// Copyright 2012 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_SYNCED_SESSION_TRACKER_H_
#define COMPONENTS_SYNC_SESSIONS_SYNCED_SESSION_TRACKER_H_

#include <stddef.h>

#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>

#include "base/macros.h"
#include "components/sessions/core/session_id.h"
#include "components/sessions/core/session_types.h"
#include "components/sync_sessions/synced_session.h"
#include "components/sync_sessions/tab_node_pool.h"

namespace sync_sessions {

class SyncSessionsClient;

// Class to manage synced sessions. The tracker will own all SyncedSession
// and SyncedSessionTab objects it creates, and deletes them appropriately on
// destruction.
//
// Note: SyncedSession objects are created for all synced sessions, including
// the local session (whose tag we maintain separately).
class SyncedSessionTracker {
 public:
  // Different ways to lookup/filter tabs.
  enum SessionLookup {
    RAW,         // Return all foreign sessions.
    PRESENTABLE  // Have one window with at least one tab with syncable content.
  };

  explicit SyncedSessionTracker(SyncSessionsClient* sessions_client);
  ~SyncedSessionTracker();

  // We track and distinguish the local session from foreign sessions.
  void SetLocalSessionTag(const std::string& local_session_tag);

  // Fill a preallocated vector with all foreign sessions we're tracking (skips
  // the local session object). SyncedSession ownership remains within the
  // SyncedSessionTracker. Lookup parameter is used to decide which foreign tabs
  // should be include.
  // Returns true if we had foreign sessions to fill it with, false otherwise.
  bool LookupAllForeignSessions(std::vector<const SyncedSession*>* sessions,
                                SessionLookup lookup) const;

  // Attempts to look up the session windows associatd with the session given
  // by |session_tag|. Ownership of SessionWindows stays within the
  // SyncedSessionTracker.
  // If lookup succeeds:
  // - Fills windows with the SessionWindow pointers, returns true.
  // Else
  // - Returns false.
  bool LookupSessionWindows(
      const std::string& session_tag,
      std::vector<const sessions::SessionWindow*>* windows) const;

  // Attempts to look up the tab associated with the given tag and tab id.
  // Ownership of the SessionTab remains within the SyncedSessionTracker.
  // If lookup succeeds:
  // - Sets tab to point to the SessionTab, and returns true.
  // Else
  // - Returns false, tab is set to null.
  bool LookupSessionTab(const std::string& session_tag,
                        SessionID::id_type tab_id,
                        const sessions::SessionTab** tab) const;

  // Allows retrieval of existing data for the local session. Unlike GetSession
  // this won't create-if-not-present.
  bool LookupLocalSession(const SyncedSession** output) const;

  // Returns a pointer to the SyncedSession object associated with
  // |session_tag|. If none exists, creates one. Ownership of the
  // SyncedSession remains within the SyncedSessionTracker.
  SyncedSession* GetSession(const std::string& session_tag);

  // Deletes the session associated with |session_tag| if it exists.
  // Returns true if the session existed and was deleted, false otherwise.
  bool DeleteSession(const std::string& session_tag);

  // Resets the tracking information for the session specified by |session_tag|.
  // This involves clearing all the windows and tabs from the session, while
  // keeping pointers saved in the synced_window_map_ and synced_tab_map_. Once
  // reset, all calls to PutWindowInSession and PutTabInWindow will denote that
  // the requested windows and tabs are owned and add them back to their
  // session. The next call to CleanupSession(...) will delete those windows and
  // tabs not owned.
  void ResetSessionTracking(const std::string& session_tag);

  // Tracks the deletion of a foreign tab by removing the given |tab_node_id|
  // from the parent session. Doesn't actually remove any tab objects because
  // the header may have or may not have already been updated to no longer
  // parent this tab. Regardless, when the header is updated then cleanup will
  // remove the actual tab data. However, this method always needs to be called
  // upon foreign tab deletion, otherwise LookupTabNodeIds(...) may return
  // already deleted tab node ids.
  void DeleteForeignTab(const std::string& session_tag, int tab_node_id);

  // Deletes those windows and tabs associated with |session_tag| that are no
  // longer owned. See ResetSessionTracking(...).
  void CleanupSession(const std::string& session_tag);

