// 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.google.gerrit.server;

import static com.google.gerrit.server.change.PatchSetInserter.ValidatePolicy.RECEIVE_COMMITS;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.MINUTES;
import static java.util.concurrent.TimeUnit.SECONDS;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.primitives.Ints;
import com.google.gerrit.common.ChangeHooks;
import com.google.gerrit.common.errors.EmailException;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.ChangeMessage;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetAncestor;
import com.google.gerrit.reviewdb.client.RevId;
import com.google.gerrit.reviewdb.client.TrackingId;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.change.ChangeInserter;
import com.google.gerrit.server.change.ChangeMessages;
import com.google.gerrit.server.change.PatchSetInserter;
import com.google.gerrit.server.config.TrackingFooter;
import com.google.gerrit.server.config.TrackingFooters;
import com.google.gerrit.server.events.CommitReceivedEvent;
import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.validators.CommitValidationException;
import com.google.gerrit.server.git.validators.CommitValidators;
import com.google.gerrit.server.index.ChangeIndexer;
import com.google.gerrit.server.mail.CommitMessageEditedSender;
import com.google.gerrit.server.mail.RevertedSender;
import com.google.gerrit.server.patch.PatchSetInfoFactory;
import com.google.gerrit.server.patch.PatchSetInfoNotAvailableException;
import com.google.gerrit.server.project.InvalidChangeOperationException;
import com.google.gerrit.server.project.NoSuchChangeException;
import com.google.gerrit.server.project.RefControl;
import com.google.gerrit.server.util.IdGenerator;
import com.google.gerrit.server.util.MagicBranch;
import com.google.gerrit.server.util.TimeUtil;
import com.google.gwtorm.server.OrmConcurrencyException;
import com.google.gwtorm.server.OrmException;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.CommitBuilder;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.FooterLine;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.transport.ReceiveCommand;
import org.eclipse.jgit.util.ChangeIdUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.sql.Timestamp;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Matcher;

public class ChangeUtil {
  /**
   * Epoch for sort key calculations, Tue Sep 30 2008 17:00:00.
   * <p>
   * We overrun approximately 4,083 years later, so ~6092.
   */
  @VisibleForTesting
  public static final long SORT_KEY_EPOCH_MINS =
      MINUTES.convert(1222819200L, SECONDS);

  private static final Object uuidLock = new Object();
  private static final int SEED = 0x2418e6f9;
  private static int uuidPrefix;
  private static int uuidSeq;

  private static final Logger log =
      LoggerFactory.getLogger(ChangeUtil.class);

  /**
   * Generate a new unique identifier for change message entities.
   *
   * @param db the database connection, used to increment the change message
   *        allocation sequence.
   * @return the new unique identifier.
   * @throws OrmException the database couldn't be incremented.
   */
  public static String messageUUID(ReviewDb db) throws OrmException {
    int p, s;
    synchronized (uuidLock) {
      if (uuidSeq == 0) {
        uuidPrefix = db.nextChangeMessageId();
        uuidSeq = Integer.MAX_VALUE;
      }
      p = uuidPrefix;
      s = uuidSeq--;
    }
    String u = IdGenerator.format(IdGenerator.mix(SEED, p));
    String l = IdGenerator.format(IdGenerator.mix(p, s));
    return u + '_' + l;
  }

  public static void touch(final Change change, ReviewDb db)
      throws OrmException {
    try {
      updated(change);
      db.changes().update(Collections.singleton(change));
    } catch (OrmConcurrencyException e) {
      // Ignore a concurrent update, we just wanted to tag it as newer.
    }
  }

  public static void bumpRowVersionNotLastUpdatedOn(Change.Id id, ReviewDb db)
      throws OrmException {
    // Empty update of Change to bump rowVersion, changing its ETag.
    Change c = db.changes().get(id);
    if (c != null) {
      db.changes().update(Collections.singleton(c));
    }
  }

  public static void updated(final Change c) {
    c.setLastUpdatedOn(TimeUtil.nowTs());
    computeSortKey(c);
  }

  public static void updateTrackingIds(ReviewDb db, Change change,
      TrackingFooters trackingFooters, List<FooterLine> footerLines)
      throws OrmException {
    if (trackingFooters.getTrackingFooters().isEmpty() || footerLines.isEmpty()) {
      return;
    }

    final Set<TrackingId> want = new HashSet<TrackingId>();
    final Set<TrackingId> have = new HashSet<TrackingId>( //
        db.trackingIds().byChange(change.getId()).toList());

    for (final TrackingFooter footer : trackingFooters.getTrackingFooters()) {
      for (final FooterLine footerLine : footerLines) {
        if (footerLine.matches(footer.footerKey())) {
          // supporting multiple tracking-ids on a single line
          final Matcher m = footer.match().matcher(footerLine.getValue());
          while (m.find()) {
            if (m.group().isEmpty()) {
              continue;
            }

