components/sync/engine_impl/conflict_resolver.h

// Copyright (c) 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_ENGINE_IMPL_CONFLICT_RESOLVER_H_
#define COMPONENTS_SYNC_ENGINE_IMPL_CONFLICT_RESOLVER_H_

#include <set>

#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "components/sync/engine_impl/syncer_types.h"

namespace syncer {

namespace syncable {
class Id;
class WriteTransaction;
}  // namespace syncable

class Cryptographer;
class StatusController;
struct UpdateCounters;

// A class that watches the syncer and attempts to resolve any conflicts that
// occur.
class ConflictResolver {
 public:
  // Enumeration of different conflict resolutions. Used for histogramming.
  enum SimpleConflictResolutions {
    OVERWRITE_LOCAL,    // Resolved by overwriting local changes.
    OVERWRITE_SERVER,   // Resolved by overwriting server changes.
    UNDELETE,           // Resolved by undeleting local item.
    IGNORE_ENCRYPTION,  // Resolved by ignoring an encryption-only server
                        // change.
    NIGORI_MERGE,       // Resolved by merging nigori nodes.
    CHANGES_MATCH,      // Resolved by ignoring both local and server
                        // changes because they matched.
    CONFLICT_RESOLUTION_SIZE,
  };

  ConflictResolver();
  ~ConflictResolver();
  // Called by the syncer at the end of a update/commit cycle.
  // Returns true if the syncer should try to apply its updates again.
  void ResolveConflicts(syncable::WriteTransaction* trans,
                        const Cryptographer* cryptographer,
                        const std::set<syncable::Id>& simple_conflict_ids,
                        StatusController* status,
                        UpdateCounters* counters);

 private:
  friend class SyncerTest;
  FRIEND_TEST_ALL_PREFIXES(SyncerTest,
                           ConflictResolverMergeOverwritesLocalEntry);

  void ProcessSimpleConflict(syncable::WriteTransaction* trans,
                             const syncable::Id& id,
                             const Cryptographer* cryptographer,
                             StatusController* status,
                             UpdateCounters* counters);

  DISALLOW_COPY_AND_ASSIGN(ConflictResolver);
};

}  // namespace syncer

#endif  // COMPONENTS_SYNC_ENGINE_IMPL_CONFLICT_RESOLVER_H_