// Copyright (C) 2008 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.google.gerrit.server.git;

import com.google.gerrit.common.ChangeHookRunner;
import com.google.gerrit.common.PageLinks;
import com.google.gerrit.common.data.ApprovalType;
import com.google.gerrit.common.data.ApprovalTypes;
import com.google.gerrit.common.errors.NoSuchAccountException;
import com.google.gerrit.reviewdb.AbstractAgreement;
import com.google.gerrit.reviewdb.Account;
import com.google.gerrit.reviewdb.AccountAgreement;
import com.google.gerrit.reviewdb.AccountGroup;
import com.google.gerrit.reviewdb.AccountGroupAgreement;
import com.google.gerrit.reviewdb.ApprovalCategory;
import com.google.gerrit.reviewdb.Branch;
import com.google.gerrit.reviewdb.Change;
import com.google.gerrit.reviewdb.ChangeMessage;
import com.google.gerrit.reviewdb.ContributorAgreement;
import com.google.gerrit.reviewdb.PatchSet;
import com.google.gerrit.reviewdb.PatchSetAncestor;
import com.google.gerrit.reviewdb.PatchSetApproval;
import com.google.gerrit.reviewdb.PatchSetInfo;
import com.google.gerrit.reviewdb.Project;
import com.google.gerrit.reviewdb.RevId;
import com.google.gerrit.reviewdb.ReviewDb;
import com.google.gerrit.server.ChangeUtil;
import com.google.gerrit.server.GerritPersonIdent;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.account.AccountResolver;
import com.google.gerrit.server.config.CanonicalWebUrl;
import com.google.gerrit.server.config.TrackingFooters;
import com.google.gerrit.server.mail.CreateChangeSender;
import com.google.gerrit.server.mail.EmailException;
import com.google.gerrit.server.mail.MergedSender;
import com.google.gerrit.server.mail.ReplacePatchSetSender;
import com.google.gerrit.server.patch.PatchSetInfoFactory;
import com.google.gerrit.server.project.ChangeControl;
import com.google.gerrit.server.project.ProjectControl;
import com.google.gerrit.server.project.RefControl;
import com.google.gwtorm.client.AtomicUpdate;
import com.google.gwtorm.client.OrmException;
import com.google.inject.Inject;
import com.google.inject.assistedinject.Assisted;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AbbreviatedObjectId;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.notes.NoteMap;
import org.eclipse.jgit.revwalk.FooterKey;
import org.eclipse.jgit.revwalk.FooterLine;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevObject;
import org.eclipse.jgit.revwalk.RevSort;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.revwalk.filter.RevFilter;
import org.eclipse.jgit.transport.PostReceiveHook;
import org.eclipse.jgit.transport.PreReceiveHook;
import org.eclipse.jgit.transport.ReceiveCommand;
import org.eclipse.jgit.transport.ReceivePack;
import org.eclipse.jgit.transport.ReceiveCommand.Result;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.annotation.Nullable;

/** Receives change upload using the Git receive-pack protocol. */
public class ReceiveCommits implements PreReceiveHook, PostReceiveHook {
  private static final Logger log =
      LoggerFactory.getLogger(ReceiveCommits.class);

  public static final String NEW_CHANGE = "refs/for/";
  private static final Pattern NEW_PATCHSET =
      Pattern.compile("^refs/changes/(?:[0-9][0-9]/)?([1-9][0-9]*)(?:/new)?$");

  private static final FooterKey REVIEWED_BY = new FooterKey("Reviewed-by");
  private static final FooterKey TESTED_BY = new FooterKey("Tested-by");
  private static final FooterKey CHANGE_ID = new FooterKey("Change-Id");

  public interface Factory {
    ReceiveCommits create(ProjectControl projectControl, Repository repository);
  }

  public static class Capable {
    public static final Capable OK = new Capable("OK");

    private final String message;

    Capable(String msg) {
      message = msg;
    }

    public String getMessage() {
      return message;
    }
  }

  private final Set<Account.Id> reviewerId = new HashSet<Account.Id>();
  private final Set<Account.Id> ccId = new HashSet<Account.Id>();

  private final IdentifiedUser currentUser;
  private final ReviewDb db;
  private final ApprovalTypes approvalTypes;
  private final AccountResolver accountResolver;
  private final CreateChangeSender.Factory createChangeSenderFactory;
  private final MergedSender.Factory mergedSenderFactory;
  private final ReplacePatchSetSender.Factory replacePatchSetFactory;
  private final ReplicationQueue replication;
  private final PatchSetInfoFactory patchSetInfoFactory;
  private final ChangeHookRunner hooks;
  private final String canonicalWebUrl;
  private final PersonIdent gerritIdent;
  private final TrackingFooters trackingFooters;
  private final TagCache tagCache;

  private final ProjectControl projectControl;
  private final Project project;
  private final Repository repo;
  private final ReceivePack rp;
  private final NoteMap rejectCommits;

  private ReceiveCommand newChange;
  private Branch.NameKey destBranch;
  private RefControl destBranchCtl;

  private final List<Change.Id> allNewChanges = new ArrayList<Change.Id>();
  private final Map<Change.Id, ReplaceRequest> replaceByChange =
      new HashMap<Change.Id, ReplaceRequest>();
  private final Map<RevCommit, ReplaceRequest> replaceByCommit =
      new HashMap<RevCommit, ReplaceRequest>();

  private Collection<ObjectId> existingObjects;
  private Map<ObjectId, Ref> refsById;

  private String destTopicName;

  @Inject
  ReceiveCommits(final ReviewDb db, final ApprovalTypes approvalTypes,
      final AccountResolver accountResolver,
      final CreateChangeSender.Factory createChangeSenderFactory,
      final MergedSender.Factory mergedSenderFactory,
      final ReplacePatchSetSender.Factory replacePatchSetFactory,
      final ReplicationQueue replication,
      final PatchSetInfoFactory patchSetInfoFactory,
      final ChangeHookRunner hooks,
      final TagCache tagCache,
      @CanonicalWebUrl @Nullable final String canonicalWebUrl,
      @GerritPersonIdent final PersonIdent gerritIdent,
      final TrackingFooters trackingFooters,

      @Assisted final ProjectControl projectControl,
      @Assisted final Repository repo) throws IOException {
    this.currentUser = (IdentifiedUser) projectControl.getCurrentUser();
    this.db = db;
    this.approvalTypes = approvalTypes;
    this.accountResolver = accountResolver;
    this.createChangeSenderFactory = createChangeSenderFactory;
    this.mergedSenderFactory = mergedSenderFactory;
    this.replacePatchSetFactory = replacePatchSetFactory;
    this.replication = replication;
    this.patchSetInfoFactory = patchSetInfoFactory;
    this.hooks = hooks;
    this.canonicalWebUrl = canonicalWebUrl;
    this.gerritIdent = gerritIdent;
    this.trackingFooters = trackingFooters;
    this.tagCache = tagCache;

    this.projectControl = projectControl;
    this.project = projectControl.getProject();
    this.repo = repo;
    this.rp = new ReceivePack(repo);
    this.rejectCommits = loadRejectCommitsMap();

    rp.setAllowCreates(true);
    rp.setAllowDeletes(true);
    rp.setAllowNonFastForwards(true);
    rp.setCheckReceivedObjects(true);

    if (!projectControl.allRefsAreVisible()) {
      rp.setCheckReferencedObjectsAreReachable(true);
      rp.setRefFilter(new VisibleRefFilter(tagCache, repo, projectControl, db, false));
    }
    rp.setRefFilter(new ReceiveCommitsRefFilter(rp.getRefFilter()));

    rp.setPreReceiveHook(this);
    rp.setPostReceiveHook(this);
  }

  /** Add reviewers for new (or updated) changes. */
  public void addReviewers(Collection<Account.Id> who) {
    reviewerId.addAll(who);
  }

  /** Add reviewers for new (or updated) changes. */
  public void addExtraCC(Collection<Account.Id> who) {
    ccId.addAll(who);
  }