            String idstr;
            if (m.groupCount() > 0) {
              idstr = m.group(1);
            } else {
              idstr = m.group();
            }

            if (idstr.isEmpty()) {
              continue;
            }
            if (idstr.length() > TrackingId.TRACKING_ID_MAX_CHAR) {
              continue;
            }

            want.add(new TrackingId(change.getId(), idstr, footer.system()));
          }
        }
      }
    }

    // Only insert the rows we don't have, and delete rows we don't match.
    //
    final Set<TrackingId> toInsert = new HashSet<TrackingId>(want);
    final Set<TrackingId> toDelete = new HashSet<TrackingId>(have);

    toInsert.removeAll(have);
    toDelete.removeAll(want);

    db.trackingIds().insert(toInsert);
    db.trackingIds().delete(toDelete);
  }

  public static void insertAncestors(ReviewDb db, 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 =
          new PatchSetAncestor(new PatchSetAncestor.Id(id, p + 1));
      a.setAncestorRevision(new RevId(src.getParent(p).getId().getName()));
      toInsert.add(a);
    }
    db.patchSetAncestors().insert(toInsert);
  }

  public static Change.Id revert(RefControl refControl, PatchSet.Id patchSetId,
      IdentifiedUser user, CommitValidators commitValidators, String message,
      ReviewDb db, RevertedSender.Factory revertedSenderFactory,
      ChangeHooks hooks, Repository git,
      PatchSetInfoFactory patchSetInfoFactory, PersonIdent myIdent,
      ChangeInserter.Factory changeInserterFactory)
          throws NoSuchChangeException, EmailException,
      OrmException, MissingObjectException, IncorrectObjectTypeException,
      IOException, InvalidChangeOperationException {
    final Change.Id changeId = patchSetId.getParentKey();
    final PatchSet patch = db.patchSets().get(patchSetId);
    if (patch == null) {
      throw new NoSuchChangeException(changeId);
    }
    final Change changeToRevert = db.changes().get(changeId);

    final RevWalk revWalk = new RevWalk(git);
    try {
      RevCommit commitToRevert =
          revWalk.parseCommit(ObjectId.fromString(patch.getRevision().get()));

      PersonIdent authorIdent =
          user.newCommitterIdent(myIdent.getWhen(), myIdent.getTimeZone());

      RevCommit parentToCommitToRevert = commitToRevert.getParent(0);
      revWalk.parseHeaders(parentToCommitToRevert);

      CommitBuilder revertCommitBuilder = new CommitBuilder();
      revertCommitBuilder.addParentId(commitToRevert);
      revertCommitBuilder.setTreeId(parentToCommitToRevert.getTree());
      revertCommitBuilder.setAuthor(authorIdent);
      revertCommitBuilder.setCommitter(authorIdent);

      if (message == null) {
        message = MessageFormat.format(
            ChangeMessages.get().revertChangeDefaultMessage,
            changeToRevert.getSubject(), patch.getRevision().get());
      }

      final ObjectId computedChangeId =
          ChangeIdUtil.computeChangeId(parentToCommitToRevert.getTree(),
              commitToRevert, authorIdent, myIdent, message);
      revertCommitBuilder.setMessage(ChangeIdUtil.insertId(message, computedChangeId, true));

      RevCommit revertCommit;
      final ObjectInserter oi = git.newObjectInserter();
      try {
        ObjectId id = oi.insert(revertCommitBuilder);
        oi.flush();
        revertCommit = revWalk.parseCommit(id);
      } finally {
        oi.release();
      }

      final Change change = new Change(
          new Change.Key("I" + computedChangeId.name()),
          new Change.Id(db.nextChangeId()),
          user.getAccountId(),
          changeToRevert.getDest(),
          TimeUtil.nowTs());
      change.setTopic(changeToRevert.getTopic());
      ChangeInserter ins =
          changeInserterFactory.create(refControl, change, revertCommit);
      PatchSet ps = ins.getPatchSet();

