// Copyright (C) 2017 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.group.db;

import static com.google.common.collect.ImmutableSet.toImmutableSet;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Streams;
import com.google.gerrit.common.data.GroupReference;
import com.google.gerrit.common.errors.NoSuchGroupException;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.AccountGroup;
import com.google.gerrit.reviewdb.client.AccountGroupById;
import com.google.gerrit.reviewdb.client.AccountGroupByIdAud;
import com.google.gerrit.reviewdb.client.AccountGroupMember;
import com.google.gerrit.reviewdb.client.AccountGroupMemberAudit;
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.group.InternalGroup;
import com.google.gerrit.server.notedb.GroupsMigration;
import com.google.gwtorm.server.OrmDuplicateKeyException;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.ResultSet;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.lib.Repository;

/**
 * A database accessor for read calls related to groups.
 *
 * <p>All calls which read group related details from the database (either ReviewDb or NoteDb) are
 * gathered here. Other classes should always use this class instead of accessing the database
 * directly. There are a few exceptions though: schema classes, wrapper classes, and classes
 * executed during init. The latter ones should use {@code GroupsOnInit} instead.
 *
 * <p>Most callers should not need to read groups directly from the database; they should use the
 * {@link com.google.gerrit.server.account.GroupCache GroupCache} instead.
 *
 * <p>If not explicitly stated, all methods of this class refer to <em>internal</em> groups.
 */
@Singleton
public class Groups {
  private final GroupsMigration groupsMigration;
  private final GitRepositoryManager repoManager;
  private final AllUsersName allUsersName;
  private final AuditLogReader auditLogReader;

  @Inject
  public Groups(
      GroupsMigration groupsMigration,
      GitRepositoryManager repoManager,
      AllUsersName allUsersName,
      AuditLogReader auditLogReader) {
    this.groupsMigration = groupsMigration;
    this.repoManager = repoManager;
    this.allUsersName = allUsersName;
    this.auditLogReader = auditLogReader;
  }

  /**
   * Returns the {@code InternalGroup} for the specified UUID if it exists.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param groupUuid the UUID of the group
   * @return the found {@code InternalGroup} if it exists, or else an empty {@code Optional}
   * @throws OrmDuplicateKeyException if multiple groups are found for the specified UUID
   * @throws OrmException if the group couldn't be retrieved from ReviewDb
   * @throws IOException if the group couldn't be retrieved from NoteDb
   * @throws ConfigInvalidException if the group couldn't be retrieved from NoteDb
   */
  public Optional<InternalGroup> getGroup(ReviewDb db, AccountGroup.UUID groupUuid)
      throws OrmException, IOException, ConfigInvalidException {
    if (groupsMigration.readFromNoteDb()) {
      try (Repository allUsersRepo = repoManager.openRepository(allUsersName)) {
        return getGroupFromNoteDb(allUsersRepo, groupUuid);
      }
    }

    Optional<AccountGroup> accountGroup = getGroupFromReviewDb(db, groupUuid);
    if (!accountGroup.isPresent()) {
      return Optional.empty();
    }
    return Optional.of(asInternalGroup(db, accountGroup.get()));
  }

  private static Optional<InternalGroup> getGroupFromNoteDb(
      Repository allUsersRepository, AccountGroup.UUID groupUuid)
      throws IOException, ConfigInvalidException {
    GroupConfig groupConfig = GroupConfig.loadForGroup(allUsersRepository, groupUuid);
    Optional<InternalGroup> loadedGroup = groupConfig.getLoadedGroup();
    if (loadedGroup.isPresent()) {
      // Check consistency with group name notes.
      GroupsNoteDbConsistencyChecker.ensureConsistentWithGroupNameNotes(
          allUsersRepository, loadedGroup.get());
    }
    return loadedGroup;
  }

  public static InternalGroup asInternalGroup(ReviewDb db, AccountGroup accountGroup)
      throws OrmException {
    ImmutableSet<Account.Id> members =
        getMembersFromReviewDb(db, accountGroup.getId()).collect(toImmutableSet());
    ImmutableSet<AccountGroup.UUID> subgroups =
        getSubgroupsFromReviewDb(db, accountGroup.getId()).collect(toImmutableSet());
    return InternalGroup.create(accountGroup, members, subgroups);
  }

