/**
 * 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
 *
 * <p>http://www.apache.org/licenses/LICENSE-2.0
 *
 * <p>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.tez.runtime.library.input;

import java.io.IOException;
import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.tez.dag.api.GroupInputEdge;
import org.apache.tez.dag.api.TezUncheckedException;
import org.apache.tez.runtime.api.*;
import org.apache.tez.runtime.library.api.KeyValuesReader;

/**
 * Implements a {@link MergedLogicalInput} that merges the incoming inputs (e.g. from a {@link
 * GroupInputEdge} and provide a unified view of the input. It concatenates all the inputs to
 * provide a unified view
 */
@Public
public class CelebornConcatenatedMergedKeyValuesInput extends MergedLogicalInput {

  private ConcatenatedMergedKeyValuesReader concatenatedMergedKeyValuesReader;

  public CelebornConcatenatedMergedKeyValuesInput(MergedInputContext context, List<Input> inputs) {
    super(context, inputs);
  }

  public class ConcatenatedMergedKeyValuesReader extends KeyValuesReader {
    private int currentReaderIndex = 0;
    private KeyValuesReader currentReader;

    @Override
    public boolean next() throws IOException {
      while ((currentReader == null) || !currentReader.next()) {
        if (currentReaderIndex == getInputs().size()) {
          hasCompletedProcessing();
          completedProcessing = true;
          getContext().notifyProgress();
          return false;
        }
        try {
          Reader reader = getInputs().get(currentReaderIndex).getReader();
          if (!(reader instanceof KeyValuesReader)) {
            throw new TezUncheckedException(
                "Expected KeyValuesReader. " + "Got: " + reader.getClass().getName());
          }
          currentReader = (KeyValuesReader) reader;
          currentReaderIndex++;
          getContext().notifyProgress();
        } catch (Exception e) {
          // An InterruptedException is not expected here since this works off of
          // underlying readers which take care of throwing IOInterruptedExceptions
          if (e instanceof IOException) {
            throw (IOException) e;
          } else {
            throw new IOException(e);
          }
        }
      }
      return true;
    }

    @Override
    public Object getCurrentKey() throws IOException {
      return currentReader.getCurrentKey();
    }

    @Override
    public Iterable<Object> getCurrentValues() throws IOException {
      return currentReader.getCurrentValues();
    }

    public float getProgress() throws IOException, InterruptedException {
      return (1.0f) * (currentReaderIndex + 1) / getInputs().size();
    }
  }

  /** Provides a {@link KeyValuesReader} that iterates over the concatenated input data */
  @Override
  public KeyValuesReader getReader() throws Exception {
    concatenatedMergedKeyValuesReader = new ConcatenatedMergedKeyValuesReader();
    return concatenatedMergedKeyValuesReader;
  }

  @Override
  public void setConstituentInputIsReady(Input input) {
    informInputReady();
  }

  @Override
  public float getProgress() throws ProgressFailedException, InterruptedException {
    try {
      return concatenatedMergedKeyValuesReader.getProgress();
    } catch (IOException e) {
      throw new ProgressFailedException("getProgress encountered IOException ", e);
    }
  }
}
