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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.state;

import org.apache.flink.annotation.Internal;

import javax.annotation.Nonnull;

/**
 * Interface to deal with state snapshot and restore of state.
 * TODO find better name?
 */
@Internal
public interface StateSnapshotRestore {

	/**
	 * Returns a snapshot of the state.
	 */
	@Nonnull
	StateSnapshot stateSnapshot();

	/**
	 * This method returns a {@link StateSnapshotKeyGroupReader} that can be used to restore the state on a
	 * per-key-group basis. This method tries to return a reader for the given version hint.
	 *
	 * @param readVersionHint the required version of the state to read.
	 * @return a reader that reads state by key-groups, for the given read version.
	 */
	@Nonnull
	StateSnapshotKeyGroupReader keyGroupReader(int readVersionHint);
}