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/*
 * 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 org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.functions.MapPartitionFunction;
import org.apache.flink.metrics.Counter;
import org.apache.flink.runtime.operators.util.metrics.CountingCollector;
import org.apache.flink.runtime.operators.util.metrics.CountingMutableObjectIterator;
import org.apache.flink.runtime.util.NonReusingMutableToRegularIteratorWrapper;
import org.apache.flink.runtime.util.ReusingMutableToRegularIteratorWrapper;
import org.apache.flink.util.Collector;
import org.apache.flink.util.MutableObjectIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * MapPartition task which is executed by a Task Manager. The task has a single
 * input and one or multiple outputs. It is provided with a MapFunction
 * implementation.
 * 
 * The MapPartitionTask creates an iterator over all key-value pairs of its input and hands that to the map_partition() method
 * of the MapFunction.
 *
 * @see MapPartitionFunction
 *
 * @param  The mapper's input data type.
 * @param  The mapper's output data type.
 */
public class MapPartitionDriver implements Driver, OT> {

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

	private TaskContext, OT> taskContext;

	private boolean objectReuseEnabled = false;

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

	@Override
	public int getNumberOfInputs() {
		return 1;
	}

	@Override
	public Class> getStubType() {
		@SuppressWarnings("unchecked")
		final Class> clazz = (Class>) (Class) MapPartitionFunction.class;
		return clazz;
	}

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

	@Override
	public void prepare() {
		ExecutionConfig executionConfig = taskContext.getExecutionConfig();
		this.objectReuseEnabled = executionConfig.isObjectReuseEnabled();

		if (LOG.isDebugEnabled()) {
			LOG.debug("MapPartitionDriver object reuse: " + (this.objectReuseEnabled ? "ENABLED" : "DISABLED") + ".");
		}
	}

	@Override
	public void run() throws Exception {
		final Counter numRecordsIn = this.taskContext.getMetricGroup().getIOMetricGroup().getNumRecordsInCounter();
		final Counter numRecordsOut = this.taskContext.getMetricGroup().getIOMetricGroup().getNumRecordsOutCounter();
		// cache references on the stack
		final MutableObjectIterator input = new CountingMutableObjectIterator<>(this.taskContext.getInput(0), numRecordsIn);
		final MapPartitionFunction function = this.taskContext.getStub();
		final Collector output = new CountingCollector<>(this.taskContext.getOutputCollector(), numRecordsOut);

		if (objectReuseEnabled) {
			final ReusingMutableToRegularIteratorWrapper inIter = new ReusingMutableToRegularIteratorWrapper(input, this.taskContext.getInputSerializer(0).getSerializer());

			function.mapPartition(inIter, output);
		} else {
			final NonReusingMutableToRegularIteratorWrapper inIter = new NonReusingMutableToRegularIteratorWrapper(input, this.taskContext.getInputSerializer(0).getSerializer());

			function.mapPartition(inIter, output);
		}
	}

	@Override
	public void cleanup() {
		// mappers need no cleanup, since no strategies are used.
	}

	@Override
	public void cancel() {}
}