      String ref = refControl.getRefName();
      final String cmdRef =
          MagicBranch.NEW_PUBLISH_CHANGE
              + ref.substring(ref.lastIndexOf('/') + 1);
      CommitReceivedEvent commitReceivedEvent =
          new CommitReceivedEvent(new ReceiveCommand(ObjectId.zeroId(),
              revertCommit.getId(), cmdRef), refControl.getProjectControl()
              .getProject(), refControl.getRefName(), revertCommit, user);

      try {
        commitValidators.validateForGerritCommits(commitReceivedEvent);
      } catch (CommitValidationException e) {
        throw new InvalidChangeOperationException(e.getMessage());
      }

      final RefUpdate ru = git.updateRef(ps.getRefName());
      ru.setExpectedOldObjectId(ObjectId.zeroId());
      ru.setNewObjectId(revertCommit);
      ru.disableRefLog();
      if (ru.update(revWalk) != RefUpdate.Result.NEW) {
        throw new IOException(String.format(
            "Failed to create ref %s in %s: %s", ps.getRefName(),
            change.getDest().getParentKey().get(), ru.getResult()));
      }

      final ChangeMessage cmsg = new ChangeMessage(
          new ChangeMessage.Key(changeId, ChangeUtil.messageUUID(db)),
          user.getAccountId(), TimeUtil.nowTs(), patchSetId);
      final StringBuilder msgBuf =
          new StringBuilder("Patch Set " + patchSetId.get() + ": Reverted");
      msgBuf.append("\n\n");
      msgBuf.append("This patchset was reverted in change: " + change.getKey().get());
      cmsg.setMessage(msgBuf.toString());

      ins.setMessage(cmsg).insert();

      try {
        final RevertedSender cm = revertedSenderFactory.create(change);
        cm.setFrom(user.getAccountId());
        cm.setChangeMessage(cmsg);
        cm.send();
      } catch (Exception err) {
        log.error("Cannot send email for revert change " + change.getId(),
            err);
      }

      return change.getId();
    } finally {
      revWalk.release();
    }
  }

  public static Change.Id editCommitMessage(final PatchSet.Id patchSetId,
      final RefControl refControl, final IdentifiedUser user,
      final String message, final ReviewDb db,
      final CommitMessageEditedSender.Factory commitMessageEditedSenderFactory,
      Repository git, PersonIdent myIdent,
      PatchSetInserter.Factory patchSetInserterFactory)
      throws NoSuchChangeException, EmailException, OrmException,
      MissingObjectException, IncorrectObjectTypeException, IOException,
      InvalidChangeOperationException, PatchSetInfoNotAvailableException {
    final Change.Id changeId = patchSetId.getParentKey();
    final PatchSet originalPS = db.patchSets().get(patchSetId);
    if (originalPS == null) {
      throw new NoSuchChangeException(changeId);
    }

    if (message == null || message.length() == 0) {
      throw new InvalidChangeOperationException(
          "The commit message cannot be empty");
    }

    final RevWalk revWalk = new RevWalk(git);
    try {
      RevCommit commit =
          revWalk.parseCommit(ObjectId.fromString(originalPS.getRevision()
              .get()));
      if (commit.getFullMessage().equals(message)) {
        throw new InvalidChangeOperationException(
            "New commit message cannot be same as existing commit message");
      }

      Date now = myIdent.getWhen();
      Change change = db.changes().get(changeId);
      PersonIdent authorIdent =
          user.newCommitterIdent(now, myIdent.getTimeZone());

      CommitBuilder commitBuilder = new CommitBuilder();
      commitBuilder.setTreeId(commit.getTree());
      commitBuilder.setParentIds(commit.getParents());
      commitBuilder.setAuthor(commit.getAuthorIdent());
      commitBuilder.setCommitter(authorIdent);
      commitBuilder.setMessage(message);

      RevCommit newCommit;
      final ObjectInserter oi = git.newObjectInserter();
      try {
        ObjectId id = oi.insert(commitBuilder);
        oi.flush();
        newCommit = revWalk.parseCommit(id);
      } finally {
        oi.release();
      }

      PatchSet.Id id = nextPatchSetId(git, change.currentPatchSetId());
      final PatchSet newPatchSet = new PatchSet(id);
      newPatchSet.setCreatedOn(new Timestamp(now.getTime()));
      newPatchSet.setUploader(user.getAccountId());
      newPatchSet.setRevision(new RevId(newCommit.name()));

      final String msg =
          "Patch Set " + newPatchSet.getPatchSetId()
              + ": Commit message was updated";

      change = patchSetInserterFactory
          .create(git, revWalk, refControl, user, change, newCommit)
          .setPatchSet(newPatchSet)
          .setMessage(msg)
          .setCopyLabels(true)
          .setValidatePolicy(RECEIVE_COMMITS)
          .setDraft(originalPS.isDraft())
          .insert();

      return change.getId();
    } finally {
      revWalk.release();
    }
  }

  public static void deleteDraftChange(PatchSet.Id patchSetId,
      GitRepositoryManager gitManager,
      GitReferenceUpdated gitRefUpdated, ReviewDb db, ChangeIndexer indexer)
      throws NoSuchChangeException, OrmException, IOException {
    final Change.Id changeId = patchSetId.getParentKey();
    deleteDraftChange(changeId, gitManager, gitRefUpdated, db, indexer);
  }