  /**
   * Returns the {@code AccountGroup} for the specified UUID.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param groupUuid the UUID of the group
   * @return the {@code AccountGroup} which has the specified UUID
   * @throws OrmDuplicateKeyException if multiple groups are found for the specified UUID
   * @throws OrmException if the group couldn't be retrieved from ReviewDb
   * @throws NoSuchGroupException if a group with such a UUID doesn't exist
   */
  static AccountGroup getExistingGroupFromReviewDb(ReviewDb db, AccountGroup.UUID groupUuid)
      throws OrmException, NoSuchGroupException {
    Optional<AccountGroup> group = getGroupFromReviewDb(db, groupUuid);
    return group.orElseThrow(() -> new NoSuchGroupException(groupUuid));
  }

  /**
   * Returns the {@code AccountGroup} for the specified UUID if it exists.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param groupUuid the UUID of the group
   * @return the found {@code AccountGroup} if it exists, or else an empty {@code Optional}
   * @throws OrmDuplicateKeyException if multiple groups are found for the specified UUID
   * @throws OrmException if the group couldn't be retrieved from ReviewDb
   */
  private static Optional<AccountGroup> getGroupFromReviewDb(
      ReviewDb db, AccountGroup.UUID groupUuid) throws OrmException {
    List<AccountGroup> accountGroups = db.accountGroups().byUUID(groupUuid).toList();
    if (accountGroups.size() == 1) {
      return Optional.of(Iterables.getOnlyElement(accountGroups));
    } else if (accountGroups.isEmpty()) {
      return Optional.empty();
    } else {
      throw new OrmDuplicateKeyException("Duplicate group UUID " + groupUuid);
    }
  }

  /**
   * Returns {@code GroupReference}s for all internal groups.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @return a stream of the {@code GroupReference}s of all internal groups
   * @throws OrmException if an error occurs while reading from ReviewDb
   * @throws IOException if an error occurs while reading from NoteDb
   * @throws ConfigInvalidException if the data in NoteDb is in an incorrect format
   */
  public Stream<GroupReference> getAllGroupReferences(ReviewDb db)
      throws OrmException, IOException, ConfigInvalidException {
    if (groupsMigration.readFromNoteDb()) {
      try (Repository allUsersRepo = repoManager.openRepository(allUsersName)) {
        return GroupNameNotes.loadAllGroups(allUsersRepo).stream();
      }
    }

    return Streams.stream(db.accountGroups().all())
        .map(group -> new GroupReference(group.getGroupUUID(), group.getName()));
  }

  /**
   * Returns the members (accounts) of a group.
   *
   * <p><strong>Note</strong>: This method doesn't check whether the accounts exist!
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param groupId the ID of the group
   * @return a stream of the IDs of the members
   * @throws OrmException if an error occurs while reading from ReviewDb
   */
  static Stream<Account.Id> getMembersFromReviewDb(ReviewDb db, AccountGroup.Id groupId)
      throws OrmException {
    ResultSet<AccountGroupMember> accountGroupMembers = db.accountGroupMembers().byGroup(groupId);
    return Streams.stream(accountGroupMembers).map(AccountGroupMember::getAccountId);
  }

  /**
   * Returns the subgroups of a group.
   *
   * <p>This parent group must be an internal group whereas the subgroups can either be internal or
   * external groups.
   *
   * <p><strong>Note</strong>: This method doesn't check whether the subgroups exist!
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param groupId the ID of the group
   * @return a stream of the UUIDs of the subgroups
   * @throws OrmException if an error occurs while reading from ReviewDb
   */
  static Stream<AccountGroup.UUID> getSubgroupsFromReviewDb(ReviewDb db, AccountGroup.Id groupId)
      throws OrmException {
    ResultSet<AccountGroupById> accountGroupByIds = db.accountGroupById().byGroup(groupId);
    return Streams.stream(accountGroupByIds).map(AccountGroupById::getIncludeUUID).distinct();
  }

