/*
 * 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.connector.file.sink;

import org.apache.flink.api.common.RuntimeExecutionMode;
import org.apache.flink.api.common.restartstrategy.RestartStrategies;
import org.apache.flink.api.common.state.ListState;
import org.apache.flink.api.common.state.ListStateDescriptor;
import org.apache.flink.api.common.time.Time;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.ExecutionOptions;
import org.apache.flink.runtime.jobgraph.JobGraph;
import org.apache.flink.runtime.state.CheckpointListener;
import org.apache.flink.runtime.state.FunctionInitializationContext;
import org.apache.flink.runtime.state.FunctionSnapshotContext;
import org.apache.flink.streaming.api.CheckpointingMode;
import org.apache.flink.streaming.api.checkpoint.CheckpointedFunction;
import org.apache.flink.streaming.api.datastream.DataStreamSink;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
import org.apache.flink.streaming.api.graph.StreamGraph;

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;

import java.util.Collections;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;

/** Tests the functionality of the {@link FileSink} in STREAMING mode. */
class StreamingExecutionFileSinkITCase extends FileSinkITBase {

    private static final Map<String, CountDownLatch> LATCH_MAP = new ConcurrentHashMap<>();

    private String latchId;

    @BeforeEach
    void setup() {
        this.latchId = UUID.randomUUID().toString();
        // We wait for two successful checkpoints in sources before shutting down. This ensures that
        // the sink can commit its data.
        // We need to keep a "static" latch here because all sources need to be kept running
        // while we're waiting for the required number of checkpoints. Otherwise, we would lock up
        // because we can only do checkpoints while all operators are running.
        LATCH_MAP.put(latchId, new CountDownLatch(NUM_SOURCES * 2));
    }

    @AfterEach
    void teardown() {
        LATCH_MAP.remove(latchId);
    }

    /**
     * Creating the testing job graph in streaming mode. The graph created is [Source] -> [File
     * Sink]. The source would trigger failover if required.
     */
    @Override
    protected JobGraph createJobGraph(boolean triggerFailover, String path) {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        Configuration config = new Configuration();
        config.set(ExecutionOptions.RUNTIME_MODE, RuntimeExecutionMode.STREAMING);
        env.configure(config, getClass().getClassLoader());

        env.enableCheckpointing(10, CheckpointingMode.EXACTLY_ONCE);

        if (triggerFailover) {
            env.setRestartStrategy(RestartStrategies.fixedDelayRestart(1, Time.milliseconds(100)));
        } else {
            env.setRestartStrategy(RestartStrategies.noRestart());
        }

        DataStreamSink<Integer> sink =
                env.addSource(
                                new StreamingExecutionTestSource(
                                        latchId, NUM_RECORDS, triggerFailover))
                        .setParallelism(NUM_SOURCES)
                        .sinkTo(createFileSink(path))
                        .setParallelism(NUM_SINKS);
        configureSink(sink);

        StreamGraph streamGraph = env.getStreamGraph();
        return streamGraph.getJobGraph();
    }

    protected void configureSink(DataStreamSink<Integer> sink) {}

    // ------------------------ Streaming mode user functions ----------------------------------

    private static class StreamingExecutionTestSource extends RichParallelSourceFunction<Integer>
            implements CheckpointListener, CheckpointedFunction {

        private final String latchId;

        private final int numberOfRecords;

        /**
         * Whether the test is executing in a scenario that induces a failover. This doesn't mean
         * that this source induces the failover.
         */
        private final boolean isFailoverScenario;

        private ListState<Integer> nextValueState;

        private int nextValue;

        private volatile boolean isCanceled;

        private volatile boolean snapshottedAfterAllRecordsOutput;

        private volatile boolean isWaitingCheckpointComplete;

        private volatile boolean hasCompletedCheckpoint;

        public StreamingExecutionTestSource(
                String latchId, int numberOfRecords, boolean isFailoverScenario) {
            this.latchId = latchId;
            this.numberOfRecords = numberOfRecords;
            this.isFailoverScenario = isFailoverScenario;
        }

        @Override
        public void initializeState(FunctionInitializationContext context) throws Exception {
            nextValueState =
                    context.getOperatorStateStore()
                            .getListState(new ListStateDescriptor<>("nextValue", Integer.class));

            if (nextValueState.get() != null && nextValueState.get().iterator().hasNext()) {
                nextValue = nextValueState.get().iterator().next();
            }
        }

        @Override
        public void run(SourceContext<Integer> ctx) throws Exception {
            if (isFailoverScenario && getRuntimeContext().getAttemptNumber() == 0) {
                // In the first execution, we first send a part of record...
                sendRecordsUntil((int) (numberOfRecords * FAILOVER_RATIO * 0.5), ctx);

                // Wait till the first part of data is committed.
                while (!hasCompletedCheckpoint) {
                    Thread.sleep(50);
                }

                // Then we write the second part of data...
                sendRecordsUntil((int) (numberOfRecords * FAILOVER_RATIO), ctx);

                // And then trigger the failover.
                if (getRuntimeContext().getIndexOfThisSubtask() == 0) {
                    throw new RuntimeException("Designated Exception");
                } else {
                    while (true) {
                        Thread.sleep(50);
                    }
                }
            } else {
                // If we are not going to trigger failover or we have already triggered failover,
                // run until finished.
                sendRecordsUntil(numberOfRecords, ctx);

                // Wait the last checkpoint to commit all the pending records.
                isWaitingCheckpointComplete = true;
                CountDownLatch latch = LATCH_MAP.get(latchId);
                latch.await();
            }
        }

        private void sendRecordsUntil(int targetNumber, SourceContext<Integer> ctx) {
            while (!isCanceled && nextValue < targetNumber) {
                synchronized (ctx.getCheckpointLock()) {
                    ctx.collect(nextValue++);
                }
            }
        }

        @Override
        public void snapshotState(FunctionSnapshotContext context) throws Exception {
            nextValueState.update(Collections.singletonList(nextValue));

            if (isWaitingCheckpointComplete) {
                snapshottedAfterAllRecordsOutput = true;
            }
        }

        @Override
        public void notifyCheckpointComplete(long checkpointId) throws Exception {
            if (isWaitingCheckpointComplete && snapshottedAfterAllRecordsOutput) {
                CountDownLatch latch = LATCH_MAP.get(latchId);
                latch.countDown();
            }

            hasCompletedCheckpoint = true;
        }

        @Override
        public void cancel() {
            isCanceled = true;
        }
    }
}
