/*
    * Copyright (C) 2016, Google Inc. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.internal.ketch;
  
  import static org.eclipse.jgit.internal.ketch.KetchReplica.CommitMethod.ALL_REFS;
  import static org.eclipse.jgit.lib.Ref.Storage.NETWORK;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.LOCK_FAILURE;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_NODELETE;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_NONFASTFORWARD;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_OTHER_REASON;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.NotSupportedException;
  import org.eclipse.jgit.errors.TransportException;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdRef;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.transport.FetchConnection;
  import org.eclipse.jgit.transport.PushConnection;
  import org.eclipse.jgit.transport.ReceiveCommand;
  import org.eclipse.jgit.transport.RemoteConfig;
  import org.eclipse.jgit.transport.RemoteRefUpdate;
  import org.eclipse.jgit.transport.Transport;
  import org.eclipse.jgit.transport.URIish;
  
  /**
   * Representation of a Git repository on a remote replica system.
   * <p>
   * {@link org.eclipse.jgit.internal.ketch.KetchLeader} will contact the replica
   * using the Git wire protocol.
   * <p>
   * The remote replica may be fully Ketch-aware, or a standard Git server.
   */
  public class RemoteGitReplica extends KetchReplica {
  	private final URIish uri;
  	private final RemoteConfig remoteConfig;
  
  	/**
  	 * Configure a new remote.
  	 *
  	 * @param leader
  	 *            instance this replica follows.
  	 * @param name
  	 *            unique-ish name identifying this remote for debugging.
  	 * @param uri
  	 *            URI to connect to the follower's repository.
  	 * @param cfg
  	 *            how Ketch should treat the remote system.
  	 * @param rc
  	 *            optional remote configuration describing how to contact the
  	 *            peer repository.
  	 */
  	public RemoteGitReplica(KetchLeader leader, String name, URIish uri,
  			ReplicaConfig cfg, @Nullable RemoteConfig rc) {
  		super(leader, name, cfg);
  		this.uri = uri;
  		this.remoteConfig = rc;
  	}
  
  	/**
  	 * Get URI to contact the remote peer repository.
  	 *
  	 * @return URI to contact the remote peer repository.
  	 */
  	public URIish getURI() {
  		return uri;
  	}
  
  	/**
  	 * Get optional configuration describing how to contact the peer.
  	 *
  	 * @return optional configuration describing how to contact the peer.
  	 */
  	@Nullable
  	protected RemoteConfig getRemoteConfig() {
  		return remoteConfig;
  	}
  
 	/** {@inheritDoc} */
 	@Override
 	protected String describeForLog() {
 		return String.format("%s @ %s", getName(), getURI()); //$NON-NLS-1$
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void startPush(ReplicaPushRequest req) {
 		getSystem().getExecutor().execute(() -> {
 			try (Repository git = getLeader().openRepository()) {
 				try {
 					push(git, req);
 					req.done(git);
 				} catch (Throwable err) {
 					req.setException(git, err);
 				}
 			} catch (IOException err) {
 				req.setException(null, err);
 			}
 		});
 	}
 
 	private void push(Repository repo, ReplicaPushRequest req)
 			throws NotSupportedException, TransportException, IOException {
 		Map<String, Ref> adv;
 		List<RemoteCommand> cmds = asUpdateList(req.getCommands());
 		try (Transport transport = Transport.open(repo, uri)) {
 			RemoteConfig rc = getRemoteConfig();
 			if (rc != null) {
 				transport.applyConfig(rc);
 			}
 			transport.setPushAtomic(true);
 			adv = push(repo, transport, cmds);
 		}
 		for (RemoteCommand c : cmds) {
 			c.copyStatusToResult();
 		}
 		req.setRefs(adv);
 	}
 
 	private Map<String, Ref> push(Repository git, Transport transport,
 			List<RemoteCommand> cmds) throws IOException {
 		Map<String, RemoteRefUpdate> updates = asUpdateMap(cmds);
 		try (PushConnection connection = transport.openPush()) {
 			Map<String, Ref> adv = connection.getRefsMap();
 			RemoteRefUpdate accepted = updates.get(getSystem().getTxnAccepted());
 			if (accepted != null && !isExpectedValue(adv, accepted)) {
 				abort(cmds);
 				return adv;
 			}
 
