/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.api.common.operators.base;

import org.apache.flink.annotation.Internal;
import org.apache.flink.annotation.Public;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.functions.CrossFunction;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.api.common.functions.util.FunctionUtils;
import org.apache.flink.api.common.operators.BinaryOperatorInformation;
import org.apache.flink.api.common.operators.DualInputOperator;
import org.apache.flink.api.common.operators.util.UserCodeClassWrapper;
import org.apache.flink.api.common.operators.util.UserCodeObjectWrapper;
import org.apache.flink.api.common.operators.util.UserCodeWrapper;
import org.apache.flink.api.common.typeutils.TypeSerializer;

import java.util.ArrayList;
import java.util.List;

/**
 * @see org.apache.flink.api.common.functions.CrossFunction
 */
@Internal
public class CrossOperatorBase<IN1, IN2, OUT, FT extends CrossFunction<IN1, IN2, OUT>> extends DualInputOperator<IN1, IN2, OUT, FT> {
	
	/**
	 * The cross hint tells the system which sizes to expect from the data sets
	 */
	@Public
	public static enum CrossHint {
		
		OPTIMIZER_CHOOSES,
		
		FIRST_IS_SMALL,
		
		SECOND_IS_SMALL
	}
	
	// --------------------------------------------------------------------------------------------
	
	private CrossHint hint = CrossHint.OPTIMIZER_CHOOSES;
	
	
	public CrossOperatorBase(UserCodeWrapper<FT> udf, BinaryOperatorInformation<IN1, IN2, OUT> operatorInfo, String name) {
		super(udf, operatorInfo, name);
		
		if (this instanceof CrossWithSmall) {
			setCrossHint(CrossHint.SECOND_IS_SMALL);
		}
		else if (this instanceof CrossWithLarge) {
			setCrossHint(CrossHint.FIRST_IS_SMALL);
		}
	}
	
	public CrossOperatorBase(FT udf, BinaryOperatorInformation<IN1, IN2, OUT> operatorInfo, String name) {
		this(new UserCodeObjectWrapper<FT>(udf), operatorInfo, name);
	}
	
	public CrossOperatorBase(Class<? extends FT> udf, BinaryOperatorInformation<IN1, IN2, OUT> operatorInfo, String name) {
		this(new UserCodeClassWrapper<FT>(udf), operatorInfo, name);
	}
	
	
	public void setCrossHint(CrossHint hint) {
		this.hint = hint == null ? CrossHint.OPTIMIZER_CHOOSES : hint;
	}
	
	public CrossHint getCrossHint() {
		return hint;
	}
	
	// --------------------------------------------------------------------------------------------

	@Override
	protected List<OUT> executeOnCollections(List<IN1> inputData1, List<IN2> inputData2, RuntimeContext ctx, ExecutionConfig executionConfig) throws Exception {
		CrossFunction<IN1, IN2, OUT> function = this.userFunction.getUserCodeObject();
		
		FunctionUtils.setFunctionRuntimeContext(function, ctx);
		FunctionUtils.openFunction(function, this.parameters);

		ArrayList<OUT> result = new ArrayList<OUT>(inputData1.size() * inputData2.size());
		
		TypeSerializer<IN1> inSerializer1 = getOperatorInfo().getFirstInputType().createSerializer(executionConfig);
		TypeSerializer<IN2> inSerializer2 = getOperatorInfo().getSecondInputType().createSerializer(executionConfig);
		TypeSerializer<OUT> outSerializer = getOperatorInfo().getOutputType().createSerializer(executionConfig);

		for (IN1 element1 : inputData1) {
			for (IN2 element2 : inputData2) {
				IN1 copy1 = inSerializer1.copy(element1);
				IN2 copy2 = inSerializer2.copy(element2);
				OUT o = function.cross(copy1, copy2);
				result.add(outSerializer.copy(o));
			}
		}

		FunctionUtils.closeFunction(function);
		return result;
	}
	
	// --------------------------------------------------------------------------------------------
	
	/**
	 * Marker interface to declare the second input as the smaller one.
	 */
	public static interface CrossWithSmall {}
	
	/**
	 * Marker interface to declare the second input as the larger one.
	 */
	public static interface CrossWithLarge {}
}