// Copyright (C) 2009 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.googlesource.gerrit.plugins.replication;

import com.google.common.base.Throwables;
import com.google.common.collect.LinkedListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Sets;
import com.google.gerrit.common.TimeUtil;
import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.client.RefNames;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.git.ChangeCache;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.PerThreadRequestScope;
import com.google.gerrit.server.git.ProjectRunnable;
import com.google.gerrit.server.git.TagCache;
import com.google.gerrit.server.git.VisibleRefFilter;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.project.ProjectControl;
import com.google.gerrit.server.util.IdGenerator;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.SchemaFactory;
import com.google.inject.Inject;
import com.google.inject.assistedinject.Assisted;

import com.googlesource.gerrit.plugins.replication.ReplicationState.RefPushResult;
import com.jcraft.jsch.JSchException;

import org.eclipse.jgit.errors.NoRemoteRepositoryException;
import org.eclipse.jgit.errors.NotSupportedException;
import org.eclipse.jgit.errors.RemoteRepositoryException;
import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.errors.TransportException;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.transport.CredentialsProvider;
import org.eclipse.jgit.transport.FetchConnection;
import org.eclipse.jgit.transport.PushResult;
import org.eclipse.jgit.transport.RefSpec;
import org.eclipse.jgit.transport.RemoteConfig;
import org.eclipse.jgit.transport.RemoteRefUpdate;
import org.eclipse.jgit.transport.Transport;
import org.eclipse.jgit.transport.URIish;
import org.slf4j.Logger;
import org.slf4j.MDC;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;

/**
 * A push to remote operation started by {@link GitReferenceUpdatedListener}.
 * <p>
 * Instance members are protected by the lock within PushQueue. Callers must
 * take that lock to ensure they are working with a current view of the object.
 */
class PushOne implements ProjectRunnable {
  private static final Logger repLog = ReplicationQueue.repLog;
  private static final ReplicationStateLogger stateLog =
      new ReplicationStateLogger(repLog);
  static final String ALL_REFS = "..all..";
  static final String ID_MDC_KEY = "pushOneId";

  interface Factory {
    PushOne create(Project.NameKey d, URIish u);
  }

  private final GitRepositoryManager gitManager;
  private final SchemaFactory<ReviewDb> schema;
  private final Destination pool;
  private final RemoteConfig config;
  private final CredentialsProvider credentialsProvider;
  private final TagCache tagCache;
  private final PerThreadRequestScope.Scoper threadScoper;
  private final ChangeCache changeCache;
  private final ReplicationQueue replicationQueue;

  private final Project.NameKey projectName;
  private final URIish uri;
  private final Set<String> delta = Sets.newHashSetWithExpectedSize(4);
  private boolean pushAllRefs;
  private Repository git;
  private boolean retrying;
  private int retryCount;
  private boolean canceled;
  private final Multimap<String,ReplicationState> stateMap =
      LinkedListMultimap.create();
  private final int maxLockRetries;
  private int lockRetryCount;
  private final int id;
  private final long createdAt;

  @Inject
  PushOne(final GitRepositoryManager grm,
      final SchemaFactory<ReviewDb> s,
      final Destination p,
      final RemoteConfig c,
      final CredentialsFactory cpFactory,
      final TagCache tc,
      final PerThreadRequestScope.Scoper ts,
      final ChangeCache cc,
      final ReplicationQueue rq,
      final IdGenerator ig,
      @Assisted final Project.NameKey d,
      @Assisted final URIish u) {
    gitManager = grm;
    schema = s;
    pool = p;
    config = c;
    credentialsProvider = cpFactory.create(c.getName());
    tagCache = tc;
    threadScoper = ts;
    changeCache = cc;
    replicationQueue = rq;
    projectName = d;
    uri = u;
    lockRetryCount = 0;
    maxLockRetries = pool.getLockErrorMaxRetries();
    id = ig.next();
    createdAt = TimeUtil.nowMs();
  }