  /** @return the ReceivePack instance to speak the native Git protocol. */
  public ReceivePack getReceivePack() {
    return rp;
  }

  /** Scan part of history and include it in the advertisement. */
  public void advertiseHistory() {
    Set<ObjectId> toInclude = new HashSet<ObjectId>();

    // Advertise some recent open changes, in case a commit is based one.
    try {
      Set<PatchSet.Id> toGet = new HashSet<PatchSet.Id>();
      for (Change change : db.changes()
          .byProjectOpenNext(project.getNameKey(), "z", 32)) {
        PatchSet.Id id = change.currentPatchSetId();
        if (id != null) {
          toGet.add(id);
        }
      }
      for (PatchSet ps : db.patchSets().get(toGet)) {
        if (ps.getRevision() != null && ps.getRevision().get() != null) {
          toInclude.add(ObjectId.fromString(ps.getRevision().get()));
        }
      }
    } catch (OrmException err) {
      log.error("Cannot list open changes of " + project.getNameKey(), err);
    }

    // Size of an additional ".have" line.
    final int haveLineLen = 4 + Constants.OBJECT_ID_STRING_LENGTH + 1 + 5 + 1;

    // Maximum number of bytes to "waste" in the advertisement with
    // a peek at this repository's current reachable history.
    final int maxExtraSize = 8192;

    // Number of recent commits to advertise immediately, hoping to
    // show a client a nearby merge base.
    final int base = 64;

    // Number of commits to skip once base has already been shown.
    final int step = 16;

    // Total number of commits to extract from the history.
    final int max = maxExtraSize / haveLineLen;

    // Scan history until the advertisement is full.
    Set<ObjectId> alreadySending = rp.getAdvertisedObjects();
    RevWalk rw = rp.getRevWalk();
    for (ObjectId haveId : alreadySending) {
      try {
        rw.markStart(rw.parseCommit(haveId));
      } catch (IOException badCommit) {
        continue;
      }
    }

    int stepCnt = 0;
    RevCommit c;
    try {
      while ((c = rw.next()) != null && toInclude.size() < max) {
        if (alreadySending.contains(c)) {
        } else if (toInclude.contains(c)) {
        } else if (c.getParentCount() > 1) {
        } else if (toInclude.size() < base) {
          toInclude.add(c);
        } else {
          stepCnt = ++stepCnt % step;
          if (stepCnt == 0) {
            toInclude.add(c);
          }
        }
      }
    } catch (IOException err) {
      log.error("Error trying to advertise history on " + project.getNameKey(), err);
    }
    rw.reset();
    rp.getAdvertisedObjects().addAll(toInclude);
  }

  /** Determine if the user can upload commits. */
  public Capable canUpload() {
    if (!projectControl.canPushToAtLeastOneRef()) {
      String reqName = project.getName();
      return new Capable("Upload denied for project '" + reqName + "'");
    }

    // Don't permit receive-pack to be executed if a refs/for/branch_name
    // reference exists in the destination repository. These block the
    // client from being able to even send us a pack file, as it is very
    // unlikely the user passed the --force flag and the new commit is
    // probably not going to fast-forward the branch.
    //
    Map<String, Ref> blockingFors;
    try {
      blockingFors = repo.getRefDatabase().getRefs("refs/for/");
    } catch (IOException err) {
      String projName = project.getName();
      log.warn("Cannot scan refs in '" + projName + "'", err);
      return new Capable("Server process cannot read '" + projName + "'");
    }
    if (!blockingFors.isEmpty()) {
      String projName = project.getName();
      log.error("Repository '" + projName
          + "' needs the following refs removed to receive changes: "
          + blockingFors.keySet());
      return new Capable("One or more refs/for/ names blocks change upload");
    }

    if (project.isUseContributorAgreements()) {
      try {
        return verifyActiveContributorAgreement();
      } catch (OrmException e) {
        log.error("Cannot query database for agreements", e);
        return new Capable("Cannot verify contribution agreement");
      }
    } else {
      return Capable.OK;
    }
  }

  @Override
  public void onPreReceive(final ReceivePack arg0,
      final Collection<ReceiveCommand> commands) {
    parseCommands(commands);
    if (newChange != null
        && newChange.getResult() == ReceiveCommand.Result.NOT_ATTEMPTED) {
      createNewChanges();
    }
    doReplaces();
  }

  @Override
  public void onPostReceive(final ReceivePack arg0,
      final Collection<ReceiveCommand> commands) {
    for (final ReceiveCommand c : commands) {
      if (c.getResult() == Result.OK) {
        switch (c.getType()) {
          case CREATE:
            if (isHead(c)) {
              autoCloseChanges(c);
            }
            break;

          case UPDATE: // otherwise known as a fast-forward
            tagCache.updateFastForward(project.getNameKey(),
                c.getRefName(),
                c.getOldId(),
                c.getNewId());
            if (isHead(c)) {
              autoCloseChanges(c);
            }
            break;

          case UPDATE_NONFASTFORWARD:
            if (isHead(c)) {
              autoCloseChanges(c);
            }
            break;
        }

        if (!c.getRefName().startsWith(NEW_CHANGE)) {
          // We only schedule direct refs updates for replication.
          // Change refs are scheduled when they are created.
          //
          replication.scheduleUpdate(project.getNameKey(), c.getRefName());
          Branch.NameKey destBranch = new Branch.NameKey(project.getNameKey(), c.getRefName());
          hooks.doRefUpdatedHook(destBranch, c.getOldId(), c.getNewId(), currentUser.getAccount());
        }
      }
    }

    if (!allNewChanges.isEmpty() && canonicalWebUrl != null) {
      final String url = canonicalWebUrl;
      rp.sendMessage("");
      rp.sendMessage("New Changes:");
      for (final Change.Id c : allNewChanges) {
        rp.sendMessage("  " + url + c.get());
      }
      rp.sendMessage("");
    }
  }

  private Capable verifyActiveContributorAgreement() throws OrmException {
    AbstractAgreement bestAgreement = null;
    ContributorAgreement bestCla = null;

    OUTER: for (AccountGroup.Id groupId : currentUser.getEffectiveGroups()) {
      final List<AccountGroupAgreement> temp =
          db.accountGroupAgreements().byGroup(groupId).toList();

      Collections.reverse(temp);

      for (final AccountGroupAgreement a : temp) {
        final ContributorAgreement cla =
            db.contributorAgreements().get(a.getAgreementId());
        if (cla == null) {
          continue;
        }

        bestAgreement = a;
        bestCla = cla;
        break OUTER;
      }
    }

    if (bestAgreement == null) {
      final List<AccountAgreement> temp =
          db.accountAgreements().byAccount(currentUser.getAccountId()).toList();

      Collections.reverse(temp);

      for (final AccountAgreement a : temp) {
        final ContributorAgreement cla =
            db.contributorAgreements().get(a.getAgreementId());
        if (cla == null) {
          continue;
        }

        bestAgreement = a;
        bestCla = cla;
        break;
      }
    }

    if (bestCla != null && !bestCla.isActive()) {
      final StringBuilder msg = new StringBuilder();
      msg.append(bestCla.getShortName());
      msg.append(" contributor agreement is expired.\n");
      if (canonicalWebUrl != null) {
        msg.append("\nPlease complete a new agreement");
        msg.append(":\n\n  ");
        msg.append(canonicalWebUrl);
        msg.append("#");
        msg.append(PageLinks.SETTINGS_AGREEMENTS);
        msg.append("\n");
      }
      msg.append("\n");
      return new Capable(msg.toString());
    }

    if (bestCla != null && bestCla.isRequireContactInformation()) {
      boolean fail = false;
      fail |= missing(currentUser.getAccount().getFullName());
      fail |= missing(currentUser.getAccount().getPreferredEmail());
      fail |= !currentUser.getAccount().isContactFiled();

