final File backup; // may be null to indicate file didn't exist
tikhomirov@617: 		public boolean success = false;
tikhomirov@617: 		public IOException failure = null;
tikhomirov@617: 		public boolean keepBackup = false;
tikhomirov@617: 		
tikhomirov@617: 		public RollbackEntry(File o, File b) {
tikhomirov@617: 			origin = o;
tikhomirov@617: 			backup = b;
tikhomirov@617: 		}
tikhomirov@617: 	}
tikhomirov@617: 	
tikhomirov@617: 	public static class Factory implements Transaction.Factory {
tikhomirov@617: 
tikhomirov@617: 		public Transaction create(SessionContext.Source ctxSource) {
tikhomirov@617: 			return new COWTransaction(ctxSource);
tikhomirov@617: 		}
tikhomirov@617: 		
tikhomirov@617: 	}
tikhomirov@617: }