/*
 * 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.streaming.connectors.kafka.testutils;

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.checkpoint.ListCheckpointed;
import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;
import org.apache.flink.test.util.SuccessException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.BitSet;
import java.util.Collections;
import java.util.List;

/**
 * A {@link RichSinkFunction} that verifies that no duplicate records are generated.
 */
public class ValidatingExactlyOnceSink extends RichSinkFunction<Integer> implements ListCheckpointed<Tuple2<Integer, BitSet>> {

	private static final Logger LOG = LoggerFactory.getLogger(ValidatingExactlyOnceSink.class);

	private static final long serialVersionUID = 1748426382527469932L;

	private final int numElementsTotal;

	private final boolean exitOnFinish;

	private BitSet duplicateChecker = new BitSet();  // this is checkpointed

	private int numElements; // this is checkpointed

	public ValidatingExactlyOnceSink(int numElementsTotal) {
		this(numElementsTotal, true);
	}

	public ValidatingExactlyOnceSink(int numElementsTotal, boolean exitOnFinish) {
		this.numElementsTotal = numElementsTotal;
		this.exitOnFinish = exitOnFinish;
	}

	@Override
	public void invoke(Integer value) throws Exception {
		numElements++;

		if (duplicateChecker.get(value)) {
			throw new Exception("Received a duplicate: " + value);
		}
		duplicateChecker.set(value);
		if (numElements == numElementsTotal) {
			// validate
			if (duplicateChecker.cardinality() != numElementsTotal) {
				throw new Exception("Duplicate checker has wrong cardinality");
			}
			else if (duplicateChecker.nextClearBit(0) != numElementsTotal) {
				throw new Exception("Received sparse sequence");
			} else if (exitOnFinish) {
				throw new SuccessException();
			}
		} else if (numElements > numElementsTotal) {
			throw new Exception("Receive too many records");
		}
	}

	@Override
	public void close() {
		if (numElements != numElementsTotal) {
			throw new RuntimeException("Receive too many records");
		}
	}

	@Override
	public List<Tuple2<Integer, BitSet>> snapshotState(long checkpointId, long timestamp) throws Exception {
		LOG.info("Snapshot of counter " + numElements + " at checkpoint " + checkpointId);
		return Collections.singletonList(new Tuple2<>(numElements, duplicateChecker));
	}

	@Override
	public void restoreState(List<Tuple2<Integer, BitSet>> state) throws Exception {
		if (state.isEmpty() || state.size() > 1) {
			throw new RuntimeException("Test failed due to unexpected recovered state size " + state.size());
		}

		Tuple2<Integer, BitSet> s = state.get(0);
		LOG.info("restoring num elements to {}", s.f0);
		this.numElements = s.f0;
		this.duplicateChecker = s.f1;
	}
}