/*
 * 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.operators;

import java.util.ArrayList;
import java.util.HashMap;

import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.functions.GroupCombineFunction;
import org.apache.flink.api.common.functions.GroupReduceFunction;
import org.apache.flink.runtime.operators.testutils.ExpectedTestException;
import org.apache.flink.types.Value;
import org.apache.flink.util.Collector;
import org.junit.Assert;
import org.apache.flink.api.common.functions.RichGroupReduceFunction;
import org.apache.flink.runtime.testutils.recordutils.RecordComparator;
import org.apache.flink.runtime.operators.testutils.DriverTestBase;
import org.apache.flink.runtime.operators.testutils.UniformRecordGenerator;
import org.apache.flink.types.IntValue;
import org.apache.flink.types.Record;
import org.junit.Test;


public class CombineTaskExternalITCase extends DriverTestBase<RichGroupReduceFunction<Record, ?>> {
	
	private static final long COMBINE_MEM = 3 * 1024 * 1024;

	private final double combine_frac;
	
	private final ArrayList<Record> outList = new ArrayList<>();
	
	@SuppressWarnings("unchecked")
	private final RecordComparator comparator = new RecordComparator(
		new int[]{0}, (Class<? extends Value>[])new Class<?>[]{ IntValue.class });

	public CombineTaskExternalITCase(ExecutionConfig config) {
		super(config, COMBINE_MEM, 0);

		combine_frac = (double)COMBINE_MEM/this.getMemoryManager().getMemorySize();
	}

	
	@Test
	public void testSingleLevelMergeCombineTask() {
		final int keyCnt = 40000;
		final int valCnt = 8;
		
		addInput(new UniformRecordGenerator(keyCnt, valCnt, false));
		addDriverComparator(this.comparator);
		addDriverComparator(this.comparator);
		setOutput(this.outList);
		
		getTaskConfig().setDriverStrategy(DriverStrategy.SORTED_GROUP_COMBINE);
		getTaskConfig().setRelativeMemoryDriver(combine_frac);
		getTaskConfig().setFilehandlesDriver(2);
		
		final GroupReduceCombineDriver<Record, Record> testTask = new GroupReduceCombineDriver<>();
		
		try {
			testDriver(testTask, MockCombiningReduceStub.class);
		} catch (Exception e) {
			e.printStackTrace();
			Assert.fail("Invoke method caused exception.");
		}
		
		int expSum = 0;
		for (int i = 1;i < valCnt; i++) {
			expSum += i;
		}
		
		// wee need to do the final aggregation manually in the test, because the
		// combiner is not guaranteed to do that
		final HashMap<IntValue, IntValue> aggMap = new HashMap<>();
		for (Record record : this.outList) {
			IntValue key = new IntValue();
			IntValue value = new IntValue();
			key = record.getField(0, key);
			value = record.getField(1, value);
			IntValue prevVal = aggMap.get(key);
			if (prevVal != null) {
				aggMap.put(key, new IntValue(prevVal.getValue() + value.getValue()));
			}
			else {
				aggMap.put(key, value);
			}
		}
		
		Assert.assertTrue("Resultset size was "+aggMap.size()+". Expected was "+keyCnt, aggMap.size() == keyCnt);
		
		for (IntValue integer : aggMap.values()) {
			Assert.assertTrue("Incorrect result", integer.getValue() == expSum);
		}
		
		this.outList.clear();
	}
	
	@Test
	public void testMultiLevelMergeCombineTask() throws Exception {
		final int keyCnt = 100000;
		final int valCnt = 8;
		
		addInput(new UniformRecordGenerator(keyCnt, valCnt, false));
		addDriverComparator(this.comparator);
		addDriverComparator(this.comparator);
		setOutput(this.outList);
		
		getTaskConfig().setDriverStrategy(DriverStrategy.SORTED_GROUP_COMBINE);
		getTaskConfig().setRelativeMemoryDriver(combine_frac);
		getTaskConfig().setFilehandlesDriver(2);
		
		final GroupReduceCombineDriver<Record, Record> testTask = new GroupReduceCombineDriver<>();

		try {
			testDriver(testTask, MockCombiningReduceStub.class);
		} catch (Exception e) {
			e.printStackTrace();
			Assert.fail("Invoke method caused exception.");
		}
		
		int expSum = 0;
		for (int i = 1;i < valCnt; i++) {
			expSum += i;
		}
		
		// wee need to do the final aggregation manually in the test, because the
		// combiner is not guaranteed to do that
		final HashMap<IntValue, IntValue> aggMap = new HashMap<>();
		for (Record record : this.outList) {
			IntValue key = new IntValue();
			IntValue value = new IntValue();
			key = record.getField(0, key);
			value = record.getField(1, value);
			IntValue prevVal = aggMap.get(key);
			if (prevVal != null) {
				aggMap.put(key, new IntValue(prevVal.getValue() + value.getValue()));
			}
			else {
				aggMap.put(key, value);
			}
		}
		
		Assert.assertTrue("Resultset size was "+aggMap.size()+". Expected was "+keyCnt, aggMap.size() == keyCnt);
		
		for (IntValue integer : aggMap.values()) {
			Assert.assertTrue("Incorrect result", integer.getValue() == expSum);
		}
		
		this.outList.clear();
	}
	
	// ------------------------------------------------------------------------
	// ------------------------------------------------------------------------

	public static class MockCombiningReduceStub implements
		GroupReduceFunction<Record, Record>, GroupCombineFunction<Record, Record>
	{
		private static final long serialVersionUID = 1L;

		private final IntValue theInteger = new IntValue();

		@Override
		public void reduce(Iterable<Record> records, Collector<Record> out) {
			Record element = null;
			int sum = 0;

			for (Record next : records) {
				element = next;
				element.getField(1, this.theInteger);

				sum += this.theInteger.getValue();
			}
			this.theInteger.setValue(sum);
			element.setField(1, this.theInteger);
			out.collect(element);
		}

		@Override
		public void combine(Iterable<Record> records, Collector<Record> out) throws Exception {
			reduce(records, out);
		}
	}

	public static final class MockFailingCombiningReduceStub implements
		GroupReduceFunction<Record, Record>, GroupCombineFunction<Record, Record>
	{
		private static final long serialVersionUID = 1L;

		private int cnt = 0;

		private final IntValue key = new IntValue();
		private final IntValue value = new IntValue();
		private final IntValue combineValue = new IntValue();

		@Override
		public void reduce(Iterable<Record> records, Collector<Record> out) {
			Record element = null;
			int sum = 0;

			for (Record next : records) {
				element = next;
				element.getField(1, this.value);

				sum += this.value.getValue();
			}
			element.getField(0, this.key);
			this.value.setValue(sum - this.key.getValue());
			element.setField(1, this.value);
			out.collect(element);
		}

		@Override
		public void combine(Iterable<Record> records, Collector<Record> out) {
			Record element = null;
			int sum = 0;

			for (Record next : records) {
				element = next;
				element.getField(1, this.combineValue);

				sum += this.combineValue.getValue();
			}

			if (++this.cnt >= 10) {
				throw new ExpectedTestException();
			}

			this.combineValue.setValue(sum);
			element.setField(1, this.combineValue);
			out.collect(element);
		}
	}
}