components/sync/service/sync_service_impl.cc

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/sync/service/sync_service_impl.h"

#include <cstddef>
#include <utility>

#include "base/barrier_callback.h"
#include "base/check_is_test.h"
#include "base/command_line.h"
#include "base/containers/flat_set.h"
#include "base/containers/to_vector.h"
#include "base/feature_list.h"
#include "base/files/file_path.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/functional/callback_helpers.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/metrics/histogram_functions.h"
#include "base/observer_list.h"
#include "base/strings/string_number_conversions.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
#include "base/trace_event/trace_event.h"
#include "build/build_config.h"
#include "components/signin/public/base/gaia_id_hash.h"
#include "components/signin/public/base/signin_metrics.h"
#include "components/signin/public/identity_manager/account_info.h"
#include "components/signin/public/identity_manager/accounts_in_cookie_jar_info.h"
#include "components/signin/public/identity_manager/identity_manager.h"
#include "components/signin/public/identity_manager/identity_utils.h"
#include "components/signin/public/identity_manager/primary_account_mutator.h"
#include "components/sync/base/command_line_switches.h"
#include "components/sync/base/features.h"
#include "components/sync/base/model_type.h"
#include "components/sync/base/stop_source.h"
#include "components/sync/base/sync_util.h"
#include "components/sync/engine/configure_reason.h"
#include "components/sync/engine/engine_components_factory_impl.h"
#include "components/sync/engine/net/http_bridge.h"
#include "components/sync/engine/net/http_post_provider_factory.h"
#include "components/sync/engine/shutdown_reason.h"
#include "components/sync/engine/sync_encryption_handler.h"
#include "components/sync/invalidations/sync_invalidations_service.h"
#include "components/sync/model/sync_error.h"
#include "components/sync/model/type_entities_count.h"
#include "components/sync/service/backend_migrator.h"
#include "components/sync/service/configure_context.h"
#include "components/sync/service/data_type_manager_impl.h"
#include "components/sync/service/get_types_with_unsynced_data_request_barrier.h"
#include "components/sync/service/local_data_description.h"
#include "components/sync/service/sync_auth_manager.h"
#include "components/sync/service/sync_engine_factory.h"
#include "components/sync/service/sync_feature_status_for_migrations_recorder.h"
#include "components/sync/service/sync_prefs.h"
#include "components/sync/service/sync_prefs_policy_handler.h"
#include "components/sync/service/sync_service_utils.h"
#include "components/sync/service/trusted_vault_histograms.h"
#include "components/sync/service/trusted_vault_synthetic_field_trial.h"
#include "google_apis/gaia/google_service_auth_error.h"
#include "services/network/public/cpp/shared_url_loader_factory.h"

#if BUILDFLAG(IS_ANDROID)
#include "base/android/build_info.h"
#include "base/android/jni_android.h"
#include "base/android/jni_array.h"
#include "base/android/jni_string.h"
#include "components/sync/android/jni_headers/ExplicitPassphrasePlatformClient_jni.h"
#include "components/sync/android/sync_service_android_bridge.h"
#include "components/sync/engine/nigori/nigori.h"
#include "components/sync/protocol/nigori_specifics.pb.h"
#endif  // BUILDFLAG(IS_ANDROID)

namespace syncer {

namespace {

BASE_FEATURE(kSyncUnsubscribeFromTypesWithPermanentErrors,
             "SyncUnsubscribeFromTypesWithPermanentErrors",
             base::FEATURE_ENABLED_BY_DEFAULT);

BASE_FEATURE(kGetTypesWithUnsyncedDataViaController,
             "GetTypesWithUnsyncedDataViaController",
             base::FEATURE_ENABLED_BY_DEFAULT);

#if BUILDFLAG(IS_ANDROID)
constexpr int kMinGmsVersionCodeWithCustomPassphraseApi = 235204000;

// Keep in sync with the corresponding string in
// ExplicitPassphrasePlatformClientTest.java
constexpr char kIgnoreMinGmsVersionWithPassphraseSupportForTest[] =
    "ignore-min-gms-version-with-passphrase-support-for-test";
#endif  // BUILDFLAG(IS_ANDROID)

// The initial state of sync, for the Sync.InitialState2 histogram. Even if
// this value indicates that sync (the feature or the transport) can start, the
// startup might fail for reasons such as network issues, or the version of
// Chrome being too old.
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
// LINT.IfChange(SyncInitialState)
enum SyncInitialState {
  // Sync-the-feature can attempt to start up.
  kFeatureCanStart = 0,
  // There is no signed in user, so neither feature nor transport can start.
  kNotSignedIn = 1,
  // The user has disabled Sync-the-feature, but the initial setup has been
  // completed. This should be very rare; it can happen after a
  // reset-via-dashboard on ChromeOS.
  kFeatureNotRequested = 2,
  // The user has not enabled Sync-the-feature. This is the expected state for
  // a Sync-the-transport (signed-in non-syncing) user.
  kFeatureNotRequestedNotSetup = 3,
  // The user has enabled Sync-the-feature, but has not completed the initial
  // setup. This should be rare; it can happen if the initial setup got
  // interrupted e.g. by a crash.
  kFeatureNotSetup = 4,
  // Sync (both feature and transport) is disallowed by enterprise policy.
  kNotAllowedByPolicy = 5,
  kObsoleteNotAllowedByPlatform = 6,
  kMaxValue = kObsoleteNotAllowedByPlatform
};
// LINT.ThenChange(/tools/metrics/histograms/metadata/sync/enums.xml:SyncInitialState)

// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
enum class DownloadStatusWaitingForUpdatesReason {
  kRefreshTokensNotLoaded = 0,
  kSyncEngineNotInitialized = 1,
  kDataTypeNotActive = 2,
  kInvalidationsNotInitialized = 3,
  kIncomingInvalidation = 4,
  kPollRequestScheduled = 5,

  kMaxValue = kPollRequestScheduled
};

void RecordSyncInitialState(SyncService::DisableReasonSet disable_reasons,
                            bool is_sync_feature_requested,
                            bool initial_sync_feature_setup_complete) {
  SyncInitialState sync_state = kFeatureCanStart;
  if (disable_reasons.Has(SyncService::DISABLE_REASON_NOT_SIGNED_IN)) {
    sync_state = kNotSignedIn;
  } else if (disable_reasons.Has(
                 SyncService::DISABLE_REASON_ENTERPRISE_POLICY)) {
    sync_state = kNotAllowedByPolicy;
  } else if (!is_sync_feature_requested) {
    if (initial_sync_feature_setup_complete) {
      sync_state = kFeatureNotRequested;
    } else {
      sync_state = kFeatureNotRequestedNotSetup;
    }
  } else if (!initial_sync_feature_setup_complete) {
    sync_state = kFeatureNotSetup;
  }
  base::UmaHistogramEnumeration("Sync.InitialState2", sync_state);
}

EngineComponentsFactory::Switches EngineSwitchesFromCommandLine() {
  EngineComponentsFactory::Switches factory_switches = {
      EngineComponentsFactory::BACKOFF_NORMAL,
      /*force_short_nudge_delay_for_test=*/false};

  base::CommandLine* cl = base::CommandLine::ForCurrentProcess();
  if (cl->HasSwitch(kSyncShortInitialRetryOverride)) {
    factory_switches.backoff_override =
        EngineComponentsFactory::BACKOFF_SHORT_INITIAL_RETRY_OVERRIDE;
  }
  if (cl->HasSwitch(kSyncShortNudgeDelayForTest)) {
    factory_switches.force_short_nudge_delay_for_test = true;
  }
  return factory_switches;
}

std::unique_ptr<HttpPostProviderFactory> CreateHttpBridgeFactory(
    const std::string& user_agent,
    std::unique_ptr<network::PendingSharedURLLoaderFactory>
        pending_url_loader_factory) {
  return std::make_unique<HttpBridgeFactory>(
      user_agent, std::move(pending_url_loader_factory));
}

base::TimeDelta GetDeferredInitDelay() {
  if (base::FeatureList::IsEnabled(kDeferredSyncStartupCustomDelay)) {
    return base::Seconds(kDeferredSyncStartupCustomDelayInSeconds.Get());
  }

  const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
  if (cmdline->HasSwitch(kSyncDeferredStartupTimeoutSeconds)) {
    int timeout = 0;
    if (base::StringToInt(
            cmdline->GetSwitchValueASCII(kSyncDeferredStartupTimeoutSeconds),
            &timeout)) {
      DCHECK_GE(timeout, 0);
      return base::Seconds(timeout);
    }
  }
  return base::Seconds(10);
}

void MaybeClearAccountKeyedPreferences(
    signin::IdentityManager* identity_manager,
    const signin::AccountsInCookieJarInfo& accounts_in_cookie_jar_info,
    SyncUserSettingsImpl& user_settings) {
#if !BUILDFLAG(IS_IOS) && !BUILDFLAG(IS_ANDROID)
  if (accounts_in_cookie_jar_info.accounts_are_fresh) {
    // Clear settings for accounts no longer in the cookie jar. On Android
    // and iOS this is done when the account is removed from the OS instead.
    std::vector<signin::GaiaIdHash> hashes =
        base::ToVector(signin::GetAllGaiaIdsForKeyedPreferences(
                           identity_manager, accounts_in_cookie_jar_info),
                       &signin::GaiaIdHash::FromGaiaId);
    user_settings.KeepAccountSettingsPrefsOnlyForUsers(hashes);
  }
#endif  // !BUILDFLAG(IS_IOS) && !BUILDFLAG(IS_ANDROID)
}

std::map<ModelType, LocalDataDescription> JoinAllTypesAndLocalDataDescriptions(
    const std::vector<std::pair<ModelType, LocalDataDescription>>& pairs) {
  std::map<ModelType, LocalDataDescription> map;
  for (const std::pair<ModelType, LocalDataDescription>& pair : pairs) {
    map.emplace(pair);
  }
  return map;
}

std::pair<ModelType, LocalDataDescription> JoinTypeAndLocalDataDescription(
    ModelType type,
    LocalDataDescription description) {
  return {type, description};
}

}  // namespace

SyncServiceImpl::InitParams::InitParams() = default;
SyncServiceImpl::InitParams::InitParams(InitParams&& other) = default;
SyncServiceImpl::InitParams::~InitParams() = default;

SyncServiceImpl::SyncServiceImpl(InitParams init_params)
    : sync_client_(std::move(init_params.sync_client)),
      sync_prefs_(sync_client_->GetPrefService()),
      identity_manager_(sync_prefs_.IsLocalSyncEnabled()
                            ? nullptr
                            : sync_client_->GetIdentityManager()),
      auth_manager_(std::make_unique<SyncAuthManager>(
          identity_manager_,
          base::BindRepeating(&SyncServiceImpl::AccountStateChanged,
                              base::Unretained(this)),
          base::BindRepeating(&SyncServiceImpl::CredentialsChanged,
                              base::Unretained(this)))),
      channel_(init_params.channel),
      debug_identifier_(std::move(init_params.debug_identifier)),
      sync_service_url_(
          GetSyncServiceURL(*base::CommandLine::ForCurrentProcess(), channel_)),
      crypto_(this, sync_client_->GetTrustedVaultClient()),
      url_loader_factory_(std::move(init_params.url_loader_factory)),
      network_connection_tracker_(
          std::move(init_params.network_connection_tracker)),
      create_http_post_provider_factory_cb_(
          base::BindRepeating(&CreateHttpBridgeFactory)) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  DCHECK(sync_client_);
  DCHECK(IsLocalSyncEnabled() || identity_manager_ != nullptr);

  // If Sync is disabled via command line flag, then SyncServiceImpl
  // shouldn't be instantiated.
  DCHECK(IsSyncAllowedByFlag());

  sync_prefs_.SetPasswordSyncAllowed(sync_client_->IsPasswordSyncAllowed());
  // base::Unretained() is safe, `this` outlives `sync_client_`.
  sync_client_->SetPasswordSyncAllowedChangeCb(base::BindRepeating(
      &SyncServiceImpl::OnPasswordSyncAllowedChanged, base::Unretained(this)));

  sync_stopped_reporter_ = std::make_unique<SyncStoppedReporter>(
      sync_service_url_, MakeUserAgentForSync(channel_), url_loader_factory_);

  if (identity_manager_) {
    identity_manager_->AddObserver(this);
  }

  observers_.emplace();

