/***********************************************************************************************************************
 *
 * 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 java.util.Map;

import eu.stratosphere.api.common.operators.SemanticProperties;
import eu.stratosphere.api.java.DataSet;
import eu.stratosphere.configuration.Configuration;

/**
 * This interface marks operators as operators that execute user-defined functions (UDFs), such as
 * {@link MapFunction}, {@link ReduceFunction} or {@link CoGroupFunction}.
 * The UDF operators stand in contrast to operators that execute built-in operations, like aggregations.
 */
public interface UdfOperator<O extends UdfOperator<O>> {
	
	// --------------------------------------------------------------------------------------------
	// Accessors
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Gets the configuration parameters that will be passed to the UDF's open method
	 * {@link AbstractFunction#open(Configuration)}. The configuration is set via the {@link #withParameters(Configuration)}
	 * method.
	 * 
	 * @return The configuration parameters for the UDF.
	 */
	Configuration getParameters();
	
	/**
	 * Gets the broadcast sets (name and data set) that have been added to context of the UDF.
	 * Broadcast sets are added to a UDF via the method {@link #withBroadcastSet(DataSet, String)}.
	 * 
	 * @return The broadcast data sets that have been added to this UDF.
	 */
	Map<String, DataSet<?>> getBroadcastSets();
	
	/**
	 * Gets the semantic properties that have been set for the user-defined functions (UDF).
	 * This method may return null, if no semantic properties have been set so far.
	 * 
	 * @return The semantic properties of the UDF.
	 */
	SemanticProperties getSematicProperties();
	
	// --------------------------------------------------------------------------------------------
	// Fluent API methods
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Sets the configuration parameters for the UDF. These are optional parameters that are passed
	 * to the UDF in the {@link AbstractFunction#open(Configuration)} method.
	 * 
	 * @param parameters The configuration parameters for the UDF.
	 * @return The operator itself, to allow chaining function calls.
	 */
	O withParameters(Configuration parameters);
	
	/**
	 * Adds a certain data set as a broadcast set to this operator. Broadcasted data sets are available at all
	 * parallel instances of this operator. A broadcast data set is registered under a certain name, and can be
	 * retrieved under that name from the operators runtime context via {@link RuntimeContext#getBroadcastVariable(String)}.
	 * The runtime context itself is available in all UDFs via {@link AbstractFunction#getRuntimeContext()}.
	 * 
	 * @param data The data set to be broadcasted.
	 * @param name The name under which the broadcast data set retrieved.
	 * @return The operator itself, to allow chaining function calls.
	 */
	O withBroadcastSet(DataSet<?> data, String name);
}