/*
 * 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.test.checkpointing;

import org.apache.flink.api.common.functions.RichFilterFunction;
import org.apache.flink.api.common.functions.RichMapFunction;
import org.apache.flink.api.common.functions.RichReduceFunction;
import org.apache.flink.api.common.restartstrategy.RestartStrategies;
import org.apache.flink.api.common.state.CheckpointListener;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.checkpoint.ListCheckpointed;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.co.RichCoFlatMapFunction;
import org.apache.flink.streaming.api.functions.sink.SinkFunction;
import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
import org.apache.flink.test.util.AbstractTestBase;
import org.apache.flink.test.util.TestUtils;
import org.apache.flink.util.Collector;

import org.junit.Test;

import java.io.IOException;
import java.io.Serializable;
import java.util.Collections;
import java.util.List;
import java.util.Random;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

/**
 * A simple test that runs a streaming topology with checkpointing enabled. This differs from {@link
 * org.apache.flink.test.checkpointing.StreamCheckpointingITCase} in that it contains a TwoInput (or
 * co-) Task.
 *
 * <p>This checks whether checkpoint barriers correctly trigger TwoInputTasks and also whether this
 * barriers are correctly forwarded.
 *
 * <p>The test triggers a failure after a while and verifies that, after completion, the state
 * reflects the "exactly once" semantics.
 */
@SuppressWarnings({"serial", "deprecation"})
public class CoStreamCheckpointingITCase extends AbstractTestBase {

    private static final long NUM_STRINGS = 10_000L;
    private static final int PARALLELISM = 4;

    /**
     * Runs the following program.
     *
     * <pre>
     *     [ (source)->(filter)->(map) ] -> [ (co-map) ] -> [ (map) ] -> [ (groupBy/reduce)->(sink) ]
     * </pre>
     */
    @Test
    public void testCoStreamCheckpointingProgram() throws Exception {
        assertTrue("Broken test setup", NUM_STRINGS % 40 == 0);

        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        env.setParallelism(PARALLELISM);
        env.enableCheckpointing(50);
        env.setRestartStrategy(RestartStrategies.fixedDelayRestart(Integer.MAX_VALUE, 0L));

        DataStream<String> stream =
                env.addSource(new StringGeneratingSourceFunction(NUM_STRINGS, NUM_STRINGS / 5));

        stream
                // -------------- first vertex, chained to the source ----------------
                .filter(new StringRichFilterFunction())

                // -------------- second vertex - stateful ----------------
                .connect(stream)
                .flatMap(new LeftIdentityCoRichFlatMapFunction())

                // -------------- third vertex - stateful  ----------------
                .map(new StringPrefixCountRichMapFunction())
                .startNewChain()
                .map(new StatefulCounterFunction())

                // -------------- fourth vertex - reducer (failing) and the sink ----------------
                .keyBy("prefix")
                .reduce(new OnceFailingReducer(NUM_STRINGS))
                .addSink(
                        new SinkFunction<PrefixCount>() {

                            @Override
                            public void invoke(PrefixCount value) {
                                // Do nothing here
                            }
                        });

        TestUtils.tryExecute(env, "Fault Tolerance Test");

        // validate the result

        long filterSum = 0;
        for (long l : StringRichFilterFunction.counts) {
            filterSum += l;
        }

        long coMapSum = 0;
        for (long l : LeftIdentityCoRichFlatMapFunction.counts) {
            coMapSum += l;
        }

        long mapSum = 0;
        for (long l : StringPrefixCountRichMapFunction.counts) {
            mapSum += l;
        }

        long countSum = 0;
        for (long l : StatefulCounterFunction.counts) {
            countSum += l;
        }

        // verify that we counted exactly right
        assertEquals(NUM_STRINGS, filterSum);
        assertEquals(NUM_STRINGS, coMapSum);
        assertEquals(NUM_STRINGS, mapSum);
        assertEquals(NUM_STRINGS, countSum);
    }

    // --------------------------------------------------------------------------------------------
    //  Custom Functions
    // --------------------------------------------------------------------------------------------

