/***********************************************************************************************************************
 * 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.functions;

import java.io.Serializable;

import eu.stratosphere.configuration.Configuration;

/**
 * An abstract stub implementation for user-defined functions. It offers default implementations
 * for {@link #open(Configuration)} and {@link #close()}. It also offers access to the
 * {@link RuntimeContext} and {@link IterationRuntimeContext}.
 */
public abstract class AbstractFunction implements Function, Serializable {
	
	private static final long serialVersionUID = 1L;
	
	// --------------------------------------------------------------------------------------------
	//  Runtime context access
	// --------------------------------------------------------------------------------------------
	
	private transient RuntimeContext runtimeContext;

	public void setRuntimeContext(RuntimeContext t) {
		if (this.runtimeContext == null) {
			this.runtimeContext = t;
		} else {
			throw new IllegalStateException("Error: The runtime context has already been set.");
		}
	}
	
	public RuntimeContext getRuntimeContext() {
		if (this.runtimeContext != null) {
			return this.runtimeContext;
		} else {
			throw new IllegalStateException("The runtime context has not been initialized.");
		}
	}
	
	public IterationRuntimeContext getIterationRuntimeContext() {
		if (this.runtimeContext == null) {
			throw new IllegalStateException("The runtime context has not been initialized.");
		} else if (this.runtimeContext instanceof IterationRuntimeContext) {
			return (IterationRuntimeContext) this.runtimeContext;
		} else {
			throw new IllegalStateException("This stub is not part of an iteration step function.");
		}
	}
	
	// --------------------------------------------------------------------------------------------
	//  Default life cycle methods
	// --------------------------------------------------------------------------------------------
	
	@Override
	public void open(Configuration parameters) throws Exception {}

	@Override
	public void close() throws Exception {}
}