Introduce a layering in the invalidation component as public and impl

components/invalidation/invalidation.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 COMPONENTS_INVALIDATION_INVALIDATION_H_
-#define COMPONENTS_INVALIDATION_INVALIDATION_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
-#include "base/sequenced_task_runner.h"
-#include "base/values.h"
-#include "components/invalidation/ack_handle.h"
-#include "components/invalidation/invalidation_export.h"
-#include "google/cacheinvalidation/include/types.h"
-
-namespace syncer {
-
-class DroppedInvalidationTracker;
-class AckHandler;
-
-// Represents a local invalidation, and is roughly analogous to
-// invalidation::Invalidation.  Unlike invalidation::Invalidation, this class
-// supports "local" ack-tracking and simple serialization to pref values.
-class INVALIDATION_EXPORT Invalidation {
- public:
-  // Factory functions.
-  static Invalidation Init(const invalidation::ObjectId& id,
-                           int64 version,
-                           const std::string& payload);
-  static Invalidation InitUnknownVersion(const invalidation::ObjectId& id);
-  static Invalidation InitFromDroppedInvalidation(const Invalidation& dropped);
-  static scoped_ptr<Invalidation> InitFromValue(
-      const base::DictionaryValue& value);
-
-  ~Invalidation();
-
-  // Compares two invalidations.  The comparison ignores ack-tracking state.
-  bool Equals(const Invalidation& other) const;
-
-  invalidation::ObjectId object_id() const;
-  bool is_unknown_version() const;
-
-  // Safe to call only if is_unknown_version() returns false.
-  int64 version() const;
-
-  // Safe to call only if is_unknown_version() returns false.
-  const std::string& payload() const;
-
-  const AckHandle& ack_handle() const;
-
-  // Sets the AckHandler to be used to track this Invalidation.
-  //
-  // This should be set by the class that generates the invalidation.  Clients
-  // of the Invalidations API should not need to call this.
-  //
-  // Note that some sources of invalidations do not support ack tracking, and do
-  // not set the ack_handler.  This will be hidden from users of this class.
-  void SetAckHandler(
-      base::WeakPtr<AckHandler> handler,
-      scoped_refptr<base::SequencedTaskRunner> handler_task_runner);
-
-  // Returns whether or not this instance supports ack tracking.  This will
-  // depend on whether or not the source of invaliadations supports
-  // invalidations.
-  //
-  // Clients can safely ignore this flag.  They can assume that all
-  // invalidations support ack tracking.  If they're wrong, then invalidations
-  // will be less reliable, but their behavior will be no less correct.
-  bool SupportsAcknowledgement() const;
-
-  // Acknowledges the receipt of this invalidation.
-  //
-  // Clients should call this on a received invalidation when they have fully
-  // processed the invalidation and persisted the results to disk.  Once this
-  // function is called, the invalidations system is under no obligation to
-  // re-deliver this invalidation in the event of a crash or restart.
-  void Acknowledge() const;
-
-  // Informs the ack tracker that this invalidation will not be serviced.
-  //
-  // If a client's buffer reaches its limit and it is forced to start dropping
-  // invalidations, it should call this function before dropping its
-  // invalidations in order to allow the ack tracker to drop the invalidation,
-  // too.
-  //
-  // To indicate recovery from a drop event, the client should call
-  // Acknowledge() on the most recently dropped inavlidation.
-  void Drop();
-
-  scoped_ptr<base::DictionaryValue> ToValue() const;
-  std::string ToString() const;
-
- private:
-  Invalidation(const invalidation::ObjectId& id,
-               bool is_unknown_version,
-               int64 version,
-               const std::string& payload,
-               AckHandle ack_handle);
-
-  // The ObjectId to which this invalidation belongs.
-  invalidation::ObjectId id_;
-
-  // This flag is set to true if this is an unknown version invalidation.
-  bool is_unknown_version_;
-
-  // The version number of this invalidation.  Should not be accessed if this is
-  // an unkown version invalidation.
-  int64 version_;
-
-  // The payaload associated with this invalidation.  Should not be accessed if
-  // this is an unknown version invalidation.
-  std::string payload_;
-
-  // A locally generated unique ID used to manage local acknowledgements.
-  AckHandle ack_handle_;
-
-  // The acknowledgement tracking handler and its thread.
-  base::WeakPtr<AckHandler> ack_handler_;
-  scoped_refptr<base::SequencedTaskRunner> ack_handler_task_runner_;
-};
-
-}  // namespace syncer
-
-#endif  // COMPONENTS_INVALIDATION_INVALIDATION_H_