// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SYNC_MODEL_IN_MEMORY_METADATA_CHANGE_LIST_H_
#define COMPONENTS_SYNC_MODEL_IN_MEMORY_METADATA_CHANGE_LIST_H_

#include <map>
#include <memory>
#include <string>

#include "components/sync/engine/commit_and_get_updates_types.h"
#include "components/sync/model/metadata_change_list.h"
#include "components/sync/protocol/data_type_state.pb.h"
#include "components/sync/protocol/entity_metadata.pb.h"

namespace syncer {

// A MetadataChangeList base class that stores changes in member fields.
// There are no accessors; TransferChangesTo() can be used to forward all
// changes to another instance.
class InMemoryMetadataChangeList : public MetadataChangeList {
 public:
  // If `allow_changes_on_destruction` is false (default), the destructor will
  // CHECK that there are no pending changes. This should only be used in cases
  // where the change list can be destroyed without being applied (e.g. when
  // it's propagated using PostTask()).
  explicit InMemoryMetadataChangeList(
      bool allow_changes_on_destruction = false);
  ~InMemoryMetadataChangeList() override;

  // Allows ignoring metadata changes reported by the processor, for advanced
  // cases where ignoring a change should also ignore changes to tracked
  // metadata.
  void DropMetadataChangeForStorageKey(const std::string& storage_key);

  // MetadataChangeList implementation.
  void UpdateDataTypeState(
      const sync_pb::DataTypeState& data_type_state) override;
  void ClearDataTypeState() override;
  void UpdateMetadata(const std::string& storage_key,
                      const sync_pb::EntityMetadata& metadata) override;
  void ClearMetadata(const std::string& storage_key) override;
  void TransferChangesTo(MetadataChangeList* other) override;
  void DropAllChanges() override;

 private:
  enum ChangeType { UPDATE, CLEAR };

  struct MetadataChange {
    ChangeType type;
    sync_pb::EntityMetadata metadata;
  };

  struct DataTypeStateChange {
    ChangeType type;
    sync_pb::DataTypeState state;
  };

  // If true, destructor will not assert if there are pending changes.
  const bool allow_changes_on_destruction_;
  std::map<std::string, MetadataChange> metadata_changes_;
  std::unique_ptr<DataTypeStateChange> state_change_;
};

}  // namespace syncer

#endif  // COMPONENTS_SYNC_MODEL_IN_MEMORY_METADATA_CHANGE_LIST_H_