  // Based on the information cached in preferences, it might be required to
  // register a synthetic field trial group. This should be done as early as
  // possible to avoid untagged metrics if they get logged before other events
  // like sync engine initialization, which could take arbitrarily long (e.g.
  // persistent auth error). Task-posting is involved to avoid infinite
  // recursions if the implementation in SyncClient leads to
  // accessing/constructing SyncService.
  base::SequencedTaskRunner::GetCurrentDefault()->PostTask(
      FROM_HERE,
      base::BindOnce(
          &SyncServiceImpl::RegisterTrustedVaultSyntheticFieldTrialsIfNecessary,
          weak_factory_.GetWeakPtr()));
}

void SyncServiceImpl::RegisterTrustedVaultSyntheticFieldTrialsIfNecessary() {
  if (registered_trusted_vault_auto_upgrade_synthetic_field_trial_group_
          .has_value()) {
    // Registration function already invoked. It cannot be invoked twice, as
    // runtime changes to the group assignment is not supported (e.g. signout).
    return;
  }

  const sync_pb::TrustedVaultAutoUpgradeExperimentGroup proto =
      sync_prefs_.GetCachedTrustedVaultAutoUpgradeExperimentGroup().value_or(
          sync_pb::TrustedVaultAutoUpgradeExperimentGroup());

  const TrustedVaultAutoUpgradeSyntheticFieldTrialGroup group =
      TrustedVaultAutoUpgradeSyntheticFieldTrialGroup::FromProto(proto);

  if (!group.is_valid()) {
    // Broadcasting an invalid group isn't allowed, as it would otherwise use
    // the only chance to invoke the registration function below, which may only
    // be invoked once.
    return;
  }

  registered_trusted_vault_auto_upgrade_synthetic_field_trial_group_ = group;
  sync_client_->RegisterTrustedVaultAutoUpgradeSyntheticFieldTrial(group);
}

SyncServiceImpl::~SyncServiceImpl() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (identity_manager_) {
    identity_manager_->RemoveObserver(this);
  }
  // Shutdown() should have been called before destruction.
  DCHECK(!engine_);
}

void SyncServiceImpl::Initialize(DataTypeController::TypeVector controllers) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  data_type_manager_ = std::make_unique<DataTypeManagerImpl>(
      std::move(controllers), &crypto_, this);

  // It's safe to pass a raw ptr, since SyncServiceImpl outlives
  // SyncUserSettingsImpl.
  user_settings_ = std::make_unique<SyncUserSettingsImpl>(
      /*delegate=*/this, &crypto_, &sync_prefs_,
      data_type_manager_->GetRegisteredDataTypes());

  sync_prefs_observation_.Observe(&sync_prefs_);

  if (!IsLocalSyncEnabled()) {
    auth_manager_->RegisterForAuthNotifications();

    // Trigger a refresh when additional data types get enabled for
    // invalidations. This is needed to get the latest data after subscribing
    // for the updates.
    sync_client_->GetSyncInvalidationsService()
        ->SetCommittedAdditionalInterestedDataTypesCallback(base::BindRepeating(
            &SyncServiceImpl::TriggerRefresh, weak_factory_.GetWeakPtr()));

    // TODO(crbug.com/40257467): revisit this logic. IsSignedIn() doesn't feel
    // the right condition to check.
    if (IsSignedIn()) {
      // Start receiving invalidations as soon as possible since GCMDriver drops
      // incoming FCM messages otherwise. The messages will be collected by
      // SyncInvalidationsService until sync engine is initialized and ready to
      // handle invalidations.
      sync_client_->GetSyncInvalidationsService()->StartListening();
    }
  }

  // *After* setting up `auth_manager_`, run pref migrations that depend on
  // the account state.
  sync_prefs_.MaybeMigratePrefsForSyncToSigninPart1(
      GetSyncAccountStateForPrefs(),
      signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia));
  sync_prefs_.MaybeMigrateCustomPassphrasePref(
      signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia));

  if (!IsLocalSyncEnabled()) {
    const bool account_info_fully_loaded =
        auth_manager_->IsActiveAccountInfoFullyLoaded();
    base::UmaHistogramBoolean("Sync.Startup.AccountInfoFullyLoaded2",
                              account_info_fully_loaded);
    if (!account_info_fully_loaded) {
      base::UmaHistogramBoolean("Sync.Startup.SignedInWithoutAccountInfo2",
                                IsSignedIn());
    }
  }

  // Update selected types prefs if a policy is applied.
  sync_prefs_policy_handler_ = std::make_unique<SyncPrefsPolicyHandler>(this);

  // If sync is disabled permanently, clean up old data that may be around (e.g.
  // crash during signout).
  if (HasDisableReason(DISABLE_REASON_ENTERPRISE_POLICY)) {
    StopAndClear(ResetEngineReason::kEnterprisePolicy);
#if BUILDFLAG(IS_CHROMEOS_ASH)
    // On ChromeOS Ash, sync-the-feature stays disabled even after the policy is
    // removed, for historic reasons. It is unclear if this behavior is
    // optional, because it is indistinguishable from the
    // sync-reset-via-dashboard case. It can be resolved by invoking
    // SetSyncFeatureRequested().
    sync_prefs_.SetSyncFeatureDisabledViaDashboard();
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)
  } else if (HasDisableReason(DISABLE_REASON_NOT_SIGNED_IN)) {
    // On ChromeOS-Ash, signout is not possible, so it's not necessary to handle
    // this case.
    // TODO(crbug.com/40272157): It *should* be harmless to handle this case on
    // ChromeOS-Ash since it's supposedly unreachable, *but* during the very
    // first startup of a fresh profile, the signed-in account isn't known yet
    // at this point (see also https://crbug.com/1458701#c7).
#if !BUILDFLAG(IS_CHROMEOS_ASH)
    StopAndClear(ResetEngineReason::kNotSignedIn);
#endif
  }

  const bool is_sync_feature_requested_for_metrics =
      IsLocalSyncEnabled() ||
#if BUILDFLAG(IS_CHROMEOS_ASH)
      !user_settings_->IsSyncFeatureDisabledViaDashboard();
#else
      HasSyncConsent();
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)

  // Note: We need to record the initial state *after* calling
  // RegisterForAuthNotifications(), because before that the authenticated
  // account isn't initialized.
  RecordSyncInitialState(GetDisableReasons(),
                         is_sync_feature_requested_for_metrics,
                         user_settings_->IsInitialSyncFeatureSetupComplete());

  if (registered_trusted_vault_auto_upgrade_synthetic_field_trial_group_
          .has_value() &&
      base::FeatureList::IsEnabled(
          syncer::kTrustedVaultAutoUpgradeSyntheticFieldTrial)) {
    CHECK(registered_trusted_vault_auto_upgrade_synthetic_field_trial_group_
              ->is_valid());
    registered_trusted_vault_auto_upgrade_synthetic_field_trial_group_
        ->LogValidationMetricsUponOnProfileLoad(GetAccountInfo().gaia);
  }

  // Call Stop() on controllers for non-preferred types to clear metadata.
  // This allows clearing metadata for types disabled in previous run early-on
  // during initialization.
  data_type_manager_->ClearMetadataWhileStoppedExceptFor(
      GetPreferredDataTypes());

  if (IsEngineAllowedToRun()) {
    if (!sync_client_->GetSyncEngineFactory()
             ->HasTransportDataIncludingFirstSync(
                 signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia))) {
      // Sync never initialized before on this profile, so let's try immediately
      // the very first time. This is particularly useful for Chrome Ash (where
      // the user is signed in to begin with) and local sync (where sign-in
      // state doesn't matter to start the engine).
      TryStart();
    } else {
      // Defer starting the engine, for browser startup performance. If another
      // TryStart() happens in the meantime, this deferred task will no-op.
      deferring_first_start_since_ = base::Time::Now();
      base::SequencedTaskRunner::GetCurrentDefault()->PostDelayedTask(
          FROM_HERE,
          base::BindOnce(&SyncServiceImpl::TryStartImpl,
                         weak_factory_.GetWeakPtr()),
          GetDeferredInitDelay());
    }
  }

  sync_status_recorder_ =
      std::make_unique<SyncFeatureStatusForMigrationsRecorder>(
          sync_client_->GetPrefService(), this);
}

void SyncServiceImpl::StartSyncingWithServer() {
  if (engine_) {
    engine_->StartSyncingWithServer();
  }
  if (IsLocalSyncEnabled()) {
    TriggerRefresh(ModelTypeSet::All());
  }
}

ModelTypeSet SyncServiceImpl::GetRegisteredDataTypesForTest() const {
  return data_type_manager_->GetRegisteredDataTypes();
}

bool SyncServiceImpl::HasAnyDatatypeErrorForTest(ModelTypeSet types) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  for (auto type : types) {
    auto it = data_type_error_map_.find(type);
    if (it != data_type_error_map_.end() &&
        it->second.error_type() == syncer::SyncError::DATATYPE_ERROR) {
      return true;
    }
  }
  return false;
}

void SyncServiceImpl::GetThrottledDataTypesForTest(
    base::OnceCallback<void(ModelTypeSet)> cb) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (!engine_ || !engine_->IsInitialized()) {
    std::move(cb).Run(ModelTypeSet());
    return;
  }

  engine_->GetThrottledDataTypesForTest(std::move(cb));
}

// static
ShutdownReason SyncServiceImpl::ShutdownReasonForResetEngineReason(
    ResetEngineReason reset_reason) {
  switch (reset_reason) {
    case ResetEngineReason::kShutdown:
      return ShutdownReason::BROWSER_SHUTDOWN_AND_KEEP_DATA;
    case ResetEngineReason::kCredentialsChanged:
      return ShutdownReason::STOP_SYNC_AND_KEEP_DATA;
    case ResetEngineReason::kUnrecoverableError:
    case ResetEngineReason::kDisabledAccount:
    case ResetEngineReason::kResetLocalData:
    case ResetEngineReason::kStopAndClear:
    case ResetEngineReason::kNotSignedIn:
    case ResetEngineReason::kEnterprisePolicy:
    case ResetEngineReason::kDisableSyncOnClient:
      return ShutdownReason::DISABLE_SYNC_AND_CLEAR_DATA;
  }
}

bool SyncServiceImpl::ShouldClearTransportDataForAccount(
    ResetEngineReason reset_reason) {
  switch (reset_reason) {
    case ResetEngineReason::kShutdown:
    case ResetEngineReason::kDisabledAccount:
    case ResetEngineReason::kStopAndClear:
    case ResetEngineReason::kCredentialsChanged:
    case ResetEngineReason::kNotSignedIn:
    case ResetEngineReason::kEnterprisePolicy:
      // Regular/benign cases; no need to clear.
      return false;
    case ResetEngineReason::kUnrecoverableError:
    case ResetEngineReason::kResetLocalData:
    case ResetEngineReason::kDisableSyncOnClient:
      // Weird error, or explicit request to reset. Clear transport data to
      // start over fresh.
      return true;
  }
}

void SyncServiceImpl::AccountStateChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (!IsSignedIn()) {
    // The account was signed out, so shut down.
    sync_disabled_by_admin_ = false;
    StopAndClear(ResetEngineReason::kNotSignedIn);
    DCHECK(!engine_);
  } else {
    // Either a new account was signed in, or the existing account's
    // |is_sync_consented| bit was changed. Start up or reconfigure.
    if (!engine_) {
      TryStart();
      NotifyObservers();
    } else {
      ReconfigureDatatypeManager(/*bypass_setup_in_progress_check=*/false);
    }
  }
}

void SyncServiceImpl::CredentialsChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // If the engine isn't allowed to start anymore due to the credentials change,
  // then shut down. This happens when there is a persistent auth error (e.g.
  // the user signs out on the web), which implies the "Sync paused" state.
  if (!IsEngineAllowedToRun()) {
    // If the engine currently exists, then ResetEngine() will notify observers
    // anyway. Otherwise, notify them here. (One relevant case is when entering
    // the PAUSED state before the engine was created, e.g. during deferred
    // startup.)
    if (!engine_) {
      DVLOG(2) << "Notify observers on credentials changed";
      NotifyObservers();
    }
    ResetEngine(ResetEngineReason::kCredentialsChanged);
    return;
  }

  if (!engine_) {
    TryStart();
  } else {
    // If the engine already exists, just propagate the new credentials.
    SyncCredentials credentials = auth_manager_->GetCredentials();
    if (credentials.access_token.empty()) {
      engine_->InvalidateCredentials();
    } else {
      engine_->UpdateCredentials(credentials);
    }
  }

