/*
 * 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.beam.runners.twister2.utils;

import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;

import edu.iu.dsc.tws.api.dataset.DataPartition;
import edu.iu.dsc.tws.api.dataset.DataPartitionConsumer;
import edu.iu.dsc.tws.api.tset.TSetContext;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import org.apache.beam.runners.core.InMemoryMultimapSideInputView;
import org.apache.beam.runners.core.SideInputReader;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.KvCoder;
import org.apache.beam.sdk.transforms.Materializations.MultimapView;
import org.apache.beam.sdk.transforms.ViewFn;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.util.WindowedValue;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.sdk.values.TupleTag;
import org.apache.beam.sdk.values.WindowingStrategy;
import org.checkerframework.checker.nullness.qual.Nullable;

@SuppressWarnings({
  "rawtypes", // TODO(https://issues.apache.org/jira/browse/BEAM-10556)
  "nullness" // TODO(https://issues.apache.org/jira/browse/BEAM-10402)
})
public class Twister2SideInputReader implements SideInputReader {

  private final TSetContext runtimeContext;
  private final Map<TupleTag<?>, WindowingStrategy<?, ?>> sideInputs;

  public Twister2SideInputReader(
      Map<TupleTag<?>, WindowingStrategy<?, ?>> indexByView, TSetContext context) {
    this.sideInputs = indexByView;
    this.runtimeContext = context;
  }

  @Override
  public <T> @Nullable T get(PCollectionView<T> view, BoundedWindow window) {
    checkNotNull(view, "View passed to sideInput cannot be null");
    TupleTag<?> tag = view.getTagInternal();
    checkNotNull(sideInputs.get(tag), "Side input for " + view + " not available.");
    return getSideInput(view, window);
  }

  @Override
  public <T> boolean contains(PCollectionView<T> view) {
    return sideInputs.containsKey(view.getTagInternal());
  }

  @Override
  public boolean isEmpty() {
    return false;
  }

  private <T> T getSideInput(PCollectionView<T> view, BoundedWindow window) {
    Map<BoundedWindow, List<WindowedValue<KV<?, ?>>>> partitionedElements = new HashMap<>();
    DataPartition<?> sideInput = runtimeContext.getInput(view.getTagInternal().getId());
    DataPartitionConsumer<?> dataPartitionConsumer = sideInput.getConsumer();
    while (dataPartitionConsumer.hasNext()) {
      WindowedValue<KV<?, ?>> winValue = (WindowedValue<KV<?, ?>>) dataPartitionConsumer.next();
      for (BoundedWindow tbw : winValue.getWindows()) {
        List<WindowedValue<KV<?, ?>>> windowedValues =
            partitionedElements.computeIfAbsent(tbw, k -> new ArrayList<>());
        windowedValues.add(winValue);
      }
    }

    Map<BoundedWindow, T> resultMap = new HashMap<>();

    for (Map.Entry<BoundedWindow, List<WindowedValue<KV<?, ?>>>> elements :
        partitionedElements.entrySet()) {

      ViewFn<MultimapView, T> viewFn = (ViewFn<MultimapView, T>) view.getViewFn();
      Coder keyCoder = ((KvCoder<?, ?>) view.getCoderInternal()).getKeyCoder();
      resultMap.put(
          elements.getKey(),
          (T)
              viewFn.apply(
                  InMemoryMultimapSideInputView.fromIterable(
                      keyCoder,
                      (Iterable)
                          elements.getValue().stream()
                              .map(WindowedValue::getValue)
                              .collect(Collectors.toList()))));
    }
    T result = resultMap.get(window);
    if (result == null) {
      ViewFn<MultimapView, T> viewFn = (ViewFn<MultimapView, T>) view.getViewFn();
      result = viewFn.apply(InMemoryMultimapSideInputView.empty());
    }
    return result;
  }
}