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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * 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 io.datakernel.stream.processor;

import com.google.common.base.Function;
import io.datakernel.eventloop.Eventloop;
import io.datakernel.stream.AbstractStreamConsumer;
import io.datakernel.stream.AbstractStreamTransformer_M_1;
import io.datakernel.stream.StreamConsumer;
import io.datakernel.stream.StreamDataReceiver;

import java.util.ArrayDeque;
import java.util.Comparator;
import java.util.PriorityQueue;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Perform aggregative functions on the elements from input streams. Searches key of item
 * with key function, selects elements with some key, reductions it and streams result sorted by key.
 * Elements from stream to input must be sorted by keys. It is {@link AbstractStreamTransformer_M_1}
 * because it represents few consumers and one producer.
 *
 * @param  type of key of element
 * @param  type of output data
 * @param  type of accumulator
 */
@SuppressWarnings({"rawtypes", "unchecked"})
public abstract class AbstractStreamReducer extends AbstractStreamTransformer_M_1 implements AbstractStreamReducerMBean {
	public static final int BUFFER_SIZE = 1024;

	private final int bufferSize;

	private InternalConsumer lastInput;
	private K key = null;
	private A accumulator;

	private final PriorityQueue priorityQueue;
	private int streamsAwaiting;

	private int jmxInputItems;
	private int jmxOnFirst;
	private int jmxOnNext;
	private int jmxOnComplete;

	/**
	 * Creates a new instance of AbstractStreamReducer
	 *
	 * @param eventloop     eventloop in which runs reducer
	 * @param keyComparator comparator for compare keys
	 * @param bufferSize    maximal size of items which can be stored before reducing
	 */
	public AbstractStreamReducer(Eventloop eventloop, final Comparator keyComparator, int bufferSize) {
		super(eventloop);
		checkArgument(bufferSize >= 0, "bufferSize must be positive value, got %s", bufferSize);
		this.bufferSize = bufferSize;
		this.priorityQueue = new PriorityQueue<>(1, new Comparator() {
			@Override
			public int compare(InternalConsumer o1, InternalConsumer o2) {
				int compare = ((Comparator) keyComparator).compare(o1.headKey, o2.headKey);
				if (compare != 0)
					return compare;
				return o1.index - o2.index;
			}
		});
	}

	/**
	 * Creates a new instance of AbstractStreamReducer with default buffer size - 1024
	 *
	 * @param eventloop     eventloop in which runs reducer
	 * @param keyComparator comparator for compare keys
	 */
	public AbstractStreamReducer(Eventloop eventloop, Comparator keyComparator) {
		this(eventloop, keyComparator, BUFFER_SIZE);
	}

	/**
	 * This method is called if consumer was changed, checks if it has consumers, if not sets status
	 * end of stream.
	 */
	@Override
	protected void onProducerStarted() {
		if (inputs.isEmpty()) {
			sendEndOfStream();
		}
	}

	@Override
	@SuppressWarnings("AssertWithSideEffects")
	protected void doProduce() {
		while (status == READY && streamsAwaiting == 0) {
			InternalConsumer