  DVLOG(2) << "Notify observers on credentials changed";
  NotifyObservers();
}

bool SyncServiceImpl::IsEngineAllowedToRun() const {
  return GetDisableReasons().empty() && !auth_manager_->IsSyncPaused();
}

void SyncServiceImpl::OnProtocolEvent(const ProtocolEvent& event) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  for (ProtocolEventObserver& observer : protocol_event_observers_) {
    observer.OnProtocolEvent(event);
  }
}

void SyncServiceImpl::OnDataTypeRequestsSyncStartup(ModelType type) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  DCHECK(UserTypes().Has(type));

  if (!GetPreferredDataTypes().Has(type)) {
    // We can get here as datatype SyncableServices are typically wired up
    // to the native datatype even if sync isn't enabled.
    DVLOG(1) << "Dropping sync startup request because type "
             << ModelTypeToDebugString(type) << "not enabled.";
    return;
  }

  if (engine_) {
    DVLOG(1) << "A data type requested sync startup, but it looks like "
                "something else beat it to the punch.";
    return;
  }

  TryStart();
}

void SyncServiceImpl::TryStart() {
  base::SequencedTaskRunner::GetCurrentDefault()->PostTask(
      FROM_HERE, base::BindOnce(&SyncServiceImpl::TryStartImpl,
                                weak_factory_.GetWeakPtr()));
}

void SyncServiceImpl::TryStartImpl() {
  base::Time deferral_time;
  std::swap(deferring_first_start_since_, deferral_time);

  if (engine_ || !IsEngineAllowedToRun()) {
    return;
  }

  if (!deferral_time.is_null()) {
    base::UmaHistogramCustomTimes("Sync.Startup.TimeDeferred2",
                                  base::Time::Now() - deferral_time,
                                  base::Seconds(0), base::Minutes(2), 60);
  }

  const CoreAccountInfo authenticated_account_info = GetAccountInfo();

  if (IsLocalSyncEnabled()) {
    // With local sync (roaming profiles) there is no identity manager and hence
    // |authenticated_account_info| is empty. This is required for
    // IsLocalSyncTransportDataValid() to work properly.
    DCHECK(authenticated_account_info.gaia.empty());
    DCHECK(authenticated_account_info.account_id.empty());
  } else {
    // Except for local sync (roaming profiles), the user must be signed in for
    // sync to start.
    DCHECK(!authenticated_account_info.gaia.empty());
    DCHECK(!authenticated_account_info.account_id.empty());
  }

  engine_ = sync_client_->GetSyncEngineFactory()->CreateSyncEngine(
      debug_identifier_,
      signin::GaiaIdHash::FromGaiaId(authenticated_account_info.gaia),
      sync_client_->GetSyncInvalidationsService());
  DCHECK(engine_);

  // Clear any old errors the first time sync starts.
  if (!user_settings_->IsInitialSyncFeatureSetupComplete()) {
    last_actionable_error_ = SyncProtocolError();
  }

  SyncEngine::InitParams params;
  params.host = this;
  params.encryption_observer_proxy = crypto_.GetEncryptionObserverProxy();

  params.extensions_activity = sync_client_->GetExtensionsActivity();
  params.service_url = sync_service_url_;
  params.http_factory_getter = base::BindOnce(
      create_http_post_provider_factory_cb_, MakeUserAgentForSync(channel_),
      url_loader_factory_->Clone());
  params.authenticated_account_info = authenticated_account_info;

  params.sync_manager_factory =
      std::make_unique<SyncManagerFactory>(network_connection_tracker_);
  if (sync_prefs_.IsLocalSyncEnabled()) {
    params.enable_local_sync_backend = true;
    params.local_sync_backend_folder =
        sync_client_->GetLocalSyncBackendFolder();
  }
  params.engine_components_factory =
      std::make_unique<EngineComponentsFactoryImpl>(
          EngineSwitchesFromCommandLine());

  if (!IsLocalSyncEnabled()) {
    auth_manager_->ConnectionOpened();

    // Ensures that invalidations are enabled, e.g. when the sync was just
    // enabled or after the engine was stopped with clearing data. Note that
    // invalidations are not supported for local sync.
    sync_client_->GetSyncInvalidationsService()->StartListening();
  }

  engine_->Initialize(std::move(params));
}

void SyncServiceImpl::Shutdown() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  TRACE_EVENT0("sync", "SyncServiceImpl::Shutdown");

  NotifyShutdown();

  // Ensure the DataTypeManager is destroyed before the engine, since it has a
  // pointer to the engine.
  std::unique_ptr<SyncEngine> engine =
      ResetEngine(ResetEngineReason::kShutdown);
  data_type_manager_.reset();
  engine.reset();

  crypto_.StopObservingTrustedVaultClient();

  // All observers must be gone now: All KeyedServices should have unregistered
  // their observers already before, in their own Shutdown(), and all others
  // should have done it now when they got the shutdown notification.
  // (Note that destroying the ObserverList triggers its "check_empty" check.)
  observers_.reset();

  auth_manager_.reset();
}

std::unique_ptr<SyncEngine> SyncServiceImpl::ResetEngine(
    ResetEngineReason reset_reason) {
  TRACE_EVENT0("sync", "SyncServiceImpl::ResetEngine");
  CHECK(data_type_manager_);

  const ShutdownReason shutdown_reason =
      ShutdownReasonForResetEngineReason(reset_reason);

  // Stop all data type controllers, if needed. Note that until Stop completes,
  // it is possible in theory to have a ChangeProcessor apply a change from a
  // native model. In that case, it will get applied to the local storage as an
  // unsynced change. That will be persisted, and committed on restart.
  if (shutdown_reason != ShutdownReason::BROWSER_SHUTDOWN_AND_KEEP_DATA) {
    data_type_manager_->Stop(
        ShutdownReasonToSyncStopMetadataFate(shutdown_reason));
    data_type_manager_->SetConfigurer(nullptr);
  }

  if (!engine_) {
    // If the engine hasn't started or is already shut down when a DISABLE_SYNC
    // happens, the Directory needs to be cleaned up here.
    if (shutdown_reason == ShutdownReason::DISABLE_SYNC_AND_CLEAR_DATA) {
      sync_client_->GetSyncEngineFactory()->CleanupOnDisableSync();
    }
    // Depending on the `reset_reason`, maybe clear account-keyed transport
    // data.
    if (ShouldClearTransportDataForAccount(reset_reason)) {
      sync_client_->GetSyncEngineFactory()->ClearTransportDataForAccount(
          signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia));
    }
    return nullptr;
  }

  base::UmaHistogramEnumeration("Sync.ResetEngineReason", reset_reason);
  switch (shutdown_reason) {
    case ShutdownReason::STOP_SYNC_AND_KEEP_DATA:
      // Do not stop listening for sync invalidations. Otherwise, GCMDriver
      // would drop all the incoming messages.
      RemoveClientFromServer();
      break;
    case ShutdownReason::DISABLE_SYNC_AND_CLEAR_DATA: {
      sync_client_->GetSyncInvalidationsService()->StopListeningPermanently();
      RemoveClientFromServer();
      break;
    }
    case ShutdownReason::BROWSER_SHUTDOWN_AND_KEEP_DATA:
      sync_client_->GetSyncInvalidationsService()->StopListening();
      break;
  }

  // First, we spin down the engine to stop change processing as soon as
  // possible.
  engine_->StopSyncingForShutdown();

  // Shutdown the migrator before the engine to ensure it doesn't pull a null
  // snapshot.
  migrator_.reset();

  engine_->Shutdown(shutdown_reason);
  std::unique_ptr<SyncEngine> engine_to_be_destroyed = std::move(engine_);

  // Clear various state.
  crypto_.Reset();
  last_snapshot_ = SyncCycleSnapshot();

  // Depending on the `reset_reason`, maybe clear account-keyed transport data.
  if (ShouldClearTransportDataForAccount(reset_reason)) {
    sync_client_->GetSyncEngineFactory()->ClearTransportDataForAccount(
        signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia));
  }

  if (!IsLocalSyncEnabled()) {
    auth_manager_->ConnectionClosed();
  }

  DVLOG(2) << "Notify observers on reset engine";
  NotifyObservers();

  // Now that everything is shut down, try to start up again.
  switch (shutdown_reason) {
    case ShutdownReason::STOP_SYNC_AND_KEEP_DATA:
    case ShutdownReason::DISABLE_SYNC_AND_CLEAR_DATA:
      // If Sync is being stopped (either temporarily or permanently),
      // immediately try to start up again. Note that this might start only the
      // transport mode, or it might not start anything at all if something is
      // preventing Sync startup (e.g. the user signed out).
      // Note that TryStart() is guaranteed to *not* have a synchronous effect
      // (it posts a task).
      TryStart();
      break;
    case ShutdownReason::BROWSER_SHUTDOWN_AND_KEEP_DATA:
      // The only exception is browser shutdown: In this case, there's clearly
      // no point in starting up again.
      break;
  }

  return engine_to_be_destroyed;
}

#if BUILDFLAG(IS_ANDROID)
base::android::ScopedJavaLocalRef<jobject> SyncServiceImpl::GetJavaObject() {
  if (!sync_service_android_) {
    sync_service_android_ = std::make_unique<SyncServiceAndroidBridge>(this);
  }
  return sync_service_android_->GetJavaObject();
}
#endif  // BUILDFLAG(IS_ANDROID)

void SyncServiceImpl::SetSyncFeatureRequested() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

#if BUILDFLAG(IS_CHROMEOS_ASH)
  user_settings_->ClearSyncFeatureDisabledViaDashboard();
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)

  // If the Sync engine was already initialized (probably running in transport
  // mode), just reconfigure.
  if (engine_ && engine_->IsInitialized()) {
    ReconfigureDatatypeManager(/*bypass_setup_in_progress_check=*/false);
  } else {
    // Otherwise try to start up. Note that there might still be other disable
    // reasons remaining, in which case this will effectively do nothing.
    TryStart();
  }

  DVLOG(2) << "Notify observers on SetSyncFeatureRequested";
  NotifyObservers();
}

SyncUserSettings* SyncServiceImpl::GetUserSettings() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return user_settings_.get();
}

const SyncUserSettings* SyncServiceImpl::GetUserSettings() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return user_settings_.get();
}

SyncService::DisableReasonSet SyncServiceImpl::GetDisableReasons() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // If Sync is disabled via command line flag, then SyncServiceImpl
  // shouldn't even be instantiated.
  DCHECK(IsSyncAllowedByFlag());
  DisableReasonSet result;

  // If local sync is enabled, most disable reasons don't apply.
  if (!IsLocalSyncEnabled()) {
    if (sync_prefs_.IsSyncClientDisabledByPolicy() || sync_disabled_by_admin_) {
      result.Put(DISABLE_REASON_ENTERPRISE_POLICY);
    }
    if (!IsSignedIn()) {
      result.Put(DISABLE_REASON_NOT_SIGNED_IN);
    }
  }

  if (unrecoverable_error_reason_) {
    result.Put(DISABLE_REASON_UNRECOVERABLE_ERROR);
  }
  return result;
}

SyncService::TransportState SyncServiceImpl::GetTransportState() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (!GetDisableReasons().empty()) {
    // Note: we generally shouldn't have an engine while in a disabled state,
    // but it can happen if this method gets called during ResetEngine().
    return TransportState::DISABLED;
  }

  if (auth_manager_->IsSyncPaused()) {
    return TransportState::PAUSED;
  }

  CHECK(IsEngineAllowedToRun());

  if (!engine_) {
    // Starting the engine is allowed but didn't happen. There are three
    // possible scenarios:
    // 1) Startup was deferred, in which case it can take noticeably long until
    //  . the engine initializes. This case can be distinguished by checking if
    //  . `deferring_first_start_since_` is set.
    // 2) Startup is about to happen because SyncServiceImpl::TryStart() was
    //  . invoked, but the posted task to run SyncServiceImpl::TryStartImpl()
    //  . hasn't been processed yet.
    // 3) The service is shutting down.
    //
    // This function reports TransportState::START_DEFERRED only for the first,
    // which is the only real deferred case.
    return deferring_first_start_since_.is_null()
               ? TransportState::INITIALIZING
               : TransportState::START_DEFERRED;
  }

  if (!engine_->IsInitialized() || !data_type_manager_) {
    return TransportState::INITIALIZING;
  }

