/***********************************************************************************************************************
 *
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.api.java.operators;

import eu.stratosphere.api.common.operators.Order;
import eu.stratosphere.api.java.DataSet;
import eu.stratosphere.api.java.aggregation.Aggregations;
import eu.stratosphere.api.java.functions.GroupReduceFunction;
import eu.stratosphere.api.java.functions.ReduceFunction;

public class UnsortedGrouping<T> extends Grouping<T> {

	public UnsortedGrouping(DataSet<T> set, Keys<T> keys) {
		super(set, keys);
	}

	// --------------------------------------------------------------------------------------------
	//  Operations / Transformations
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Applies an Aggregate transformation on a grouped {@link Tuple} {@link DataSet}.<br/>
	 * <b>Note: Only Tuple DataSets can be aggregated.</b>
	 * The transformation applies a built-in {@link Aggregations Aggregation} on a specified field 
	 *   of a Tuple group. Additional aggregation functions can be added to the resulting 
	 *   {@link AggregateOperator} by calling {@link AggregateOperator#and(Aggregations, int)}.
	 * 
	 * @param agg The built-in aggregation function that is computed.
	 * @param field The index of the Tuple field on which the aggregation function is applied.
	 * @return An AggregateOperator that represents the aggregated DataSet. 
	 * 
	 * @see Tuple
	 * @see Aggregations
	 * @see AggregateOperator
	 * @see DataSet
	 */
	public AggregateOperator<T> aggregate(Aggregations agg, int field) {
		return new AggregateOperator<T>(this, agg, field);
	}
	
	/**
	 * Applies a Reduce transformation on a grouped {@link DataSet}.<br/>
	 * For each group, the transformation consecutively calls a {@link ReduceFunction} 
	 *   until only a single element for each group remains. 
	 * A ReduceFunction combines two elements into one new element of the same type.
	 * 
	 * @param reducer The ReduceFunction that is applied on each group of the DataSet.
	 * @return A ReduceOperator that represents the reduced DataSet.
	 * 
	 * @see ReduceFunction
	 * @see ReduceOperator
	 * @see DataSet
	 */
	public ReduceOperator<T> reduce(ReduceFunction<T> reducer) {
		if (reducer == null) {
			throw new NullPointerException("Reduce function must not be null.");
		}
		return new ReduceOperator<T>(this, reducer);
	}
	
	/**
	 * Applies a GroupReduce transformation on a grouped {@link DataSet}.<br/>
	 * The transformation calls a {@link GroupReduceFunction} for each group of the DataSet.
	 * A GroupReduceFunction can iterate over all elements of a group and emit any
	 *   number of output elements including none.
	 * 
	 * @param reducer The GroupReduceFunction that is applied on each group of the DataSet.
	 * @return A GroupReduceOperator that represents the reduced DataSet.
	 * 
	 * @see GroupReduceFunction
	 * @see GroupReduceOperator
	 * @see DataSet
	 */
	public <R> ReduceGroupOperator<T, R> reduceGroup(GroupReduceFunction<T, R> reducer) {
		if (reducer == null) {
			throw new NullPointerException("GroupReduce function must not be null.");
		}
		return new ReduceGroupOperator<T, R>(this, reducer);
	}

	// --------------------------------------------------------------------------------------------
	//  Group Operations
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Sorts {@link Tuple} elements within a group on the specified field in the specified {@link Order}.</br>
	 * <b>Note: Only groups of Tuple elements can be sorted.</b><br/>
	 * Groups can be sorted by multiple fields by chaining {@link #sortGroup(int, Order)} calls.
	 * 
	 * @param field The Tuple field on which the group is sorted.
	 * @param order The Order in which the specified Tuple field is sorted.
	 * @return A SortedGrouping with specified order of group element.
	 * 
	 * @see Tuple
	 * @see Order
	 */
	public SortedGrouping<T> sortGroup(int field, Order order) {
		return new SortedGrouping<T>(this.dataSet, this.keys, field, order);
	}
	
}