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// 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 SYNC_ENGINE_ENTITY_TRACKER_H_
#define SYNC_ENGINE_ENTITY_TRACKER_H_
#include <stdint.h>
#include <string>
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "base/time/time.h"
#include "sync/base/sync_export.h"
#include "sync/protocol/sync.pb.h"
namespace syncer_v2 {
struct CommitRequestData;
struct UpdateResponseData;
// Manages the pending commit and update state for an entity on the sync
// thread.
//
// It should be considered a helper class internal to the
// ModelTypeWorker.
//
// Maintains the state associated with a particular sync entity which is
// necessary for decision-making on the sync thread. It can track pending
// commit state, received update state, and can detect conflicts.
//
// This object may contain state associated with a pending commit, pending
// update, or both.
class SYNC_EXPORT EntityTracker {
public:
~EntityTracker();
// Initialize a new entity based on an update response.
static scoped_ptr<EntityTracker> FromUpdateResponse(
const UpdateResponseData& data);
// Initialize a new entity based on a commit request.
static scoped_ptr<EntityTracker> FromCommitRequest(
const CommitRequestData& data);
// Returns true if this entity should be commited to the server.
bool HasPendingCommit() const;
// Populates a sync_pb::SyncEntity for a commit. Also sets the
// |sequence_number|, so we can track it throughout the commit process.
void PrepareCommitProto(sync_pb::SyncEntity* commit_entity,
int64_t* sequence_number) const;
// Updates this entity with data from the latest version that the
// model asked us to commit. May clobber state related to the
// model's previous commit attempt(s).
void RequestCommit(const CommitRequestData& data);
// Handles the receipt of a commit response.
//
// Since commits happen entirely on the sync thread, we can safely assume
// that our item's state at the end of the commit is the same as it was at
// the start.
void ReceiveCommitResponse(const std::string& response_id,
int64_t response_version,
int64_t sequence_number);
// Handles receipt of an update from the server.
void ReceiveUpdate(int64_t version);
// Handles the receipt of an pending update from the server.
//
// Returns true if the tracker decides this item is worth keeping. Returns
// false if the item is discarded, which could happen if the version number
// is out of date.
bool ReceivePendingUpdate(const UpdateResponseData& data);
// Functions to fetch the latest pending update.
bool HasPendingUpdate() const;
UpdateResponseData GetPendingUpdate() const;
// Clears the pending update. Allows us to resume regular commit behavior.
void ClearPendingUpdate();
private:
// Initializes the entity tracker's main fields. Does not initialize state
// related to a pending commit.
EntityTracker(const std::string& id,
const std::string& client_tag_hash,
int64_t highest_commit_response_version,
int64_t highest_gu_response_version);
// Checks if the current state indicates a conflict.
//
// This can be true only while a call to this object is in progress.
// Conflicts are always cleared before the method call ends.
bool IsInConflict() const;
// Checks if the server knows about this item.
bool IsServerKnown() const;
// Clears flag and optionally clears state associated with a pending commit.
void ClearPendingCommit();
// The ID for this entry. May be empty if the entry has never been committed.
std::string id_;
// The hashed client tag for this entry.
std::string client_tag_hash_;
// The highest version seen in a commit response for this entry.
int64_t highest_commit_response_version_;
// The highest version seen in a GU response for this entry.
int64_t highest_gu_response_version_;
// Used to track in-flight commit requests on the model thread. All we need
// to do here is return it back to the model thread when the pending commit
// is completed and confirmed. Not valid if no commit is pending.
int64_t sequence_number_;
// The server version on which this item is based.
int64_t base_version_;
// A commit for this entity waiting for a sync cycle to be committed.
scoped_ptr<CommitRequestData> pending_commit_;
// An update for this entity which can't be applied right now. The presence
// of an pending update prevents commits. As of this writing, the only
// source of pending updates is updates that can't currently be decrypted.
scoped_ptr<UpdateResponseData> pending_update_;
DISALLOW_COPY_AND_ASSIGN(EntityTracker);
};
} // namespace syncer_v2
#endif // SYNC_ENGINE_ENTITY_TRACKER_H_