// Copyright (C) 2015 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 java.nio.charset.StandardCharsets.UTF_8;

import com.google.auto.value.AutoValue;
import com.google.common.base.CharMatcher;
import com.google.common.base.Function;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.base.Splitter;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.Iterables;
import com.google.common.primitives.Ints;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Change;
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.config.AllUsersName;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.index.change.ChangeField;
import com.google.gerrit.server.index.change.ChangeIndexer;
import com.google.gerrit.server.project.NoSuchChangeException;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.query.change.InternalChangeQuery;
import com.google.gwtorm.server.OrmException;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;

import org.eclipse.jgit.lib.BatchRefUpdate;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectLoader;
import org.eclipse.jgit.lib.ObjectReader;
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.RevWalk;
import org.eclipse.jgit.transport.ReceiveCommand;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

@Singleton
public class StarredChangesUtil {
  @AutoValue
  public abstract static class StarField {
    private static final String SEPARATOR = ":";

    public static StarField parse(String s) {
      int p = s.indexOf(SEPARATOR);
      if (p >= 0) {
        Integer id = Ints.tryParse(s.substring(0, p));
        if (id == null) {
          return null;
        }
        Account.Id accountId = new Account.Id(id);
        String label = s.substring(p + 1);
        return create(accountId, label);
      }
      return null;
    }

    public static StarField create(Account.Id accountId, String label) {
      return new AutoValue_StarredChangesUtil_StarField(accountId, label);
    }

    public abstract Account.Id accountId();
    public abstract String label();

    @Override
    public String toString() {
      return accountId() + SEPARATOR + label();
    }
  }

  public static class IllegalLabelException extends IllegalArgumentException {
    private static final long serialVersionUID = 1L;

    static IllegalLabelException invalidLabels(Set<String> invalidLabels) {
      return new IllegalLabelException(
          String.format("invalid labels: %s",
              Joiner.on(", ").join(invalidLabels)));
    }

    static IllegalLabelException mutuallyExclusiveLabels(String label1,
        String label2) {
      return new IllegalLabelException(
          String.format("The labels %s and %s are mutually exclusive."
              + " Only one of them can be set.", label1, label2));
    }

    IllegalLabelException(String message) {
      super(message);
    }
  }

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

  public static final String DEFAULT_LABEL = "star";
  public static final String IGNORE_LABEL = "ignore";
  public static final ImmutableSortedSet<String> DEFAULT_LABELS =
      ImmutableSortedSet.of(DEFAULT_LABEL);

  private final GitRepositoryManager repoManager;
  private final AllUsersName allUsers;
  private final Provider<ReviewDb> dbProvider;
  private final PersonIdent serverIdent;
  private final ChangeIndexer indexer;
  private final Provider<InternalChangeQuery> queryProvider;

  @Inject
  StarredChangesUtil(GitRepositoryManager repoManager,
      AllUsersName allUsers,
      Provider<ReviewDb> dbProvider,
      @GerritPersonIdent PersonIdent serverIdent,
      ChangeIndexer indexer,
      Provider<InternalChangeQuery> queryProvider) {
    this.repoManager = repoManager;
    this.allUsers = allUsers;
    this.dbProvider = dbProvider;
    this.serverIdent = serverIdent;
    this.indexer = indexer;
    this.queryProvider = queryProvider;
  }

  public ImmutableSortedSet<String> getLabels(Account.Id accountId,
      Change.Id changeId) throws OrmException {
    try (Repository repo = repoManager.openRepository(allUsers)) {
      return ImmutableSortedSet.copyOf(
          readLabels(repo, RefNames.refsStarredChanges(changeId, accountId)));
    } catch (IOException e) {
      throw new OrmException(
          String.format("Reading stars from change %d for account %d failed",
              changeId.get(), accountId.get()), e);
    }
  }

  public ImmutableSortedSet<String> star(Account.Id accountId,
      Project.NameKey project, Change.Id changeId, Set<String> labelsToAdd,
      Set<String> labelsToRemove) throws OrmException {
    try (Repository repo = repoManager.openRepository(allUsers)) {
      String refName = RefNames.refsStarredChanges(changeId, accountId);
      ObjectId oldObjectId = getObjectId(repo, refName);