      if (fail) {
        final StringBuilder msg = new StringBuilder();
        msg.append(bestCla.getShortName());
        msg.append(" contributor agreement requires");
        msg.append(" current contact information.\n");
        if (canonicalWebUrl != null) {
          msg.append("\nPlease review your contact information");
          msg.append(":\n\n  ");
          msg.append(canonicalWebUrl);
          msg.append("#");
          msg.append(PageLinks.SETTINGS_CONTACT);
          msg.append("\n");
        }
        msg.append("\n");
        return new Capable(msg.toString());
      }
    }

    if (bestAgreement != null) {
      switch (bestAgreement.getStatus()) {
        case VERIFIED:
          return Capable.OK;
        case REJECTED:
          return new Capable(bestCla.getShortName()
              + " contributor agreement was rejected."
              + "\n       (rejected on " + bestAgreement.getReviewedOn()
              + ")\n");
        case NEW:
          return new Capable(bestCla.getShortName()
              + " contributor agreement is still pending review.\n");
      }
    }

    final StringBuilder msg = new StringBuilder();
    msg.append(" A Contributor Agreement must be completed before uploading");
    if (canonicalWebUrl != null) {
      msg.append(":\n\n  ");
      msg.append(canonicalWebUrl);
      msg.append("#");
      msg.append(PageLinks.SETTINGS_AGREEMENTS);
      msg.append("\n");
    } else {
      msg.append(".");
    }
    msg.append("\n");
    return new Capable(msg.toString());
  }

  private static boolean missing(final String value) {
    return value == null || value.trim().equals("");
  }

  private Account.Id toAccountId(final String nameOrEmail) throws OrmException,
      NoSuchAccountException {
    final Account a = accountResolver.findByNameOrEmail(nameOrEmail);
    if (a == null) {
      throw new NoSuchAccountException("\"" + nameOrEmail
          + "\" is not registered");
    }
    return a.getId();
  }

  private void parseCommands(final Collection<ReceiveCommand> commands) {
    for (final ReceiveCommand cmd : commands) {
      if (cmd.getResult() != ReceiveCommand.Result.NOT_ATTEMPTED) {
        // Already rejected by the core receive process.
        //
        continue;
      }

      if (!Repository.isValidRefName(cmd.getRefName())
          || cmd.getRefName().contains("//")) {
        reject(cmd, "not valid ref");
        continue;
      }

      if (cmd.getRefName().startsWith(NEW_CHANGE)) {
        parseNewChangeCommand(cmd);
        continue;
      }

      final Matcher m = NEW_PATCHSET.matcher(cmd.getRefName());
      if (m.matches()) {
        // The referenced change must exist and must still be open.
        //
        final Change.Id changeId = Change.Id.parse(m.group(1));
        parseReplaceCommand(cmd, changeId);
        continue;
      }

      switch (cmd.getType()) {
        case CREATE:
          parseCreate(cmd);
          continue;

        case UPDATE:
          parseUpdate(cmd);
          continue;

        case DELETE:
          parseDelete(cmd);
          continue;

        case UPDATE_NONFASTFORWARD:
          parseRewind(cmd);
          continue;
      }

      // Everything else is bogus as far as we are concerned.
      //
      reject(cmd);
    }
  }

  private void parseCreate(final ReceiveCommand cmd) {
    RevObject obj;
    try {
      obj = rp.getRevWalk().parseAny(cmd.getNewId());
    } catch (IOException err) {
      log.error("Invalid object " + cmd.getNewId().name() + " for "
          + cmd.getRefName() + " creation", err);
      reject(cmd, "invalid object");
      return;
    }

    if (isHead(cmd) && !isCommit(cmd)) {
      return;
    }

    RefControl ctl = projectControl.controlForRef(cmd.getRefName());
    if (ctl.canCreate(rp.getRevWalk(), obj)) {
      validateNewCommits(ctl, cmd);

      // Let the core receive process handle it
    } else {
      reject(cmd);
    }
  }

  private void parseUpdate(final ReceiveCommand cmd) {
    RefControl ctl = projectControl.controlForRef(cmd.getRefName());
    if (ctl.canUpdate()) {
      if (isHead(cmd) && !isCommit(cmd)) {
        return;
      }

      validateNewCommits(ctl, cmd);
      // Let the core receive process handle it
    } else {
      reject(cmd);
    }
  }

  private boolean isCommit(final ReceiveCommand cmd) {
    RevObject obj;
    try {
      obj = rp.getRevWalk().parseAny(cmd.getNewId());
    } catch (IOException err) {
      log.error("Invalid object " + cmd.getNewId().name() + " for "
          + cmd.getRefName(), err);
      reject(cmd, "invalid object");
      return false;
    }

    if (obj instanceof RevCommit) {
      return true;
    } else {
      reject(cmd, "not a commit");
      return false;
    }
  }

  private void parseDelete(final ReceiveCommand cmd) {
    RefControl ctl = projectControl.controlForRef(cmd.getRefName());
    if (ctl.canDelete()) {
      // Let the core receive process handle it
    } else {
      reject(cmd);
    }
  }

  private void parseRewind(final ReceiveCommand cmd) {
    RevCommit newObject;
    try {
      newObject = rp.getRevWalk().parseCommit(cmd.getNewId());
    } catch (IncorrectObjectTypeException notCommit) {
      newObject = null;
    } catch (IOException err) {
      log.error("Invalid object " + cmd.getNewId().name() + " for "
          + cmd.getRefName() + " forced update", err);
      reject(cmd, "invalid object");
      return;
    }

    RefControl ctl = projectControl.controlForRef(cmd.getRefName());
    if (newObject != null) {
      validateNewCommits(ctl, cmd);
      if (cmd.getResult() != ReceiveCommand.Result.NOT_ATTEMPTED) {
        return;
      }
    }

    if (ctl.canForceUpdate()) {
      // Let the core receive process handle it
    } else {
      cmd.setResult(ReceiveCommand.Result.REJECTED_NONFASTFORWARD);
    }
  }

  private void parseNewChangeCommand(final ReceiveCommand cmd) {
    // Permit exactly one new change request per push.
    //
    if (newChange != null) {
      reject(cmd, "duplicate request");
      return;
    }

    newChange = cmd;
    String destBranchName = cmd.getRefName().substring(NEW_CHANGE.length());
    if (!destBranchName.startsWith(Constants.R_REFS)) {
      destBranchName = Constants.R_HEADS + destBranchName;
    }

    final String head;
    try {
      head = repo.getFullBranch();
    } catch (IOException e) {
      log.error("Cannot read HEAD symref", e);
      reject(cmd, "internal error");
      return;
    }

    // Split the destination branch by branch and topic.  The topic
    // suffix is entirely optional, so it might not even exist.
    //
    int split = destBranchName.length();
    for (;;) {
      String name = destBranchName.substring(0, split);

      if (rp.getAdvertisedRefs().containsKey(name)) {
        // We advertised the branch to the client so we know
        // the branch exists. Target this branch for the upload.
        //
        break;
      } else if (head.equals(name)) {
        // We didn't advertise the branch, because it doesn't exist yet.
        // Allow it anyway as HEAD is a symbolic reference to the name.
        //
        break;
      }

      split = name.lastIndexOf('/', split - 1);
      if (split <= Constants.R_REFS.length()) {
        String n = destBranchName;
        if (n.startsWith(Constants.R_HEADS))
          n = n.substring(Constants.R_HEADS.length());
        reject(cmd, "branch " + n + " not found");
        return;
      }
    }

    if (split < destBranchName.length()) {
      destTopicName = destBranchName.substring(split + 1);
      if (destTopicName.isEmpty()) {
        destTopicName = null;
      }
    } else {
      destTopicName = null;
    }
    destBranch = new Branch.NameKey(project.getNameKey(), //
        destBranchName.substring(0, split));
    destBranchCtl = projectControl.controlForRef(destBranch);
    if (!destBranchCtl.canUpload()) {
      reject(cmd);
      return;
    }