  @Override
  public Project.NameKey getProjectNameKey() {
    return projectName;
  }

  @Override
  public String getRemoteName() {
    return config.getName();
  }

  @Override
  public boolean hasCustomizedPrint() {
    return true;
  }

  @Override
  public String toString() {
    String print = "[" + IdGenerator.format(id) + "] push " + uri;

    if (retryCount > 0) {
      print = "(retry " + retryCount + ") " + print;
    }
    return print;
  }

  boolean isRetrying() {
    return retrying;
  }

  void setToRetry() {
    retrying = true;
    retryCount++;
  }

  void cancel() {
    canceled = true;
  }

  boolean wasCanceled() {
    return canceled;
  }

  URIish getURI() {
    return uri;
  }

  void addRef(String ref) {
    if (ALL_REFS.equals(ref)) {
      delta.clear();
      pushAllRefs = true;
      repLog.trace("Added all refs for replication to " + uri);
    } else if (!pushAllRefs) {
      delta.add(ref);
      repLog.trace("Added ref " + ref + " for replication to " + uri);
    }
  }

  Set<String> getRefs() {
    return pushAllRefs ? Sets.newHashSet(ALL_REFS) : delta;
  }

  void addRefs(Set<String> refs) {
    if (!pushAllRefs) {
      for (String ref : refs) {
        addRef(ref);
      }
    }
  }

  void addState(String ref, ReplicationState state) {
    stateMap.put(ref, state);
  }

  Multimap<String,ReplicationState> getStates() {
    return stateMap;
  }

  ReplicationState[] getStatesAsArray() {
    Set<ReplicationState> statesSet = new HashSet<>();
    statesSet.addAll(stateMap.values());
    return statesSet.toArray(new ReplicationState[statesSet.size()]);
  }

  ReplicationState[] getStatesByRef(String ref) {
    Collection<ReplicationState> states = stateMap.get(ref);
    return states.toArray(new ReplicationState[states.size()]);
  }

  void addStates(Multimap<String,ReplicationState> states) {
    stateMap.putAll(states);
  }

  void removeStates() {
    stateMap.clear();
  }

  private void statesCleanUp() {
    if (!stateMap.isEmpty() && !isRetrying()) {
      for (Map.Entry<String,ReplicationState> entry : stateMap.entries()) {
        entry.getValue().notifyRefReplicated(projectName.get(), entry.getKey(), uri,
            RefPushResult.FAILED);
      }
    }
  }

  @Override
  public void run() {
    try {
      threadScoper.scope(new Callable<Void>(){
        @Override
        public Void call() {
          runPushOperation();
          return null;
        }
      }).call();
    } catch (Exception e) {
      throw Throwables.propagate(e);
    } finally {
      statesCleanUp();
    }
  }

  private void runPushOperation() {
    // Lock the queue, and remove ourselves, so we can't be modified once
    // we start replication (instead a new instance, with the same URI, is
    // created and scheduled for a future point in time.)
    //
    MDC.put(ID_MDC_KEY, IdGenerator.format(id));
    if (!pool.requestRunway(this)) {
      if (!canceled) {
        repLog.info("Rescheduling replication to " + uri
            + " to avoid collision with an in-flight push.");
        pool.reschedule(this, Destination.RetryReason.COLLISION);
      }
      return;
    }

    long startedAt = TimeUtil.nowMs();
    repLog.info("Replication to " + uri + " started...");
    try {
      git = gitManager.openRepository(projectName);
      runImpl();
      long finishedAt = TimeUtil.nowMs();
      repLog.info("Replication to " + uri + " completed in "
          + (finishedAt - startedAt) + "ms, "
          + (startedAt - createdAt) + "ms delay, " + retryCount + " retries");
    } catch (RepositoryNotFoundException e) {
      stateLog.error("Cannot replicate " + projectName
          + "; Local repository error: "
          + e.getMessage(), getStatesAsArray());

