/*
 * 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.apex.translation;

import static com.google.common.base.Preconditions.checkArgument;

import com.datatorrent.api.Context.PortContext;
import com.datatorrent.api.DAG;
import com.datatorrent.api.Operator;
import com.datatorrent.api.Operator.InputPort;
import com.datatorrent.api.Operator.OutputPort;
import com.google.common.collect.Iterables;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.beam.runners.apex.ApexPipelineOptions;
import org.apache.beam.runners.apex.translation.utils.ApexStateInternals;
import org.apache.beam.runners.apex.translation.utils.ApexStateInternals.ApexStateBackend;
import org.apache.beam.runners.apex.translation.utils.ApexStreamTuple;
import org.apache.beam.runners.apex.translation.utils.CoderAdapterStreamCodec;
import org.apache.beam.runners.core.construction.TransformInputs;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.runners.AppliedPTransform;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.apache.beam.sdk.util.WindowedValue.FullWindowedValueCoder;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.sdk.values.PInput;
import org.apache.beam.sdk.values.PValue;
import org.apache.beam.sdk.values.TupleTag;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.apache.commons.lang3.tuple.Pair;

/**
 * Maintains context data for {@link TransformTranslator}s.
 */
@SuppressWarnings({"rawtypes", "unchecked", "TypeParameterUnusedInFormals"})
class TranslationContext {

  private final ApexPipelineOptions pipelineOptions;
  private AppliedPTransform<?, ?, ?> currentTransform;
  private final Map<PCollection, Pair<OutputPortInfo, List<InputPortInfo>>> streams =
          new HashMap<>();
  private final Map<String, Operator> operators = new HashMap<>();
  private final Map<PCollectionView<?>, PInput> viewInputs = new HashMap<>();
  private Map<PInput, PInput> aliasCollections = new HashMap<>();

  public void addView(PCollectionView<?> view) {
    this.viewInputs.put(view, this.getInput());
  }

  public <InputT extends PInput> InputT getViewInput(PCollectionView<?> view) {
    PInput input = this.viewInputs.get(view);
    checkArgument(input != null, "unknown view " + view.getName());
    return (InputT) input;
  }

  TranslationContext(ApexPipelineOptions pipelineOptions) {
    this.pipelineOptions = pipelineOptions;
  }

  public void setCurrentTransform(AppliedPTransform<?, ?, ?> transform) {
    this.currentTransform = transform;
  }

  public ApexPipelineOptions getPipelineOptions() {
    return pipelineOptions;
  }

  public String getFullName() {
    return getCurrentTransform().getFullName();
  }

  public Map<TupleTag<?>, PValue> getInputs() {
    return getCurrentTransform().getInputs();
  }

  public <InputT extends PValue> InputT getInput() {
    return (InputT)
        Iterables.getOnlyElement(TransformInputs.nonAdditionalInputs(getCurrentTransform()));
  }

  public Map<TupleTag<?>, PValue> getOutputs() {
    return getCurrentTransform().getOutputs();
  }

  public <OutputT extends PValue> OutputT getOutput() {
    return (OutputT) Iterables.getOnlyElement(getCurrentTransform().getOutputs().values());
  }

  private AppliedPTransform<?, ?, ?> getCurrentTransform() {
    checkArgument(currentTransform != null, "current transform not set");
    return currentTransform;
  }

  public void addOperator(Operator operator, OutputPort port) {
    addOperator(operator, port, getOutput());
  }

  /**
   * Register operator and output ports for the given collections.
   * @param operator
   * @param ports
   */
  public void addOperator(Operator operator, Map<PCollection<?>, OutputPort<?>> ports) {
    boolean first = true;
    for (Map.Entry<PCollection<?>, OutputPort<?>> portEntry : ports.entrySet()) {
      if (first) {
        addOperator(operator, portEntry.getValue(), portEntry.getKey());
        first = false;
      } else {
        this.streams.put(portEntry.getKey(),
                         (Pair) new ImmutablePair<>(new OutputPortInfo(portEntry.getValue(),
                                                                       getCurrentTransform()),
                                                    new ArrayList<>()));
      }
    }
  }