    // Validate that the new commits are connected with the target
    // branch.  If they aren't, we want to abort. We do this check by
    // looking to see if we can compute a merge base between the new
    // commits and the target branch head.
    //
    try {
      final RevWalk walk = rp.getRevWalk();

      final RevCommit tip = walk.parseCommit(newChange.getNewId());
      Ref targetRef = rp.getAdvertisedRefs().get(destBranchName);
      if (targetRef == null || targetRef.getObjectId() == null) {
        // The destination branch does not yet exist. Assume the
        // history being sent for review will start it and thus
        // is "connected" to the branch.
        return;
      }
      final RevCommit h = walk.parseCommit(targetRef.getObjectId());

      final RevFilter oldRevFilter = walk.getRevFilter();
      try {
        walk.reset();
        walk.setRevFilter(RevFilter.MERGE_BASE);
        walk.markStart(tip);
        walk.markStart(h);
        if (walk.next() == null) {
          reject(newChange, "no common ancestry");
          return;
        }
      } finally {
        walk.reset();
        walk.setRevFilter(oldRevFilter);
      }
    } catch (IOException e) {
      newChange.setResult(Result.REJECTED_MISSING_OBJECT);
      log.error("Invalid pack upload; one or more objects weren't sent", e);
      return;
    }
  }

  /**
   * Loads a list of commits to reject from {@code refs/meta/reject-commits}.
   *
   * @return NoteMap of commits to be rejected, null if there are none.
   * @throws IOException the map cannot be loaded.
   */
  private NoteMap loadRejectCommitsMap() throws IOException {
    try {
      Ref ref = repo.getRef(GitRepositoryManager.REF_REJECT_COMMITS);
      if (ref == null) {
        return NoteMap.newEmptyMap();
      }

      RevWalk rw = rp.getRevWalk();
      RevCommit map = rw.parseCommit(ref.getObjectId());
      return NoteMap.read(rw.getObjectReader(), map);
    } catch (IOException badMap) {
      throw new IOException("Cannot load "
          + GitRepositoryManager.REF_REJECT_COMMITS, badMap);
    }
  }

  private void parseReplaceCommand(final ReceiveCommand cmd,
      final Change.Id changeId) {
    if (cmd.getType() != ReceiveCommand.Type.CREATE) {
      reject(cmd, "invalid usage");
      return;
    }

    final RevCommit newCommit;
    try {
      newCommit = rp.getRevWalk().parseCommit(cmd.getNewId());
    } catch (IOException e) {
      log.error("Cannot parse " + cmd.getNewId().name() + " as commit", e);
      reject(cmd, "invalid commit");
      return;
    }

    final Change changeEnt;
    try {
      changeEnt = db.changes().get(changeId);
    } catch (OrmException e) {
      log.error("Cannot lookup existing change " + changeId, e);
      reject(cmd, "database error");
      return;
    }
    if (changeEnt == null) {
      reject(cmd, "change " + changeId + " not found");
      return;
    }
    if (!project.getNameKey().equals(changeEnt.getProject())) {
      reject(cmd, "change " + changeId + " does not belong to project " + project.getName());
      return;
    }

    requestReplace(cmd, true, changeEnt, newCommit);
  }

  private boolean requestReplace(final ReceiveCommand cmd,
      final boolean checkMergedInto, final Change change,
      final RevCommit newCommit) {
    if (change.getStatus().isClosed()) {
      reject(cmd, "change " + change.getId() + " closed");
      return false;
    }

    final ReplaceRequest req =
        new ReplaceRequest(change.getId(), newCommit, cmd, checkMergedInto);
    if (replaceByChange.containsKey(req.ontoChange)) {
      reject(cmd, "duplicate request");
      return false;
    }
    if (replaceByCommit.containsKey(req.newCommit)) {
      reject(cmd, "duplicate request");
      return false;
    }
    replaceByChange.put(req.ontoChange, req);
    replaceByCommit.put(req.newCommit, req);
    return true;
  }

  private void createNewChanges() {
    final List<RevCommit> toCreate = new ArrayList<RevCommit>();
    final RevWalk walk = rp.getRevWalk();
    walk.reset();
    walk.sort(RevSort.TOPO);
    walk.sort(RevSort.REVERSE, true);
    try {
      walk.markStart(walk.parseCommit(newChange.getNewId()));
      for (ObjectId id : existingObjects()) {
        try {
          walk.markUninteresting(walk.parseCommit(id));
        } catch (IOException e) {
          continue;
        }
      }

      final Set<Change.Key> newChangeIds = new HashSet<Change.Key>();
      for (;;) {
        final RevCommit c = walk.next();
        if (c == null) {
          break;
        }
        if (replaceByCommit.containsKey(c)) {
          // This commit was already scheduled to replace an existing PatchSet.
          //
          continue;
        }
        if (!validCommit(destBranchCtl, newChange, c)) {
          // Not a change the user can propose? Abort as early as possible.
          //
          return;
        }

        final List<String> idList = c.getFooterLines(CHANGE_ID);
        if (!idList.isEmpty()) {
          final String idStr = idList.get(idList.size() - 1).trim();
          if (idStr.matches("^I00*$")) {
            // Reject this invalid line from EGit.
            reject(newChange, "invalid Change-Id");
            return;
          }

          final Change.Key key = new Change.Key(idStr);

          if (newChangeIds.contains(key)) {
            reject(newChange, "squash commits first");
            return;
          }

          final List<Change> changes =
              db.changes().byBranchKey(destBranch, key).toList();
          if (changes.size() > 1) {
            // WTF, multiple changes in this project have the same key?
            // Since the commit is new, the user should recreate it with
            // a different Change-Id. In practice, we should never see
            // this error message as Change-Id should be unique.
            //
            reject(newChange, key.get() + " has duplicates");
            return;

          }

          if (changes.size() == 1) {
            // Schedule as a replacement to this one matching change.
            //
            if (requestReplace(newChange, false, changes.get(0), c)) {
              continue;
            } else {
              return;
            }
          }

          if (changes.size() == 0) {
            if (!isValidChangeId(idStr)) {
              reject(newChange, "invalid Change-Id");
              return;
            }

            newChangeIds.add(key);
          }
        }

        toCreate.add(c);
      }
    } catch (IOException e) {
      // Should never happen, the core receive process would have
      // identified the missing object earlier before we got control.
      //
      newChange.setResult(Result.REJECTED_MISSING_OBJECT);
      log.error("Invalid pack upload; one or more objects weren't sent", e);
      return;
    } catch (OrmException e) {
      log.error("Cannot query database to locate prior changes", e);
      reject(newChange, "database error");
      return;
    }

    if (toCreate.isEmpty() && replaceByChange.isEmpty()) {
      reject(newChange, "no new changes");
      return;
    }

    for (final RevCommit c : toCreate) {
      try {
        createChange(walk, c);
      } catch (IOException e) {
        log.error("Error computing patch of commit " + c.name(), e);
        reject(newChange, "diff error");
        return;
      } catch (OrmException e) {
        log.error("Error creating change for commit " + c.name(), e);
        reject(newChange, "database error");
        return;
      }
    }
    newChange.setResult(ReceiveCommand.Result.OK);
  }

  private static boolean isValidChangeId(String idStr) {
    return idStr.matches("^I[0-9a-fA-F]{40}$") && !idStr.matches("^I00*$");
  }

  private void createChange(final RevWalk walk, final RevCommit c)
      throws OrmException, IOException {
    walk.parseBody(c);
    warnMalformedMessage(c);

    final Account.Id me = currentUser.getAccountId();
    Change.Key changeKey = new Change.Key("I" + c.name());
    final Set<Account.Id> reviewers = new HashSet<Account.Id>(reviewerId);
    final Set<Account.Id> cc = new HashSet<Account.Id>(ccId);
    final List<FooterLine> footerLines = c.getFooterLines();
    for (final FooterLine footerLine : footerLines) {
      try {
        if (footerLine.matches(CHANGE_ID)) {
          final String v = footerLine.getValue().trim();
          if (isValidChangeId(v)) {
            changeKey = new Change.Key(v);
          }
        } else if (isReviewer(footerLine)) {
          reviewers.add(toAccountId(footerLine.getValue().trim()));
        } else if (footerLine.matches(FooterKey.CC)) {
          cc.add(toAccountId(footerLine.getValue().trim()));
        }
      } catch (NoSuchAccountException e) {
        continue;
      }
    }
    reviewers.remove(me);
    cc.remove(me);
    cc.removeAll(reviewers);