  // At this point we should usually be able to configure our data types (so the
  // DataTypeManager should not be STOPPED anymore), unless setup is in
  // progress. But it can also happen if this gets called from DataTypeManager
  // itself.
  if (data_type_manager_->state() == DataTypeManager::STOPPED) {
    return TransportState::PENDING_DESIRED_CONFIGURATION;
  }

  if (data_type_manager_->state() != DataTypeManager::CONFIGURED) {
    return TransportState::CONFIGURING;
  }

  return TransportState::ACTIVE;
}

SyncService::UserActionableError SyncServiceImpl::GetUserActionableError()
    const {
  const GoogleServiceAuthError auth_error = GetAuthError();
  DCHECK(!auth_error.IsTransientError());

  switch (auth_error.state()) {
    case GoogleServiceAuthError::NONE:
      break;
    case GoogleServiceAuthError::SERVICE_UNAVAILABLE:
    case GoogleServiceAuthError::CONNECTION_FAILED:
    case GoogleServiceAuthError::REQUEST_CANCELED:
    case GoogleServiceAuthError::CHALLENGE_RESPONSE_REQUIRED:
      // Transient errors aren't reachable.
      NOTREACHED_IN_MIGRATION();
      break;
    case GoogleServiceAuthError::SERVICE_ERROR:
    case GoogleServiceAuthError::SCOPE_LIMITED_UNRECOVERABLE_ERROR:
    case GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS:
      return UserActionableError::kSignInNeedsUpdate;
    case GoogleServiceAuthError::USER_NOT_SIGNED_UP:
    case GoogleServiceAuthError::UNEXPECTED_SERVICE_RESPONSE:
      // Not shown to the user.
      // TODO(crbug.com/40890809): It looks like desktop code in
      // chrome/browser/sync/sync_ui_util.cc does display this to the user.
      break;
    // Conventional value for counting the states, never used.
    case GoogleServiceAuthError::NUM_STATES:
      NOTREACHED_IN_MIGRATION();
      break;
  }

  if (user_settings_->IsPassphraseRequiredForPreferredDataTypes()) {
    return UserActionableError::kNeedsPassphrase;
  }
  if (user_settings_->IsTrustedVaultKeyRequiredForPreferredDataTypes()) {
    return user_settings_->IsEncryptEverythingEnabled()
               ? UserActionableError::kNeedsTrustedVaultKeyForEverything
               : UserActionableError::kNeedsTrustedVaultKeyForPasswords;
  }
  if (user_settings_->IsTrustedVaultRecoverabilityDegraded()) {
    return user_settings_->IsEncryptEverythingEnabled()
               ? UserActionableError::
                     kTrustedVaultRecoverabilityDegradedForEverything
               : UserActionableError::
                     kTrustedVaultRecoverabilityDegradedForPasswords;
  }
  return UserActionableError::kNone;
}

void SyncServiceImpl::NotifyObservers() {
  CHECK(observers_);
  for (SyncServiceObserver& observer : *observers_) {
    observer.OnStateChanged(this);
  }
}

void SyncServiceImpl::NotifySyncCycleCompleted() {
  CHECK(observers_);
  for (SyncServiceObserver& observer : *observers_) {
    observer.OnSyncCycleCompleted(this);
  }
}

void SyncServiceImpl::NotifyShutdown() {
  CHECK(observers_);
  for (SyncServiceObserver& observer : *observers_) {
    observer.OnSyncShutdown(this);
  }
}

void SyncServiceImpl::ClearUnrecoverableError() {
  unrecoverable_error_reason_ = std::nullopt;
  unrecoverable_error_message_.clear();
  unrecoverable_error_location_ = base::Location();
}

void SyncServiceImpl::OnUnrecoverableErrorImpl(
    const base::Location& from_here,
    const std::string& message,
    UnrecoverableErrorReason reason) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  unrecoverable_error_reason_ = reason;
  unrecoverable_error_message_ = message;
  unrecoverable_error_location_ = from_here;

  LOG(ERROR) << "Unrecoverable error detected at " << from_here.ToString()
             << " -- SyncServiceImpl unusable: " << message;

  // Shut the Sync machinery down. The existence of
  // |unrecoverable_error_reason_| and thus |DISABLE_REASON_UNRECOVERABLE_ERROR|
  // will prevent Sync from starting up again (even in transport-only mode).
  ResetEngine(ResetEngineReason::kUnrecoverableError);
}

void SyncServiceImpl::DataTypePreconditionChanged(ModelType type) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (!engine_ || !engine_->IsInitialized() || !data_type_manager_) {
    return;
  }
  data_type_manager_->DataTypePreconditionChanged(type);
}

void SyncServiceImpl::OnEngineInitialized(bool success,
                                          bool is_first_time_sync_configure) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  DCHECK(IsEngineAllowedToRun());

  // The very first time the backend initializes is effectively the first time
  // we can say we successfully "synced".
  is_first_time_sync_configure_ = is_first_time_sync_configure;

  if (!success) {
    // Something went unexpectedly wrong.  Play it safe: stop syncing at once
    // and surface error UI to alert the user sync has stopped.
    OnUnrecoverableErrorImpl(FROM_HERE, "BackendInitialize failure",
                             ERROR_REASON_ENGINE_INIT_FAILURE);
    return;
  }

  if (!protocol_event_observers_.empty()) {
    engine_->RequestBufferedProtocolEventsAndEnableForwarding();
  }

  data_type_manager_->SetConfigurer(engine_.get());

  crypto_.SetSyncEngine(GetAccountInfo(), engine_.get());

  sync_prefs_.MaybeMigratePrefsForSyncToSigninPart2(
      signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia),
      user_settings_->IsUsingExplicitPassphrase());

  // Cache trusted vault debug info into prefs, to make it synchronously
  // available upon future profile startups.
  CacheTrustedVaultDebugInfoToPrefsFromEngine();

  if (CanConfigureDataTypes(/*bypass_setup_in_progress_check=*/false)) {
    // Datatype downloads on restart are generally due to newly supported
    // datatypes (although it's also possible we're picking up where a failed
    // previous configuration left off).
    // TODO(sync): consider detecting configuration recovery and setting
    // the reason here appropriately.
    ConfigureDataTypeManager(CONFIGURE_REASON_NEWLY_ENABLED_DATA_TYPE);
  }

  // Check for a cookie jar mismatch.
  if (identity_manager_) {
    signin::AccountsInCookieJarInfo accounts_in_cookie_jar_info =
        identity_manager_->GetAccountsInCookieJar();
    if (accounts_in_cookie_jar_info.accounts_are_fresh) {
      OnAccountsInCookieUpdated(accounts_in_cookie_jar_info,
                                GoogleServiceAuthError::AuthErrorNone());
    }
  }

  DVLOG(2) << "Notify on engine initialized";
  NotifyObservers();
}

void SyncServiceImpl::OnSyncCycleCompleted(const SyncCycleSnapshot& snapshot) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(engine_);
  CHECK(engine_->IsInitialized());

  last_snapshot_ = snapshot;

  // Cache trusted vault debug info into prefs, to make it synchronously
  // available upon future profile startups. In most cases this will happen in
  // OnEngineInitialized(), but it may also happen that the information was just
  // populated server-side and downloaded, after (or long after) the engine is
  // initialized.
  CacheTrustedVaultDebugInfoToPrefsFromEngine();

  DVLOG(2) << "Notifying observers sync cycle completed";
  NotifySyncCycleCompleted();
}

void SyncServiceImpl::OnConnectionStatusChange(ConnectionStatus status) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (!IsLocalSyncEnabled()) {
    auth_manager_->ConnectionStatusChanged(status);
  }
  DVLOG(2) << "Notify observers OnConnectionStatusChange";
  NotifyObservers();
}

void SyncServiceImpl::OnMigrationNeededForTypes(ModelTypeSet types) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  DCHECK(engine_);
  DCHECK(engine_->IsInitialized());

  // Migrator must be valid, because we don't sync until it is created and this
  // callback originates from a sync cycle.
  migrator_->MigrateTypes(types);
}

void SyncServiceImpl::OnActionableProtocolError(
    const SyncProtocolError& error) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  last_actionable_error_ = error;
  DCHECK_NE(last_actionable_error_.action, UNKNOWN_ACTION);
  switch (error.action) {
    case UPGRADE_CLIENT:
      if (IsSetupInProgress()) {
        StopAndClear();
      }
      // Trigger an unrecoverable error to stop syncing.
      OnUnrecoverableErrorImpl(FROM_HERE,
                               last_actionable_error_.error_description,
                               ERROR_REASON_ACTIONABLE_ERROR);
      break;
    case DISABLE_SYNC_ON_CLIENT:
      if (error.error_type == NOT_MY_BIRTHDAY ||
          error.error_type == ENCRYPTION_OBSOLETE) {
        // Note: For legacy reasons, `kImplicitPassphrase` is used to represent
        // the "unknown" state.
        base::UmaHistogramEnumeration(
            "Sync.PassphraseTypeUponNotMyBirthdayOrEncryptionObsolete",
            crypto_.GetPassphraseType().value_or(
                PassphraseType::kImplicitPassphrase));
        // Account passphrase pref should be cleared when sync is reset from the
        // dashboard because then the cached passphrase wouldn't be useful
        // anymore.
        sync_prefs_.ClearEncryptionBootstrapTokenForAccount(
            signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia));
      }

      // Security domain state might be reset, reset local state as well.
      sync_client_->GetTrustedVaultClient()->ClearLocalDataForAccount(
          GetAccountInfo());

      // Note: This method might get called again in the following code when
      // clearing the primary account. But due to rarity of the event, this
      // should be okay.
      StopAndClear(ResetEngineReason::kDisableSyncOnClient);

#if BUILDFLAG(IS_CHROMEOS_ASH)
      // On Ash, the primary account is always set and sync the feature
      // turned on, so a dedicated bit is needed to ensure that
      // Sync-the-feature remains off. Note that sync-the-transport will restart
      // immediately because IsEngineAllowedToRun() is almost certainly true at
      // this point and StopAndClear() leads to TryStart().
      user_settings_->SetSyncFeatureDisabledViaDashboard();
#else  // !BUILDFLAG(IS_CHROMEOS_ASH)
      // On every platform except ash, revoke the Sync consent/Clear primary
      // account after a dashboard clear.
      // TODO(crbug.com/40066949): Simplify once kSync becomes unreachable or is
      // deleted from the codebase. See ConsentLevel::kSync documentation for
      // details.
      if (!IsLocalSyncEnabled() &&
          identity_manager_->HasPrimaryAccount(signin::ConsentLevel::kSync)) {
        signin::PrimaryAccountMutator* account_mutator =
            identity_manager_->GetPrimaryAccountMutator();
        // GetPrimaryAccountMutator() returns nullptr on ChromeOS only.
        DCHECK(account_mutator);

        // TODO(crbug.com/40220945): make the behaviour consistent across
        // platforms. Any platforms which support a single-step flow that signs
        // in and enables sync should clear the primary account here for
        // symmetry.
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_IOS)
        // On mobile, fully sign out the user (clear the primary account) but
        // do not remove the list of known accounts, as the user may sign in
        // again.
        account_mutator->RemovePrimaryAccountButKeepTokens(
            signin_metrics::ProfileSignout::kServerForcedDisable);
#else
        // Note: On some platforms, revoking the sync consent will also clear
        // the primary account as transitioning from ConsentLevel::kSync to
        // ConsentLevel::kSignin is not supported.
        account_mutator->RevokeSyncConsent(
            signin_metrics::ProfileSignout::kServerForcedDisable);
#endif  // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_IOS)
      }
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)
      break;
    case STOP_SYNC_FOR_DISABLED_ACCOUNT:
      // Sync disabled by domain admin. Stop syncing until next restart.
      sync_disabled_by_admin_ = true;
      ResetEngine(ResetEngineReason::kDisabledAccount);
      break;
    case RESET_LOCAL_SYNC_DATA:
      ResetEngine(ResetEngineReason::kResetLocalData);
      break;
    case UNKNOWN_ACTION:
      NOTREACHED_IN_MIGRATION();
  }
  DVLOG(2) << "Notify observers OnActionableProtocolError";
  NotifyObservers();
}

void SyncServiceImpl::OnBackedOffTypesChanged() {
  DVLOG(2) << "Notify observers OnBackedOffTypesChanged";
  NotifyObservers();
}

void SyncServiceImpl::OnInvalidationStatusChanged() {
  DVLOG(2) << "Notify observers OnInvalidationStatusChanged";
  NotifyObservers();
}

void SyncServiceImpl::OnNewInvalidatedDataTypes() {
  DVLOG(2) << "Notify observers OnNewInvalidatedDataTypes";
  NotifyObservers();
}

void SyncServiceImpl::OnConfigureDone(
    const DataTypeManager::ConfigureResult& result) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  data_type_error_map_ = result.data_type_status_table.GetAllErrors();

  DVLOG(1) << "SyncServiceImpl::OnConfigureDone called with status: "
           << result.status;
  // The possible status values:
  //    ABORT - Configuration was aborted. This is not an error, if
  //            initiated by user.
  //    OK - Some or all types succeeded.

