/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * 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 Eclipse Foundation, Inc. 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.eclipse.jgit.transport;

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

import java.io.BufferedOutputStream;
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.eclipse.jgit.errors.TransportException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdRef;
import org.eclipse.jgit.lib.PackWriter;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefWriter;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.lib.Ref.Storage;
import org.eclipse.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) {
		Transport t = (Transport)walkTransport;
		local = t.local;
		uri = t.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 {
				os = new BufferedOutputStream(os);
				pw.writePack(os);
			} finally {
				os.close();
			}

			os = dest.writeFile(pathIdx, monitor, wt + "..idx");
			try {
				os = new BufferedOutputStream(os);
				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 ObjectIdRef.Unpeeled(
					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();
	}
}