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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.ttl;

import org.apache.flink.api.common.functions.AggregateFunction;
import org.apache.flink.api.common.state.StateTtlConfig;
import org.apache.flink.util.FlinkRuntimeException;
import org.apache.flink.util.Preconditions;
import org.apache.flink.util.function.ThrowingConsumer;
import org.apache.flink.util.function.ThrowingRunnable;

/**
 * This class wraps aggregating function with TTL logic.
 *
 * @param   The type of the values that are aggregated (input values)
 * @param  The type of the accumulator (intermediate aggregate state).
 * @param  The type of the aggregated result
 */
class TtlAggregateFunction
	extends AbstractTtlDecorator>
	implements AggregateFunction, OUT> {
	ThrowingRunnable stateClear;
	ThrowingConsumer, Exception> updater;

	TtlAggregateFunction(AggregateFunction aggFunction, StateTtlConfig config, TtlTimeProvider timeProvider) {
		super(aggFunction, config, timeProvider);
	}

	@Override
	public TtlValue createAccumulator() {
		return wrapWithTs(original.createAccumulator());
	}

	@Override
	public TtlValue add(IN value, TtlValue accumulator) {
		ACC userAcc = getUnexpired(accumulator);
		userAcc = userAcc == null ? original.createAccumulator() : userAcc;
		return wrapWithTs(original.add(value, userAcc));
	}

	@Override
	public OUT getResult(TtlValue accumulator) {
		Preconditions.checkNotNull(updater, "State updater should be set in TtlAggregatingState");
		Preconditions.checkNotNull(stateClear, "State clearing should be set in TtlAggregatingState");
		ACC userAcc;
		try {
			userAcc = getWithTtlCheckAndUpdate(() -> accumulator, updater, stateClear);
		} catch (Exception e) {
			throw new FlinkRuntimeException("Failed to retrieve original internal aggregating state", e);
		}
		return userAcc == null ? null : original.getResult(userAcc);
	}

	@Override
	public TtlValue merge(TtlValue a, TtlValue b) {
		ACC userA = getUnexpired(a);
		ACC userB = getUnexpired(b);
		if (userA != null && userB != null) {
			return wrapWithTs(original.merge(userA, userB));
		} else if (userA != null) {
			return rewrapWithNewTs(a);
		} else if (userB != null) {
			return rewrapWithNewTs(b);
		} else {
			return null;
		}
	}
}