    final Change change =
        new Change(changeKey, new Change.Id(db.nextChangeId()), me, destBranch);
    change.setTopic(destTopicName);
    change.nextPatchSetId();

    final PatchSet ps = new PatchSet(change.currPatchSetId());
    ps.setCreatedOn(change.getCreatedOn());
    ps.setUploader(me);
    ps.setRevision(toRevId(c));
    insertAncestors(ps.getId(), c);
    db.patchSets().insert(Collections.singleton(ps));

    final PatchSetInfo info = patchSetInfoFactory.get(c, ps.getId());
    change.setCurrentPatchSet(info);
    ChangeUtil.updated(change);
    db.changes().insert(Collections.singleton(change));

    final Set<Account.Id> haveApprovals = new HashSet<Account.Id>();
    final List<ApprovalType> allTypes = approvalTypes.getApprovalTypes();
    haveApprovals.add(me);

    if (allTypes.size() > 0) {
      final Account.Id authorId =
          info.getAuthor() != null ? info.getAuthor().getAccount() : null;
      final Account.Id committerId =
          info.getCommitter() != null ? info.getCommitter().getAccount() : null;
      final ApprovalCategory.Id catId =
          allTypes.get(allTypes.size() - 1).getCategory().getId();
      if (authorId != null && haveApprovals.add(authorId)) {
        insertDummyApproval(change, ps.getId(), authorId, catId, db);
      }
      if (committerId != null && haveApprovals.add(committerId)) {
        insertDummyApproval(change, ps.getId(), committerId, catId, db);
      }
      for (final Account.Id reviewer : reviewers) {
        if (haveApprovals.add(reviewer)) {
          insertDummyApproval(change, ps.getId(), reviewer, catId, db);
        }
      }
    }

    final RefUpdate ru = repo.updateRef(ps.getRefName());
    ru.setNewObjectId(c);
    ru.disableRefLog();
    if (ru.update(walk) != RefUpdate.Result.NEW) {
      throw new IOException("Failed to create ref " + ps.getRefName() + " in "
          + repo.getDirectory() + ": " + ru.getResult());
    }
    replication.scheduleUpdate(project.getNameKey(), ru.getName());

    allNewChanges.add(change.getId());

    try {
      final CreateChangeSender cm;
      cm = createChangeSenderFactory.create(change);
      cm.setFrom(me);
      cm.setPatchSet(ps, info);
      cm.addReviewers(reviewers);
      cm.addExtraCC(cc);
      cm.send();
    } catch (EmailException e) {
      log.error("Cannot send email for new change " + change.getId(), e);
    }

    ChangeUtil.updateTrackingIds(db, change, trackingFooters, footerLines);
    hooks.doPatchsetCreatedHook(change, ps);
  }

  private static boolean isReviewer(final FooterLine candidateFooterLine) {
    return candidateFooterLine.matches(FooterKey.SIGNED_OFF_BY)
        || candidateFooterLine.matches(FooterKey.ACKED_BY)
        || candidateFooterLine.matches(REVIEWED_BY)
        || candidateFooterLine.matches(TESTED_BY);
  }

  private void doReplaces() {
    for (final ReplaceRequest request : replaceByChange.values()) {
      try {
        doReplace(request);
      } catch (IOException err) {
        log.error("Error computing replacement patch for change "
            + request.ontoChange + ", commit " + request.newCommit.name(), err);
        reject(request.cmd, "diff error");
      } catch (OrmException err) {
        log.error("Error storing replacement patch for change "
            + request.ontoChange + ", commit " + request.newCommit.name(), err);
        reject(request.cmd, "database error");
      }
      if (request.cmd.getResult() == ReceiveCommand.Result.NOT_ATTEMPTED) {
        log.error("Replacement patch for change " + request.ontoChange
            + ", commit " + request.newCommit.name() + " wasn't attempted."
            + "  This is a bug in the receive process implementation.");
        reject(request.cmd, "internal error");
      }
    }
  }

  private PatchSet.Id doReplace(final ReplaceRequest request)
      throws IOException, OrmException {
    final RevCommit c = request.newCommit;
    rp.getRevWalk().parseBody(c);
    warnMalformedMessage(c);

    final Account.Id me = currentUser.getAccountId();
    final Set<Account.Id> reviewers = new HashSet<Account.Id>(reviewerId);
    final Set<Account.Id> cc = new HashSet<Account.Id>(ccId);
    final List<FooterLine> footerLines = c.getFooterLines();
    for (final FooterLine footerLine : footerLines) {
      try {
        if (isReviewer(footerLine)) {
          reviewers.add(toAccountId(footerLine.getValue().trim()));
        } else if (footerLine.matches(FooterKey.CC)) {
          cc.add(toAccountId(footerLine.getValue().trim()));
        }
      } catch (NoSuchAccountException e) {
        continue;
      }
    }
    reviewers.remove(me);
    cc.remove(me);
    cc.removeAll(reviewers);

    final ReplaceResult result = new ReplaceResult();
    final Set<Account.Id> oldReviewers = new HashSet<Account.Id>();
    final Set<Account.Id> oldCC = new HashSet<Account.Id>();

    Change change = db.changes().get(request.ontoChange);
    if (change == null) {
      reject(request.cmd, "change " + request.ontoChange + " not found");
      return null;
    }
    if (change.getStatus().isClosed()) {
      reject(request.cmd, "change " + request.ontoChange + " closed");
      return null;
    }

    final ChangeControl changeCtl = projectControl.controlFor(change);
    if (!changeCtl.canAddPatchSet()) {
      reject(request.cmd, "cannot replace " + request.ontoChange);
      return null;
    }
    if (!validCommit(changeCtl.getRefControl(), request.cmd, c)) {
      return null;
    }

    final PatchSet.Id priorPatchSet = change.currentPatchSetId();
    for (final PatchSet ps : db.patchSets().byChange(request.ontoChange)) {
      if (ps.getRevision() == null) {
        log.warn("Patch set " + ps.getId() + " has no revision");
        reject(request.cmd, "change state corrupt");
        return null;
      }

      final String revIdStr = ps.getRevision().get();
      final ObjectId commitId;
      try {
        commitId = ObjectId.fromString(revIdStr);
      } catch (IllegalArgumentException e) {
        log.warn("Invalid revision in " + ps.getId() + ": " + revIdStr);
        reject(request.cmd, "change state corrupt");
        return null;
      }

      try {
        final RevCommit prior = rp.getRevWalk().parseCommit(commitId);

        // Don't allow a change to directly depend upon itself. This is a
        // very common error due to users making a new commit rather than
        // amending when trying to address review comments.
        //
        if (rp.getRevWalk().isMergedInto(prior, c)) {
          reject(request.cmd, "squash commits first");
          return null;
        }

        // Don't allow the same commit to appear twice on the same change
        //
        if (c == prior) {
          reject(request.cmd, "commit already exists");
          return null;
        }