    /**
     * A generating source that is slow before the first two checkpoints went through and will
     * indefinitely stall at a certain point to allow the checkpoint to complete.
     *
     * <p>After the checkpoints are through, it continues with full speed.
     */
    private static class StringGeneratingSourceFunction extends RichParallelSourceFunction<String>
            implements ListCheckpointed<Integer>, CheckpointListener {

        private static volatile int numCompletedCheckpoints = 0;

        private final long numElements;
        private final long checkpointLatestAt;

        private int index = -1;

        private volatile boolean isRunning = true;

        StringGeneratingSourceFunction(long numElements, long checkpointLatestAt) {
            this.numElements = numElements;
            this.checkpointLatestAt = checkpointLatestAt;
        }

        @Override
        public void run(SourceContext<String> ctx) throws Exception {
            final Random rnd = new Random();
            final StringBuilder stringBuilder = new StringBuilder();

            final Object lockingObject = ctx.getCheckpointLock();

            final int step = getRuntimeContext().getNumberOfParallelSubtasks();
            if (index < 0) {
                // not been restored, so initialize
                index = getRuntimeContext().getIndexOfThisSubtask();
            }

            while (isRunning && index < numElements) {
                char first = (char) ((index % 40) + 40);

                stringBuilder.setLength(0);
                stringBuilder.append(first);

                String result = randomString(stringBuilder, rnd);

                //noinspection SynchronizationOnLocalVariableOrMethodParameter
                synchronized (lockingObject) {
                    index += step;
                    ctx.collect(result);
                }

                if (numCompletedCheckpoints < 2) {
                    // not yet completed enough checkpoints, so slow down
                    if (index < checkpointLatestAt) {
                        // mild slow down
                        Thread.sleep(1);
                    } else {
                        // wait until the checkpoints are completed
                        while (isRunning && numCompletedCheckpoints < 2) {
                            Thread.sleep(5);
                        }
                    }
                }
            }
        }

        @Override
        public void cancel() {
            isRunning = false;
        }

        @Override
        public List<Integer> snapshotState(long checkpointId, long timestamp) throws Exception {
            return Collections.singletonList(this.index);
        }

        @Override
        public void restoreState(List<Integer> state) throws Exception {
            if (state.isEmpty() || state.size() > 1) {
                throw new RuntimeException(
                        "Test failed due to unexpected recovered state size " + state.size());
            }
            this.index = state.get(0);
        }

        @Override
        public void notifyCheckpointComplete(long checkpointId) throws Exception {
            if (getRuntimeContext().getIndexOfThisSubtask() == 0) {
                numCompletedCheckpoints++;
            }
        }

        @Override
        public void notifyCheckpointAborted(long checkpointId) {}

        private static String randomString(StringBuilder bld, Random rnd) {
            final int len = rnd.nextInt(10) + 5;

            for (int i = 0; i < len; i++) {
                char next = (char) (rnd.nextInt(20000) + 33);
                bld.append(next);
            }

            return bld.toString();
        }
    }

    private static class StatefulCounterFunction extends RichMapFunction<PrefixCount, PrefixCount>
            implements ListCheckpointed<Long> {

        static long[] counts = new long[PARALLELISM];

        private long count;

        @Override
        public PrefixCount map(PrefixCount value) throws Exception {
            count++;
            return value;
        }

        @Override
        public void close() throws IOException {
            counts[getRuntimeContext().getIndexOfThisSubtask()] = count;
        }

        @Override
        public List<Long> snapshotState(long checkpointId, long timestamp) throws Exception {
            return Collections.singletonList(this.count);
        }

        @Override
        public void restoreState(List<Long> state) throws Exception {
            if (state.isEmpty() || state.size() > 1) {
                throw new RuntimeException(
                        "Test failed due to unexpected recovered state size " + state.size());
            }
            this.count = state.get(0);
        }
    }

    private static class OnceFailingReducer extends RichReduceFunction<PrefixCount> {

        private static volatile boolean hasFailed = false;

        private final long numElements;

        private long failurePos;
        private long count;

