text: // Copyright 2014 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_SESSIONS_SYNC_MANAGER_H_
  #define COMPONENTS_SYNC_SESSIONS_SESSIONS_SYNC_MANAGER_H_
  
  #include <stddef.h>
  
  #include <map>
  #include <memory>
  #include <set>
  #include <string>
  #include <vector>
  
  #include "base/callback_forward.h"
  #include "base/gtest_prod_util.h"
  #include "base/macros.h"
  #include "base/memory/weak_ptr.h"
  #include "base/time/time.h"
  #include "components/sessions/core/session_id.h"
  #include "components/sessions/core/session_types.h"
  #include "components/sync/base/sync_prefs.h"
  #include "components/sync/device_info/device_info.h"
  #include "components/sync/model/syncable_service.h"
  #include "components/sync_sessions/favicon_cache.h"
  #include "components/sync_sessions/local_session_event_router.h"
  #include "components/sync_sessions/lost_navigations_recorder.h"
  #include "components/sync_sessions/open_tabs_ui_delegate.h"
  #include "components/sync_sessions/revisit/page_revisit_broadcaster.h"
  #include "components/sync_sessions/synced_session.h"
  #include "components/sync_sessions/synced_session_tracker.h"
  #include "components/sync_sessions/tab_node_pool.h"
  
  namespace syncer {
  class LocalDeviceInfoProvider;
  class SyncErrorFactory;
  class SyncPrefs;
  }  // namespace syncer
  
  namespace sync_pb {
  class SessionHeader;
  class SessionSpecifics;
  class SessionTab;
  class SessionWindow;
  class TabNavigation;
  }  // namespace sync_pb
  
  namespace extensions {
  class ExtensionSessionsTest;
  }  // namespace extensions
  
  namespace sync_sessions {
  
  class SyncedTabDelegate;
  class SyncedWindowDelegatesGetter;
  
  // Contains all logic for associating the Chrome sessions model and
  // the sync sessions model.
  class SessionsSyncManager : public syncer::SyncableService,
                              public OpenTabsUIDelegate,
                              public LocalSessionEventHandler {
   public:
    SessionsSyncManager(SyncSessionsClient* sessions_client,
                        syncer::SyncPrefs* sync_prefs,
                        syncer::LocalDeviceInfoProvider* local_device,
                        std::unique_ptr<LocalSessionEventRouter> router,
                        const base::Closure& sessions_updated_callback,
                        const base::Closure& datatype_refresh_callback);
    ~SessionsSyncManager() override;
  
    // syncer::SyncableService implementation.
    syncer::SyncMergeResult MergeDataAndStartSyncing(
        syncer::ModelType type,
        const syncer::SyncDataList& initial_sync_data,
        std::unique_ptr<syncer::SyncChangeProcessor> sync_processor,
        std::unique_ptr<syncer::SyncErrorFactory> error_handler) override;
    void StopSyncing(syncer::ModelType type) override;
    syncer::SyncDataList GetAllSyncData(syncer::ModelType type) const override;
    syncer::SyncError ProcessSyncChanges(
        const tracked_objects::Location& from_here,
        const syncer::SyncChangeList& change_list) override;
  
    // OpenTabsUIDelegate implementation.
    bool GetSyncedFaviconForPageURL(
        const std::string& pageurl,
        scoped_refptr<base::RefCountedMemory>* favicon_png) const override;
    bool GetAllForeignSessions(
        std::vector<const SyncedSession*>* sessions) override;
    bool GetForeignSession(
        const std::string& tag,
        std::vector<const sessions::SessionWindow*>* windows) override;
    bool GetForeignTab(const std::string& tag,
                       SessionID::id_type tab_id,
                       const sessions::SessionTab** tab) override;
    bool GetForeignSessionTabs(
        const std::string& tag,
        std::vector<const sessions::SessionTab*>* tabs) override;
    void DeleteForeignSession(const std::string& tag) override;
    bool GetLocalSession(const SyncedSession** local_session) override;
  
    // LocalSessionEventHandler implementation.
    void OnLocalTabModified(SyncedTabDelegate* modified_tab) override;
    void OnFaviconsChanged(const std::set<GURL>& page_urls,
                           const GURL& icon_url) override;
  
    // Returns the tag used to uniquely identify this machine's session in the
    // sync model.
    const std::string& current_machine_tag() const {
      DCHECK(!current_machine_tag_.empty());
      return current_machine_tag_;
    }
  
    FaviconCache* GetFaviconCache();
  
    // Triggers garbage collection of stale sessions (as defined by
    // |stale_session_threshold_days_|). This is called every time we see new
    // sessions data downloaded (sync cycles complete).
    void DoGarbageCollection();
  
   private:
    // Keep all the links to local tab data in one place. A tab_node_id and tab
    // must be passed at creation. The tab_node_id is not mutable, although
    // all other fields are.
    class TabLink {
     public:
      TabLink(int tab_node_id, const SyncedTabDelegate* tab)
          : tab_node_id_(tab_node_id), tab_(tab) {}
  
      void set_tab(const SyncedTabDelegate* tab) { tab_ = tab; }
      void set_url(const GURL& url) { url_ = url; }
  
      int tab_node_id() const { return tab_node_id_; }
      const SyncedTabDelegate* tab() const { return tab_; }
      const GURL& url() const { return url_; }
  
     private:
      // The id for the sync node this tab is stored in.
      const int tab_node_id_;
  