      SortedSet<String> labels = readLabels(repo, oldObjectId);
      if (labelsToAdd != null) {
        labels.addAll(labelsToAdd);
      }
      if (labelsToRemove != null) {
        labels.removeAll(labelsToRemove);
      }

      if (labels.isEmpty()) {
        deleteRef(repo, refName, oldObjectId);
      } else {
        checkMutuallyExclusiveLabels(labels);
        updateLabels(repo, refName, oldObjectId, labels);
      }

      indexer.index(dbProvider.get(), project, changeId);
      return ImmutableSortedSet.copyOf(labels);
    } catch (IOException e) {
      throw new OrmException(
          String.format("Star change %d for account %d failed",
              changeId.get(), accountId.get()), e);
    }
  }

  public void unstarAll(Project.NameKey project, Change.Id changeId)
      throws OrmException, NoSuchChangeException {
    try (Repository repo = repoManager.openRepository(allUsers);
        RevWalk rw = new RevWalk(repo)) {
      BatchRefUpdate batchUpdate = repo.getRefDatabase().newBatchUpdate();
      batchUpdate.setAllowNonFastForwards(true);
      batchUpdate.setRefLogIdent(serverIdent);
      batchUpdate.setRefLogMessage("Unstar change " + changeId.get(), true);
      for (Account.Id accountId : byChangeFromIndex(changeId).keySet()) {
        String refName = RefNames.refsStarredChanges(changeId, accountId);
        Ref ref = repo.getRefDatabase().getRef(refName);
        batchUpdate.addCommand(new ReceiveCommand(ref.getObjectId(),
            ObjectId.zeroId(), refName));
      }
      batchUpdate.execute(rw, NullProgressMonitor.INSTANCE);
      for (ReceiveCommand command : batchUpdate.getCommands()) {
        if (command.getResult() != ReceiveCommand.Result.OK) {
          throw new IOException(String.format(
              "Unstar change %d failed, ref %s could not be deleted: %s",
              changeId.get(), command.getRefName(), command.getResult()));
        }
      }
      indexer.index(dbProvider.get(), project, changeId);
    } catch (IOException e) {
      throw new OrmException(
          String.format("Unstar change %d failed", changeId.get()), e);
    }
  }

  public ImmutableMultimap<Account.Id, String> byChange(Change.Id changeId)
      throws OrmException {
    try (Repository repo = repoManager.openRepository(allUsers)) {
      ImmutableMultimap.Builder<Account.Id, String> builder =
          new ImmutableMultimap.Builder<>();
      for (String refPart : getRefNames(repo,
          RefNames.refsStarredChangesPrefix(changeId))) {
        Integer id = Ints.tryParse(refPart);
        if (id == null) {
          continue;
        }
        Account.Id accountId = new Account.Id(id);
        builder.putAll(accountId,
            readLabels(repo, RefNames.refsStarredChanges(changeId, accountId)));
      }
      return builder.build();
    } catch (IOException e) {
      throw new OrmException(String.format(
          "Get accounts that starred change %d failed", changeId.get()), e);
    }
  }

  public Set<Account.Id> byChange(final Change.Id changeId,
      final String label) throws OrmException {
    try (final Repository repo = repoManager.openRepository(allUsers)) {
      return FluentIterable
          .from(getRefNames(repo, RefNames.refsStarredChangesPrefix(changeId)))
          .transform(new Function<String, Account.Id>() {
            @Override
            public Account.Id apply(String refPart) {
              return Account.Id.parse(refPart);
            }
          })
          .filter(new Predicate<Account.Id>() {
            @Override
            public boolean apply(Account.Id accountId) {
              try {
                return readLabels(repo,
                    RefNames.refsStarredChanges(changeId, accountId))
                        .contains(label);
              } catch (IOException e) {
                log.error(String.format(
                    "Cannot query stars by account %d on change %d",
                    accountId.get(), changeId.get()), e);
                return false;
              }
            }
          }).toSet();
    } catch (IOException e) {
      throw new OrmException(
          String.format("Get accounts that starred change %d failed",
              changeId.get()), e);
    }
  }

  @Deprecated
  // To be used only for IsStarredByLegacyPredicate.
  public Set<Change.Id> byAccount(final Account.Id accountId,
      final String label) throws OrmException {
    try (final Repository repo = repoManager.openRepository(allUsers)) {
      return FluentIterable
          .from(getRefNames(repo, RefNames.REFS_STARRED_CHANGES))
          .filter(new Predicate<String>() {
            @Override
            public boolean apply(String refPart) {
              return refPart.endsWith("/" + accountId.get());
            }
          })
          .transform(new Function<String, Change.Id>() {
            @Override
            public Change.Id apply(String refPart) {
              return Change.Id.fromRefPart(refPart);
            }
          })
          .filter(new Predicate<Change.Id>() {
            @Override
            public boolean apply(Change.Id changeId) {
              try {
                return readLabels(repo,
                    RefNames.refsStarredChanges(changeId, accountId))
                        .contains(label);
              } catch (IOException e) {
                log.error(String.format(
                    "Cannot query stars by account %d on change %d",
                    accountId.get(), changeId.get()), e);
                return false;
              }
            }
          }).toSet();
    } catch (IOException e) {
      throw new OrmException(
          String.format("Get changes that were starred by %d failed",
              accountId.get()), e);
    }
  }

  public ImmutableMultimap<Account.Id, String> byChangeFromIndex(
      Change.Id changeId) throws OrmException, NoSuchChangeException {
    Set<String> fields = ImmutableSet.of(
        ChangeField.ID.getName(),
        ChangeField.STAR.getName());
    List<ChangeData> changeData = queryProvider.get().setRequestedFields(fields)
        .byLegacyChangeId(changeId);
    if (changeData.size() != 1) {
      throw new NoSuchChangeException(changeId);
    }
    return changeData.get(0).stars();
  }