    } catch (RemoteRepositoryException e) {
      // Tried to replicate to a remote via anonymous git:// but the repository
      // does not exist.  In this case NoRemoteRepositoryException is not
      // raised.
      final String msg = e.getMessage();
      if (msg.contains("access denied") || msg.contains("no such repository")) {
        createRepository();
      } else {
        repLog.error("Cannot replicate " + projectName
            + "; Remote repository error: " + msg);
      }

    } catch (NoRemoteRepositoryException e) {
      createRepository();
    } catch (NotSupportedException e) {
      stateLog.error("Cannot replicate to " + uri, e, getStatesAsArray());

    } catch (TransportException e) {
      Throwable cause = e.getCause();
      if (cause instanceof JSchException
          && cause.getMessage().startsWith("UnknownHostKey:")) {
        repLog.error("Cannot replicate to " + uri + ": " + cause.getMessage());
      } else if (e instanceof LockFailureException) {
        lockRetryCount++;
        // The LockFailureException message contains both URI and reason
        // for this failure.
        repLog.error("Cannot replicate to " + e.getMessage());

        // The remote push operation should be retried.
        if (lockRetryCount <= maxLockRetries) {
          pool.reschedule(this, Destination.RetryReason.TRANSPORT_ERROR);
        } else {
          repLog.error("Giving up after " + lockRetryCount
              + " of this error during replication to " + e.getMessage());
        }
      } else {
        repLog.error("Cannot replicate to " + uri, e);
        // The remote push operation should be retried.
        pool.reschedule(this, Destination.RetryReason.TRANSPORT_ERROR);
      }
    } catch (IOException e) {
      stateLog.error("Cannot replicate to " + uri, e, getStatesAsArray());
    } catch (RuntimeException | Error e) {
      stateLog.error("Unexpected error during replication to " + uri, e, getStatesAsArray());
    } finally {
      if (git != null) {
        git.close();
      }
      pool.notifyFinished(this);
    }
  }

  private void createRepository() {
    if (pool.isCreateMissingRepos()) {
      try {
        final Ref head = git.getRef(Constants.HEAD);
        if (replicationQueue.createProject(projectName, head != null ? head.getName() : null)) {
          repLog.warn("Missing repository created; retry replication to " + uri);
          pool.reschedule(this, Destination.RetryReason.REPOSITORY_MISSING);
        } else {
          repLog.warn("Missing repository could not be created when replicating " + uri +
              ". You can only create missing repositories locally, over SSH or when " +
              "using adminUrl in replication.config. See documentation for more information.");
        }
      } catch (IOException ioe) {
        stateLog.error("Cannot replicate to " + uri + "; failed to create missing repository",
            ioe, getStatesAsArray());
      }
    } else {
      stateLog.error("Cannot replicate to " + uri + "; repository not found", getStatesAsArray());
    }
  }

  private void runImpl() throws IOException {
    Transport tn = Transport.open(git, uri);
    PushResult res;
    try {
      res = pushVia(tn);
      updateHead();
    } finally {
      try {
        tn.close();
      } catch (Throwable e2) {
        repLog.warn("Unexpected error while closing " + uri, e2);
      }
    }

    updateStates(res.getRemoteUpdates());
  }

  private PushResult pushVia(Transport tn)
      throws IOException, NotSupportedException, TransportException {
    tn.applyConfig(config);
    tn.setCredentialsProvider(credentialsProvider);

    List<RemoteRefUpdate> todo = generateUpdates(tn);
    if (todo.isEmpty()) {
      // If we have no commands selected, we have nothing to do.
      // Calling JGit at this point would just redo the work we
      // already did, and come up with the same answer. Instead
      // send back an empty result.
      return new PushResult();
    }

    repLog.info("Push to " + uri + " references: " + todo);

    return tn.push(NullProgressMonitor.INSTANCE, todo);
  }

  private List<RemoteRefUpdate> generateUpdates(Transport tn)
      throws IOException {
    ProjectControl pc;
    try {
      pc = pool.controlFor(projectName);
    } catch (NoSuchProjectException e) {
      return Collections.emptyList();
    }

