// Copyright (C) 2011 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.account;

import static com.google.common.collect.ImmutableSet.toImmutableSet;
import static com.google.gerrit.server.project.ProjectCache.noSuchProject;

import com.google.common.collect.Sets;
import com.google.common.collect.Streams;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.AccountGroup;
import com.google.gerrit.entities.Project;
import com.google.gerrit.server.group.InternalGroup;
import com.google.gerrit.server.group.InternalGroupDescription;
import com.google.gerrit.server.group.SystemGroupBackend;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.project.ProjectCache;
import com.google.gerrit.server.project.ProjectState;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Optional;
import java.util.Set;

@Singleton
public class GroupMembers {

  private final GroupCache groupCache;
  private final GroupControl.Factory groupControlFactory;
  private final AccountCache accountCache;
  private final ProjectCache projectCache;

  @Inject
  GroupMembers(
      GroupCache groupCache,
      GroupControl.Factory groupControlFactory,
      AccountCache accountCache,
      ProjectCache projectCache) {
    this.groupCache = groupCache;
    this.groupControlFactory = groupControlFactory;
    this.accountCache = accountCache;
    this.projectCache = projectCache;
  }

  /**
   * Recursively enumerate the members of the given group. Should not be used with the
   * PROJECT_OWNERS magical group.
   *
   * <p>Group members for which an account doesn't exist are filtered out.
   */
  public Set<Account> listAccounts(AccountGroup.UUID groupUUID) throws IOException {
    if (SystemGroupBackend.PROJECT_OWNERS.equals(groupUUID)) {
      throw new IllegalStateException("listAccounts called with PROJECT_OWNERS argument");
    }
    try {
      return listAccounts(groupUUID, null, new HashSet<>());
    } catch (NoSuchProjectException e) {
      throw new IllegalStateException(e);
    }
  }

  /**
   * Recursively enumerate the members of the given group. The project should be specified so the
   * PROJECT_OWNERS magical group can be expanded.
   *
   * <p>Group members for which an account doesn't exist are filtered out.
   */
  public Set<Account> listAccounts(AccountGroup.UUID groupUUID, Project.NameKey project)
      throws NoSuchProjectException, IOException {
    return listAccounts(groupUUID, project, new HashSet<>());
  }

  private Set<Account> listAccounts(
      final AccountGroup.UUID groupUUID,
      @Nullable final Project.NameKey project,
      final Set<AccountGroup.UUID> seen)
      throws NoSuchProjectException, IOException {
    if (SystemGroupBackend.PROJECT_OWNERS.equals(groupUUID)) {
      return getProjectOwners(project, seen);
    }
    Optional<InternalGroup> group = groupCache.get(groupUUID);
    if (group.isPresent()) {
      return getGroupMembers(group.get(), project, seen);
    }
    return Collections.emptySet();
  }

  private Set<Account> getProjectOwners(final Project.NameKey project, Set<AccountGroup.UUID> seen)
      throws NoSuchProjectException, IOException {
    seen.add(SystemGroupBackend.PROJECT_OWNERS);
    if (project == null) {
      return Collections.emptySet();
    }

    ProjectState projectState = projectCache.get(project).orElseThrow(noSuchProject(project));
    final HashSet<Account> projectOwners = new HashSet<>();
    for (AccountGroup.UUID ownerGroup : projectState.getAllOwners()) {
      if (!seen.contains(ownerGroup)) {
        projectOwners.addAll(listAccounts(ownerGroup, project, seen));
      }
    }
    return projectOwners;
  }

  private Set<Account> getGroupMembers(
      InternalGroup group, @Nullable Project.NameKey project, Set<AccountGroup.UUID> seen)
      throws NoSuchProjectException, IOException {
    seen.add(group.getGroupUUID());
    GroupControl groupControl = groupControlFactory.controlFor(new InternalGroupDescription(group));

    Set<Account> directMembers =
        group.getMembers().stream()
            .filter(groupControl::canSeeMember)
            .map(accountCache::get)
            .flatMap(Streams::stream)
            .map(AccountState::account)
            .collect(toImmutableSet());

    Set<Account> indirectMembers = new HashSet<>();
    if (groupControl.canSeeGroup()) {
      for (AccountGroup.UUID subgroupUuid : group.getSubgroups()) {
        if (!seen.contains(subgroupUuid)) {
          indirectMembers.addAll(listAccounts(subgroupUuid, project, seen));
        }
      }
    }

    return Sets.union(directMembers, indirectMembers);
  }
}