  public static void deleteDraftChange(Change.Id changeId,
      GitRepositoryManager gitManager,
      GitReferenceUpdated gitRefUpdated, ReviewDb db, ChangeIndexer indexer)
      throws NoSuchChangeException, OrmException, IOException {
    Change change = db.changes().get(changeId);
    if (change == null || change.getStatus() != Change.Status.DRAFT) {
      throw new NoSuchChangeException(changeId);
    }

    for (PatchSet ps : db.patchSets().byChange(changeId)) {
      // These should all be draft patch sets.
      deleteOnlyDraftPatchSet(ps, change, gitManager, gitRefUpdated, db);
    }

    db.changeMessages().delete(db.changeMessages().byChange(changeId));
    db.starredChanges().delete(db.starredChanges().byChange(changeId));
    db.trackingIds().delete(db.trackingIds().byChange(changeId));
    db.changes().delete(Collections.singleton(change));
    indexer.delete(change);
  }

  public static void deleteOnlyDraftPatchSet(final PatchSet patch,
      final Change change, GitRepositoryManager gitManager,
      final GitReferenceUpdated gitRefUpdated, final ReviewDb db)
      throws NoSuchChangeException, OrmException, IOException {
    final PatchSet.Id patchSetId = patch.getId();
    if (!patch.isDraft()) {
      throw new NoSuchChangeException(patchSetId.getParentKey());
    }

    Repository repo = gitManager.openRepository(change.getProject());
    try {
      RefUpdate update = repo.updateRef(patch.getRefName());
      update.setForceUpdate(true);
      update.disableRefLog();
      switch (update.delete()) {
        case NEW:
        case FAST_FORWARD:
        case FORCED:
        case NO_CHANGE:
          // Successful deletion.
          break;
        default:
          throw new IOException("Failed to delete ref " + patch.getRefName() +
              " in " + repo.getDirectory() + ": " + update.getResult());
      }
      gitRefUpdated.fire(change.getProject(), update);
    } finally {
      repo.close();
    }

    db.accountPatchReviews().delete(db.accountPatchReviews().byPatchSet(patchSetId));
    db.changeMessages().delete(db.changeMessages().byPatchSet(patchSetId));
    db.patchComments().delete(db.patchComments().byPatchSet(patchSetId));
    db.patchSetApprovals().delete(db.patchSetApprovals().byPatchSet(patchSetId));
    db.patchSetAncestors().delete(db.patchSetAncestors().byPatchSet(patchSetId));

    db.patchSets().delete(Collections.singleton(patch));
  }

  public static String sortKey(long lastUpdatedMs, int id){
    long lastUpdatedMins = MINUTES.convert(lastUpdatedMs, MILLISECONDS);
    long minsSinceEpoch = lastUpdatedMins - SORT_KEY_EPOCH_MINS;
    StringBuilder r = new StringBuilder(16);
    r.setLength(16);
    formatHexInt(r, 0, Ints.checkedCast(minsSinceEpoch));
    formatHexInt(r, 8, id);
    return r.toString();
  }

  public static long parseSortKey(String sortKey) {
    if ("z".equals(sortKey)) {
      return Long.MAX_VALUE;
    }
    return Long.parseLong(sortKey, 16);
  }

  public static void computeSortKey(Change c) {
    long lastUpdatedMs = c.getLastUpdatedOn().getTime();
    int id = c.getId().get();
    c.setSortKey(sortKey(lastUpdatedMs, id));
  }

  public static PatchSet.Id nextPatchSetId(Map<String, Ref> allRefs,
      PatchSet.Id id) {
    PatchSet.Id next = nextPatchSetId(id);
    while (allRefs.containsKey(next.toRefName())) {
      next = nextPatchSetId(next);
    }
    return next;
  }

  public static PatchSet.Id nextPatchSetId(Repository git, PatchSet.Id id)
      throws IOException {
    return nextPatchSetId(git.getRefDatabase().getRefs(RefDatabase.ALL), id);
  }

  private static PatchSet.Id nextPatchSetId(PatchSet.Id id) {
    return new PatchSet.Id(id.getParentKey(), id.get() + 1);
  }

  private static final char[] hexchar =
      {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', //
          'a', 'b', 'c', 'd', 'e', 'f'};

  private static void formatHexInt(final StringBuilder dst, final int p, int w) {
    int o = p + 7;
    while (o >= p && w != 0) {
      dst.setCharAt(o--, hexchar[w & 0xf]);
      w >>>= 4;
    }
    while (o >= p) {
      dst.setCharAt(o--, '0');
    }
  }
}