        // Don't allow the same tree if the commit message is unmodified
        // or no parents were updated (rebase), else warn that only part
        // of the commit was modified.
        //
        if (priorPatchSet.equals(ps.getId()) && c.getTree() == prior.getTree()) {
          rp.getRevWalk().parseBody(prior);
          final boolean messageEq =
              eq(c.getFullMessage(), prior.getFullMessage());
          final boolean parentsEq = parentsEqual(c, prior);
          final boolean authorEq = authorEqual(c, prior);

          if (messageEq && parentsEq && authorEq) {
            reject(request.cmd, "no changes made");
            return null;
          } else {
            ObjectReader reader = rp.getRevWalk().getObjectReader();
            StringBuilder msg = new StringBuilder();
            msg.append("(W) ");
            msg.append(reader.abbreviate(c).name());
            msg.append(":");
            msg.append(" no files changed");
            if (!authorEq) {
              msg.append(", author changed");
            }
            if (!messageEq) {
              msg.append(", message updated");
            }
            if (!parentsEq) {
              msg.append(", was rebased");
            }
            rp.sendMessage(msg.toString());
          }
        }
      } catch (IOException e) {
        log.error("Change " + change.getId() + " missing " + revIdStr, e);
        reject(request.cmd, "change state corrupt");
        return null;
      }
    }

    change =
        db.changes().atomicUpdate(change.getId(), new AtomicUpdate<Change>() {
          @Override
          public Change update(Change change) {
            if (change.getStatus().isOpen()) {
              change.nextPatchSetId();
              return change;
            } else {
              return null;
            }
          }
        });
    if (change == null) {
      reject(request.cmd, "change is closed");
      return null;
    }

    final PatchSet ps = new PatchSet(change.currPatchSetId());
    ps.setCreatedOn(new Timestamp(System.currentTimeMillis()));
    ps.setUploader(currentUser.getAccountId());
    ps.setRevision(toRevId(c));
    insertAncestors(ps.getId(), c);
    db.patchSets().insert(Collections.singleton(ps));

    if (request.checkMergedInto) {
      final Ref mergedInto = findMergedInto(change.getDest().get(), c);
      result.mergedIntoRef = mergedInto != null ? mergedInto.getName() : null;
    }
    result.change = change;
    result.patchSet = ps;
    result.info = patchSetInfoFactory.get(c, ps.getId());

    final Account.Id authorId =
        result.info.getAuthor() != null ? result.info.getAuthor().getAccount()
            : null;
    final Account.Id committerId =
        result.info.getCommitter() != null ? result.info.getCommitter()
            .getAccount() : null;

    boolean haveAuthor = false;
    boolean haveCommitter = false;
    final Set<Account.Id> haveApprovals = new HashSet<Account.Id>();

    oldReviewers.clear();
    oldCC.clear();

    for (PatchSetApproval a : db.patchSetApprovals().byChange(change.getId())) {
      haveApprovals.add(a.getAccountId());

      if (a.getValue() != 0) {
        oldReviewers.add(a.getAccountId());
      } else {
        oldCC.add(a.getAccountId());
      }

      final ApprovalType type =
          approvalTypes.getApprovalType(a.getCategoryId());
      if (a.getPatchSetId().equals(priorPatchSet)
          && type.getCategory().isCopyMinScore() && type.isMaxNegative(a)) {
        // If there was a negative vote on the prior patch set, carry it
        // into this patch set.
        //
        db.patchSetApprovals().insert(
            Collections.singleton(new PatchSetApproval(ps.getId(), a)));
      }

      if (!haveAuthor && authorId != null && a.getAccountId().equals(authorId)) {
        haveAuthor = true;
      }
      if (!haveCommitter && committerId != null
          && a.getAccountId().equals(committerId)) {
        haveCommitter = true;
      }
    }

    final ChangeMessage msg =
        new ChangeMessage(new ChangeMessage.Key(change.getId(), ChangeUtil
            .messageUUID(db)), me, ps.getCreatedOn());
    msg.setMessage("Uploaded patch set " + ps.getPatchSetId() + ".");
    db.changeMessages().insert(Collections.singleton(msg));
    result.msg = msg;

    if (result.mergedIntoRef != null) {
      // Change was already submitted to a branch, close it.
      //
      markChangeMergedByPush(db, result);
    } else {
      // Change should be new, so it can go through review again.
      //
      change =
          db.changes().atomicUpdate(change.getId(), new AtomicUpdate<Change>() {
            @Override
            public Change update(Change change) {
              if (change.getStatus().isOpen()) {
                if (destTopicName != null) {
                  change.setTopic(destTopicName);
                }
                change.setStatus(Change.Status.NEW);
                change.setCurrentPatchSet(result.info);
                ChangeUtil.updated(change);
                return change;
              } else {
                return null;
              }
            }
          });
      if (change == null) {
        db.patchSets().delete(Collections.singleton(ps));
        db.changeMessages().delete(Collections.singleton(msg));
        reject(request.cmd, "change is closed");
        return null;
      }
    }

    final List<ApprovalType> allTypes = approvalTypes.getApprovalTypes();
    if (allTypes.size() > 0) {
      final ApprovalCategory.Id catId =
          allTypes.get(allTypes.size() - 1).getCategory().getId();
      if (authorId != null && haveApprovals.add(authorId)) {
        insertDummyApproval(result, authorId, catId, db);
      }
      if (committerId != null && haveApprovals.add(committerId)) {
        insertDummyApproval(result, committerId, catId, db);
      }
      for (final Account.Id reviewer : reviewers) {
        if (haveApprovals.add(reviewer)) {
          insertDummyApproval(result, reviewer, catId, db);
        }
      }
    }

    final RefUpdate ru = repo.updateRef(ps.getRefName());
    ru.setNewObjectId(c);
    ru.disableRefLog();
    if (ru.update(rp.getRevWalk()) != RefUpdate.Result.NEW) {
      throw new IOException("Failed to create ref " + ps.getRefName() + " in "
          + repo.getDirectory() + ": " + ru.getResult());
    }
    replication.scheduleUpdate(project.getNameKey(), ru.getName());
    hooks.doPatchsetCreatedHook(result.change, ps);
    request.cmd.setResult(ReceiveCommand.Result.OK);

    try {
      final ReplacePatchSetSender cm;
      cm = replacePatchSetFactory.create(result.change);
      cm.setFrom(me);
      cm.setPatchSet(ps, result.info);
      cm.setChangeMessage(result.msg);
      cm.addReviewers(reviewers);
      cm.addExtraCC(cc);
      cm.addReviewers(oldReviewers);
      cm.addExtraCC(oldCC);
      cm.send();
    } catch (EmailException e) {
      log.error("Cannot send email for new patch set " + ps.getId(), e);
    }

    ChangeUtil.updateTrackingIds(db, change, trackingFooters, footerLines);
    sendMergedEmail(result);
    return result != null ? result.info.getKey() : null;
  }

  static boolean parentsEqual(RevCommit a, RevCommit b) {
    if (a.getParentCount() != b.getParentCount()) {
      return false;
    }
    for (int i = 0; i < a.getParentCount(); i++) {
      if (a.getParent(i) != b.getParent(i)) {
        return false;
      }
    }
    return true;
  }

  static boolean authorEqual(RevCommit a, RevCommit b) {
    PersonIdent aAuthor = a.getAuthorIdent();
    PersonIdent bAuthor = b.getAuthorIdent();

    if (aAuthor == null && bAuthor == null) {
      return true;
    } else if (aAuthor == null || bAuthor == null) {
      return false;
    }

    return eq(aAuthor.getName(), bAuthor.getName())
        && eq(aAuthor.getEmailAddress(), bAuthor.getEmailAddress());
  }

  static boolean eq(String a, String b) {
    if (a == null && b == null) {
      return true;
    } else if (a == null || b == null) {
      return false;
    } else {
      return a.equals(b);
    }
  }

  private void insertDummyApproval(final ReplaceResult result,
      final Account.Id forAccount, final ApprovalCategory.Id catId,
      final ReviewDb db) throws OrmException {
    insertDummyApproval(result.change, result.patchSet.getId(), forAccount,
        catId, db);
  }

  private void insertDummyApproval(final Change change, final PatchSet.Id psId,
      final Account.Id forAccount, final ApprovalCategory.Id catId,
      final ReviewDb db) throws OrmException {
    final PatchSetApproval ca =
        new PatchSetApproval(new PatchSetApproval.Key(psId, forAccount, catId),
            (short) 0);
    ca.cache(change);
    db.patchSetApprovals().insert(Collections.singleton(ca));
  }

  private Ref findMergedInto(final String first, final RevCommit commit) {
    try {
      final Map<String, Ref> all = repo.getAllRefs();
      Ref firstRef = all.get(first);
      if (firstRef != null && isMergedInto(commit, firstRef)) {
        return firstRef;
      }
      for (Ref ref : all.values()) {
        if (isHead(ref)) {
          if (isMergedInto(commit, ref)) {
            return ref;
          }
        }
      }
      return null;
    } catch (IOException e) {
      log.warn("Can't check for already submitted change", e);
      return null;
    }
  }

  private boolean isMergedInto(final RevCommit commit, final Ref ref)
      throws IOException {
    final RevWalk rw = rp.getRevWalk();
    return rw.isMergedInto(commit, rw.parseCommit(ref.getObjectId()));
  }

  private static class ReplaceRequest {
    final Change.Id ontoChange;
    final RevCommit newCommit;
    final ReceiveCommand cmd;
    final boolean checkMergedInto;

