/***********************************************************************************************************************
 * 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.common.operators.base;

import eu.stratosphere.api.common.functions.GenericCombine;
import eu.stratosphere.api.common.functions.GenericGroupReduce;
import eu.stratosphere.api.common.operators.Ordering;
import eu.stratosphere.api.common.operators.SingleInputOperator;
import eu.stratosphere.api.common.operators.UnaryOperatorInformation;
import eu.stratosphere.api.common.operators.util.UserCodeClassWrapper;
import eu.stratosphere.api.common.operators.util.UserCodeObjectWrapper;
import eu.stratosphere.api.common.operators.util.UserCodeWrapper;


/**
 * @see GenericGroupReduce
 */
public class GroupReduceOperatorBase<IN, OUT, FT extends GenericGroupReduce<IN, OUT>> extends SingleInputOperator<IN, OUT, FT> {

	/**
	 * The ordering for the order inside a reduce group.
	 */
	private Ordering groupOrder;

	private boolean combinable;
	
	
	public GroupReduceOperatorBase(UserCodeWrapper<FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, int[] keyPositions, String name) {
		super(udf, operatorInfo, keyPositions, name);
	}
	
	public GroupReduceOperatorBase(FT udf, UnaryOperatorInformation<IN, OUT> operatorInfo, int[] keyPositions, String name) {
		super(new UserCodeObjectWrapper<FT>(udf), operatorInfo, keyPositions, name);
	}
	
	public GroupReduceOperatorBase(Class<? extends FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, int[] keyPositions, String name) {
		super(new UserCodeClassWrapper<FT>(udf), operatorInfo, keyPositions, name);
	}
	
	public GroupReduceOperatorBase(UserCodeWrapper<FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(udf, operatorInfo, name);
	}
	
	public GroupReduceOperatorBase(FT udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(new UserCodeObjectWrapper<FT>(udf), operatorInfo, name);
	}
	
	public GroupReduceOperatorBase(Class<? extends FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(new UserCodeClassWrapper<FT>(udf), operatorInfo, name);
	}
	

	/**
	 * Sets the order of the elements within a reduce group.
	 * 
	 * @param order The order for the elements in a reduce group.
	 */
	public void setGroupOrder(Ordering order) {
		this.groupOrder = order;
	}

	/**
	 * Gets the order of elements within a reduce group. If no such order has been
	 * set, this method returns null.
	 * 
	 * @return The secondary order.
	 */
	public Ordering getGroupOrder() {
		return this.groupOrder;
	}
	
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Marks the group reduce operation as combinable. Combinable operations may pre-reduce the
	 * data before the actual group reduce operations. Combinable user-defined functions
	 * must implement the interface {@link GenericCombine}.
	 * 
	 * @param combinable Flag to mark the group reduce operation as combinable.
	 */
	public void setCombinable(boolean combinable) {
		// sanity check
		if (combinable && !GenericCombine.class.isAssignableFrom(this.userFunction.getUserCodeClass())) {
			throw new IllegalArgumentException("Cannot set a UDF as combinable if it does not implement the interface " + 
					GenericCombine.class.getName());
		} else {
			this.combinable = combinable;
		}
	}
	
	/**
	 * Checks whether the operation is combinable.
	 * 
	 * @return True, if the UDF is combinable, false if not.
	 * 
	 * @see #setCombinable(boolean)
	 */
	public boolean isCombinable() {
		return this.combinable;
	}

}