/*
 * 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.io.IOException;
import java.util.Iterator;
import org.apache.flink.api.common.functions.CoGroupFunction;
import org.apache.flink.runtime.operators.util.TaskConfig;
import org.apache.flink.util.Collector;
import org.apache.flink.util.MutableObjectIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CoGroupRawDriver<IT1, IT2, OT> implements Driver<CoGroupFunction<IT1, IT2, OT>, OT> {

	private static final Logger LOG = LoggerFactory.getLogger(CoGroupRawDriver.class);

	private TaskContext<CoGroupFunction<IT1, IT2, OT>, OT> taskContext;

	private SimpleIterable<IT1> coGroupIterator1;
	private SimpleIterable<IT2> coGroupIterator2;

	@Override
	public void setup(TaskContext<CoGroupFunction<IT1, IT2, OT>, OT> context) {
		this.taskContext = context;
	}

	@Override
	public int getNumberOfInputs() {
		return 2;
	}

	@Override
	public int getNumberOfDriverComparators() {
		return 0;
	}

	@Override
	public Class<CoGroupFunction<IT1, IT2, OT>> getStubType() {
		@SuppressWarnings("unchecked")
		final Class<CoGroupFunction<IT1, IT2, OT>> clazz = (Class<CoGroupFunction<IT1, IT2, OT>>) (Class<?>) CoGroupFunction.class;
		return clazz;
	}

	@Override
	public void prepare() throws Exception {
		final TaskConfig config = this.taskContext.getTaskConfig();
		if (config.getDriverStrategy() != DriverStrategy.CO_GROUP_RAW) {
			throw new Exception("Unrecognized driver strategy for CoGoup Python driver: " + config.getDriverStrategy().name());
		}

		final MutableObjectIterator<IT1> in1 = this.taskContext.getInput(0);
		final MutableObjectIterator<IT2> in2 = this.taskContext.getInput(1);

		IT1 reuse1 = this.taskContext.<IT1>getInputSerializer(0).getSerializer().createInstance();
		IT2 reuse2 = this.taskContext.<IT2>getInputSerializer(1).getSerializer().createInstance();

		this.coGroupIterator1 = new SimpleIterable<IT1>(reuse1, in1);
		this.coGroupIterator2 = new SimpleIterable<IT2>(reuse2, in2);

		if (LOG.isDebugEnabled()) {
			LOG.debug(this.taskContext.formatLogString("CoGroup task iterator ready."));
		}
	}

	@Override
	public void run() throws Exception {
		final CoGroupFunction<IT1, IT2, OT> coGroupStub = this.taskContext.getStub();
		final Collector<OT> collector = this.taskContext.getOutputCollector();
		final SimpleIterable<IT1> i1 = this.coGroupIterator1;
		final SimpleIterable<IT2> i2 = this.coGroupIterator2;

		coGroupStub.coGroup(i1, i2, collector);
	}

	@Override
	public void cleanup() throws Exception {
	}

	@Override
	public void cancel() throws Exception {
		cleanup();
	}

	public static class SimpleIterable<IN> implements Iterable<IN> {
		private IN reuse;
		private final MutableObjectIterator<IN> iterator;

		public SimpleIterable(IN reuse, MutableObjectIterator<IN> iterator) throws IOException {
			this.iterator = iterator;
			this.reuse = reuse;
		}

		@Override
		public Iterator<IN> iterator() {
			return new SimpleIterator<IN>(reuse, iterator);
		}

		protected class SimpleIterator<IN> implements Iterator<IN> {
			private IN reuse;
			private final MutableObjectIterator<IN> iterator;
			private boolean consumed = true;

			public SimpleIterator(IN reuse, MutableObjectIterator<IN> iterator) {
				this.iterator = iterator;
				this.reuse = reuse;
			}

			@Override
			public boolean hasNext() {
				try {
					if (!consumed) {
						return true;
					}
					IN result = iterator.next(reuse);
					consumed = result == null;
					return !consumed;
				} catch (IOException ioex) {
					throw new RuntimeException("An error occurred while reading the next record: "
							+ ioex.getMessage(), ioex);
				}
			}

			@Override
			public IN next() {
				consumed = true;
				return reuse;
			}

			@Override
			public void remove() { //unused
			}
		}
	}
}