/*
 * 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.examples.java.graph;

import org.apache.flink.api.common.functions.CoGroupFunction;
import org.apache.flink.api.common.functions.GroupReduceFunction;
import org.apache.flink.api.common.functions.JoinFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.operators.IterativeDataSet;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.examples.java.graph.util.ConnectedComponentsData;
import org.apache.flink.util.Collector;

import java.util.HashSet;
import java.util.Set;

@SuppressWarnings("serial")
public class TransitiveClosureNaive {

	public static void main (String... args) throws Exception {

		// Checking input parameters
		final ParameterTool params = ParameterTool.fromArgs(args);

		// set up execution environment
		ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

		// make parameters available in the web interface
		env.getConfig().setGlobalJobParameters(params);

		final int maxIterations = params.getInt("iterations", 10);

		DataSet<Tuple2<Long, Long>> edges;
		if (params.has("edges")) {
			edges = env.readCsvFile(params.get("edges")).fieldDelimiter(" ").types(Long.class, Long.class);
		} else {
			System.out.println("Executing TransitiveClosureNaive example with default edges data set.");
			System.out.println("Use --edges to specify file input.");
			edges = ConnectedComponentsData.getDefaultEdgeDataSet(env);
		}

		IterativeDataSet<Tuple2<Long,Long>> paths = edges.iterate(maxIterations);

		DataSet<Tuple2<Long,Long>> nextPaths = paths
				.join(edges)
				.where(1)
				.equalTo(0)
				.with(new JoinFunction<Tuple2<Long, Long>, Tuple2<Long, Long>, Tuple2<Long, Long>>() {
					@Override
					/**
						left: Path (z,x) - x is reachable by z
						right: Edge (x,y) - edge x-->y exists
						out: Path (z,y) - y is reachable by z
					 */
					public Tuple2<Long, Long> join(Tuple2<Long, Long> left, Tuple2<Long, Long> right) throws Exception {
						return new Tuple2<Long, Long>(left.f0, right.f1);
					}
				}).withForwardedFieldsFirst("0").withForwardedFieldsSecond("1")
				.union(paths)
				.groupBy(0, 1)
				.reduceGroup(new GroupReduceFunction<Tuple2<Long, Long>, Tuple2<Long, Long>>() {
					@Override
					public void reduce(Iterable<Tuple2<Long, Long>> values, Collector<Tuple2<Long, Long>> out) throws Exception {
						out.collect(values.iterator().next());
					}
				}).withForwardedFields("0;1");

		DataSet<Tuple2<Long,Long>> newPaths = paths
				.coGroup(nextPaths)
				.where(0).equalTo(0)
				.with(new CoGroupFunction<Tuple2<Long, Long>, Tuple2<Long, Long>, Tuple2<Long, Long>>() {
					Set<Tuple2<Long,Long>> prevSet = new HashSet<Tuple2<Long,Long>>();
					@Override
					public void coGroup(Iterable<Tuple2<Long, Long>> prevPaths, Iterable<Tuple2<Long, Long>> nextPaths, Collector<Tuple2<Long, Long>> out) throws Exception {
						for (Tuple2<Long,Long> prev : prevPaths) {
							prevSet.add(prev);
						}
						for (Tuple2<Long,Long> next: nextPaths) {
							if (!prevSet.contains(next)) {
								out.collect(next);
							}
						}
					}
				}).withForwardedFieldsFirst("0").withForwardedFieldsSecond("0");

		DataSet<Tuple2<Long, Long>> transitiveClosure = paths.closeWith(nextPaths, newPaths);


		// emit result
		if (params.has("output")) {
			transitiveClosure.writeAsCsv(params.get("output"), "\n", " ");

			// execute program explicitly, because file sinks are lazy
			env.execute("Transitive Closure Example");
		} else {
			System.out.println("Printing result to stdout. Use --output to specify output path.");
			transitiveClosure.print();
		}
	}
}