Componentize tab_node_pool to sync_driver

chrome/browser/sync/sessions/tab_node_pool.h

-// 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 CHROME_BROWSER_SYNC_SESSIONS_TAB_NODE_POOL_H_
-#define CHROME_BROWSER_SYNC_SESSIONS_TAB_NODE_POOL_H_
-
-#include <map>
-#include <set>
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/gtest_prod_util.h"
-#include "components/sessions/session_id.h"
-#include "sync/api/sync_change_processor.h"
-
-namespace syncer {
-class SyncChangeProcessor;
-}
-
-namespace browser_sync {
-
-// A pool for managing free/used tab sync nodes for the *local* session.
-// Performs lazy creation of sync nodes when necessary.
-// Note: We make use of the following "id's"
-// - a tab_id: created by session service, unique to this client
-// - a tab_node_id: the id for a particular sync tab node. This is used
-//   to generate the sync tab node tag through:
-//       tab_tag = StringPrintf("%s_%ui", local_session_tag, tab_node_id);
-//
-// A sync node can be in one of the three states:
-// 1. Associated   : Sync node is used and associated with a tab.
-// 2. Unassociated : Sync node is used but currently unassociated with any tab.
-//                   This is true for old nodes that remain from a session
-//                   restart. Nodes are only unassociated temporarily while the
-//                   model associator figures out which tabs belong to which
-//                   nodes. Eventually any remaining unassociated nodes are
-//                   freed.
-// 3. Free         : Sync node is unused.
-
-class TabNodePool {
- public:
-   TabNodePool();
-  ~TabNodePool();
-  enum InvalidTab {
-    kInvalidTabID = -1
-  };
-
-  // If free nodes > kFreeNodesHighWatermark, delete all free nodes until
-  // free nodes <= kFreeNodesLowWatermark.
-  static const size_t kFreeNodesLowWatermark;
-
-  // Maximum limit of FreeNodes allowed on the client.
-  static const size_t kFreeNodesHighWatermark;
-
-  static const int kInvalidTabNodeID;
-
-  // Build a sync tag from tab_node_id.
-  static std::string TabIdToTag(const std::string machine_tag,
-                                int tab_node_id);
-
-  // Returns the tab_node_id for the next free tab node. If none are available,
-  // creates a new tab node and adds it to free nodes pool. The free node can
-  // then be used to associate with a tab by calling AssociateTabNode.
-  // Note: The node is considered free until it has been associated. Repeated
-  // calls to GetFreeTabNode will return the same id until node has been
-  // associated.
-  // |change_output| *must* be provided. It is the TabNodePool's link to
-  // the SyncChange pipeline that exists in the caller context. If the need
-  // to create nodes arises in the implementation, associated SyncChanges will
-  // be appended to this list for later application by the caller via the
-  // SyncChangeProcessor.
-  int GetFreeTabNode(syncer::SyncChangeList* change_output);
-
-  // Removes association for |tab_node_id| and returns it to the free node pool.
-  // |change_output| *must* be provided. It is the TabNodePool's link to
-  // the SyncChange pipeline that exists in the caller's context. If the need
-  // to delete sync nodes arises in the implementation, associated SyncChanges
-  // will be appended to this list for later application by the caller via the
-  // SyncChangeProcessor.
-  void FreeTabNode(int tab_node_id, syncer::SyncChangeList* change_output);
-
-  // Associates |tab_node_id| with |tab_id|. |tab_node_id| should either be
-  // unassociated or free. If |tab_node_id| is free, |tab_node_id| is removed
-  // from the free node pool In order to associate a non free sync node,
-  // use ReassociateTabNode.
-  void AssociateTabNode(int tab_node_id, SessionID::id_type tab_id);
-
-  // Adds |tab_node_id| as an unassociated sync node.
-  // Note: this should only be called when we discover tab sync nodes from
-  // previous sessions, not for freeing tab nodes we created through
-  // GetFreeTabNode (use FreeTabNode below for that).
-  void AddTabNode(int tab_node_id);
-
-  // Returns the tab_id for |tab_node_id| if it is associated else returns
-  // kInvalidTabID.
-  SessionID::id_type GetTabIdFromTabNodeId(int tab_node_id) const;
-
-  // Reassociates |tab_node_id| with |tab_id|. |tab_node_id| must be either
-  // associated with a tab or in the set of unassociated nodes.
-  void ReassociateTabNode(int tab_node_id, SessionID::id_type tab_id);
-
-  // Returns true if |tab_node_id| is an unassociated tab node.
-  bool IsUnassociatedTabNode(int tab_node_id);
-
-  // Returns any unassociated nodes to the free node pool.
-  // |change_output| *must* be provided. It is the TabNodePool's link to
-  // the SyncChange pipeline that exists in the caller's context.
-  // See FreeTabNode for more detail.
-  void DeleteUnassociatedTabNodes(syncer::SyncChangeList* change_output);
-
-  // Clear tab pool.
-  void Clear();
-
-  // Return the number of tab nodes this client currently has allocated
-  // (including both free, unassociated and associated nodes)
-  size_t Capacity() const;
-
-  // Return empty status (all tab nodes are in use).
-  bool Empty() const;
-
-  // Return full status (no tab nodes are in use).
-  bool Full();
-
-  void SetMachineTag(const std::string& machine_tag);
-
- private:
-  friend class SyncTabNodePoolTest;
-  typedef std::map<int, SessionID::id_type> TabNodeIDToTabIDMap;
-
-  // Adds |tab_node_id| to free node pool.
-  // |change_output| *must* be provided. It is the TabNodePool's link to
-  // the SyncChange pipeline that exists in the caller's context.
-  // See FreeTabNode for more detail.
-  void FreeTabNodeInternal(int tab_node_id,
-                           syncer::SyncChangeList* change_output);
-
-  // Stores mapping of node ids associated with tab_ids, these are the used
-  // nodes of tab node pool.
-  // The nodes in the map can be returned to free tab node pool by calling
-  // FreeTabNode(tab_node_id).
-  TabNodeIDToTabIDMap nodeid_tabid_map_;
-
-  // The node ids for the set of free sync nodes.
-  std::set<int> free_nodes_pool_;
-
-  // The node ids that are added to pool using AddTabNode and are currently
-  // not associated with any tab. They can be reassociated using
-  // ReassociateTabNode.
-  std::set<int> unassociated_nodes_;
-
-  // The maximum used tab_node id for a sync node. A new sync node will always
-  // be created with max_used_tab_node_id_ + 1.
-  int max_used_tab_node_id_;
-
-  // The machine tag associated with this tab pool. Used in the title of new
-  // sync nodes.
-  std::string machine_tag_;
-
-  DISALLOW_COPY_AND_ASSIGN(TabNodePool);
-};
-
-}  // namespace browser_sync
-
-#endif  // CHROME_BROWSER_SYNC_SESSIONS_TAB_NODE_POOL_H_