/*
 * 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.io;


import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.api.common.io.statistics.BaseStatistics;
import org.apache.flink.api.common.operators.base.InnerJoinOperatorBase;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.io.InputSplit;
import org.apache.flink.core.io.InputSplitAssigner;

import java.io.IOException;

/**
 * A ReplicatingInputFormat replicates any {@link InputFormat} to all parallel instances of a DataSource,
 * i.e., the full input of the replicated InputFormat is completely processed by each parallel instance of the DataSource.
 * This is done by assigning all {@link org.apache.flink.core.io.InputSplit}s generated by the
 * replicated InputFormat to each parallel instance.
 *
 * Replicated data can only be used as input for a {@link InnerJoinOperatorBase} or
 * {@link org.apache.flink.api.common.operators.base.CrossOperatorBase} with the same parallelism as the DataSource.
 * Before being used as an input to a Join or Cross operator, replicated data might be processed in local pipelines by
 * by Map-based operators with the same parallelism as the source. Map-based operators are
 * {@link org.apache.flink.api.common.operators.base.MapOperatorBase},
 * {@link org.apache.flink.api.common.operators.base.FlatMapOperatorBase},
 * {@link org.apache.flink.api.common.operators.base.FilterOperatorBase}, and
 * {@link org.apache.flink.api.common.operators.base.MapPartitionOperatorBase}.
 *
 * Replicated DataSources can be used for local join processing (no data shipping) if one input is accessible on all
 * parallel instance of a join and the other input is (randomly) partitioned across all parallel instances.
 *
 * However, a replicated DataSource is a plan hint that can invalidate a Flink program if not used correctly (see
 * usage instructions above). In such situations, the optimizer is not able to generate a valid execution plan and
 * the program execution will fail.
 *
 * @param <OT> The output type of the wrapped InputFormat.
 * @param <S> The InputSplit type of the wrapped InputFormat.
 *
 * @see org.apache.flink.api.common.io.InputFormat
 * @see org.apache.flink.api.common.io.RichInputFormat
 * @see InnerJoinOperatorBase
 * @see org.apache.flink.api.common.operators.base.CrossOperatorBase
 * @see org.apache.flink.api.common.operators.base.MapOperatorBase
 * @see org.apache.flink.api.common.operators.base.FlatMapOperatorBase
 * @see org.apache.flink.api.common.operators.base.FilterOperatorBase
 * @see org.apache.flink.api.common.operators.base.MapPartitionOperatorBase
 */
@PublicEvolving
public final class ReplicatingInputFormat<OT, S extends InputSplit> extends RichInputFormat<OT, S> {

	private static final long serialVersionUID = 1L;

	private InputFormat<OT, S> replicatedIF;

	public ReplicatingInputFormat(InputFormat<OT, S> wrappedIF) {
		this.replicatedIF = wrappedIF;
	}

	public InputFormat<OT, S> getReplicatedInputFormat() {
		return this.replicatedIF;
	}

	@Override
	public void configure(Configuration parameters) {
		this.replicatedIF.configure(parameters);
	}

	@Override
	public BaseStatistics getStatistics(BaseStatistics cachedStatistics) throws IOException {
		return this.replicatedIF.getStatistics(cachedStatistics);
	}

	@Override
	public S[] createInputSplits(int minNumSplits) throws IOException {
		return this.replicatedIF.createInputSplits(minNumSplits);
	}

	@Override
	public InputSplitAssigner getInputSplitAssigner(S[] inputSplits) {
		return new ReplicatingInputSplitAssigner(inputSplits);
	}

	@Override
	public void open(S split) throws IOException {
		this.replicatedIF.open(split);
	}

	@Override
	public boolean reachedEnd() throws IOException {
		return this.replicatedIF.reachedEnd();
	}

	@Override
	public OT nextRecord(OT reuse) throws IOException {
		return this.replicatedIF.nextRecord(reuse);
	}

	@Override
	public void close() throws IOException {
		this.replicatedIF.close();
	}

	@Override
	public void setRuntimeContext(RuntimeContext context) {
		if (this.replicatedIF instanceof RichInputFormat) {
			((RichInputFormat)this.replicatedIF).setRuntimeContext(context);
		}
	}

	@Override
	public RuntimeContext getRuntimeContext(){
		if (this.replicatedIF instanceof RichInputFormat) {
			return ((RichInputFormat)this.replicatedIF).getRuntimeContext();
		} else{
			throw new RuntimeException("The underlying input format to this ReplicatingInputFormat isn't context aware");
		}
	}

	@Override
	public void openInputFormat() throws IOException {
		if (this.replicatedIF instanceof RichInputFormat) {
			((RichInputFormat)this.replicatedIF).openInputFormat();
		}
	}

	@Override
	public void closeInputFormat() throws IOException {
		if (this.replicatedIF instanceof RichInputFormat) {
			((RichInputFormat)this.replicatedIF).closeInputFormat();
		}
	}
}