// 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.googlesource.gerrit.owners.common;

import static com.google.gerrit.server.account.externalids.ExternalId.SCHEME_GERRIT;
import static com.google.gerrit.server.account.externalids.ExternalId.SCHEME_MAILTO;
import static com.google.gerrit.server.account.externalids.ExternalId.SCHEME_USERNAME;

import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.Account.Id;
import com.google.gerrit.entities.AccountGroup;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.account.AccountCache;
import com.google.gerrit.server.account.AccountResolver;
import com.google.gerrit.server.account.AccountState;
import com.google.gerrit.server.account.GroupCache;
import com.google.gerrit.server.account.GroupMembers;
import com.google.gerrit.server.account.externalids.ExternalId;
import com.google.gerrit.server.group.InternalGroup;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.util.ManualRequestContext;
import com.google.gerrit.server.util.OneOffRequestContext;
import com.google.inject.Inject;
import java.io.IOException;
import java.util.Collections;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class AccountsImpl implements Accounts {
  private static final Logger log = LoggerFactory.getLogger(AccountsImpl.class);

  private final AccountResolver resolver;
  private final AccountCache byId;
  private final GroupCache groupCache;
  private final GroupMembers groupMembers;
  private final IdentifiedUser adminUser;
  private final OneOffRequestContext oneOffRequestContext;

  @Inject
  public AccountsImpl(
      AccountResolver resolver,
      AccountCache byId,
      GroupCache groupCache,
      GroupMembers groupMembers,
      OneOffRequestContext oneOffRequestContext,
      IdentifiedUser.GenericFactory userFactory) {
    this.resolver = resolver;
    this.byId = byId;
    this.groupCache = groupCache;
    this.groupMembers = groupMembers;
    this.adminUser = userFactory.create(Account.id(1000000));
    this.oneOffRequestContext = oneOffRequestContext;
  }

  @Override
  public Set<Account.Id> find(String nameOrEmailOrGroup) {
    if (nameOrEmailOrGroup.startsWith(GROUP_PREFIX)) {
      return findAccountsInGroup(nameOrEmailOrGroup.substring(GROUP_PREFIX.length()));
    }
    return findUserOrEmail(nameOrEmailOrGroup);
  }

  private Set<Id> findAccountsInGroup(String groupNameOrUUID) {
    Optional<InternalGroup> group =
        groupCache
            .get(AccountGroup.nameKey(groupNameOrUUID))
            .map(Optional::of)
            .orElse(groupCache.get(AccountGroup.uuid(groupNameOrUUID)));

    if (!group.isPresent()) {
      log.warn("Group {} was not found", groupNameOrUUID);
      return Collections.emptySet();
    }

    try (ManualRequestContext ctx = oneOffRequestContext.openAs(adminUser.getAccountId())) {

      return groupMembers.listAccounts(group.get().getGroupUUID(), null).stream()
          .map(Account::id)
          .collect(Collectors.toSet());
    } catch (NoSuchProjectException | IOException e) {
      log.error("Unable to list accounts in group " + group, e);
      return Collections.emptySet();
    }
  }

  private Set<Account.Id> findUserOrEmail(String nameOrEmail) {
    try (ManualRequestContext ctx = oneOffRequestContext.open()) {
      Set<Id> accountIds = resolver.resolve(nameOrEmail).asIdSet();
      if (accountIds.isEmpty()) {
        log.warn("User '{}' does not resolve to any account.", nameOrEmail);
        return accountIds;
      }

      Set<Id> activeAccountIds =
          accountIds.stream().filter(this::isActive).collect(Collectors.toSet());
      if (activeAccountIds.isEmpty()) {
        log.warn(
            "User '{}' resolves to {} accounts {}, but none of them are active",
            nameOrEmail,
            accountIds.size(),
            accountIds);
        return activeAccountIds;
      }

      Set<Id> fulllyMatchedAccountIds =
          activeAccountIds.stream()
              .filter(id -> isFullMatch(id, nameOrEmail))
              .collect(Collectors.toSet());
      if (fulllyMatchedAccountIds.isEmpty()) {
        log.warn(
            "User '{}' resolves to {} accounts {}, but does not correspond to any them",
            nameOrEmail,
            accountIds.size(),
            accountIds);
        return fulllyMatchedAccountIds;
      }

      return accountIds;
    } catch (IOException | ConfigInvalidException e) {
      log.error("Error trying to resolve user " + nameOrEmail, e);
      return Collections.emptySet();
    }
  }

  private boolean isFullMatch(Account.Id id, String nameOrEmail) {
    Optional<AccountState> accountState = byId.get(id);
    if (!accountState.isPresent()) {
      return false;
    }

    Account account = accountState.get().account();
    return isFullNameMatch(account, nameOrEmail)
        || nameOrEmail.equalsIgnoreCase(account.preferredEmail())
        || accountState.get().externalIds().stream()
            .anyMatch(eid -> isEMailMatch(eid, nameOrEmail) || isUsernameMatch(eid, nameOrEmail));
  }

  private boolean isFullNameMatch(Account account, String fullName) {
    return Optional.ofNullable(account.fullName())
        .filter(n -> n.trim().equalsIgnoreCase(fullName))
        .isPresent();
  }

  private boolean isUsernameMatch(ExternalId externalId, String username) {
    return OptionalUtils.combine(
            keySchemeRest(SCHEME_GERRIT, externalId.key()),
            keySchemeRest(SCHEME_USERNAME, externalId.key()))
        .filter(name -> name.equals(username))
        .isPresent();
  }

  private boolean isEMailMatch(ExternalId externalId, String email) {
    ExternalId.Key externalKey = externalId.key();
    return OptionalUtils.combine(
            Optional.ofNullable(externalId.email()).filter(mail -> mail.equalsIgnoreCase(email)),
            keySchemeRest(SCHEME_MAILTO, externalKey).filter(mail -> mail.equalsIgnoreCase(email)))
        .isPresent();
  }

  private boolean isActive(Account.Id accountId) {
    return byId.get(accountId).map(AccountState::account).map(Account::isActive).orElse(false);
  }

  private Optional<String> keySchemeRest(String scheme, ExternalId.Key key) {
    if (scheme != null && key.isScheme(scheme)) {
      return Optional.of(key.get().substring(scheme.length() + 1));
    }
    return Optional.empty();
  }
}