      // The tab object itself.
      const SyncedTabDelegate* tab_;
  
      // The currently visible url of the tab (used for syncing favicons).
      GURL url_;
  
      DISALLOW_COPY_AND_ASSIGN(TabLink);
    };
  
    // Container for accessing local tab data by tab id.
    typedef std::map<SessionID::id_type, linked_ptr<TabLink>> TabLinksMap;
  
    friend class extensions::ExtensionSessionsTest;
    friend class SessionsSyncManagerTest;
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, PopulateSessionHeader);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, PopulateSessionWindow);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, ValidTabs);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, SetSessionTabFromDelegate);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             SetSessionTabFromDelegateNavigationIndex);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             SetSessionTabFromDelegateCurrentInvalid);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, BlockedNavigations);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, DeleteForeignSession);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             ProcessForeignDeleteTabsWithShadowing);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             ProcessForeignDeleteTabsWithReusedNodeIds);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             SaveUnassociatedNodesForReassociation);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, MergeDeletesCorruptNode);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, MergeDeletesBadHash);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             MergeLocalSessionExistingTabs);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             CheckPrerenderedWebContentsSwap);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             AssociateWindowsDontReloadTabs);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, SwappedOutOnRestore);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                             ProcessRemoteDeleteOfLocalSession);
    FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, SetVariationIds);
  
    void InitializeCurrentMachineTag();
  
    // Load and add window or tab data for a foreign session to our internal
    // tracking.
    void UpdateTrackerWithForeignSession(
        const sync_pb::SessionSpecifics& specifics,
        const base::Time& modification_time);
  
    // Returns true if |sync_data| contained a header node for the current
    // machine, false otherwise. |restored_tabs| is a filtered tab-only
    // subset of |sync_data| returned by this function for convenience.
    // |new_changes| is a link to the SyncChange pipeline that exists in the
    // caller's context. This function will append necessary changes for
    // processing later.
    bool InitFromSyncModel(const syncer::SyncDataList& sync_data,
                           syncer::SyncDataList* restored_tabs,
                           syncer::SyncChangeList* new_changes);
  
    // Helper to construct a deletion SyncChange for a *tab node*.
    // Caller should check IsValid() on the returned change, as it's possible
    // this node could not be deleted.
    syncer::SyncChange TombstoneTab(const sync_pb::SessionSpecifics& tab);
  
    // Helper method to load the favicon data from the tab specifics. If the
    // favicon is valid, stores the favicon data into the favicon cache.
    void RefreshFaviconVisitTimesFromForeignTab(
        const sync_pb::SessionTab& tab,
        const base::Time& modification_time);
  
    // Removes a foreign session from our internal bookkeeping.
    // Returns true if the session was found and deleted, false if no data was
    // found for that session.  This will *NOT* trigger sync deletions. See
    // DeleteForeignSession below.
    bool DisassociateForeignSession(const std::string& foreign_session_tag);
  
    // Delete a foreign session and all its sync data.
    // |change_output| *must* be provided as a link to the SyncChange pipeline
    // that exists in the caller's context. This function will append necessary
    // changes for processing later.
    void DeleteForeignSessionInternal(const std::string& tag,
                                      syncer::SyncChangeList* change_output);
  
    // Used to populate a session header from the session specifics header
    // provided.
    static void PopulateSessionHeaderFromSpecifics(
        const sync_pb::SessionHeader& header_specifics,
        base::Time mtime,
        SyncedSession* session_header);
  
    // Builds |session_window| from the session specifics window
    // provided and updates the SessionTracker with foreign session data created.
    void BuildSyncedSessionFromSpecifics(const std::string& session_tag,
                                         const sync_pb::SessionWindow& specifics,
                                         base::Time mtime,
                                         sessions::SessionWindow* session_window);
  
    // Resync local window information. Updates the local sessions header node
    // with the status of open windows and the order of tabs they contain. Should
    // only be called for changes that affect a window, not a change within a
    // single tab.
    //
    // RELOAD_TABS will additionally cause a resync of all tabs (same as calling
    // AssociateTabs with a vector of all tabs).
    //
    // |restored_tabs| is a filtered tab-only subset of initial sync data, if
    // available (during MergeDataAndStartSyncing). It can be used to obtain
    // baseline SessionSpecifics for tabs we can't fully associate any other
    // way because they don't yet have a WebContents.
    //
    // Returns: false if the local session's sync nodes were deleted and
    // reassociation is necessary, true otherwise.
    //
    // |change_output| *must* be provided as a link to the SyncChange pipeline
    // that exists in the caller's context. This function will append necessary
    // changes for processing later.
    enum ReloadTabsOption { RELOAD_TABS, DONT_RELOAD_TABS };
    void AssociateWindows(ReloadTabsOption option,
                          const syncer::SyncDataList& restored_tabs,
                          syncer::SyncChangeList* change_output);
  
