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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.iterative.event;

import org.apache.flink.api.common.aggregators.Aggregator;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataInputViewStreamWrapper;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
import org.apache.flink.runtime.event.TaskEvent;
import org.apache.flink.types.Value;
import org.apache.flink.util.InstantiationUtil;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Map;

/**
 * Base class for iteration {@link TaskEvent} transmitting operator aggregators.
 */
public abstract class IterationEventWithAggregators extends TaskEvent {

	protected static final String[] NO_STRINGS = new String[0];
	protected static final Value[] NO_VALUES = new Value[0];

	private String[] aggNames;

	private String[] classNames;
	private byte[][] serializedData;

	private Value[] aggregates;

	protected IterationEventWithAggregators() {
		this.aggNames = NO_STRINGS;
		this.aggregates = NO_VALUES;
	}

	protected IterationEventWithAggregators(String aggregatorName, Value aggregate) {
		if (aggregatorName == null || aggregate == null) {
			throw new NullPointerException();
		}

		this.aggNames = new String[] { aggregatorName };
		this.aggregates = new Value[] { aggregate };
	}

	protected IterationEventWithAggregators(Map> aggregators) {
		int num = aggregators.size();
		if (num == 0) {
			this.aggNames = NO_STRINGS;
			this.aggregates = NO_VALUES;
		} else {
			this.aggNames = new String[num];
			this.aggregates = new Value[num];

			int i = 0;
			for (Map.Entry> entry : aggregators.entrySet()) {
				this.aggNames[i] = entry.getKey();
				this.aggregates[i] = entry.getValue().getAggregate();
				i++;
			}
		}
	}

	public String[] getAggregatorNames() {
		return this.aggNames;
	}

	public Value[] getAggregates(ClassLoader classResolver) {
		if (aggregates == null) {
			// we have read the binary data, but not yet turned into the objects
			final int num = aggNames.length;
			aggregates = new Value[num];
			for (int i = 0; i < num; i++) {
				Value v;
				try {
					Class valClass = Class.forName(classNames[i], true, classResolver).asSubclass(Value.class);
					v = InstantiationUtil.instantiate(valClass, Value.class);
				}
				catch (ClassNotFoundException e) {
					throw new RuntimeException("Could not load user-defined class '" + classNames[i] + "'.", e);
				}
				catch (ClassCastException e) {
					throw new RuntimeException("User-defined aggregator class is not a value sublass.");
				}

				try (DataInputViewStreamWrapper in = new DataInputViewStreamWrapper(
					new ByteArrayInputStream(serializedData[i]))) {
					v.read(in);
				}
				catch (IOException e) {
					throw new RuntimeException("Error while deserializing the user-defined aggregate class.", e);
				}

				aggregates[i] = v;
			}
		}

		return this.aggregates;
	}

	@Override
	public void write(DataOutputView out) throws IOException {
		int num = this.aggNames.length;
		out.writeInt(num);

		ByteArrayOutputStream boas = new ByteArrayOutputStream();
		DataOutputViewStreamWrapper bufferStream = new DataOutputViewStreamWrapper(boas);

		for (int i = 0; i < num; i++) {
			// aggregator name and type
			out.writeUTF(this.aggNames[i]);
			out.writeUTF(this.aggregates[i].getClass().getName());

			// aggregator value indirect as a byte array
			this.aggregates[i].write(bufferStream);
			bufferStream.flush();
			byte[] bytes = boas.toByteArray();
			out.writeInt(bytes.length);
			out.write(bytes);
			boas.reset();
		}
		bufferStream.close();
		boas.close();
	}

	@Override
	public void read(DataInputView in) throws IOException {
		int num = in.readInt();
		if (num == 0) {
			this.aggNames = NO_STRINGS;
			this.aggregates = NO_VALUES;
		} else {
			if (this.aggNames == null || num > this.aggNames.length) {
				this.aggNames = new String[num];
			}
			if (this.classNames == null || num > this.classNames.length) {
				this.classNames = new String[num];
			}
			if (this.serializedData == null || num > this.serializedData.length) {
				this.serializedData = new byte[num][];
			}

			for (int i = 0; i < num; i++) {
				this.aggNames[i] = in.readUTF();
				this.classNames[i] = in.readUTF();

				int len = in.readInt();
				byte[] data = new byte[len];
				this.serializedData[i] = data;
				in.readFully(data);

			}

			this.aggregates = null;
		}
	}
}