  // Adds the window with id |window_id| to the session specified by
  // |session_tag|. If none existed for that session, creates one. Similarly, if
  // the session did not exist yet, creates it. Ownership of the SessionWindow
  // remains within the SyncedSessionTracker.
  void PutWindowInSession(const std::string& session_tag,
                          SessionID::id_type window_id);

  // Adds the tab with id |tab_id| to the window |window_id|. If none existed
  // for that session, creates one. Ownership of the SessionTab remains within
  // the SyncedSessionTracker.
  //
  // Note: GetSession(..) must have already been called with |session_tag| to
  // ensure we having mapping information for this session.
  void PutTabInWindow(const std::string& session_tag,
                      SessionID::id_type window_id,
                      SessionID::id_type tab_id,
                      size_t tab_index);

  // Returns a pointer to the SessionTab object associated with |tab_id| for
  // the session specified with |session_tag|. If none exists, creates one.
  // Ownership of the SessionTab remains within the SyncedSessionTracker.
  // |tab_node_id| must be a valid node id for the node backing this tab.
  sessions::SessionTab* GetTab(const std::string& session_tag,
                               SessionID::id_type tab_id,
                               int tab_node_id);

  // Fills |tab_node_ids| with the tab node ids (see GetTab) for all the tabs*
  // associated with the session having tag |session_tag|.
  void LookupTabNodeIds(const std::string& session_tag,
                        std::set<int>* tab_node_ids);

  // Free the memory for all dynamically allocated objects and clear the
  // tracking structures.
  void Clear();

  bool Empty() const {
    return synced_tab_map_.empty() && synced_session_map_.empty();
  }

  // Includes both foreign sessions and the local session.
  size_t num_synced_sessions() const { return synced_session_map_.size(); }

  // Returns the number of tabs associated with the specified session tag.
  size_t num_synced_tabs(const std::string& session_tag) const {
    auto iter = synced_tab_map_.find(session_tag);
    if (iter != synced_tab_map_.end()) {
      return iter->second.size();
    } else {
      return 0;
    }
  }

 private:
  // Implementation for GetTab(...) above, permits invalid tab_node_id.
  sessions::SessionTab* GetTabImpl(const std::string& session_tag,
                                   SessionID::id_type tab_id,
                                   int tab_node_id);

  // The client of the sync sessions datatype.
  SyncSessionsClient* const sessions_client_;

  // The mapping of tab/window ids to their SessionTab/SessionWindow objects.
  // The SessionTab/SessionWindow objects referred to may be owned either by the
  // session in the |synced_session_map_| or be temporarily unmapped and live in
  // the |unmapped_tabs_|/|unmapped_windows_| collections.
  //
  // Map: session tag -> (tab/window id -> SessionTab*/SessionWindow*)
  std::map<std::string, std::map<SessionID::id_type, sessions::SessionTab*>>
      synced_tab_map_;
  std::map<std::string, std::map<SessionID::id_type, sessions::SessionWindow*>>
      synced_window_map_;

  // The collection that owns the SyncedSessions, and transitively, all of the
  // windows and tabs they contain.
  //
  // Map: session tag -> owned SyncedSession
  std::map<std::string, std::unique_ptr<SyncedSession>> synced_session_map_;

  // The collection of tabs/windows not owned by a SyncedSession. This is the
  // case either because 1. (in the case of tabs) they were newly created by
  // GetTab() and not yet added to a session, or 2. they were removed from their
  // owning session by a call to ResetSessionTracking() and not yet added back.
  //
  // Map: session tag -> (tab/window id -> owned SessionTab/SessionWindow)
  std::map<std::string,
           std::map<SessionID::id_type, std::unique_ptr<sessions::SessionTab>>>
      unmapped_tabs_;
  std::map<
      std::string,
      std::map<SessionID::id_type, std::unique_ptr<sessions::SessionWindow>>>
      unmapped_windows_;

  // The tag for this machine's local session, so we can distinguish the foreign
  // sessions.
  std::string local_session_tag_;

  DISALLOW_COPY_AND_ASSIGN(SyncedSessionTracker);
};

}  // namespace sync_sessions

#endif  // COMPONENTS_SYNC_SESSIONS_SYNCED_SESSION_TRACKER_H_