// 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.ImmutableList.toImmutableList;

import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.MultimapBuilder;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.AccountGroup;
import com.google.gerrit.entities.AccountGroupByIdAudit;
import com.google.gerrit.entities.AccountGroupMemberAudit;
import com.google.gerrit.entities.RefNames;
import com.google.gerrit.server.config.AllUsersName;
import com.google.gerrit.server.notedb.NoteDbUtil;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.FooterLine;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevSort;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.util.RawParseUtils;

/** NoteDb reader for group audit log. */
@Singleton
public class AuditLogReader {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();

  private final AllUsersName allUsersName;

  @Inject
  public AuditLogReader(AllUsersName allUsersName) {
    this.allUsersName = allUsersName;
  }

  // Having separate methods for reading the two types of audit records mirrors the split in
  // ReviewDb. Now that ReviewDb is gone, the audit record interface is more flexible and this may
  // be changed, e.g. to do only a single walk, or even change the record types.

  public ImmutableList<AccountGroupMemberAudit> getMembersAudit(
      Repository allUsersRepo, AccountGroup.UUID uuid) throws IOException, ConfigInvalidException {
    return getMembersAudit(getGroupId(allUsersRepo, uuid), parseCommits(allUsersRepo, uuid));
  }

  private ImmutableList<AccountGroupMemberAudit> getMembersAudit(
      AccountGroup.Id groupId, List<ParsedCommit> commits) {
    ListMultimap<MemberKey, AccountGroupMemberAudit.Builder> audits =
        MultimapBuilder.hashKeys().linkedListValues().build();
    List<AccountGroupMemberAudit.Builder> result = new ArrayList<>();
    for (ParsedCommit pc : commits) {
      for (Account.Id id : pc.addedMembers()) {
        MemberKey key = MemberKey.create(groupId, id);
        AccountGroupMemberAudit.Builder audit =
            AccountGroupMemberAudit.builder()
                .memberId(id)
                .groupId(groupId)
                .addedOn(pc.when())
                .addedBy(pc.authorId());
        audits.put(key, audit);
        result.add(audit);
      }
      for (Account.Id id : pc.removedMembers()) {
        List<AccountGroupMemberAudit.Builder> adds = audits.get(MemberKey.create(groupId, id));
        if (!adds.isEmpty()) {
          AccountGroupMemberAudit.Builder audit = adds.remove(0);
          audit.removed(pc.authorId(), pc.when());
        } else {
          // Match old behavior of DbGroupAuditListener and add a "legacy" add/remove pair.
          AccountGroupMemberAudit.Builder audit =
              AccountGroupMemberAudit.builder()
                  .groupId(groupId)
                  .memberId(id)
                  .addedOn(pc.when())
                  .addedBy(pc.authorId())
                  .removedLegacy();
          result.add(audit);
        }
      }
    }
    return result.stream().map(AccountGroupMemberAudit.Builder::build).collect(toImmutableList());
  }

  public ImmutableList<AccountGroupByIdAudit> getSubgroupsAudit(
      Repository repo, AccountGroup.UUID uuid) throws IOException, ConfigInvalidException {
    return getSubgroupsAudit(getGroupId(repo, uuid), parseCommits(repo, uuid));
  }

  private ImmutableList<AccountGroupByIdAudit> getSubgroupsAudit(
      AccountGroup.Id groupId, List<ParsedCommit> commits) {
    ListMultimap<SubgroupKey, AccountGroupByIdAudit.Builder> audits =
        MultimapBuilder.hashKeys().linkedListValues().build();
    List<AccountGroupByIdAudit.Builder> result = new ArrayList<>();
    for (ParsedCommit pc : commits) {
      for (AccountGroup.UUID uuid : pc.addedSubgroups()) {
        SubgroupKey key = SubgroupKey.create(groupId, uuid);
        AccountGroupByIdAudit.Builder audit =
            AccountGroupByIdAudit.builder()
                .groupId(groupId)
                .includeUuid(uuid)
                .addedOn(pc.when())
                .addedBy(pc.authorId());
        audits.put(key, audit);
        result.add(audit);
      }
      for (AccountGroup.UUID uuid : pc.removedSubgroups()) {
        List<AccountGroupByIdAudit.Builder> adds = audits.get(SubgroupKey.create(groupId, uuid));
        if (!adds.isEmpty()) {
          AccountGroupByIdAudit.Builder audit = adds.remove(0);
          audit.removed(pc.authorId(), pc.when());
        } else {
          // Unlike members, DbGroupAuditListener didn't insert an add/remove pair here.
        }
      }
    }
    return result.stream().map(AccountGroupByIdAudit.Builder::build).collect(toImmutableList());
  }

  private Optional<ParsedCommit> parse(AccountGroup.UUID uuid, RevCommit c) {
    Optional<Account.Id> authorId = NoteDbUtil.parseIdent(c.getAuthorIdent());
    if (!authorId.isPresent()) {
      // Only report audit events from identified users, since this was a non-nullable field in
      // ReviewDb. May be revisited.
      return Optional.empty();
    }