    Map<String, Ref> local = git.getAllRefs();
    if (!pc.allRefsAreVisible()) {
      if (!pushAllRefs) {
        // If we aren't mirroring, reduce the space we need to filter
        // to only the references we will update during this operation.
        //
        Map<String, Ref> n = Maps.newHashMap();
        for (String src : delta) {
          Ref r = local.get(src);
          if (r != null) {
            n.put(src, r);
          }
        }
        local = n;
      }

      ReviewDb db;
      try {
        db = schema.open();
      } catch (OrmException e) {
        stateLog.error("Cannot read database to replicate to " + projectName, e, getStatesAsArray());
        return Collections.emptyList();
      }
      try {
        local = new VisibleRefFilter(tagCache, changeCache, git, pc, db, true)
            .filter(local, true);
      } finally {
        db.close();
      }
    }

    return pushAllRefs ? doPushAll(tn, local) : doPushDelta(local);
  }

  private List<RemoteRefUpdate> doPushAll(Transport tn, Map<String, Ref> local)
      throws NotSupportedException, TransportException, IOException {
    List<RemoteRefUpdate> cmds = Lists.newArrayList();
    boolean noPerms = !pool.isReplicatePermissions();
    Map<String, Ref> remote = listRemote(tn);
    for (Ref src : local.values()) {
      if (!canPushRef(src.getName(), noPerms)) {
        continue;
      }

      RefSpec spec = matchSrc(src.getName());
      if (spec != null) {
        Ref dst = remote.get(spec.getDestination());
        if (dst == null || !src.getObjectId().equals(dst.getObjectId())) {
          // Doesn't exist yet, or isn't the same value, request to push.
          push(cmds, spec, src);
        }
      }
    }

    if (config.isMirror()) {
      for (Ref ref : remote.values()) {
        if (!Constants.HEAD.equals(ref.getName())) {
          RefSpec spec = matchDst(ref.getName());
          if (spec != null && !local.containsKey(spec.getSource())) {
            // No longer on local side, request removal.
            delete(cmds, spec);
          }
        }
      }
    }
    return cmds;
  }

  private List<RemoteRefUpdate> doPushDelta(Map<String, Ref> local)
      throws IOException {
    List<RemoteRefUpdate> cmds = Lists.newArrayList();
    boolean noPerms = !pool.isReplicatePermissions();
    for (String src : delta) {
      RefSpec spec = matchSrc(src);
      if (spec != null) {
        // If the ref still exists locally, send it, otherwise delete it.
        Ref srcRef = local.get(src);
        if (srcRef != null && canPushRef(src, noPerms)) {
          push(cmds, spec, srcRef);
        } else if (config.isMirror()) {
          delete(cmds, spec);
        }
      }
    }
    return cmds;
  }

  private boolean canPushRef(String ref, boolean noPerms) {
    return !(noPerms && RefNames.REFS_CONFIG.equals(ref)) &&
        !ref.startsWith(RefNames.REFS_CACHE_AUTOMERGE);
  }

  private Map<String, Ref> listRemote(Transport tn)
      throws NotSupportedException, TransportException {
    FetchConnection fc = tn.openFetch();
    try {
      return fc.getRefsMap();
    } finally {
      fc.close();
    }
  }

  private RefSpec matchSrc(String ref) {
    for (RefSpec s : config.getPushRefSpecs()) {
      if (s.matchSource(ref)) {
        return s.expandFromSource(ref);
      }
    }
    return null;
  }

  private RefSpec matchDst(String ref) {
    for (RefSpec s : config.getPushRefSpecs()) {
      if (s.matchDestination(ref)) {
        return s.expandFromDestination(ref);
      }
    }
    return null;
  }