  // First handle the abort case.
  if (result.status == DataTypeManager::ABORTED) {
    DVLOG(0) << "SyncServiceImpl sync configuration aborted";
    return;
  }

  DCHECK_EQ(DataTypeManager::OK, result.status);

  // We should never get in a state where we have no encrypted datatypes
  // enabled, and yet we still think we require a passphrase for decryption.
  DCHECK(!user_settings_->IsPassphraseRequiredForPreferredDataTypes() ||
         user_settings_->IsEncryptedDatatypePreferred());

  DVLOG(2) << "Notify observers OnConfigureDone";
  NotifyObservers();

  // Update configured data types and start handling incoming invalidations. The
  // order is important to guarantee that data types are configured to prevent
  // filtering out invalidations.
  UpdateDataTypesForInvalidations();
  engine_->StartHandlingInvalidations();

  if (migrator_.get() && migrator_->state() != BackendMigrator::IDLE) {
    // Migration in progress.  Let the migrator know we just finished
    // configuring something.  It will be up to the migrator to call
    // StartSyncingWithServer() if migration is now finished.
    migrator_->OnConfigureDone(result);
    return;
  }

  RecordMemoryUsageAndCountsHistograms();

  StartSyncingWithServer();
}

void SyncServiceImpl::OnConfigureStart() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  engine_->StartConfiguration();
  DVLOG(2) << "Notify observers OnConfigureStart";
  NotifyObservers();
}

void SyncServiceImpl::CryptoStateChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  DVLOG(2) << "Notify observers on CryptoStateChanged";
  NotifyObservers();
}

void SyncServiceImpl::CryptoRequiredUserActionChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  MaybeRecordTrustedVaultHistograms();
}

void SyncServiceImpl::MaybeRecordTrustedVaultHistograms() {
  if (should_record_trusted_vault_error_shown_on_startup_ &&
      crypto_.IsTrustedVaultKeyRequiredStateKnown() &&
      user_settings_->IsEncryptedDatatypePreferred()) {
    // If the key-required state is known, the engine must exist.
    DCHECK(engine_);

    should_record_trusted_vault_error_shown_on_startup_ = false;
    if (crypto_.GetPassphraseType() ==
        PassphraseType::kTrustedVaultPassphrase) {
      RecordTrustedVaultHistogramBooleanWithMigrationSuffix(
          "Sync.TrustedVaultErrorShownOnStartup",
          user_settings_->IsTrustedVaultKeyRequiredForPreferredDataTypes(),
          engine_->GetDetailedStatus());

      if (is_first_time_sync_configure_) {
        // A 'first time sync configure' is an indication that the account was
        // added to the browser recently (sign in).
        base::UmaHistogramBoolean(
            "Sync.TrustedVaultErrorShownOnFirstTimeSync2",
            user_settings_->IsTrustedVaultKeyRequiredForPreferredDataTypes());
      }
    }
  }
}

void SyncServiceImpl::ReconfigureDataTypesDueToCrypto() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (CanConfigureDataTypes(/*bypass_setup_in_progress_check=*/false)) {
    ConfigureDataTypeManager(CONFIGURE_REASON_CRYPTO);
  }

  // Notify observers that the passphrase status may have changed, regardless of
  // whether we triggered configuration or not. This is needed for the
  // IsSetupInProgress() case where the UI needs to be updated to reflect that
  // the passphrase was accepted (https://crbug.com/870256).
  DVLOG(2) << "Notify observers on ReconfigureDataTypesDueToCrypto";
  NotifyObservers();
}

void SyncServiceImpl::PassphraseTypeChanged(PassphraseType passphrase_type) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  // if kReplaceSyncPromosWithSignInPromos is enabled, kAutofill should be
  // disabled for newly sign in users who have already custom passphrase set.
  // The first `PassphraseTypeChanged()` call reflects the server-side
  // passphrase type before signing in.
  if (!sync_prefs_.GetCachedPassphraseType().has_value() &&
      IsExplicitPassphrase(passphrase_type) &&
      GetSyncAccountStateForPrefs() ==
          SyncPrefs::SyncAccountState::kSignedInNotSyncing &&
      base::FeatureList::IsEnabled(kReplaceSyncPromosWithSignInPromos)) {
    GetUserSettings()->SetSelectedType(UserSelectableType::kAutofill, false);
  }
  sync_prefs_.SetCachedPassphraseType(passphrase_type);
}

std::optional<PassphraseType> SyncServiceImpl::GetPassphraseType() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return sync_prefs_.GetCachedPassphraseType();
}

void SyncServiceImpl::SetEncryptionBootstrapToken(
    const std::string& bootstrap_token) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  user_settings_->SetEncryptionBootstrapToken(bootstrap_token);
  SendExplicitPassphraseToPlatformClient();
}

std::string SyncServiceImpl::GetEncryptionBootstrapToken() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return user_settings_->GetEncryptionBootstrapToken();
}

bool SyncServiceImpl::IsCustomPassphraseAllowed() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return sync_client_->IsCustomPassphraseAllowed();
}

SyncPrefs::SyncAccountState SyncServiceImpl::GetSyncAccountStateForPrefs()
    const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (IsLocalSyncEnabled()) {
    // Local sync should behave like a syncing user.
    return SyncPrefs::SyncAccountState::kSyncing;
  }
  if (!IsSignedIn()) {
    return SyncPrefs::SyncAccountState::kNotSignedIn;
  }
  // This doesn't check IsSyncFeatureEnabled() so it covers the case of advanced
  // sync setup, where IsInitialSyncFeatureSetupComplete() is not true yet.
  return HasSyncConsent() ? SyncPrefs::SyncAccountState::kSyncing
                          : SyncPrefs::SyncAccountState::kSignedInNotSyncing;
}

CoreAccountInfo SyncServiceImpl::GetSyncAccountInfoForPrefs() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return GetAccountInfo();
}

bool SyncServiceImpl::IsSetupInProgress() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return outstanding_setup_in_progress_handles_ > 0;
}

bool SyncServiceImpl::QueryDetailedSyncStatusForDebugging(
    SyncStatus* result) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (engine_ && engine_->IsInitialized()) {
    *result = engine_->GetDetailedStatus();
    return true;
  }
  SyncStatus status;
  status.sync_protocol_error = last_actionable_error_;
  *result = status;
  return false;
}

GoogleServiceAuthError SyncServiceImpl::GetAuthError() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return auth_manager_->GetLastAuthError();
}

base::Time SyncServiceImpl::GetAuthErrorTime() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return auth_manager_->GetLastAuthErrorTime();
}

bool SyncServiceImpl::RequiresClientUpgrade() const {
  return last_actionable_error_.action == UPGRADE_CLIENT;
}

bool SyncServiceImpl::CanConfigureDataTypes(
    bool bypass_setup_in_progress_check) const {
  return engine_ && engine_->IsInitialized() &&
         (bypass_setup_in_progress_check || !IsSetupInProgress());
}

std::unique_ptr<SyncSetupInProgressHandle>
SyncServiceImpl::GetSetupInProgressHandle() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (++outstanding_setup_in_progress_handles_ == 1) {
    TryStart();

    DVLOG(2) << "Notify observers GetSetupInProgressHandle";
    NotifyObservers();
  }

  return std::make_unique<SyncSetupInProgressHandle>(
      base::BindRepeating(&SyncServiceImpl::OnSetupInProgressHandleDestroyed,
                          weak_factory_.GetWeakPtr()));
}

bool SyncServiceImpl::IsLocalSyncEnabled() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return sync_prefs_.IsLocalSyncEnabled();
}

void SyncServiceImpl::TriggerRefresh(const ModelTypeSet& types) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (engine_ && engine_->IsInitialized()) {
    engine_->TriggerRefresh(types);
  }
}

bool SyncServiceImpl::IsSignedIn() const {
  // Sync is logged in if there is a non-empty account id.
  return !GetAccountInfo().account_id.empty();
}

base::Time SyncServiceImpl::GetLastSyncedTimeForDebugging() const {
  if (!engine_ || !engine_->IsInitialized()) {
    return base::Time();
  }

  return engine_->GetLastSyncedTimeForDebugging();
}

void SyncServiceImpl::OnSelectedTypesPrefChange() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (data_type_manager_) {
    data_type_manager_->ResetDataTypeErrors();
  }

  ReconfigureDatatypeManager(/*bypass_setup_in_progress_check=*/false);
}

SyncClient* SyncServiceImpl::GetSyncClientForTest() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return sync_client_.get();
}

void SyncServiceImpl::ReportDataTypeErrorForTest(ModelType type) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK_IS_TEST();
  CHECK(data_type_manager_->GetControllerMap().find(type) !=
        data_type_manager_->GetControllerMap().end());
  data_type_manager_->GetControllerMap()
      .find(type)
      ->second->ReportBridgeErrorForTest();  // IN-TEST
}

void SyncServiceImpl::AddObserver(SyncServiceObserver* observer) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(observers_);
  observers_->AddObserver(observer);
}

void SyncServiceImpl::RemoveObserver(SyncServiceObserver* observer) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(observers_);
  observers_->RemoveObserver(observer);
}

bool SyncServiceImpl::HasObserver(const SyncServiceObserver* observer) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(observers_);
  return observers_->HasObserver(observer);
}

ModelTypeSet SyncServiceImpl::GetPreferredDataTypes() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  // Some questionable callers exercise this function after Shutdown(). The
  // semantics aren't clear, but for cases like GetUploadToGoogleState() a
  // sensible behavior is to return an empty set.
  if (!data_type_manager_) {
    return ModelTypeSet();
  }
  ModelTypeSet types = user_settings_->GetPreferredDataTypes();
  // SyncUserSettings already filters out UserSelectableTypes that aren't
  // supported in transport mode. However, there are two reasons why the
  // ModelTypes still need to be filtered here:
  // 1) For some UserSelectableTypes, some of their ModelTypes are supported
  //    while others aren't.
  // 2) Some ModelTypes implement additional preconditions in
  //    ShouldRunInTransportOnlyMode() (e.g. related to passphrase type).
  if (UseTransportOnlyMode()) {
    types = Intersection(
        types, data_type_manager_->GetDataTypesForTransportOnlyMode());
  }
  return types;
}

ModelTypeSet SyncServiceImpl::GetActiveDataTypes() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  if (!engine_ || !engine_->IsInitialized() || !data_type_manager_) {
    return ModelTypeSet();
  }

