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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.graph.gsa;

import org.apache.flink.api.common.aggregators.Aggregator;
import org.apache.flink.api.common.functions.IterationRuntimeContext;
import org.apache.flink.types.Value;

import java.io.Serializable;
import java.util.Collection;

@SuppressWarnings("serial")
public abstract class SumFunction implements Serializable {

	public abstract M sum(M arg0, M arg1);

	/**
	 * This method is executed once per superstep before the vertex update function is invoked for each vertex.
	 *
	 * @throws Exception Exceptions in the pre-superstep phase cause the superstep to fail.
	 */
	public void preSuperstep() {}

	/**
	 * This method is executed once per superstep after the vertex update function has been invoked for each vertex.
	 *
	 * @throws Exception Exceptions in the post-superstep phase cause the superstep to fail.
	 */
	public void postSuperstep() {}

	/**
	 * Gets the number of the superstep, starting at 1.
	 *
	 * @return The number of the current superstep.
	 */
	public int getSuperstepNumber() {
		return this.runtimeContext.getSuperstepNumber();
	}

	/**
	 * Gets the iteration aggregator registered under the given name. The iteration aggregator combines
	 * all aggregates globally once per superstep and makes them available in the next superstep.
	 *
	 * @param name The name of the aggregator.
	 * @return The aggregator registered under this name, or null, if no aggregator was registered.
	 */
	public > T getIterationAggregator(String name) {
		return this.runtimeContext.getIterationAggregator(name);
	}

	/**
	 * Get the aggregated value that an aggregator computed in the previous iteration.
	 *
	 * @param name The name of the aggregator.
	 * @return The aggregated value of the previous iteration.
	 */
	public  T getPreviousIterationAggregate(String name) {
		return this.runtimeContext.getPreviousIterationAggregate(name);
	}

	/**
	 * Gets the broadcast data set registered under the given name. Broadcast data sets
	 * are available on all parallel instances of a function.
	 *
	 * @param name The name under which the broadcast set is registered.
	 * @return The broadcast data set.
	 */
	public  Collection getBroadcastSet(String name) {
		return this.runtimeContext.getBroadcastVariable(name);
	}

	// --------------------------------------------------------------------------------------------
	//  Internal methods
	// --------------------------------------------------------------------------------------------

	private IterationRuntimeContext runtimeContext;

	public void init(IterationRuntimeContext iterationRuntimeContext) {
		this.runtimeContext = iterationRuntimeContext;
	}
}