/*
 * 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.api.common.ExecutionConfig;
import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.api.common.functions.util.CopyingListCollector;
import org.apache.flink.api.common.functions.util.FunctionUtils;
import org.apache.flink.api.common.operators.SingleInputOperator;
import org.apache.flink.api.common.operators.UnaryOperatorInformation;
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.FlatMapFunction
 */
@Internal
public class FlatMapOperatorBase<IN, OUT, FT extends FlatMapFunction<IN, OUT>> extends SingleInputOperator<IN, OUT, FT> {
	
	public FlatMapOperatorBase(UserCodeWrapper<FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(udf, operatorInfo, name);
	}

	public FlatMapOperatorBase(FT udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(new UserCodeObjectWrapper<FT>(udf), operatorInfo, name);
	}

	public FlatMapOperatorBase(Class<? extends FT> udf, UnaryOperatorInformation<IN, OUT> operatorInfo, String name) {
		super(new UserCodeClassWrapper<FT>(udf), operatorInfo, name);
	}

	// ------------------------------------------------------------------------

	@Override
	protected List<OUT> executeOnCollections(List<IN> input, RuntimeContext ctx, ExecutionConfig executionConfig) throws Exception {
		FlatMapFunction<IN, OUT> function = userFunction.getUserCodeObject();
		
		FunctionUtils.setFunctionRuntimeContext(function, ctx);
		FunctionUtils.openFunction(function, parameters);

		ArrayList<OUT> result = new ArrayList<OUT>(input.size());

		TypeSerializer<IN> inSerializer = getOperatorInfo().getInputType().createSerializer(executionConfig);
		TypeSerializer<OUT> outSerializer = getOperatorInfo().getOutputType().createSerializer(executionConfig);

		CopyingListCollector<OUT> resultCollector = new CopyingListCollector<OUT>(result, outSerializer);

		for (IN element : input) {
			IN inCopy = inSerializer.copy(element);
			function.flatMap(inCopy, resultCollector);
		}

		FunctionUtils.closeFunction(function);

		return result;
	}
}