  private void push(List<RemoteRefUpdate> cmds, RefSpec spec, Ref src)
      throws IOException {
    String dst = spec.getDestination();
    boolean force = spec.isForceUpdate();
    cmds.add(new RemoteRefUpdate(git, src, dst, force, null, null));
  }

  private void delete(List<RemoteRefUpdate> cmds, RefSpec spec)
      throws IOException {
    String dst = spec.getDestination();
    boolean force = spec.isForceUpdate();
    cmds.add(new RemoteRefUpdate(git, (Ref) null, dst, force, null, null));
  }

  private void updateHead() throws IOException {
    replicationQueue.updateHead(projectName, git.getRef(Constants.HEAD)
        .getTarget().getName());
  }

  private void updateStates(Collection<RemoteRefUpdate> refUpdates)
      throws LockFailureException {
    Set<String> doneRefs = new HashSet<>();
    boolean anyRefFailed = false;

    for (RemoteRefUpdate u : refUpdates) {
      RefPushResult pushStatus = RefPushResult.SUCCEEDED;
      Set<ReplicationState> logStates = new HashSet<>();

      logStates.addAll(stateMap.get(u.getSrcRef()));
      logStates.addAll(stateMap.get(ALL_REFS));
      ReplicationState[] logStatesArray = logStates.toArray(new ReplicationState[logStates.size()]);

      doneRefs.add(u.getSrcRef());
      switch (u.getStatus()) {
        case OK:
        case UP_TO_DATE:
        case NON_EXISTING:
          break;

        case NOT_ATTEMPTED:
        case AWAITING_REPORT:
        case REJECTED_NODELETE:
        case REJECTED_NONFASTFORWARD:
        case REJECTED_REMOTE_CHANGED:
          stateLog.error(String.format("Failed replicate of %s to %s: status %s",
              u.getRemoteName(), uri, u.getStatus()), logStatesArray);
          pushStatus = RefPushResult.FAILED;
          anyRefFailed = true;
          break;

        case REJECTED_OTHER_REASON:
          if ("non-fast-forward".equals(u.getMessage())) {
            stateLog.error(String.format("Failed replicate of %s to %s"
                + ", remote rejected non-fast-forward push."
                + "  Check receive.denyNonFastForwards variable in config file"
                + " of destination repository.", u.getRemoteName(), uri), logStatesArray);
          } else if ("failed to lock".equals(u.getMessage())) {
            throw new LockFailureException(uri, u.getMessage());
          } else {
            stateLog.error(String.format(
                "Failed replicate of %s to %s, reason: %s",
                u.getRemoteName(), uri, u.getMessage()), logStatesArray);
          }
          pushStatus = RefPushResult.FAILED;
          anyRefFailed = true;
          break;
      }

      for (ReplicationState rs : getStatesByRef(u.getSrcRef())) {
        rs.notifyRefReplicated(projectName.get(), u.getSrcRef(),
              uri, pushStatus);
      }
    }

    doneRefs.add(ALL_REFS);
    for (ReplicationState rs : getStatesByRef(ALL_REFS)) {
      rs.notifyRefReplicated(projectName.get(), ALL_REFS,
          uri, anyRefFailed ? RefPushResult.FAILED : RefPushResult.SUCCEEDED);
    }
    for (Map.Entry<String,ReplicationState> entry : stateMap.entries()) {
      if (!doneRefs.contains(entry.getKey())) {
        entry.getValue().notifyRefReplicated(projectName.get(), entry.getKey(), uri,
            RefPushResult.NOT_ATTEMPTED);
      }
    }
    stateMap.clear();
  }

  public class LockFailureException extends TransportException {
    private static final long serialVersionUID = 1L;

    public LockFailureException(URIish uri, String message) {
      super(uri, message);
    }
  }
}