/*
 * 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.state.api;

import org.apache.flink.api.common.eventtime.WatermarkStrategy;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.common.state.ReducingState;
import org.apache.flink.api.common.state.ReducingStateDescriptor;
import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.common.typeutils.base.LongSerializer;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.runtime.state.StateBackend;
import org.apache.flink.state.api.functions.WindowReaderFunction;
import org.apache.flink.state.api.utils.AggregateSum;
import org.apache.flink.state.api.utils.JobResultRetriever;
import org.apache.flink.state.api.utils.ReduceSum;
import org.apache.flink.state.api.utils.SavepointTestBase;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.sink.v2.DiscardingSink;
import org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction;
import org.apache.flink.streaming.api.functions.windowing.WindowFunction;
import org.apache.flink.streaming.api.windowing.assigners.GlobalWindows;
import org.apache.flink.streaming.api.windowing.assigners.TumblingEventTimeWindows;
import org.apache.flink.streaming.api.windowing.evictors.Evictor;
import org.apache.flink.streaming.api.windowing.triggers.CountTrigger;
import org.apache.flink.streaming.api.windowing.triggers.PurgingTrigger;
import org.apache.flink.streaming.api.windowing.windows.GlobalWindow;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
import org.apache.flink.streaming.api.windowing.windows.Window;
import org.apache.flink.streaming.runtime.operators.windowing.TimestampedValue;
import org.apache.flink.util.Collector;

import org.hamcrest.Matchers;
import org.junit.Assert;
import org.junit.Test;

import java.time.Duration;
import java.util.List;

/** IT Case for reading window operator state. */
public abstract class SavepointWindowReaderITCase<B extends StateBackend>
        extends SavepointTestBase {
    private static final String uid = "stateful-operator";

    private static final Integer[] numbers = {1, 2, 3};

    protected abstract Tuple2<Configuration, B> getStateBackendTuple();

    @Test
    public void testReduceWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .reduce(new ReduceSum())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .reduce(uid, new ReduceSum(), Types.INT, Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testReduceEvictorWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .evictor(new NoOpEvictor<>())
                .reduce(new ReduceSum())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .evictor()
                                .reduce(uid, new ReduceSum(), Types.INT, Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testAggregateWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .aggregate(new AggregateSum())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .aggregate(
                                        uid, new AggregateSum(), Types.INT, Types.INT, Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testAggregateEvictorWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .evictor(new NoOpEvictor<>())
                .aggregate(new AggregateSum())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .evictor()
                                .aggregate(
                                        uid, new AggregateSum(), Types.INT, Types.INT, Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testProcessWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .process(new NoOpProcessWindowFunction())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .process(
                                        uid,
                                        new BasicReaderFunction(),
                                        Types.INT,
                                        Types.INT,
                                        Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testProcessEvictorWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .evictor(new NoOpEvictor<>())
                .process(new NoOpProcessWindowFunction())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .evictor()
                                .process(
                                        uid,
                                        new BasicReaderFunction(),
                                        Types.INT,
                                        Types.INT,
                                        Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testApplyWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .apply(new NoOpWindowFunction())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                                .process(
                                        uid,
                                        new BasicReaderFunction(),
                                        Types.INT,
                                        Types.INT,
                                        Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testApplyEvictorWindowStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .assignTimestampsAndWatermarks(
                        WatermarkStrategy.<Integer>noWatermarks()
                                .withTimestampAssigner((event, timestamp) -> 0))
                .keyBy(id -> id)
                .window(TumblingEventTimeWindows.of(Duration.ofMillis(10)))
                .evictor(new NoOpEvictor<>())
                .apply(new NoOpWindowFunction())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Integer> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(TumblingEventTimeWindows.of(Duration.ofMillis(1)))
                                .evictor()
                                .process(
                                        uid,
                                        new BasicReaderFunction(),
                                        Types.INT,
                                        Types.INT,
                                        Types.INT));

        Assert.assertThat(
                "Unexpected results from keyed state",
                results,
                Matchers.containsInAnyOrder(numbers));
    }

    @Test
    public void testWindowTriggerStateReader() throws Exception {
        Tuple2<Configuration, B> backendTuple = getStateBackendTuple();
        StreamExecutionEnvironment env =
                StreamExecutionEnvironment.getExecutionEnvironment(backendTuple.f0);
        env.setParallelism(4);

        env.addSource(createSource(numbers))
                .rebalance()
                .keyBy(id -> id)
                .window(GlobalWindows.create())
                .trigger(PurgingTrigger.of(CountTrigger.of(10)))
                .reduce(new ReduceSum())
                .uid(uid)
                .sinkTo(new DiscardingSink<>());

        String savepointPath = takeSavepoint(env);

        SavepointReader savepoint = SavepointReader.read(env, savepointPath, backendTuple.f1);

        List<Long> results =
                JobResultRetriever.collect(
                        savepoint
                                .window(new GlobalWindow.Serializer())
                                .reduce(
                                        uid,
                                        new ReduceSum(),
                                        new TriggerReaderFunction(),
                                        Types.INT,
                                        Types.INT,
                                        Types.LONG));

        Assert.assertThat(
                "Unexpected results from trigger state", results, Matchers.contains(1L, 1L, 1L));
    }

    private static class NoOpProcessWindowFunction
            extends ProcessWindowFunction<Integer, Integer, Integer, TimeWindow> {

        @Override
        public void process(
                Integer integer,
                Context context,
                Iterable<Integer> elements,
                Collector<Integer> out) {}
    }

    private static class NoOpWindowFunction
            implements WindowFunction<Integer, Integer, Integer, TimeWindow> {

        @Override
        public void apply(
                Integer integer,
                TimeWindow window,
                Iterable<Integer> input,
                Collector<Integer> out) {}
    }

    private static class BasicReaderFunction
            extends WindowReaderFunction<Integer, Integer, Integer, TimeWindow> {

        @Override
        public void readWindow(
                Integer key,
                Context<TimeWindow> context,
                Iterable<Integer> elements,
                Collector<Integer> out)
                throws Exception {
            Assert.assertEquals("Unexpected window", new TimeWindow(0, 10), context.window());
            Assert.assertThat(
                    "Unexpected registered timers",
                    context.registeredEventTimeTimers(),
                    Matchers.contains(9L));

            out.collect(elements.iterator().next());
        }
    }

    private static class NoOpEvictor<W extends Window> implements Evictor<Integer, W> {

        @Override
        public void evictBefore(
                Iterable<TimestampedValue<Integer>> elements,
                int size,
                W window,
                EvictorContext evictorContext) {}

        @Override
        public void evictAfter(
                Iterable<TimestampedValue<Integer>> elements,
                int size,
                W window,
                EvictorContext evictorContext) {}
    }

    private static class TriggerReaderFunction
            extends WindowReaderFunction<Integer, Long, Integer, GlobalWindow> {

        private final ReducingStateDescriptor<Long> triggerCountDesc =
                new ReducingStateDescriptor<>("count", new LongSum(), LongSerializer.INSTANCE);

        @Override
        public void readWindow(
                Integer integer,
                Context<GlobalWindow> context,
                Iterable<Integer> elements,
                Collector<Long> out)
                throws Exception {
            ReducingState<Long> state = context.triggerState(triggerCountDesc);
            out.collect(state.get());
        }
    }

    private static class LongSum implements ReduceFunction<Long> {
        private static final long serialVersionUID = 1L;

        @Override
        public Long reduce(Long value1, Long value2) throws Exception {
            return value1 + value2;
        }
    }
}