  private static Set<String> getRefNames(Repository repo, String prefix)
      throws IOException {
    RefDatabase refDb = repo.getRefDatabase();
    return refDb.getRefs(prefix).keySet();
  }

  public ObjectId getObjectId(Account.Id accountId, Change.Id changeId) {
    try (Repository repo = repoManager.openRepository(allUsers)) {
      return getObjectId(repo,
          RefNames.refsStarredChanges(changeId, accountId));
    } catch (IOException e) {
      log.error(String.format(
          "Getting star object ID for account %d on change %d failed",
          accountId.get(), changeId.get()), e);
      return ObjectId.zeroId();
    }
  }

  private static ObjectId getObjectId(Repository repo, String refName)
      throws IOException {
    Ref ref = repo.exactRef(refName);
    return ref != null ? ref.getObjectId() : ObjectId.zeroId();
  }

  private static SortedSet<String> readLabels(Repository repo, String refName)
      throws IOException {
    return readLabels(repo, getObjectId(repo, refName));
  }

  private static TreeSet<String> readLabels(Repository repo, ObjectId id)
      throws IOException {
    if (ObjectId.zeroId().equals(id)) {
      return new TreeSet<>();
    }

    try (ObjectReader reader = repo.newObjectReader()) {
      ObjectLoader obj = reader.open(id, Constants.OBJ_BLOB);
      TreeSet<String> labels = new TreeSet<>();
      Iterables.addAll(labels,
          Splitter.on(CharMatcher.whitespace()).omitEmptyStrings()
              .split(new String(obj.getCachedBytes(Integer.MAX_VALUE), UTF_8)));
      return labels;
    }
  }

  public static ObjectId writeLabels(Repository repo, SortedSet<String> labels)
      throws IOException {
    validateLabels(labels);
    try (ObjectInserter oi = repo.newObjectInserter()) {
      ObjectId id = oi.insert(Constants.OBJ_BLOB,
          Joiner.on("\n").join(labels).getBytes(UTF_8));
      oi.flush();
      return id;
    }
  }

  private static void checkMutuallyExclusiveLabels(Set<String> labels) {
    if (labels.containsAll(ImmutableSet.of(DEFAULT_LABEL, IGNORE_LABEL))) {
      throw IllegalLabelException.mutuallyExclusiveLabels(DEFAULT_LABEL,
          IGNORE_LABEL);
    }
  }

  private static void validateLabels(Set<String> labels) {
    if (labels == null) {
      return;
    }

    SortedSet<String> invalidLabels = new TreeSet<>();
    for (String label : labels) {
      if (CharMatcher.whitespace().matchesAnyOf(label)) {
        invalidLabels.add(label);
      }
    }
    if (!invalidLabels.isEmpty()) {
      throw IllegalLabelException.invalidLabels(invalidLabels);
    }
  }

  private void updateLabels(Repository repo, String refName,
      ObjectId oldObjectId, SortedSet<String> labels)
          throws IOException, OrmException {
    try (RevWalk rw = new RevWalk(repo)) {
      RefUpdate u = repo.updateRef(refName);
      u.setExpectedOldObjectId(oldObjectId);
      u.setForceUpdate(true);
      u.setNewObjectId(writeLabels(repo, labels));
      u.setRefLogIdent(serverIdent);
      u.setRefLogMessage("Update star labels", true);
      RefUpdate.Result result = u.update(rw);
      switch (result) {
        case NEW:
        case FORCED:
        case NO_CHANGE:
        case FAST_FORWARD:
          return;
        case IO_FAILURE:
        case LOCK_FAILURE:
        case NOT_ATTEMPTED:
        case REJECTED:
        case REJECTED_CURRENT_BRANCH:
        case RENAMED:
          throw new OrmException(
              String.format("Update star labels on ref %s failed: %s", refName,
                  result.name()));
      }
    }
  }

  private void deleteRef(Repository repo, String refName, ObjectId oldObjectId)
      throws IOException, OrmException {
    RefUpdate u = repo.updateRef(refName);
    u.setForceUpdate(true);
    u.setExpectedOldObjectId(oldObjectId);
    u.setRefLogIdent(serverIdent);
    u.setRefLogMessage("Unstar change", true);
    RefUpdate.Result result = u.delete();
    switch (result) {
      case FORCED:
        return;
      case NEW:
      case NO_CHANGE:
      case FAST_FORWARD:
      case IO_FAILURE:
      case LOCK_FAILURE:
      case NOT_ATTEMPTED:
      case REJECTED:
      case REJECTED_CURRENT_BRANCH:
      case RENAMED:
        throw new OrmException(String.format("Delete star ref %s failed: %s",
            refName, result.name()));
    }
  }
}