  // Persistent auth errors lead to PAUSED, which implies
  // engine_==null above.
  CHECK(!GetAuthError().IsPersistentError());

  return data_type_manager_->GetActiveDataTypes();
}

ModelTypeSet SyncServiceImpl::GetTypesWithPendingDownloadForInitialSync()
    const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(data_type_manager_);

  if (GetTransportState() == TransportState::INITIALIZING &&
      !sync_client_->GetSyncEngineFactory()->HasTransportDataIncludingFirstSync(
          signin::GaiaIdHash::FromGaiaId(GetAccountInfo().gaia))) {
    // The engine is initializing for the very first sync (usually after
    // sign-in). In this case all types are reported as pending download,
    // optimistically assuming datatype preconditions will be met.
    return GetPreferredDataTypes();
  }

  return data_type_manager_->GetTypesWithPendingDownloadForInitialSync();
}

void SyncServiceImpl::ConfigureDataTypeManager(ConfigureReason reason) {
  DCHECK(engine_);
  DCHECK(engine_->IsInitialized());
  DCHECK(!engine_->GetCacheGuid().empty());
  DVLOG(1) << "Started DataTypeManager configuration, reason: "
           << static_cast<int>(reason);

  ConfigureContext configure_context = {
      .authenticated_account_id = GetAccountInfo().account_id,
      .cache_guid = engine_->GetCacheGuid(),
      .sync_mode = SyncMode::kFull,
      .reason = reason,
      .configuration_start_time = base::Time::Now()};

  DCHECK(!configure_context.cache_guid.empty());

  if (!migrator_) {
    // We create the migrator at the same time.
    migrator_ = std::make_unique<BackendMigrator>(
        debug_identifier_, data_type_manager_.get(),
        base::BindRepeating(&SyncServiceImpl::ConfigureDataTypeManager,
                            base::Unretained(this), CONFIGURE_REASON_MIGRATION),
        base::BindRepeating(&SyncServiceImpl::StartSyncingWithServer,
                            base::Unretained(this)));

    // Override reason if no configuration has completed ever.
    if (is_first_time_sync_configure_) {
      configure_context.reason = CONFIGURE_REASON_NEW_CLIENT;
    }
  }

  DCHECK(!configure_context.authenticated_account_id.empty() ||
         IsLocalSyncEnabled());
  DCHECK(!configure_context.cache_guid.empty());
  DCHECK_NE(configure_context.reason, CONFIGURE_REASON_UNKNOWN);

  const bool use_transport_only_mode = UseTransportOnlyMode();

  if (use_transport_only_mode) {
    configure_context.sync_mode = SyncMode::kTransportOnly;
  }
  data_type_manager_->Configure(GetPreferredDataTypes(), configure_context);

  // Record in UMA whether we're configuring the full Sync feature or only the
  // transport. These values are persisted to logs. Entries should not be
  // renumbered and numeric values should never be reused. Keep in sync with
  // SyncFeatureOrTransport in tools/metrics/histograms/metadata/sync/enums.xml.
  // LINT.IfChange(SyncFeatureOrTransport)
  enum class ConfigureDataTypeManagerOption {
    kFeature = 0,
    kTransport = 1,
    kMaxValue = kTransport
  };
  // LINT.ThenChange(/tools/metrics/histograms/metadata/sync/enums.xml:SyncFeatureOrTransport)
  base::UmaHistogramEnumeration("Sync.ConfigureDataTypeManagerOption",
                                use_transport_only_mode
                                    ? ConfigureDataTypeManagerOption::kTransport
                                    : ConfigureDataTypeManagerOption::kFeature);

  // Record the user's choice of data types - in different ways depending on
  // whether Sync-the-feature is enabled (which uses "SyncEverything") or not
  // (which doesn't).
  if (use_transport_only_mode) {
    for (UserSelectableType type : user_settings_->GetSelectedTypes()) {
      ModelTypeForHistograms canonical_model_type =
          ModelTypeHistogramValue(UserSelectableTypeToCanonicalModelType(type));
      base::UmaHistogramEnumeration("Sync.SelectedTypesInTransportMode",
                                    canonical_model_type);
    }
  } else {
    bool sync_everything = sync_prefs_.HasKeepEverythingSynced();
    base::UmaHistogramBoolean("Sync.SyncEverything2", sync_everything);

    if (!sync_everything) {
      for (UserSelectableType type : user_settings_->GetSelectedTypes()) {
        ModelTypeForHistograms canonical_model_type = ModelTypeHistogramValue(
            UserSelectableTypeToCanonicalModelType(type));
        base::UmaHistogramEnumeration("Sync.CustomSync3", canonical_model_type);
      }
    }

#if BUILDFLAG(IS_CHROMEOS_ASH)
    bool sync_everything_os = sync_prefs_.IsSyncAllOsTypesEnabled();
    base::UmaHistogramBoolean("Sync.SyncEverythingOS", sync_everything_os);
    if (!sync_everything_os) {
      for (UserSelectableOsType type : user_settings_->GetSelectedOsTypes()) {
        ModelTypeForHistograms canonical_model_type = ModelTypeHistogramValue(
            UserSelectableOsTypeToCanonicalModelType(type));
        base::UmaHistogramEnumeration("Sync.CustomOSSync",
                                      canonical_model_type);
      }
    }
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)
  }
}

bool SyncServiceImpl::UseTransportOnlyMode() const {
  // Note: When local Sync is enabled, then we want full-sync mode (not just
  // transport), even though Sync-the-feature is not considered enabled.
  return !IsSyncFeatureEnabled() && !IsLocalSyncEnabled();
}

void SyncServiceImpl::UpdateDataTypesForInvalidations() {
  // Wait for configuring data types. This is needed to consider proxy types
  // which become known during configuration.
  if (!data_type_manager_ ||
      data_type_manager_->state() != DataTypeManager::CONFIGURED) {
    return;
  }

  // No need to register invalidations for non-protocol or commit-only types.
  ModelTypeSet types = Intersection(GetPreferredDataTypes(), ProtocolTypes());
  types.RemoveAll(CommitOnlyTypes());
  if (!sessions_invalidations_enabled_) {
    types.Remove(SESSIONS);
  }

  if (!data_type_manager_->GetDataTypesWithPermanentErrors().empty() &&
      base::FeatureList::IsEnabled(
          kSyncUnsubscribeFromTypesWithPermanentErrors)) {
    // Unsubscribe from data types with permanent errors. Types which are
    // unready or have crypto errors are intentionally kept because they will
    // may change their state.
    types.RemoveAll(data_type_manager_->GetDataTypesWithPermanentErrors());
  }

#if BUILDFLAG(IS_ANDROID)
  // On Android, don't subscribe to HISTORY invalidations, to save network
  // traffic.
  types.Remove(HISTORY);
#endif
  types.RemoveAll(data_type_manager_->GetActiveProxyDataTypes());

  sync_client_->GetSyncInvalidationsService()->SetInterestedDataTypes(types);
}

SyncCycleSnapshot SyncServiceImpl::GetLastCycleSnapshotForDebugging() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return last_snapshot_;
}

void SyncServiceImpl::HasUnsyncedItemsForTest(
    base::OnceCallback<void(bool)> cb) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  DCHECK(engine_);
  DCHECK(engine_->IsInitialized());
  engine_->HasUnsyncedItemsForTest(std::move(cb));
}

BackendMigrator* SyncServiceImpl::GetBackendMigratorForTest() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return migrator_.get();
}

base::Value::List SyncServiceImpl::GetTypeStatusMapForDebugging() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  base::Value::List result;

  if (!engine_ || !engine_->IsInitialized()) {
    return result;
  }

  const SyncStatus& detailed_status = engine_->GetDetailedStatus();
  const ModelTypeSet& throttled_types(detailed_status.throttled_types);
  const ModelTypeSet& backed_off_types(detailed_status.backed_off_types);

  auto type_status_header = base::Value::Dict()
                                .Set("status", "header")
                                .Set("name", "Model Type")
                                .Set("num_entries", "Total Entries")
                                .Set("num_live", "Live Entries")
                                .Set("message", "Message")
                                .Set("state", "State");
  result.Append(std::move(type_status_header));

  for (const auto& [type, controller] :
       data_type_manager_->GetControllerMap()) {
    base::Value::Dict type_status;
    type_status.Set("name", ModelTypeToDebugString(type));

    if (data_type_error_map_.find(type) != data_type_error_map_.end()) {
      const SyncError& error = data_type_error_map_.find(type)->second;
      DCHECK(error.IsSet());
      switch (error.GetSeverity()) {
        case SyncError::SYNC_ERROR_SEVERITY_ERROR:
          type_status.Set("status", "severity_error");
          type_status.Set("message", "Error: " + error.location().ToString() +
                                         ", " + error.GetMessagePrefix() +
                                         error.message());
          break;
        case SyncError::SYNC_ERROR_SEVERITY_INFO:
          type_status.Set("status", "severity_info");
          type_status.Set("message", error.message());
          break;
      }
    } else if (throttled_types.Has(type)) {
      type_status.Set("status", "severity_warning");
      type_status.Set("message", " Throttled");
    } else if (backed_off_types.Has(type)) {
      type_status.Set("status", "severity_warning");
      type_status.Set("message", "Backed off");
    } else {
      type_status.Set("message", "");

      // Determine the row color based on the controller's state.
      switch (controller->state()) {
        case DataTypeController::NOT_RUNNING:
          // One common case is that the sync was just disabled by the user,
          // which is not very different to certain SYNC_ERROR_SEVERITY_INFO
          // cases like preconditions not having been met due to user
          // configuration.
          type_status.Set("status", "severity_info");
          break;
        case DataTypeController::MODEL_STARTING:
        case DataTypeController::MODEL_LOADED:
        case DataTypeController::STOPPING:
          // These are all transitional states that should be rare to observe.
          type_status.Set("status", "transitioning");
          break;
        case DataTypeController::RUNNING:
          type_status.Set("status", "ok");
          break;
        case DataTypeController::FAILED:
          // Note that most of the errors (possibly all) should have been
          // handled earlier via |data_type_error_map_|.
          type_status.Set("status", "severity_error");
          break;
      }
    }

    type_status.Set("state",
                    DataTypeController::StateToString(controller->state()));

    result.Append(std::move(type_status));
  }
  return result;
}

void SyncServiceImpl::GetEntityCountsForDebugging(
    base::RepeatingCallback<void(const TypeEntitiesCount&)> callback) const {
  for (const auto& [type, controller] :
       data_type_manager_->GetControllerMap()) {
    controller->GetTypeEntitiesCount(callback);
  }
}

void SyncServiceImpl::OnSyncManagedPrefChange(bool is_sync_managed) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // Local sync is not controlled by the "sync managed" policy, so these pref
  // changes make no difference to the service state.
  if (IsLocalSyncEnabled()) {
    return;
  }

  if (is_sync_managed) {
    StopAndClear(ResetEngineReason::kEnterprisePolicy);
#if BUILDFLAG(IS_CHROMEOS_ASH)
    // On ChromeOS Ash, sync-the-feature stays disabled even after the policy is
    // removed, for historic reasons. It is unclear if this behavior is
    // optional, because it is indistinguishable from the
    // sync-reset-via-dashboard case. It can be resolved by invoking
    // SetSyncFeatureRequested().
    sync_prefs_.SetSyncFeatureDisabledViaDashboard();
#endif  // BUILDFLAG(IS_CHROMEOS_ASH)
  } else {
    // Sync is no longer disabled by policy. Try starting it up if appropriate.
    DCHECK(!engine_);
    TryStart();
    DVLOG(2) << "Notify observers OnSyncManagedPrefChange";
    NotifyObservers();
  }
}

#if !BUILDFLAG(IS_CHROMEOS_ASH)
void SyncServiceImpl::OnFirstSetupCompletePrefChange(
    bool is_initial_sync_feature_setup_complete) {
  if (engine_ && engine_->IsInitialized()) {
    ReconfigureDatatypeManager(/*bypass_setup_in_progress_check=*/false);
    // IsSyncFeatureEnabled() likely changed, it might be time to record
    // histograms.
    MaybeRecordTrustedVaultHistograms();
  }
}
#endif  // !BUILDFLAG(IS_CHROMEOS_ASH)

void SyncServiceImpl::OnAccountsCookieDeletedByUserAction() {
  // Pass an empty `signin::AccountsInCookieJarInfo` to simulate empty cookies.
  MaybeClearAccountKeyedPreferences(
      identity_manager_, signin::AccountsInCookieJarInfo(), *user_settings_);
}

void SyncServiceImpl::OnAccountsInCookieUpdated(
    const signin::AccountsInCookieJarInfo& accounts_in_cookie_jar_info,
    const GoogleServiceAuthError& error) {
  OnAccountsInCookieUpdatedWithCallback(accounts_in_cookie_jar_info,
                                        base::NullCallback());
}

void SyncServiceImpl::OnPrimaryAccountChanged(
    const signin::PrimaryAccountChangeEvent& event_details) {
  if (event_details.GetEventTypeFor(signin::ConsentLevel::kSignin) !=
      signin::PrimaryAccountChangeEvent::Type::kCleared) {
    return;
  }

