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/***********************************************************************************************************************
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * Licensed 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 eu.stratosphere.pact.runtime.task;

import java.util.List;

import eu.stratosphere.api.common.functions.GenericJoiner;
import eu.stratosphere.api.common.typeutils.TypeComparator;
import eu.stratosphere.api.common.typeutils.TypePairComparatorFactory;
import eu.stratosphere.api.common.typeutils.TypeSerializer;
import eu.stratosphere.core.memory.MemorySegment;
import eu.stratosphere.pact.runtime.hash.MutableHashTable;
import eu.stratosphere.pact.runtime.task.util.TaskConfig;
import eu.stratosphere.pact.runtime.util.EmptyMutableObjectIterator;
import eu.stratosphere.util.Collector;
import eu.stratosphere.util.MutableObjectIterator;

public abstract class AbstractCachedBuildSideMatchDriver extends MatchDriver implements ResettablePactDriver, OT> {
	
	/**
	 * We keep it without generic parameters, because they vary depending on which input is the build side.
	 */
	protected volatile MutableHashTable hashJoin;

	
	private final int buildSideIndex;
	
	private final int probeSideIndex;
	
	protected AbstractCachedBuildSideMatchDriver(int buildSideIndex, int probeSideIndex) {
		this.buildSideIndex = buildSideIndex;
		this.probeSideIndex = probeSideIndex;
	}
	
	// --------------------------------------------------------------------------------------------
	
	@Override
	public boolean isInputResettable(int inputNum) {
		if (inputNum < 0 || inputNum > 1) {
			throw new IndexOutOfBoundsException();
		}
		return inputNum == buildSideIndex;
	}

	@Override
	public void initialize() throws Exception {
		TaskConfig config = this.taskContext.getTaskConfig();
		
		TypeSerializer serializer1 = this.taskContext.getInputSerializer(0).getSerializer();
		TypeSerializer serializer2 = this.taskContext.getInputSerializer(1).getSerializer();
		TypeComparator comparator1 = this.taskContext.getInputComparator(0);
		TypeComparator comparator2 = this.taskContext.getInputComparator(1);
		MutableObjectIterator input1 = this.taskContext.getInput(0);
		MutableObjectIterator input2 = this.taskContext.getInput(1);

		TypePairComparatorFactory pairComparatorFactory = 
				this.taskContext.getTaskConfig().getPairComparatorFactory(this.taskContext.getUserCodeClassLoader());

		int numMemoryPages = this.taskContext.getMemoryManager().computeNumberOfPages(config.getMemoryDriver());
		List memSegments = this.taskContext.getMemoryManager().allocatePages(
			this.taskContext.getOwningNepheleTask(), numMemoryPages);

		if (buildSideIndex == 0 && probeSideIndex == 1) {
			MutableHashTable hashJoin = new MutableHashTable(serializer1, serializer2, comparator1, comparator2,
					pairComparatorFactory.createComparator21(comparator1, comparator2), memSegments, this.taskContext.getIOManager());
			this.hashJoin = hashJoin;
			hashJoin.open(input1, EmptyMutableObjectIterator.get());
		} else if (buildSideIndex == 1 && probeSideIndex == 0) {
			MutableHashTable hashJoin = new MutableHashTable(serializer2, serializer1, comparator2, comparator1,
					pairComparatorFactory.createComparator12(comparator1, comparator2), memSegments, this.taskContext.getIOManager());
			this.hashJoin = hashJoin;
			hashJoin.open(input2, EmptyMutableObjectIterator.get());
		} else {
			throw new Exception("Error: Inconcistent setup for repeatable hash join driver.");
		}
	}

	@Override
	public void prepare() throws Exception {
		// nothing
	}

	@Override
	public void run() throws Exception {

		final GenericJoiner matchStub = this.taskContext.getStub();
		final Collector collector = this.taskContext.getOutputCollector();
		
		if (buildSideIndex == 0) {
			final TypeSerializer buildSideSerializer = taskContext. getInputSerializer(0).getSerializer();
			final TypeSerializer probeSideSerializer = taskContext. getInputSerializer(1).getSerializer();
			
			IT1 buildSideRecordFirst;
			IT1 buildSideRecordOther;
			IT2 probeSideRecord;
			IT2 probeSideRecordCopy;
			final IT1 buildSideRecordFirstReuse = buildSideSerializer.createInstance();
			final IT1 buildSideRecordOtherReuse = buildSideSerializer.createInstance();
			final IT2 probeSideRecordReuse = probeSideSerializer.createInstance();
			final IT2 probeSideRecordCopyReuse = probeSideSerializer.createInstance();
			
			@SuppressWarnings("unchecked")
			final MutableHashTable join = (MutableHashTable) this.hashJoin;
			
			final MutableObjectIterator probeSideInput = taskContext.getInput(1);
			
			while (this.running && ((probeSideRecord = probeSideInput.next(probeSideRecordReuse)) != null)) {
				final MutableHashTable.HashBucketIterator bucket = join.getMatchesFor(probeSideRecord);
				
				if ((buildSideRecordFirst = bucket.next(buildSideRecordFirstReuse)) != null) {
					while ((buildSideRecordOther = bucket.next(buildSideRecordOtherReuse)) != null) {
						probeSideRecordCopy = probeSideSerializer.copy(probeSideRecord, probeSideRecordCopyReuse);
						matchStub.join(buildSideRecordOther, probeSideRecordCopy, collector);
					}
					matchStub.join(buildSideRecordFirst, probeSideRecord, collector);
				}
			}
		} else if (buildSideIndex == 1) {
			final TypeSerializer buildSideSerializer = taskContext.getInputSerializer(1).getSerializer();
			final TypeSerializer probeSideSerializer = taskContext.getInputSerializer(0).getSerializer();
			
			IT2 buildSideRecordFirst;
			IT2 buildSideRecordOther;
			IT1 probeSideRecord;
			IT1 probeSideRecordCopy;
			final IT2 buildSideRecordFirstReuse = buildSideSerializer.createInstance();
			final IT2 buildSideRecordOtherReuse = buildSideSerializer.createInstance();
			final IT1 probeSideRecordReuse = probeSideSerializer.createInstance();
			final IT1 probeSideRecordCopyReuse = probeSideSerializer.createInstance();

			@SuppressWarnings("unchecked")
			final MutableHashTable join = (MutableHashTable) this.hashJoin;
			
			final MutableObjectIterator probeSideInput = taskContext.getInput(0);
			
			while (this.running && ((probeSideRecord = probeSideInput.next(probeSideRecordReuse)) != null)) {
				final MutableHashTable.HashBucketIterator bucket = join.getMatchesFor(probeSideRecord);
				
				if ((buildSideRecordFirst = bucket.next(buildSideRecordFirstReuse)) != null) {
					while ((buildSideRecordOther = bucket.next(buildSideRecordOtherReuse)) != null) {
						probeSideRecordCopy = probeSideSerializer.copy(probeSideRecord, probeSideRecordCopyReuse);
						matchStub.join(probeSideRecordCopy, buildSideRecordOther, collector);
					}
					matchStub.join(probeSideRecord, buildSideRecordFirst, collector);
				}
			}
		} else {
			throw new Exception();
		}
	}

	@Override
	public void cleanup() throws Exception {}
	
	@Override
	public void reset() throws Exception {}

	@Override
	public void teardown() {
		MutableHashTable ht = this.hashJoin;
		if (ht != null) {
			ht.close();
		}
	}

	@Override
	public void cancel() {
		this.running = false;
		if (this.hashJoin != null) {
			this.hashJoin.close();
		}
	}
}