Simplify the PackWriter.preparePack() API

[jgit.git] / org.spearce.jgit / src / org / spearce / jgit / transport / WalkPushConnection.java

/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Git Development Community nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.spearce.jgit.transport;

import static org.spearce.jgit.transport.WalkRemoteObjectDatabase.ROOT_DIR;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import org.spearce.jgit.errors.TransportException;
import org.spearce.jgit.lib.AnyObjectId;
import org.spearce.jgit.lib.Constants;
import org.spearce.jgit.lib.ObjectId;
import org.spearce.jgit.lib.PackWriter;
import org.spearce.jgit.lib.ProgressMonitor;
import org.spearce.jgit.lib.Ref;
import org.spearce.jgit.lib.RefWriter;
import org.spearce.jgit.lib.Repository;
import org.spearce.jgit.lib.Ref.Storage;
import org.spearce.jgit.transport.RemoteRefUpdate.Status;

/**
 * Generic push support for dumb transport protocols.
 * <p>
 * Since there are no Git-specific smarts on the remote side of the connection
 * the client side must handle everything on its own. The generic push support
 * requires being able to delete, create and overwrite files on the remote side,
 * as well as create any missing directories (if necessary). Typically this can
 * be handled through an FTP style protocol.
 * <p>
 * Objects not on the remote side are uploaded as pack files, using one pack
 * file per invocation. This simplifies the implementation as only two data
 * files need to be written to the remote repository.
 * <p>
 * Push support supplied by this class is not multiuser safe. Concurrent pushes
 * to the same repository may yield an inconsistent reference database which may
 * confuse fetch clients.
 * <p>
 * A single push is concurrently safe with multiple fetch requests, due to the
 * careful order of operations used to update the repository. Clients fetching
 * may receive transient failures due to short reads on certain files if the
 * protocol does not support atomic file replacement.
 *
 * @see WalkRemoteObjectDatabase
 */
class WalkPushConnection extends BaseConnection implements PushConnection {
        /** The repository this transport pushes out of. */
        private final Repository local;

        /** Location of the remote repository we are writing to. */
        private final URIish uri;

        /** Database connection to the remote repository. */
        private final WalkRemoteObjectDatabase dest;

        /**
         * Packs already known to reside in the remote repository.
         * <p>
         * This is a LinkedHashMap to maintain the original order.
         */
        private LinkedHashMap<String, String> packNames;

        /** Complete listing of refs the remote will have after our push. */
        private Map<String, Ref> newRefs;

        /**
         * Updates which require altering the packed-refs file to complete.
         * <p>
         * If this collection is non-empty then any refs listed in {@link #newRefs}
         * with a storage class of {@link Storage#PACKED} will be written.
         */
        private Collection<RemoteRefUpdate> packedRefUpdates;

        WalkPushConnection(final WalkTransport walkTransport,
                        final WalkRemoteObjectDatabase w) {
                local = walkTransport.local;
                uri = walkTransport.getURI();
                dest = w;
        }

        public void push(final ProgressMonitor monitor,
                        final Map<String, RemoteRefUpdate> refUpdates)
                        throws TransportException {
                markStartedOperation();
                packNames = null;
                newRefs = new TreeMap<String, Ref>(getRefsMap());
                packedRefUpdates = new ArrayList<RemoteRefUpdate>(refUpdates.size());

                // Filter the commands and issue all deletes first. This way we
                // can correctly handle a directory being cleared out and a new
                // ref using the directory name being created.
                //
                final List<RemoteRefUpdate> updates = new ArrayList<RemoteRefUpdate>();
                for (final RemoteRefUpdate u : refUpdates.values()) {
                        final String n = u.getRemoteName();
                        if (!n.startsWith("refs/") || !Repository.isValidRefName(n)) {
                                u.setStatus(Status.REJECTED_OTHER_REASON);
                                u.setMessage("funny refname");
                                continue;
                        }

                        if (AnyObjectId.equals(ObjectId.zeroId(), u.getNewObjectId()))
                                deleteCommand(u);
                        else
                                updates.add(u);
                }

                // If we have any updates we need to upload the objects first, to
                // prevent creating refs pointing at non-existent data. Then we
                // can update the refs, and the info-refs file for dumb transports.
                //
                if (!updates.isEmpty())
                        sendpack(updates, monitor);
                for (final RemoteRefUpdate u : updates)
                        updateCommand(u);

                // Is this a new repository? If so we should create additional
                // metadata files so it is properly initialized during the push.
                //
                if (!updates.isEmpty() && isNewRepository())
                        createNewRepository(updates);

                RefWriter refWriter = new RefWriter(newRefs.values()) {
                        @Override
                        protected void writeFile(String file, byte[] content)
                                        throws IOException {
                                dest.writeFile(ROOT_DIR + file, content);
                        }
                };
                if (!packedRefUpdates.isEmpty()) {
                        try {
                                refWriter.writePackedRefs();
                                for (final RemoteRefUpdate u : packedRefUpdates)
                                        u.setStatus(Status.OK);
                        } catch (IOException err) {
                                for (final RemoteRefUpdate u : packedRefUpdates) {
                                        u.setStatus(Status.REJECTED_OTHER_REASON);
                                        u.setMessage(err.getMessage());
                                }
                                throw new TransportException(uri, "failed updating refs", err);
                        }
                }

                try {
                        refWriter.writeInfoRefs();
                } catch (IOException err) {
                        throw new TransportException(uri, "failed updating refs", err);
                }
        }