  MaybeClearAccountKeyedPreferences(identity_manager_,
                                    identity_manager_->GetAccountsInCookieJar(),
                                    *user_settings_);
}

void SyncServiceImpl::OnAccountsInCookieUpdatedWithCallback(
    const signin::AccountsInCookieJarInfo& accounts_in_cookie_jar_info,
    base::OnceClosure callback) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  MaybeClearAccountKeyedPreferences(
      identity_manager_, accounts_in_cookie_jar_info, *user_settings_);

  if (!engine_ || !engine_->IsInitialized()) {
    return;
  }

  bool cookie_jar_mismatch =
      HasCookieJarMismatch(accounts_in_cookie_jar_info.signed_in_accounts);
  bool cookie_jar_empty =
      accounts_in_cookie_jar_info.signed_in_accounts.empty();

  DVLOG(1) << "Cookie jar mismatch: " << cookie_jar_mismatch;
  DVLOG(1) << "Cookie jar empty: " << cookie_jar_empty;
  engine_->OnCookieJarChanged(cookie_jar_mismatch, std::move(callback));
}

bool SyncServiceImpl::HasCookieJarMismatch(
    const std::vector<gaia::ListedAccount>& cookie_jar_accounts) {
  CoreAccountId account_id = GetAccountInfo().account_id;
  // Iterate through list of accounts, looking for current sync account.
  for (const gaia::ListedAccount& account : cookie_jar_accounts) {
    if (account.id == account_id) {
      return false;
    }
  }
  return true;
}

void SyncServiceImpl::AddProtocolEventObserver(
    ProtocolEventObserver* observer) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  protocol_event_observers_.AddObserver(observer);
  if (engine_) {
    engine_->RequestBufferedProtocolEventsAndEnableForwarding();
  }
}

void SyncServiceImpl::RemoveProtocolEventObserver(
    ProtocolEventObserver* observer) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  protocol_event_observers_.RemoveObserver(observer);
  if (engine_ && protocol_event_observers_.empty()) {
    engine_->DisableProtocolEventForwarding();
  }
}

namespace {

class GetAllNodesRequestHelper
    : public base::RefCountedThreadSafe<GetAllNodesRequestHelper> {
 public:
  GetAllNodesRequestHelper(
      ModelTypeSet requested_types,
      base::OnceCallback<void(base::Value::List)> callback);

  GetAllNodesRequestHelper(const GetAllNodesRequestHelper&) = delete;
  GetAllNodesRequestHelper& operator=(const GetAllNodesRequestHelper&) = delete;

  void OnReceivedNodesForType(const ModelType type,
                              base::Value::List node_list);

 private:
  friend class base::RefCountedThreadSafe<GetAllNodesRequestHelper>;
  virtual ~GetAllNodesRequestHelper();

  base::Value::List result_accumulator_;
  ModelTypeSet awaiting_types_;
  base::OnceCallback<void(base::Value::List)> callback_;
  SEQUENCE_CHECKER(sequence_checker_);
};

GetAllNodesRequestHelper::GetAllNodesRequestHelper(
    ModelTypeSet requested_types,
    base::OnceCallback<void(base::Value::List)> callback)
    : awaiting_types_(requested_types), callback_(std::move(callback)) {}

GetAllNodesRequestHelper::~GetAllNodesRequestHelper() {
  if (!awaiting_types_.empty()) {
    DLOG(WARNING)
        << "GetAllNodesRequest deleted before request was fulfilled.  "
        << "Missing types are: " << ModelTypeSetToDebugString(awaiting_types_);
  }
}

// Called when the set of nodes for a type has been returned.
// Only return one type of nodes each time.
void GetAllNodesRequestHelper::OnReceivedNodesForType(
    const ModelType type,
    base::Value::List node_list) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // Add these results to our list.
  auto type_dict = base::Value::Dict()
                       .Set("type", ModelTypeToDebugString(type))
                       .Set("nodes", std::move(node_list));
  result_accumulator_.Append(std::move(type_dict));

  // Remember that this part of the request is satisfied.
  awaiting_types_.Remove(type);

  if (awaiting_types_.empty()) {
    std::move(callback_).Run(std::move(result_accumulator_));
  }
}

}  // namespace

void SyncServiceImpl::GetAllNodesForDebugging(
    base::OnceCallback<void(base::Value::List)> callback) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  // If the engine isn't initialized yet, then there are no nodes to return.
  if (!engine_ || !engine_->IsInitialized()) {
    std::move(callback).Run(base::Value::List());
    return;
  }

  ModelTypeSet all_types = GetActiveDataTypes();
  all_types.PutAll(ControlTypes());
  scoped_refptr<GetAllNodesRequestHelper> helper =
      new GetAllNodesRequestHelper(all_types, std::move(callback));

  for (ModelType type : all_types) {
    const auto dtc_iter = data_type_manager_->GetControllerMap().find(type);
    if (dtc_iter == data_type_manager_->GetControllerMap().end()) {
      // We should have no data type controller only for Nigori.
      DCHECK_EQ(type, NIGORI);
      engine_->GetNigoriNodeForDebugging(base::BindOnce(
          &GetAllNodesRequestHelper::OnReceivedNodesForType, helper));
      continue;
    }

    DataTypeController* controller = dtc_iter->second.get();
    if (controller->state() == DataTypeController::NOT_RUNNING) {
      // In the NOT_RUNNING state it's not allowed to call GetAllNodes on the
      // DataTypeController, so just return an empty result.
      // This can happen e.g. if we're waiting for a custom passphrase to be
      // entered - the data types are already considered active in this case,
      // but their DataTypeControllers are still NOT_RUNNING.
      helper->OnReceivedNodesForType(type, base::Value::List());
    } else {
      controller->GetAllNodes(base::BindOnce(
          &GetAllNodesRequestHelper::OnReceivedNodesForType, helper));
    }
  }
}

SyncService::ModelTypeDownloadStatus SyncServiceImpl::GetDownloadStatusFor(
    ModelType type) const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  // Download status doesn't make sense for non-real data types.
  CHECK(IsRealDataType(type));

  if (!IsLocalSyncEnabled()) {
    // TODO(crbug.com/40260679): Verify whether it's actually necessary to check
    // IsActiveAccountInfoFullyLoaded() - can the engine actually start, and
    // data types become active, if that isn't true?
    if (!auth_manager_->IsActiveAccountInfoFullyLoaded()) {
      DVLOG(1) << "Waiting for refresh tokens to be loaded from the disk";
      // GetDisableReasons() won't be empty until then.
      return ModelTypeDownloadStatus::kWaitingForUpdates;
    }

    if (auth_manager_->IsSyncPaused()) {
      DVLOG(1) << "Error download status because sync is paused";
      return ModelTypeDownloadStatus::kError;
    }
  }

  // TODO(crbug.com/40260679): check whether this works when local sync is
  // enabled.
  if (!GetDisableReasons().empty() || !GetPreferredDataTypes().Has(type)) {
    DVLOG(1)
        << "Sync or " << ModelTypeToDebugString(type)
        << " is disabled hence updates won't be downloaded from the server";
    return ModelTypeDownloadStatus::kError;
  }

  if (!engine_ || !engine_->IsInitialized()) {
    DVLOG(1) << "Waiting for the sync engine to be fully initialized";
    return ModelTypeDownloadStatus::kWaitingForUpdates;
  }

  if (data_type_manager_->GetDataTypesWithPermanentErrors().Has(type)) {
    DVLOG(1) << "Permanent error for " << ModelTypeToDebugString(type);
    return ModelTypeDownloadStatus::kError;
  }

  if (!GetActiveDataTypes().Has(type)) {
    DVLOG(1) << "Data type is not active yet";
    return ModelTypeDownloadStatus::kWaitingForUpdates;
  }

  if (!engine_->GetDetailedStatus().notifications_enabled) {
    DVLOG(1) << "Waiting for invalidations to be initialized";
    return ModelTypeDownloadStatus::kWaitingForUpdates;
  }

  // If there are any incoming invalidations or poll time elapsed, there can be
  // new updates to download from the server.
  if (engine_->GetDetailedStatus().invalidated_data_types.Has(type)) {
    DVLOG(1) << "There are incoming invalidations for: "
             << ModelTypeToDebugString(type);
    return ModelTypeDownloadStatus::kWaitingForUpdates;
  }

  // Wait for the poll request only during browser startup (i.e. when there were
  // not completed sync cycles). IsNextPollTimeInThePast() uses base::Time which
  // while poll scheduler uses base::TimeTicks. They may diverge in sleep mode
  // (TimeTicks may be paused) and it's possible that the actual timer for
  // polling will take longer. This might result in a long-standing
  // `kWaitingForUpdates` status.
  if (!HasCompletedSyncCycle() && engine_->IsNextPollTimeInThePast()) {
    DVLOG(1) << "Waiting for updates due an upcoming poll request";
    return ModelTypeDownloadStatus::kWaitingForUpdates;
  }

  return ModelTypeDownloadStatus::kUpToDate;
}

void SyncServiceImpl::OnPasswordSyncAllowedChanged() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  sync_prefs_.SetPasswordSyncAllowed(sync_client_->IsPasswordSyncAllowed());
}

void SyncServiceImpl::CacheTrustedVaultDebugInfoToPrefsFromEngine() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  CHECK(engine_);
  CHECK(engine_->IsInitialized());

  sync_prefs_.SetCachedTrustedVaultAutoUpgradeExperimentGroup(
      engine_->GetDetailedStatus()
          .trusted_vault_debug_info.auto_upgrade_experiment_group());

  RegisterTrustedVaultSyntheticFieldTrialsIfNecessary();
}

CoreAccountInfo SyncServiceImpl::GetAccountInfo() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (!auth_manager_) {
    // Some crashes on iOS (crbug.com/962384) suggest that SyncServiceImpl
    // gets called after it has been already shutdown. It's not clear why this
    // actually happens. We add this null check here to protect against such
    // crashes.
    return CoreAccountInfo();
  }
  return auth_manager_->GetActiveAccountInfo().account_info;
}

bool SyncServiceImpl::HasSyncConsent() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (!auth_manager_) {
    // This is a precautionary check to be consistent with the check in
    // GetAccountInfo().
    return false;
  }
  return auth_manager_->GetActiveAccountInfo().is_sync_consented;
}

void SyncServiceImpl::SetInvalidationsForSessionsEnabled(bool enabled) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  sessions_invalidations_enabled_ = enabled;
  UpdateDataTypesForInvalidations();
}

void SyncServiceImpl::SendExplicitPassphraseToPlatformClient() {
#if BUILDFLAG(IS_ANDROID)
  int version_code = 0;
  bool has_min_gms_version =
      base::StringToInt(
          base::android::BuildInfo::GetInstance()->gms_version_code(),
          &version_code) &&
      version_code >= kMinGmsVersionCodeWithCustomPassphraseApi;
  has_min_gms_version |= base::CommandLine::ForCurrentProcess()->HasSwitch(
      kIgnoreMinGmsVersionWithPassphraseSupportForTest);
  if (!has_min_gms_version) {
    return;
  }

  std::unique_ptr<syncer::Nigori> nigori_key =
      user_settings_->GetExplicitPassphraseDecryptionNigoriKey();
  if (!nigori_key) {
    return;
  }

  sync_pb::NigoriKey proto;
  proto.set_deprecated_name(nigori_key->GetKeyName());
  nigori_key->ExportKeys(proto.mutable_deprecated_user_key(),
                         proto.mutable_encryption_key(),
                         proto.mutable_mac_key());
  int32_t byte_size = proto.ByteSize();
  std::vector<uint8_t> bytes(byte_size);
  proto.SerializeToArray(bytes.data(), byte_size);
  JNIEnv* env = base::android::AttachCurrentThread();
  Java_ExplicitPassphrasePlatformClient_setExplicitDecryptionPassphrase(
      env, ConvertToJavaCoreAccountInfo(env, GetAccountInfo()),
      base::android::ToJavaByteArray(env, bytes));
#endif  // BUILDFLAG(IS_ANDROID)
}

void SyncServiceImpl::StopAndClear() {
  StopAndClear(ResetEngineReason::kStopAndClear);
}

void SyncServiceImpl::StopAndClear(ResetEngineReason reset_engine_reason) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  ClearUnrecoverableError();
  ResetEngine(reset_engine_reason);