  /**
   * Returns all known external groups. External groups are 'known' when they are specified as a
   * subgroup of an internal group.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @return a stream of the UUIDs of the known external groups
   * @throws OrmException if an error occurs while reading from ReviewDb
   * @throws IOException if an error occurs while reading from NoteDb
   * @throws ConfigInvalidException if the data in NoteDb is in an incorrect format
   */
  public Stream<AccountGroup.UUID> getExternalGroups(ReviewDb db)
      throws OrmException, IOException, ConfigInvalidException {
    if (groupsMigration.readFromNoteDb()) {
      try (Repository allUsersRepo = repoManager.openRepository(allUsersName)) {
        return getExternalGroupsFromNoteDb(allUsersRepo);
      }
    }

    return Streams.stream(db.accountGroupById().all())
        .map(AccountGroupById::getIncludeUUID)
        .distinct()
        .filter(groupUuid -> !AccountGroup.isInternalGroup(groupUuid));
  }

  private static Stream<AccountGroup.UUID> getExternalGroupsFromNoteDb(Repository allUsersRepo)
      throws IOException, ConfigInvalidException {
    ImmutableList<GroupReference> allInternalGroups = GroupNameNotes.loadAllGroups(allUsersRepo);
    ImmutableSet.Builder<AccountGroup.UUID> allSubgroups = ImmutableSet.builder();
    for (GroupReference internalGroup : allInternalGroups) {
      Optional<InternalGroup> group = getGroupFromNoteDb(allUsersRepo, internalGroup.getUUID());
      group.map(InternalGroup::getSubgroups).ifPresent(allSubgroups::addAll);
    }
    return allSubgroups
        .build()
        .stream()
        .filter(groupUuid -> !AccountGroup.isInternalGroup(groupUuid));
  }

  /**
   * Returns the membership audit records for a given group.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param repo All-Users repository.
   * @param groupUuid the UUID of the group
   * @return the audit records, in arbitrary order; empty if the group does not exist
   * @throws OrmException if an error occurs while reading from ReviewDb
   * @throws IOException if an error occurs while reading from NoteDb
   * @throws ConfigInvalidException if the group couldn't be retrieved from NoteDb
   */
  public List<AccountGroupMemberAudit> getMembersAudit(
      ReviewDb db, Repository repo, AccountGroup.UUID groupUuid)
      throws OrmException, IOException, ConfigInvalidException {
    if (groupsMigration.readFromNoteDb()) {
      return auditLogReader.getMembersAudit(repo, groupUuid);
    }
    Optional<AccountGroup> group = getGroupFromReviewDb(db, groupUuid);
    if (!group.isPresent()) {
      return ImmutableList.of();
    }

    return db.accountGroupMembersAudit().byGroup(group.get().getId()).toList();
  }

  /**
   * Returns the subgroup audit records for a given group.
   *
   * @param db the {@code ReviewDb} instance to use for lookups
   * @param repo All-Users repository.
   * @param groupUuid the UUID of the group
   * @return the audit records, in arbitrary order; empty if the group does not exist
   * @throws OrmException if an error occurs while reading from ReviewDb
   * @throws IOException if an error occurs while reading from NoteDb
   * @throws ConfigInvalidException if the group couldn't be retrieved from NoteDb
   */
  public List<AccountGroupByIdAud> getSubgroupsAudit(
      ReviewDb db, Repository repo, AccountGroup.UUID groupUuid)
      throws OrmException, IOException, ConfigInvalidException {
    if (groupsMigration.readFromNoteDb()) {
      return auditLogReader.getSubgroupsAudit(repo, groupUuid);
    }
    Optional<AccountGroup> group = getGroupFromReviewDb(db, groupUuid);
    if (!group.isPresent()) {
      return ImmutableList.of();
    }

    return db.accountGroupByIdAud().byGroup(group.get().getId()).toList();
  }
}