        @Override
        public void close() {
                dest.close();
        }

        private void sendpack(final List<RemoteRefUpdate> updates,
                        final ProgressMonitor monitor) throws TransportException {
                String pathPack = null;
                String pathIdx = null;

                try {
                        final PackWriter pw = new PackWriter(local, monitor);
                        final List<ObjectId> need = new ArrayList<ObjectId>();
                        final List<ObjectId> have = new ArrayList<ObjectId>();
                        for (final RemoteRefUpdate r : updates)
                                need.add(r.getNewObjectId());
                        for (final Ref r : getRefs()) {
                                have.add(r.getObjectId());
                                if (r.getPeeledObjectId() != null)
                                        have.add(r.getPeeledObjectId());
                        }
                        pw.preparePack(need, have);

                        // We don't have to continue further if the pack will
                        // be an empty pack, as the remote has all objects it
                        // needs to complete this change.
                        //
                        if (pw.getObjectsNumber() == 0)
                                return;

                        packNames = new LinkedHashMap<String, String>();
                        for (final String n : dest.getPackNames())
                                packNames.put(n, n);

                        final String base = "pack-" + pw.computeName().name();
                        final String packName = base + ".pack";
                        pathPack = "pack/" + packName;
                        pathIdx = "pack/" + base + ".idx";

                        if (packNames.remove(packName) != null) {
                                // The remote already contains this pack. We should
                                // remove the index before overwriting to prevent bad
                                // offsets from appearing to clients.
                                //
                                dest.writeInfoPacks(packNames.keySet());
                                dest.deleteFile(pathIdx);
                        }

                        // Write the pack file, then the index, as readers look the
                        // other direction (index, then pack file).
                        //
                        final String wt = "Put " + base.substring(0, 12);
                        OutputStream os = dest.writeFile(pathPack, monitor, wt + "..pack");
                        try {
                                pw.writePack(os);
                        } finally {
                                os.close();
                        }

                        os = dest.writeFile(pathIdx, monitor, wt + "..idx");
                        try {
                                pw.writeIndex(os);
                        } finally {
                                os.close();
                        }

                        // Record the pack at the start of the pack info list. This
                        // way clients are likely to consult the newest pack first,
                        // and discover the most recent objects there.
                        //
                        final ArrayList<String> infoPacks = new ArrayList<String>();
                        infoPacks.add(packName);
                        infoPacks.addAll(packNames.keySet());
                        dest.writeInfoPacks(infoPacks);

                } catch (IOException err) {
                        safeDelete(pathIdx);
                        safeDelete(pathPack);

                        throw new TransportException(uri, "cannot store objects", err);
                }
        }

        private void safeDelete(final String path) {
                if (path != null) {
                        try {
                                dest.deleteFile(path);
                        } catch (IOException cleanupFailure) {
                                // Ignore the deletion failure. We probably are
                                // already failing and were just trying to pick
                                // up after ourselves.
                        }
                }
        }

        private void deleteCommand(final RemoteRefUpdate u) {
                final Ref r = newRefs.remove(u.getRemoteName());
                if (r == null) {
                        // Already gone.
                        //
                        u.setStatus(Status.OK);
                        return;
                }

                if (r.getStorage().isPacked())
                        packedRefUpdates.add(u);

                if (r.getStorage().isLoose()) {
                        try {
                                dest.deleteRef(u.getRemoteName());
                                u.setStatus(Status.OK);
                        } catch (IOException e) {
                                u.setStatus(Status.REJECTED_OTHER_REASON);
                                u.setMessage(e.getMessage());
                        }
                }

                try {
                        dest.deleteRefLog(u.getRemoteName());
                } catch (IOException e) {
                        u.setStatus(Status.REJECTED_OTHER_REASON);
                        u.setMessage(e.getMessage());
                }
        }

        private void updateCommand(final RemoteRefUpdate u) {
                try {
                        dest.writeRef(u.getRemoteName(), u.getNewObjectId());
                        newRefs.put(u.getRemoteName(), new Ref(Storage.LOOSE, u
                                        .getRemoteName(), u.getNewObjectId()));
                        u.setStatus(Status.OK);
                } catch (IOException e) {
                        u.setStatus(Status.REJECTED_OTHER_REASON);
                        u.setMessage(e.getMessage());
                }
        }

        private boolean isNewRepository() {
                return getRefsMap().isEmpty() && packNames != null
                                && packNames.isEmpty();
        }

        private void createNewRepository(final List<RemoteRefUpdate> updates)
                        throws TransportException {
                try {
                        final String ref = "ref: " + pickHEAD(updates) + "\n";
                        final byte[] bytes = Constants.encode(ref);
                        dest.writeFile(ROOT_DIR + Constants.HEAD, bytes);
                } catch (IOException e) {
                        throw new TransportException(uri, "cannot create HEAD", e);
                }

                try {
                        final String config = "[core]\n"
                                        + "\trepositoryformatversion = 0\n";
                        final byte[] bytes = Constants.encode(config);
                        dest.writeFile(ROOT_DIR + "config", bytes);
                } catch (IOException e) {
                        throw new TransportException(uri, "cannot create config", e);
                }
        }

        private static String pickHEAD(final List<RemoteRefUpdate> updates) {
                // Try to use master if the user is pushing that, it is the
                // default branch and is likely what they want to remain as
                // the default on the new remote.
                //
                for (final RemoteRefUpdate u : updates) {
                        final String n = u.getRemoteName();
                        if (n.equals(Constants.R_HEADS + Constants.MASTER))
                                return n;
                }

                // Pick any branch, under the assumption the user pushed only
                // one to the remote side.
                //
                for (final RemoteRefUpdate u : updates) {
                        final String n = u.getRemoteName();
                        if (n.startsWith(Constants.R_HEADS))
                                return n;
                }
                return updates.get(0).getRemoteName();
        }
}