    List<Account.Id> addedMembers = new ArrayList<>();
    List<AccountGroup.UUID> addedSubgroups = new ArrayList<>();
    List<Account.Id> removedMembers = new ArrayList<>();
    List<AccountGroup.UUID> removedSubgroups = new ArrayList<>();

    for (FooterLine line : c.getFooterLines()) {
      if (line.matches(GroupConfigCommitMessage.FOOTER_ADD_MEMBER)) {
        parseAccount(uuid, c, line).ifPresent(addedMembers::add);
      } else if (line.matches(GroupConfigCommitMessage.FOOTER_REMOVE_MEMBER)) {
        parseAccount(uuid, c, line).ifPresent(removedMembers::add);
      } else if (line.matches(GroupConfigCommitMessage.FOOTER_ADD_GROUP)) {
        parseGroup(uuid, c, line).ifPresent(addedSubgroups::add);
      } else if (line.matches(GroupConfigCommitMessage.FOOTER_REMOVE_GROUP)) {
        parseGroup(uuid, c, line).ifPresent(removedSubgroups::add);
      }
    }
    return Optional.of(
        new AutoValue_AuditLogReader_ParsedCommit(
            authorId.get(),
            c.getAuthorIdent().getWhenAsInstant(),
            ImmutableList.copyOf(addedMembers),
            ImmutableList.copyOf(removedMembers),
            ImmutableList.copyOf(addedSubgroups),
            ImmutableList.copyOf(removedSubgroups)));
  }

  private Optional<Account.Id> parseAccount(AccountGroup.UUID uuid, RevCommit c, FooterLine line) {
    Optional<Account.Id> result =
        Optional.ofNullable(RawParseUtils.parsePersonIdent(line.getValue()))
            .flatMap(ident -> NoteDbUtil.parseIdent(ident));
    if (!result.isPresent()) {
      logInvalid(uuid, c, line);
    }
    return result;
  }

  private static Optional<AccountGroup.UUID> parseGroup(
      AccountGroup.UUID uuid, RevCommit c, FooterLine line) {
    PersonIdent ident = RawParseUtils.parsePersonIdent(line.getValue());
    if (ident == null) {
      logInvalid(uuid, c, line);
      return Optional.empty();
    }
    return Optional.of(AccountGroup.uuid(ident.getEmailAddress()));
  }

  private static void logInvalid(AccountGroup.UUID uuid, RevCommit c, FooterLine line) {
    logger.atFine().log(
        "Invalid footer line in commit %s while parsing audit log for group %s: %s",
        c.name(), uuid, line);
  }

  private ImmutableList<ParsedCommit> parseCommits(Repository repo, AccountGroup.UUID uuid)
      throws IOException {
    try (RevWalk rw = new RevWalk(repo)) {
      Ref ref = repo.exactRef(RefNames.refsGroups(uuid));
      if (ref == null) {
        return ImmutableList.of();
      }

      rw.reset();
      rw.markStart(rw.parseCommit(ref.getObjectId()));
      rw.setRetainBody(true);
      rw.sort(RevSort.COMMIT_TIME_DESC, true);
      rw.sort(RevSort.REVERSE, true);

      ImmutableList.Builder<ParsedCommit> result = ImmutableList.builder();
      RevCommit c;
      while ((c = rw.next()) != null) {
        parse(uuid, c).ifPresent(result::add);
      }
      return result.build();
    }
  }

  private AccountGroup.Id getGroupId(Repository allUsersRepo, AccountGroup.UUID uuid)
      throws ConfigInvalidException, IOException {
    // TODO(dborowitz): This re-walks all commits just to find createdOn, which we don't need.
    return GroupConfig.loadForGroup(allUsersName, allUsersRepo, uuid)
        .getLoadedGroup()
        .get()
        .getId();
  }

  @AutoValue
  abstract static class MemberKey {
    static MemberKey create(AccountGroup.Id groupId, Account.Id memberId) {
      return new AutoValue_AuditLogReader_MemberKey(groupId, memberId);
    }

    abstract AccountGroup.Id groupId();

    abstract Account.Id memberId();
  }

  @AutoValue
  abstract static class SubgroupKey {
    static SubgroupKey create(AccountGroup.Id groupId, AccountGroup.UUID subgroupUuid) {
      return new AutoValue_AuditLogReader_SubgroupKey(groupId, subgroupUuid);
    }

    abstract AccountGroup.Id groupId();

    abstract AccountGroup.UUID subgroupUuid();
  }

  @AutoValue
  abstract static class ParsedCommit {
    abstract Account.Id authorId();

    abstract Instant when();

    abstract ImmutableList<Account.Id> addedMembers();

    abstract ImmutableList<Account.Id> removedMembers();

    abstract ImmutableList<AccountGroup.UUID> addedSubgroups();

    abstract ImmutableList<AccountGroup.UUID> removedSubgroups();
  }
}