// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SYNC_SESSIONS_SESSION_SYNC_BRIDGE_H_
#define COMPONENTS_SYNC_SESSIONS_SESSION_SYNC_BRIDGE_H_

#include <memory>
#include <string>

#include "base/callback_forward.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "components/sync/model/model_error.h"
#include "components/sync/model/model_type_store.h"
#include "components/sync/model/model_type_sync_bridge.h"
#include "components/sync_sessions/favicon_cache.h"
#include "components/sync_sessions/local_session_event_handler_impl.h"
#include "components/sync_sessions/open_tabs_ui_delegate_impl.h"
#include "components/sync_sessions/session_store.h"
#include "components/sync_sessions/sessions_global_id_mapper.h"

namespace sync_sessions {

class LocalSessionEventRouter;
class SyncSessionsClient;

// Sync bridge implementation for SESSIONS model type. Takes care of propagating
// local sessions to other clients as well as providing a representation of
// foreign sessions.
//
// This is achieved by implementing the interface ModelTypeSyncBridge, which
// ClientTagBasedModelTypeProcessor will use to interact, ultimately, with the
// sync server. See
// https://chromium.googlesource.com/chromium/src/+/lkcr/docs/sync/model_api.md#Implementing-ModelTypeSyncBridge
// for details.
class SessionSyncBridge : public syncer::ModelTypeSyncBridge,
                          public LocalSessionEventHandlerImpl::Delegate {
 public:
  // Raw pointers must not be null and their pointees must outlive this object.
  SessionSyncBridge(
      const base::RepeatingClosure& notify_foreign_session_updated_cb,
      SyncSessionsClient* sessions_client,
      std::unique_ptr<syncer::ModelTypeChangeProcessor> change_processor);
  ~SessionSyncBridge() override;

  FaviconCache* GetFaviconCache();
  SessionsGlobalIdMapper* GetGlobalIdMapper();
  OpenTabsUIDelegate* GetOpenTabsUIDelegate();

  // ModelTypeSyncBridge implementation.
  void OnSyncStarting(
      const syncer::DataTypeActivationRequest& request) override;
  std::unique_ptr<syncer::MetadataChangeList> CreateMetadataChangeList()
      override;
  base::Optional<syncer::ModelError> MergeSyncData(
      std::unique_ptr<syncer::MetadataChangeList> metadata_change_list,
      syncer::EntityChangeList entity_data) override;
  base::Optional<syncer::ModelError> ApplySyncChanges(
      std::unique_ptr<syncer::MetadataChangeList> metadata_change_list,
      syncer::EntityChangeList entity_changes) override;
  void GetData(StorageKeyList storage_keys, DataCallback callback) override;
  void GetAllDataForDebugging(DataCallback callback) override;
  std::string GetClientTag(const syncer::EntityData& entity_data) override;
  std::string GetStorageKey(const syncer::EntityData& entity_data) override;
  void ApplyStopSyncChanges(std::unique_ptr<syncer::MetadataChangeList>
                                delete_metadata_change_list) override;

  // LocalSessionEventHandlerImpl::Delegate implementation.
  std::unique_ptr<LocalSessionEventHandlerImpl::WriteBatch>
  CreateLocalSessionWriteBatch() override;
  bool IsTabNodeUnsynced(int tab_node_id) override;
  void TrackLocalNavigationId(base::Time timestamp, int unique_id) override;
  void OnPageFaviconUpdated(const GURL& page_url) override;
  void OnFaviconVisited(const GURL& page_url, const GURL& favicon_url) override;

 private:
  void OnStoreInitialized(
      const base::Optional<syncer::ModelError>& error,
      std::unique_ptr<SessionStore> store,
      std::unique_ptr<syncer::MetadataBatch> metadata_batch);
  void StartLocalSessionEventHandler();
  void DeleteForeignSessionFromUI(const std::string& tag);
  void DoGarbageCollection(SessionStore::WriteBatch* write_batch);
  std::unique_ptr<SessionStore::WriteBatch> CreateSessionStoreWriteBatch();
  void DeleteForeignSessionWithBatch(const std::string& session_tag,
                                     SessionStore::WriteBatch* batch);
  void ResubmitLocalSession();
  void ReportError(const syncer::ModelError& error);

  const base::RepeatingClosure notify_foreign_session_updated_cb_;
  SyncSessionsClient* const sessions_client_;
  LocalSessionEventRouter* const local_session_event_router_;

  FaviconCache favicon_cache_;
  SessionsGlobalIdMapper global_id_mapper_;
  std::unique_ptr<SessionStore> store_;

  // All data dependent on sync being starting or started.
  struct SyncingState {
    SyncingState();
    ~SyncingState();

    std::unique_ptr<OpenTabsUIDelegateImpl> open_tabs_ui_delegate;
    std::unique_ptr<LocalSessionEventHandlerImpl> local_session_event_handler;

    // Tracks whether our local representation of which sync nodes map to what
    // tabs (belonging to the current local session) is inconsistent.  This can
    // happen if a foreign client deems our session as "stale" and decides to
    // delete it. Rather than respond by bullishly re-creating our nodes
    // immediately, which could lead to ping-pong sequences, we give the benefit
    // of the doubt and hold off until another local navigation occurs, which
    // proves that we are still relevant.
    bool local_data_out_of_sync = false;
  };

  // TODO(mastiz): We should rather rename this to |syncing_state_|.
  base::Optional<SyncingState> syncing_;

  base::WeakPtrFactory<SessionSyncBridge> weak_ptr_factory_{this};

  DISALLOW_COPY_AND_ASSIGN(SessionSyncBridge);
};

}  // namespace sync_sessions

#endif  // COMPONENTS_SYNC_SESSIONS_SESSION_SYNC_BRIDGE_H_