    ReplaceRequest(final Change.Id toChange, final RevCommit newCommit,
        final ReceiveCommand cmd, final boolean checkMergedInto) {
      this.ontoChange = toChange;
      this.newCommit = newCommit;
      this.cmd = cmd;
      this.checkMergedInto = checkMergedInto;
    }
  }

  private static class ReplaceResult {
    Change change;
    PatchSet patchSet;
    PatchSetInfo info;
    ChangeMessage msg;
    String mergedIntoRef;
  }

  private void validateNewCommits(RefControl ctl, ReceiveCommand cmd) {
    final RevWalk walk = rp.getRevWalk();
    walk.reset();
    walk.sort(RevSort.NONE);
    try {
      walk.markStart(walk.parseCommit(cmd.getNewId()));
      for (ObjectId id : existingObjects()) {
        try {
          walk.markUninteresting(walk.parseCommit(id));
        } catch (IOException e) {
          continue;
        }
      }

      RevCommit c;
      while ((c = walk.next()) != null) {
        if (!validCommit(ctl, cmd, c)) {
          break;
        }
      }
    } catch (IOException err) {
      cmd.setResult(Result.REJECTED_MISSING_OBJECT);
      log.error("Invalid pack upload; one or more objects weren't sent", err);
    }
  }

  private Collection<ObjectId> existingObjects() {
    if (existingObjects == null) {
      Map<String, Ref> refs = repo.getAllRefs();
      existingObjects = new ArrayList<ObjectId>(refs.size());
      for (Ref r : refs.values()) {
        existingObjects.add(r.getObjectId());
      }
    }
    return existingObjects;
  }

  private boolean validCommit(final RefControl ctl, final ReceiveCommand cmd,
      final RevCommit c) throws MissingObjectException, IOException {
    rp.getRevWalk().parseBody(c);
    final PersonIdent committer = c.getCommitterIdent();
    final PersonIdent author = c.getAuthorIdent();

    // Require permission to upload merges.
    if (c.getParentCount() > 1 && !ctl.canUploadMerges()) {
      reject(cmd, "you are not allowed to upload merges");
      return false;
    }

    // Don't allow the user to amend a merge created by Gerrit Code Review.
    // This seems to happen all too often, due to users not paying any
    // attention to what they are doing.
    //
    if (c.getParentCount() > 1
        && author.getName().equals(gerritIdent.getName())
        && author.getEmailAddress().equals(gerritIdent.getEmailAddress())
        && !ctl.canForgeGerritServerIdentity()) {
      reject(cmd, "do not amend merges not made by you");
      return false;
    }

    // Require that author matches the uploader.
    //
    if (!currentUser.getEmailAddresses().contains(author.getEmailAddress())
        && !ctl.canForgeAuthor()) {
      sendInvalidEmailError(c, "author", author);
      reject(cmd, "invalid author");
      return false;
    }

    // Require that committer matches the uploader.
    //
    if (!currentUser.getEmailAddresses().contains(committer.getEmailAddress())
        && !ctl.canForgeCommitter()) {
      sendInvalidEmailError(c, "committer", committer);
      reject(cmd, "invalid committer");
      return false;
    }

    if (project.isUseSignedOffBy()) {
      // If the project wants Signed-off-by / Acked-by lines, verify we
      // have them for the blamable parties involved on this change.
      //
      boolean sboAuthor = false, sboCommitter = false, sboMe = false;
      for (final FooterLine footer : c.getFooterLines()) {
        if (footer.matches(FooterKey.SIGNED_OFF_BY)) {
          final String e = footer.getEmailAddress();
          if (e != null) {
            sboAuthor |= author.getEmailAddress().equals(e);
            sboCommitter |= committer.getEmailAddress().equals(e);
            sboMe |= currentUser.getEmailAddresses().contains(e);
          }
        }
      }
      if (!sboAuthor && !sboCommitter && !sboMe && !ctl.canForgeCommitter()) {
        reject(cmd, "not Signed-off-by author/committer/uploader");
        return false;
      }
    }

    final List<String> idList = c.getFooterLines(CHANGE_ID);
    if (idList.isEmpty()) {
      if (project.isRequireChangeID() && (cmd.getRefName().startsWith(NEW_CHANGE)
  || NEW_PATCHSET.matcher(cmd.getRefName()).matches())) {
        String errMsg = "missing Change-Id in commit message";
        reject(cmd, errMsg);
        rp.sendMessage(getFixedCommitMsgWithChangeId(errMsg, c));
        return false;
      }
    } else if (idList.size() > 1) {
      reject(cmd, "multiple Change-Id lines in commit message");
      return false;
    } else {
      final String v = idList.get(idList.size() - 1).trim();
      if (!v.matches("^I[0-9a-f]{8,}.*$")) {
        final String errMsg = "missing or invalid Change-Id line format in commit message";
        reject(cmd, errMsg);
        rp.sendMessage(getFixedCommitMsgWithChangeId(errMsg, c));
        return false;
      }
    }

    // Check for banned commits to prevent them from entering the tree again.
    if (rejectCommits.contains(c)) {
      reject(newChange, "contains banned commit " + c.getName());
      return false;
    }

    return true;
  }

  private String getFixedCommitMsgWithChangeId(String errMsg, RevCommit c) {
    // We handle 3 cases:
    // 1. No change id in the commit message at all.
    // 2. change id last in the commit message but missing empty line to create the footer.
    // 3. there is a change-id somewhere in the commit message, but we ignore it.
    final String changeId = "Change-Id:";
    StringBuilder sb = new StringBuilder();
    sb.append("ERROR: ").append(errMsg);
    sb.append("\n");
    sb.append("Suggestion for commit message:\n");

    if (c.getFullMessage().indexOf(changeId)==-1) {
      sb.append(c.getFullMessage());
      sb.append("\n");
      sb.append(changeId).append(" I").append(c.name());
    } else {
      String lines[] = c.getFullMessage().trim().split("\n");
      String lastLine = lines.length > 0 ? lines[lines.length - 1] : "";

      if (lastLine.indexOf(changeId)==0) {
        for (int i = 0; i < lines.length - 1; i++) {
          sb.append(lines[i]);
          sb.append("\n");
        }

        sb.append("\n");
        sb.append(lastLine);
      } else {
        sb.append(c.getFullMessage());
        sb.append("\n");
        sb.append(changeId).append(" I").append(c.name());
        sb.append("\nHint: A potential Change-Id was found, but it was not in the footer of the commit message.");
      }
    }

    return sb.toString();
  }

  private void sendInvalidEmailError(RevCommit c, String type, PersonIdent who) {
    StringBuilder sb = new StringBuilder();
    sb.append("\n");
    sb.append("ERROR:  In commit " + c.name() + "\n");
    sb.append("ERROR:  " + type + " email address " + who.getEmailAddress() + "\n");
    sb.append("ERROR:  does not match your user account.\n");
    sb.append("ERROR:\n");
    if (currentUser.getEmailAddresses().isEmpty()) {
      sb.append("ERROR:  You have not registered any email addresses.\n");
    } else {
      sb.append("ERROR:  The following addresses are currently registered:\n");
      for (String address : currentUser.getEmailAddresses()) {
        sb.append("ERROR:    " + address + "\n");
      }
    }
    sb.append("ERROR:\n");
    if (canonicalWebUrl != null) {
      sb.append("ERROR:  To register an email address, please visit:\n");
      sb.append("ERROR:  " + canonicalWebUrl + "#" + PageLinks.SETTINGS_CONTACT + "\n");
    }
    sb.append("\n");
    getReceivePack().sendMessage(sb.toString());
  }