 			RemoteRefUpdate committed = updates.get(getSystem().getTxnCommitted());
 			if (committed != null && !isExpectedValue(adv, committed)) {
 				abort(cmds);
 				return adv;
 			}
 			if (committed != null && getCommitMethod() == ALL_REFS) {
 				prepareCommit(git, cmds, updates, adv,
 						committed.getNewObjectId());
 			}
 
 			connection.push(NullProgressMonitor.INSTANCE, updates);
 			return adv;
 		}
 	}
 
 	private static boolean isExpectedValue(Map<String, Ref> adv,
 			RemoteRefUpdate u) {
 		Ref r = adv.get(u.getRemoteName());
 		if (!AnyObjectId.isEqual(getId(r), u.getExpectedOldObjectId())) {
 			((RemoteCommand) u).cmd.setResult(LOCK_FAILURE);
 			return false;
 		}
 		return true;
 	}
 
 	private void prepareCommit(Repository git, List<RemoteCommand> cmds,
 			Map<String, RemoteRefUpdate> updates, Map<String, Ref> adv,
 			ObjectId committed) throws IOException {
 		for (ReceiveCommand cmd : prepareCommit(git, adv, committed)) {
 			RemoteCommand c = new RemoteCommand(cmd);
 			cmds.add(c);
 			updates.put(c.getRemoteName(), c);
 		}
 	}
 
 	private static List<RemoteCommand> asUpdateList(
 			Collection<ReceiveCommand> cmds) {
 		try {
 			List<RemoteCommand> toPush = new ArrayList<>(cmds.size());
 			for (ReceiveCommand cmd : cmds) {
 				toPush.add(new RemoteCommand(cmd));
 			}
 			return toPush;
 		} catch (IOException e) {
 			// Cannot occur as no IO was required to build the command.
 			throw new IllegalStateException(e);
 		}
 	}
 
 	private static Map<String, RemoteRefUpdate> asUpdateMap(
 			List<RemoteCommand> cmds) {
 		Map<String, RemoteRefUpdate> m = new LinkedHashMap<>();
 		for (RemoteCommand cmd : cmds) {
 			m.put(cmd.getRemoteName(), cmd);
 		}
 		return m;
 	}
 
 	private static void abort(List<RemoteCommand> cmds) {
 		List<ReceiveCommand> tmp = new ArrayList<>(cmds.size());
 		for (RemoteCommand cmd : cmds) {
 			tmp.add(cmd.cmd);
 		}
 		ReceiveCommand.abort(tmp);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void blockingFetch(Repository repo, ReplicaFetchRequest req)
 			throws NotSupportedException, TransportException {
 		try (Transport transport = Transport.open(repo, uri)) {
 			RemoteConfig rc = getRemoteConfig();
 			if (rc != null) {
 				transport.applyConfig(rc);
 			}
 			fetch(transport, req);
 		}
 	}
 
 	private void fetch(Transport transport, ReplicaFetchRequest req)
 			throws NotSupportedException, TransportException {
 		try (FetchConnection conn = transport.openFetch()) {
 			Map<String, Ref> remoteRefs = conn.getRefsMap();
 			req.setRefs(remoteRefs);
 
 			List<Ref> want = new ArrayList<>();
 			for (String name : req.getWantRefs()) {
 				Ref ref = remoteRefs.get(name);
 				if (ref != null && ref.getObjectId() != null) {
 					want.add(ref);
 				}
 			}
 			for (ObjectId id : req.getWantObjects()) {
 				want.add(new ObjectIdRef.Unpeeled(NETWORK, id.name(), id));
 			}
 
 			conn.fetch(NullProgressMonitor.INSTANCE, want,
 					Collections.<ObjectId> emptySet());
 		}
 	}
 
 	static class RemoteCommand extends RemoteRefUpdate {
 		final ReceiveCommand cmd;
 
 		RemoteCommand(ReceiveCommand cmd) throws IOException {
 			super(null, null,
 					cmd.getNewId(), cmd.getRefName(),
 					true /* force update */,
 					null /* no local tracking ref */,
 					cmd.getOldId());
 			this.cmd = cmd;
 		}
 
 		void copyStatusToResult() {
 			if (cmd.getResult() == NOT_ATTEMPTED) {
 				switch (getStatus()) {
 				case OK:
 				case UP_TO_DATE:
 				case NON_EXISTING:
 					cmd.setResult(OK);
 					break;
 
 				case REJECTED_NODELETE:
 					cmd.setResult(REJECTED_NODELETE);
 					break;
 
 				case REJECTED_NONFASTFORWARD:
 					cmd.setResult(REJECTED_NONFASTFORWARD);
 					break;
 
 				case REJECTED_OTHER_REASON:
 					cmd.setResult(REJECTED_OTHER_REASON, getMessage());
 					break;
 
 				default:
 					cmd.setResult(REJECTED_OTHER_REASON, getStatus().name());
 					break;
 				}
 			}
 		}
 	}
 }