  // For explicit passphrase users, clear the encryption key, such that they
  // will need to reenter it if sync gets re-enabled. Note: the gaia-keyed
  // passphrase pref should be cleared before clearing
  // InitialSyncFeatureSetupComplete().
  sync_prefs_.ClearAllEncryptionBootstrapTokens();
#if !BUILDFLAG(IS_CHROMEOS_ASH)
  // Note: ResetEngine() does *not* clear directly user-controlled prefs (such
  // as the set of selected types), so that if the user ever chooses to enable
  // Sync again, they start off with their previous settings by default.
  // However, they do have to go through the initial setup again.
  sync_prefs_.ClearInitialSyncFeatureSetupComplete();
#endif  // !BUILDFLAG(IS_CHROMEOS_ASH)
  sync_prefs_.ClearPassphrasePromptMutedProductVersion();
  // Cached information provided by SyncEngine must be cleared.
  sync_prefs_.ClearCachedPassphraseType();
  sync_prefs_.ClearCachedTrustedVaultAutoUpgradeExperimentGroup();
  // If the migration didn't finish before StopAndClear() was called, mark it as
  // done so it doesn't trigger again if the user signs in later.
  sync_prefs_.MarkPartialSyncToSigninMigrationFullyDone();

  // Also let observers know that Sync-the-feature is now fully disabled
  // (before it possibly starts up again in transport-only mode).
  DVLOG(2) << "Notify observers on StopAndClear";
  NotifyObservers();
}

void SyncServiceImpl::ReconfigureDatatypeManager(
    bool bypass_setup_in_progress_check) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (engine_ && engine_->IsInitialized()) {
    DCHECK(engine_);
    // Don't configure datatypes if the setup UI is still on the screen - this
    // is to help multi-screen setting UIs (like iOS) where they don't want to
    // start syncing data until the user is done configuring encryption options,
    // etc. ReconfigureDatatypeManager() will get called again once the last
    // SyncSetupInProgressHandle is released.
    if (CanConfigureDataTypes(bypass_setup_in_progress_check)) {
      ConfigureDataTypeManager(CONFIGURE_REASON_RECONFIGURATION);
    } else {
      DVLOG(0) << "ConfigureDataTypeManager not invoked because datatypes "
               << "cannot be configured now";
    }
  } else if (HasDisableReason(DISABLE_REASON_UNRECOVERABLE_ERROR)) {
    // There is nothing more to configure.
    DVLOG(1) << "ConfigureDataTypeManager not invoked because of an "
             << "Unrecoverable error.";
  } else {
    DVLOG(0) << "ConfigureDataTypeManager not invoked because engine is not "
             << "initialized";
  }

  // In any case, notify the observers. Whatever triggered the reconfigure
  // (attempt) might be interesting to them.
  DVLOG(2) << "Notify observers on ReconfigureDatatypeManager";
  NotifyObservers();
}

bool SyncServiceImpl::IsRetryingAccessTokenFetchForTest() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return auth_manager_->IsRetryingAccessTokenFetchForTest();
}

std::string SyncServiceImpl::GetAccessTokenForTest() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return auth_manager_->access_token();
}

SyncTokenStatus SyncServiceImpl::GetSyncTokenStatusForDebugging() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return auth_manager_->GetSyncTokenStatus();
}

void SyncServiceImpl::OverrideNetworkForTest(
    const CreateHttpPostProviderFactory& create_http_post_provider_factory_cb) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  // If the engine has already been created, then it has a copy of the previous
  // HttpPostProviderFactory creation callback. In that case, shut down and
  // recreate the engine, so that it uses the correct (overridden) callback.
  // This is a horrible hack; the proper fix would be to inject the
  // callback in the ctor instead of adding it retroactively.
  // Note that ResetEngine() can't be used here, because it would caues the
  // engine to immediately restart.
  // TODO(crbug.com/41451146): Clean this up and inject required upon
  // construction.
  bool restart = false;
  if (engine_) {
    engine_->StopSyncingForShutdown();

    data_type_manager_->Stop(SyncStopMetadataFate::KEEP_METADATA);
    data_type_manager_->SetConfigurer(nullptr);

    migrator_.reset();

    crypto_.Reset();

    engine_->Shutdown(ShutdownReason::STOP_SYNC_AND_KEEP_DATA);
    engine_.reset();

    auth_manager_->ConnectionClosed();

    restart = true;
  }
  DCHECK(!engine_);

  // If a previous request (with the wrong callback) already failed, the next
  // one would be backed off, which breaks tests. So reset the backoff.
  auth_manager_->ResetRequestAccessTokenBackoffForTest();

  create_http_post_provider_factory_cb_ = create_http_post_provider_factory_cb;

  // For allowing tests to easily reset to the default (real) callback.
  if (!create_http_post_provider_factory_cb_) {
    create_http_post_provider_factory_cb_ =
        base::BindRepeating(&CreateHttpBridgeFactory);
  }

  if (restart) {
    TryStart();
  }
}

SyncEncryptionHandler::Observer*
SyncServiceImpl::GetEncryptionObserverForTest() {
  return &crypto_;
}

void SyncServiceImpl::RemoveClientFromServer() const {
  if (!engine_ || !engine_->IsInitialized()) {
    return;
  }
  const std::string cache_guid = engine_->GetCacheGuid();
  const std::string birthday = engine_->GetBirthday();
  DCHECK(!cache_guid.empty());
  const std::string& access_token = auth_manager_->access_token();
  const bool report_sync_stopped = !access_token.empty() && !birthday.empty();
  base::UmaHistogramBoolean("Sync.SyncStoppedReported", report_sync_stopped);
  if (report_sync_stopped) {
    sync_stopped_reporter_->ReportSyncStopped(access_token, cache_guid,
                                              birthday);
  }
}

void SyncServiceImpl::RecordMemoryUsageAndCountsHistograms() {
  CHECK(engine_);
  ModelTypeSet active_types = GetActiveDataTypes();
  for (ModelType type : active_types) {
    auto dtc_it = data_type_manager_->GetControllerMap().find(type);
    if (dtc_it != data_type_manager_->GetControllerMap().end()) {
      dtc_it->second->RecordMemoryUsageAndCountsHistograms();
    } else if (type == NIGORI) {
      // DTC for NIGORI is stored in the engine on sync thread.
      engine_->RecordNigoriMemoryUsageAndCountsHistograms();
    }
  }
}

const GURL& SyncServiceImpl::GetSyncServiceUrlForDebugging() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return sync_service_url_;
}

std::string SyncServiceImpl::GetUnrecoverableErrorMessageForDebugging() const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return unrecoverable_error_message_;
}

base::Location SyncServiceImpl::GetUnrecoverableErrorLocationForDebugging()
    const {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  return unrecoverable_error_location_;
}

void SyncServiceImpl::OnSetupInProgressHandleDestroyed() {
  DCHECK_GT(outstanding_setup_in_progress_handles_, 0);

  --outstanding_setup_in_progress_handles_;

  if (engine_ && engine_->IsInitialized()) {
    // The user closed a setup UI, and will expect their changes to actually
    // take effect now. So we reconfigure here even if another setup UI happens
    // to be open right now.
    ReconfigureDatatypeManager(/*bypass_setup_in_progress_check=*/true);
  }

  DVLOG(2) << "Notify observers OnSetupInProgressHandleDestroyed";
  NotifyObservers();
}

void SyncServiceImpl::GetTypesWithUnsyncedData(
    ModelTypeSet requested_types,
    base::OnceCallback<void(ModelTypeSet)> callback) const {
  if (!base::FeatureList::IsEnabled(kGetTypesWithUnsyncedDataViaController)) {
    if (!engine_ || !engine_->IsInitialized()) {
      // TODO(crbug.com/40071018): Wait for the sync engine to be initialized.
      std::move(callback).Run(ModelTypeSet());
      return;
    }
    engine_->GetTypesWithUnsyncedData(base::BindOnce(
        [](ModelTypeSet requested_types,
           base::OnceCallback<void(ModelTypeSet)> callback,
           ModelTypeSet types) {
          std::move(callback).Run(base::Intersection(types, requested_types));
        },
        requested_types, std::move(callback)));
    return;
  }

  // NIGORI currently isn't supported, because its controller isn't managed by
  // DataTypeManager. If needed, support could be added via SyncEngine.
  CHECK(!requested_types.Has(NIGORI));

  if (requested_types.empty()) {
    base::SequencedTaskRunner::GetCurrentDefault()->PostTask(
        FROM_HERE, base::BindOnce(std::move(callback), ModelTypeSet()));
    return;
  }

  auto helper = base::MakeRefCounted<GetTypesWithUnsyncedDataRequestBarrier>(
      requested_types, std::move(callback));

  for (ModelType type : requested_types) {
    auto it = data_type_manager_->GetControllerMap().find(type);
    if (it == data_type_manager_->GetControllerMap().end()) {
      // This should be rare, but can happen e.g. if a requested type is
      // disabled via feature flag.
      helper->OnReceivedResultForType(type, /*has_unsynced_data=*/false);
      continue;
    }
    DataTypeController* controller = it->second.get();
    controller->HasUnsyncedData(base::BindOnce(
        &GetTypesWithUnsyncedDataRequestBarrier::OnReceivedResultForType,
        helper, type));
  }
}

void SyncServiceImpl::GetLocalDataDescriptions(
    ModelTypeSet types,
    base::OnceCallback<void(std::map<ModelType, LocalDataDescription>)>
        callback) {
  // Syncing users do not use separate local and account storages. Thus, there's
  // no local-only data.
  if (HasSyncConsent()) {
    std::move(callback).Run({});
    return;
  }

  // Only retain types that are not only preferred but also active, that is,
  // those which are configured and have not encountered any error.
  types.RetainAll(GetActiveDataTypes());

  types.RetainAll(GetModelTypesWithLocalDataBatchUploader());
  auto barrier_callback =
      base::BarrierCallback<std::pair<ModelType, LocalDataDescription>>(
          types.size(), base::BindOnce(&JoinAllTypesAndLocalDataDescriptions)
                            .Then(std::move(callback)));
  for (ModelType type : types) {
    data_type_manager_->GetControllerMap()
        .at(type)
        ->GetLocalDataBatchUploader()
        ->GetLocalDataDescription(
            base::BindOnce(&JoinTypeAndLocalDataDescription, type)
                .Then(barrier_callback));
  }
}

void SyncServiceImpl::TriggerLocalDataMigration(ModelTypeSet types) {
  for (ModelType type : types) {
    base::UmaHistogramEnumeration("Sync.BatchUpload.Requests3",
                                  syncer::ModelTypeHistogramValue(type));
  }

  // Syncing users do not use separate local and account storages. Thus, there's
  // no local-only data to migrate.
  if (HasSyncConsent()) {
    return;
  }

  // Only retain types that are not only preferred but also active, that is,
  // those which are configured and have not encountered any error.
  types.RetainAll(GetActiveDataTypes());

  types.RetainAll(GetModelTypesWithLocalDataBatchUploader());
  for (ModelType type : types) {
    data_type_manager_->GetControllerMap()
        .at(type)
        ->GetLocalDataBatchUploader()
        ->TriggerLocalDataMigration();
  }
}

ModelTypeSet SyncServiceImpl::GetModelTypesWithLocalDataBatchUploader() const {
  ModelTypeSet types;
  for (const auto& [type, controller] :
       data_type_manager_->GetControllerMap()) {
    if (controller->GetLocalDataBatchUploader()) {
      types.Put(type);
    }
  }
  return types;
}

}  // namespace syncer