        OnceFailingReducer(long numElements) {
            this.numElements = numElements;
        }

        @Override
        public void open(Configuration parameters) {
            long failurePosMin =
                    (long) (0.4 * numElements / getRuntimeContext().getNumberOfParallelSubtasks());
            long failurePosMax =
                    (long) (0.7 * numElements / getRuntimeContext().getNumberOfParallelSubtasks());

            failurePos =
                    (new Random().nextLong() % (failurePosMax - failurePosMin)) + failurePosMin;
            count = 0;
        }

        @Override
        public PrefixCount reduce(PrefixCount value1, PrefixCount value2) throws Exception {
            count++;
            if (!hasFailed && count >= failurePos) {
                hasFailed = true;
                throw new Exception("Test Failure");
            }

            value1.count += value2.count;
            return value1;
        }
    }

    private static class StringRichFilterFunction extends RichFilterFunction<String>
            implements ListCheckpointed<Long> {

        static long[] counts = new long[PARALLELISM];

        private long count = 0L;

        @Override
        public boolean filter(String value) {
            count++;
            return value.length() < 100;
        }

        @Override
        public void close() {
            counts[getRuntimeContext().getIndexOfThisSubtask()] = count;
        }

        @Override
        public List<Long> snapshotState(long checkpointId, long timestamp) throws Exception {
            return Collections.singletonList(this.count);
        }

        @Override
        public void restoreState(List<Long> state) throws Exception {
            if (state.isEmpty() || state.size() > 1) {
                throw new RuntimeException(
                        "Test failed due to unexpected recovered state size " + state.size());
            }
            this.count = state.get(0);
        }
    }

    private static class StringPrefixCountRichMapFunction
            extends RichMapFunction<String, PrefixCount> implements ListCheckpointed<Long> {

        static long[] counts = new long[PARALLELISM];

        private long count;

        @Override
        public PrefixCount map(String value) {
            count += 1;
            return new PrefixCount(value.substring(0, 1), value, 1L);
        }

        @Override
        public List<Long> snapshotState(long checkpointId, long timestamp) throws Exception {
            return Collections.singletonList(this.count);
        }

        @Override
        public void restoreState(List<Long> state) throws Exception {
            if (state.isEmpty() || state.size() > 1) {
                throw new RuntimeException(
                        "Test failed due to unexpected recovered state size " + state.size());
            }
            this.count = state.get(0);
        }

        @Override
        public void close() throws IOException {
            counts[getRuntimeContext().getIndexOfThisSubtask()] = count;
        }
    }

    private static class LeftIdentityCoRichFlatMapFunction
            extends RichCoFlatMapFunction<String, String, String>
            implements ListCheckpointed<Long> {

        static long[] counts = new long[PARALLELISM];

        private long count;

        @Override
        public void flatMap1(String value, Collector<String> out) {
            count += 1;

            out.collect(value);
        }

        @Override
        public void flatMap2(String value, Collector<String> out) {
            // we ignore the values from the second input
        }

        @Override
        public List<Long> snapshotState(long checkpointId, long timestamp) throws Exception {
            return Collections.singletonList(this.count);
        }

        @Override
        public void restoreState(List<Long> state) throws Exception {
            if (state.isEmpty() || state.size() > 1) {
                throw new RuntimeException(
                        "Test failed due to unexpected recovered state size " + state.size());
            }
            this.count = state.get(0);
        }

        @Override
        public void close() throws IOException {
            counts[getRuntimeContext().getIndexOfThisSubtask()] = count;
        }
    }

    /** POJO storing a prefix, value, and count. */
    public static class PrefixCount implements Serializable {

        public String prefix;
        public String value;
        public long count;

        @SuppressWarnings("unused")
        public PrefixCount() {}

        public PrefixCount(String prefix, String value, long count) {
            this.prefix = prefix;
            this.value = value;
            this.count = count;
        }

        @Override
        public String toString() {
            return prefix + " / " + value;
        }
    }
}