/*
 * Copyright (c) 2011-2015 EPFL DATA Laboratory
 * Copyright (c) 2014-2015 The Squall Collaboration (see NOTICE)
 *
 * All rights reserved.
 *
 * 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 ch.epfl.data.squall.storm_components.stream_grouping;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Random;

import backtype.storm.generated.GlobalStreamId;
import backtype.storm.grouping.CustomStreamGrouping;
import backtype.storm.task.WorkerTopologyContext;
import ch.epfl.data.squall.utilities.MyUtilities;

/*
 * If the list of all possible hash values isspecified,
 *   it uses uniform key (not number of tuples!) distribution
 * Otherwise, we encode fieldGrouping exactly the same as the Storm authors.
 * Because of NoACK possibility, have to be used everywhere in the code.
 */
public class ShuffleStreamGrouping implements CustomStreamGrouping {
    private static final long serialVersionUID = 1L;
    // the number of tasks on the level this stream grouping is sending to
    private int _numTargetTasks;
    private List<Integer> _targetTasks;

    private final Map _map;

    private Random _rndGen = new Random();

    /*
     * fullHashList is null if grouping is not balanced
     */
    public ShuffleStreamGrouping(Map map) {
	_map = map;
    }

    @Override
    public List<Integer> chooseTasks(int taskId, List<Object> stormTuple) {
	final List<String> tuple = (List<String>) stormTuple.get(1);
	if (MyUtilities.isFinalAck(tuple, _map)) {
	    // send to everyone
	    return _targetTasks;
	} else
	    return Arrays.asList(_targetTasks.get(_rndGen
		    .nextInt(_numTargetTasks)));
    }

    @Override
    public void prepare(WorkerTopologyContext wtc, GlobalStreamId gsi,
	    List<Integer> targetTasks) {
	_targetTasks = targetTasks;
	_numTargetTasks = targetTasks.size();
    }

}