[Sync] Implements the loopback sync server.

components/sync/engine_impl/loopback_server/loopback_server.h

Index: components/sync/engine_impl/loopback_server/loopback_server.h
diff --git a/components/sync/engine_impl/loopback_server/loopback_server.h b/components/sync/engine_impl/loopback_server/loopback_server.h
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+// Copyright 2016 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_ENGINE_IMPL_LOOPBACK_SERVER_LOOPBACK_SERVER_H_
+#define COMPONENTS_SYNC_ENGINE_IMPL_LOOPBACK_SERVER_LOOPBACK_SERVER_H_
+
+#include <stdint.h>
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/threading/thread_checker.h"
+#include "base/values.h"
+#include "components/sync/base/model_type.h"
+#include "components/sync/engine_impl/loopback_server/loopback_server_entity.h"
+#include "components/sync/engine_impl/net/server_connection_manager.h"
+#include "components/sync/protocol/loopback_server.pb.h"
+#include "components/sync/protocol/sync.pb.h"
+
+namespace syncer {
+
+// A loopback version of the Sync server used for local profile serialization.
+class LoopbackServer {
+ public:
+  LoopbackServer(const base::FilePath& persistent_file);
+  virtual ~LoopbackServer();
+
+  // Handles a /command POST (with the given |request|) to the server. Three
+  // output arguments, |server_status|, |response_code|, and |response|, are
+  // used to pass data back to the caller. The command has failed if the value
+  // pointed to by |error_code| is nonzero.
+  void HandleCommand(const std::string& request,
+                     HttpResponse::ServerConnectionCode* server_status,
+                     int64_t* response_code,
+                     std::string* response);
+
+ private:
+  using EntityMap =
+      std::map<std::string, std::unique_ptr<LoopbackServerEntity>>;
+
+  // Gets LoopbackServer ready for syncing.
+  void Init();
+
+  // Processes a GetUpdates call.
+  bool HandleGetUpdatesRequest(const sync_pb::GetUpdatesMessage& get_updates,
+                               sync_pb::GetUpdatesResponse* response);
+
+  // Processes a Commit call.
+  bool HandleCommitRequest(const sync_pb::CommitMessage& message,
+                           const std::string& invalidator_client_id,
+                           sync_pb::CommitResponse* response);
+
+  void ClearServerData();
+
+  // Creates and saves a permanent folder for Bookmarks (e.g., Bookmark Bar).
+  bool CreatePermanentBookmarkFolder(const std::string& server_tag,
+                                     const std::string& name);
+
+  // Inserts the default permanent items in |entities_|.
+  bool CreateDefaultPermanentItems();
+
+  std::string GenerateNewKeystoreKey() const;
+
+  // Saves a |entity| to |entities_|.
+  void SaveEntity(std::unique_ptr<LoopbackServerEntity> entity);
+
+  // Commits a client-side SyncEntity to the server as a LoopbackServerEntity.
+  // The client that sent the commit is identified via |client_guid|. The
+  // parent ID string present in |client_entity| should be ignored in favor
+  // of |parent_id|. If the commit is successful, the entity's server ID string
+  // is returned and a new LoopbackServerEntity is saved in |entities_|.
+  std::string CommitEntity(
+      const sync_pb::SyncEntity& client_entity,
+      sync_pb::CommitResponse_EntryResponse* entry_response,
+      const std::string& client_guid,
+      const std::string& parent_id);
+
+  // Populates |entry_response| based on the stored entity identified by
+  // |entity_id|. It is assumed that the entity identified by |entity_id| has
+  // already been stored using SaveEntity.
+  void BuildEntryResponseForSuccessfulCommit(
+      const std::string& entity_id,
+      sync_pb::CommitResponse_EntryResponse* entry_response);
+
+  // Determines whether the SyncEntity with id_string |id| is a child of an
+  // entity with id_string |potential_parent_id|.
+  bool IsChild(const std::string& id, const std::string& potential_parent_id);
+
+  // Creates and saves tombstones for all children of the entity with the given
+  // |id|. A tombstone is not created for the entity itself.
+  void DeleteChildren(const std::string& id);
+
+  // Updates the |entity| to a new version and increments the version counter
+  // that the server uses to assign versions.
+  void UpdateEntityVersion(LoopbackServerEntity* entity);
+
+  // Returns the store birthday.
+  std::string GetStoreBirthday() const;
+
+  // Serializes the server state to |proto|.
+  void SerializeState(sync_pb::LoopbackServerProto* proto) const;
+
+  // Populates the server state from |proto|. Returns true iff successful.
+  bool DeSerializeState(const sync_pb::LoopbackServerProto& proto);
+
+  // Saves all entities and server state to a protobuf file in |filename|.
+  bool SaveStateToFile(const base::FilePath& filename) const;
+
+  // Loads all entities and server state from a protobuf file in |filename|.
+  bool LoadStateFromFile(const base::FilePath& filename);
+
+  // This is the last version number assigned to an entity. The next entity will
+  // have a version number of version_ + 1.
+  int64_t version_;
+
+  int64_t store_birthday_;
+
+  EntityMap entities_;
+  std::vector<std::string> keystore_keys_;
+
+  // The file used to store the local sync data.
+  base::FilePath persistent_file_;
+
+  // Used to verify that LoopbackServer is only used from one thread.
+  base::ThreadChecker thread_checker_;
+};
+
+}  // namespace syncer
+
+#endif  // COMPONENTS_SYNC_ENGINE_IMPL_LOOPBACK_SERVER_LOOPBACK_SERVER_H_