    // Loads and reassociates the local tabs referenced in |tabs|.
    // |change_output| *must* be provided as a link to the SyncChange pipeline
    // that exists in the caller's context. This function will append necessary
    // changes for processing later.
    void AssociateTab(SyncedTabDelegate* const tab,
                      syncer::SyncChangeList* change_output);
  
    // Set |session_tab| from |tab_delegate| and |mtime|.
    void SetSessionTabFromDelegate(const SyncedTabDelegate& tab_delegate,
                                   base::Time mtime,
                                   sessions::SessionTab* session_tab);
  
    // Sets |variation_ids| field of |session_tab| with the ids of the currently
    // assigned variations which should be sent to sync.
    static void SetVariationIds(sessions::SessionTab* session_tab);
  
    // Populates |specifics| based on the data in |tab_delegate|.
    void LocalTabDelegateToSpecifics(const SyncedTabDelegate& tab_delegate,
                                     sync_pb::SessionSpecifics* specifics);
  
    // It's possible that when we associate windows, tabs aren't all loaded
    // into memory yet (e.g on android) and we don't have a WebContents. In this
    // case we can't do a full association, but we still want to update tab IDs
    // as they may have changed after a session was restored.  This method
    // compares new_tab_id and new_window_id against the previously persisted tab
    // ID and window ID (from our TabNodePool) and updates them if either differs.
    // |restored_tabs| is a filtered tab-only subset of initial sync data, if
    // available (during MergeDataAndStartSyncing). It can be used to obtain
    // baseline SessionSpecifics for tabs we can't fully associate any other
    // way because they don't yet have a WebContents.
    // TODO(tim): Bug 98892. We should be able to test this for this on android
    // even though we didn't have tests for old API-based sessions sync.
    void AssociateRestoredPlaceholderTab(
        const SyncedTabDelegate& tab_delegate,
        SessionID::id_type new_tab_id,
        SessionID::id_type new_window_id,
        const syncer::SyncDataList& restored_tabs,
        syncer::SyncChangeList* change_output);
  
    // Stops and re-starts syncing to rebuild association mappings.
    // See |local_tab_pool_out_of_sync_|.
    void RebuildAssociations();
  
    // Validates the content of a SessionHeader protobuf.
    // Returns false if validation fails.
    static bool IsValidSessionHeader(const sync_pb::SessionHeader& header);
  
    // Calculates the tag hash from a specifics object. Calculating the hash is
    // something we typically want to avoid doing in the model type like this.
    // However, the only place that understands how to generate a tag from the
    // specifics is the model type, ie us. We need to generate the tag because it
    // is not passed over the wire for remote data. The use case this function was
    // created for is detecting bad tag hashes from remote data, see
    // crbug.com/604657.
    static std::string TagHashFromSpecifics(
        const sync_pb::SessionSpecifics& specifics);
  
    SyncedWindowDelegatesGetter* synced_window_delegates_getter() const;
  
    // The client of this sync sessions datatype.
    SyncSessionsClient* const sessions_client_;
  
    // Mapping of current open (local) tabs to their sync identifiers.
    TabLinksMap local_tab_map_;
  
    SyncedSessionTracker session_tracker_;
    FaviconCache favicon_cache_;
  
    // Pool of used/available sync nodes associated with local tabs.
    TabNodePool local_tab_pool_;
  
    // 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_tab_pool_out_of_sync_;
  
    syncer::SyncPrefs* sync_prefs_;
  
    std::unique_ptr<syncer::SyncErrorFactory> error_handler_;
    std::unique_ptr<syncer::SyncChangeProcessor> sync_processor_;
  
    // Local device info provider, owned by ProfileSyncService.
    const syncer::LocalDeviceInfoProvider* const local_device_;
  
    // Unique client tag.
    std::string current_machine_tag_;
  
    // User-visible machine name.
    std::string current_session_name_;
  
    // SyncID for the sync node containing all the window information for this
    // client.
    int local_session_header_node_id_;
  
    // Number of days without activity after which we consider a session to be
    // stale and a candidate for garbage collection.
    int stale_session_threshold_days_;
  
    std::unique_ptr<LocalSessionEventRouter> local_event_router_;
  
    // Owns revisiting instrumentation logic for page visit events.
    PageRevisitBroadcaster page_revisit_broadcaster_;
  
    std::unique_ptr<sync_sessions::LostNavigationsRecorder>
        lost_navigations_recorder_;
  
    // Callback to inform interested observer that new sessions data has arrived.
    base::Closure sessions_updated_callback_;
  
    // Callback to inform sync that a sync data refresh is requested.
    base::Closure datatype_refresh_callback_;
  
    DISALLOW_COPY_AND_ASSIGN(SessionsSyncManager);
  };
  
  }  // namespace sync_sessions
  
  #endif  // COMPONENTS_SYNC_SESSIONS_SESSIONS_SYNC_MANAGER_H_
  