  private void warnMalformedMessage(RevCommit c) {
    ObjectReader reader = rp.getRevWalk().getObjectReader();
    if (65 < c.getShortMessage().length()) {
      AbbreviatedObjectId id;
      try {
        id = reader.abbreviate(c);
      } catch (IOException err) {
        id = c.abbreviate(6);
      }
      rp.sendMessage("(W) " + id.name() //
          + ": commit subject >65 characters; use shorter first paragraph");
    }

    int longLineCnt = 0, nonEmptyCnt = 0;
    for (String line : c.getFullMessage().split("\n")) {
      if (!line.trim().isEmpty()) {
        nonEmptyCnt++;
      }
      if (70 < line.length()) {
        longLineCnt++;
      }
    }

    if (0 < longLineCnt && 33 < longLineCnt * 100 / nonEmptyCnt) {
      AbbreviatedObjectId id;
      try {
        id = reader.abbreviate(c);
      } catch (IOException err) {
        id = c.abbreviate(6);
      }
      rp.sendMessage("(W) " + id.name() //
          + ": commit message lines >70 characters; manually wrap lines");
    }
  }

  private void autoCloseChanges(final ReceiveCommand cmd) {
    final RevWalk rw = rp.getRevWalk();
    try {
      rw.reset();
      rw.markStart(rw.parseCommit(cmd.getNewId()));
      if (!ObjectId.zeroId().equals(cmd.getOldId())) {
        rw.markUninteresting(rw.parseCommit(cmd.getOldId()));
      }

      final Map<ObjectId, Ref> byCommit = changeRefsById();
      final Map<Change.Key, Change.Id> byKey = openChangesByKey(
          new Branch.NameKey(project.getNameKey(), cmd.getRefName()));
      final List<ReplaceRequest> toClose = new ArrayList<ReplaceRequest>();
      RevCommit c;
      while ((c = rw.next()) != null) {
        final Ref ref = byCommit.get(c.copy());
        if (ref != null) {
          rw.parseBody(c);
          closeChange(cmd, PatchSet.Id.fromRef(ref.getName()), c);
          continue;
        }

        rw.parseBody(c);
        for (final String changeId : c.getFooterLines(CHANGE_ID)) {
          final Change.Id onto = byKey.get(new Change.Key(changeId.trim()));
          if (onto != null) {
            toClose.add(new ReplaceRequest(onto, c, cmd, false));
            break;
          }
        }
      }

      for (final ReplaceRequest req : toClose) {
        final PatchSet.Id psi = doReplace(req);
        if (psi != null) {
          closeChange(req.cmd, psi, req.newCommit);
        }
      }
    } catch (IOException e) {
      log.error("Can't scan for changes to close", e);
    } catch (OrmException e) {
      log.error("Can't scan for changes to close", e);
    }
  }

  private void closeChange(final ReceiveCommand cmd, final PatchSet.Id psi,
      final RevCommit commit) throws OrmException {
    final String refName = cmd.getRefName();
    final Change.Id cid = psi.getParentKey();

    final Change change = db.changes().get(cid);
    final PatchSet ps = db.patchSets().get(psi);
    if (change == null || ps == null) {
      log.warn(project.getName() + " " + psi + " is missing");
      return;
    }

    if (change.getStatus() == Change.Status.MERGED) {
      // If its already merged, don't make further updates, it
      // might just be moving from an experimental branch into
      // a more stable branch.
      //
      return;
    }

    final ReplaceResult result = new ReplaceResult();
    result.change = change;
    result.patchSet = ps;
    result.info = patchSetInfoFactory.get(commit, psi);
    result.mergedIntoRef = refName;

    markChangeMergedByPush(db, result);
    sendMergedEmail(result);
  }

  private Map<ObjectId, Ref> changeRefsById() throws IOException {
    if (refsById == null) {
      refsById = new HashMap<ObjectId, Ref>();
      for (Ref r : repo.getRefDatabase().getRefs("refs/changes/").values()) {
        if (PatchSet.isRef(r.getName())) {
          refsById.put(r.getObjectId(), r);
        }
      }
    }
    return refsById;
  }

  private Map<Change.Key, Change.Id> openChangesByKey(Branch.NameKey branch)
      throws OrmException {
    final Map<Change.Key, Change.Id> r = new HashMap<Change.Key, Change.Id>();
    for (Change c : db.changes().byBranchOpenAll(branch)) {
      r.put(c.getKey(), c.getId());
    }
    return r;
  }

  private void markChangeMergedByPush(final ReviewDb db,
      final ReplaceResult result) throws OrmException {
    final Change change = result.change;
    final String mergedIntoRef = result.mergedIntoRef;

    change.setCurrentPatchSet(result.info);
    change.setStatus(Change.Status.MERGED);
    ChangeUtil.updated(change);

    final List<PatchSetApproval> approvals =
        db.patchSetApprovals().byChange(change.getId()).toList();
    for (PatchSetApproval a : approvals) {
      a.cache(change);
    }
    db.patchSetApprovals().update(approvals);

    final StringBuilder msgBuf = new StringBuilder();
    msgBuf.append("Change has been successfully pushed");
    if (!mergedIntoRef.equals(change.getDest().get())) {
      msgBuf.append(" into ");
      if (mergedIntoRef.startsWith(Constants.R_HEADS)) {
        msgBuf.append("branch ");
        msgBuf.append(Repository.shortenRefName(mergedIntoRef));
      } else {
        msgBuf.append(mergedIntoRef);
      }
    }
    msgBuf.append(".");
    final ChangeMessage msg =
        new ChangeMessage(new ChangeMessage.Key(change.getId(), ChangeUtil
            .messageUUID(db)), currentUser.getAccountId());
    msg.setMessage(msgBuf.toString());

    db.changeMessages().insert(Collections.singleton(msg));

    db.changes().atomicUpdate(change.getId(), new AtomicUpdate<Change>() {
      @Override
      public Change update(Change change) {
        if (change.getStatus().isOpen()) {
          change.setCurrentPatchSet(result.info);
          change.setStatus(Change.Status.MERGED);
          ChangeUtil.updated(change);
        }
        return change;
      }
    });
  }

  private void sendMergedEmail(final ReplaceResult result) {
    if (result != null && result.mergedIntoRef != null) {
      try {
        final MergedSender cm = mergedSenderFactory.create(result.change);
        cm.setFrom(currentUser.getAccountId());
        cm.setPatchSet(result.patchSet, result.info);
        cm.send();
      } catch (EmailException e) {
        final PatchSet.Id psi = result.patchSet.getId();
        log.error("Cannot send email for submitted patch set " + psi, e);
      }

      hooks.doChangeMergedHook(result.change, currentUser.getAccount(),
          result.patchSet);
    }
  }

  private void insertAncestors(PatchSet.Id id, RevCommit src)
      throws OrmException {
    final int cnt = src.getParentCount();
    List<PatchSetAncestor> toInsert = new ArrayList<PatchSetAncestor>(cnt);
    for (int p = 0; p < cnt; p++) {
      PatchSetAncestor a;

      a = new PatchSetAncestor(new PatchSetAncestor.Id(id, p + 1));
      a.setAncestorRevision(toRevId(src.getParent(p)));
      toInsert.add(a);
    }
    db.patchSetAncestors().insert(toInsert);
  }

  private static RevId toRevId(final RevCommit src) {
    return new RevId(src.getId().name());
  }

  private static void reject(final ReceiveCommand cmd) {
    reject(cmd, "prohibited by Gerrit");
  }

  private static void reject(final ReceiveCommand cmd, final String why) {
    cmd.setResult(ReceiveCommand.Result.REJECTED_OTHER_REASON, why);
  }

  private static boolean isHead(final Ref ref) {
    return ref.getName().startsWith(Constants.R_HEADS);
  }

  private static boolean isHead(final ReceiveCommand cmd) {
    return cmd.getRefName().startsWith(Constants.R_HEADS);
  }
}