  /**
   * Add the operator with its output port for the given result {link PCollection}.
   * @param operator
   * @param port
   * @param output
   */
  public void addOperator(Operator operator, OutputPort port, PCollection output) {
    // Apex DAG requires a unique operator name
    // use the transform's name and make it unique
    String name = getCurrentTransform().getFullName();
    for (int i = 1; this.operators.containsKey(name); i++) {
      name = getCurrentTransform().getFullName() + i;
    }
    this.operators.put(name, operator);
    this.streams.put(output, (Pair) new ImmutablePair<>(
            new OutputPortInfo(port, getCurrentTransform()),
            new ArrayList<>()));
  }

  public void addStream(PInput input, InputPort inputPort) {
    while (aliasCollections.containsKey(input)) {
      input = aliasCollections.get(input);
    }

    Pair<OutputPortInfo, List<InputPortInfo>> stream = this.streams.get(input);
    checkArgument(stream != null, "no upstream operator defined for " + input);
    stream.getRight().add(new InputPortInfo(inputPort, getCurrentTransform()));
  }

  /**
   * Set the given output as alias for another input,
   * i.e. there won't be a stream representation in the target DAG.
   * @param alias
   * @param source
   */
  public void addAlias(PValue alias, PInput source) {
    aliasCollections.put(alias, source);
  }

  public void populateDAG(DAG dag) {
    for (Map.Entry<String, Operator> nameAndOperator : this.operators.entrySet()) {
      dag.addOperator(nameAndOperator.getKey(), nameAndOperator.getValue());
    }

    int streamIndex = 0;
    for (Map.Entry<PCollection, Pair<OutputPortInfo, List<InputPortInfo>>> streamEntry : this.
        streams.entrySet()) {
      List<InputPortInfo> destInfo = streamEntry.getValue().getRight();
      InputPort[] sinks = new InputPort[destInfo.size()];
      for (int i = 0; i < sinks.length; i++) {
        sinks[i] = destInfo.get(i).port;
      }

      if (sinks.length > 0) {
        DAG.StreamMeta streamMeta = dag.addStream("stream" + streamIndex++,
                                                  streamEntry.getValue().getLeft().port, sinks);
        if (pipelineOptions.isParDoFusionEnabled()) {
          optimizeStreams(streamMeta, streamEntry);
        }

        for (InputPort port : sinks) {
          PCollection pc = streamEntry.getKey();
          Coder coder = pc.getCoder();
          if (pc.getWindowingStrategy() != null) {
            coder = FullWindowedValueCoder.of(pc.getCoder(),
                pc.getWindowingStrategy().getWindowFn().windowCoder()
                );
          }
          Coder<Object> wrapperCoder = ApexStreamTuple.ApexStreamTupleCoder.of(coder);
          CoderAdapterStreamCodec streamCodec = new CoderAdapterStreamCodec(wrapperCoder);
          dag.setInputPortAttribute(port, PortContext.STREAM_CODEC, streamCodec);
        }
      }
    }
  }

  private void optimizeStreams(DAG.StreamMeta streamMeta,
                               Map.Entry<PCollection,
                                         Pair<OutputPortInfo, List<InputPortInfo>>> streamEntry) {
    DAG.Locality loc = null;

    List<InputPortInfo> sinks = streamEntry.getValue().getRight();
    OutputPortInfo source = streamEntry.getValue().getLeft();
    PTransform sourceTransform = source.transform.getTransform();
    if (sourceTransform instanceof ParDo.MultiOutput
        || sourceTransform instanceof Window.Assign) {
      // source qualifies for chaining, check sink(s)
      for (InputPortInfo sink : sinks) {
        PTransform transform = sink.transform.getTransform();
        if (transform instanceof ParDo.MultiOutput) {
          ParDo.MultiOutput t = (ParDo.MultiOutput) transform;
          if (t.getSideInputs().size() > 0) {
            loc = DAG.Locality.CONTAINER_LOCAL;
            break;
          } else {
            loc = DAG.Locality.THREAD_LOCAL;
          }
        } else if (transform instanceof Window.Assign) {
          loc = DAG.Locality.THREAD_LOCAL;
        } else {
          // cannot chain, if there is any other sink
          loc = null;
          break;
        }
      }
    }

    streamMeta.setLocality(loc);
  }

  /**
   * Return the state backend for the pipeline translation.
   * @return
   */
  public ApexStateBackend getStateBackend() {
    return new ApexStateInternals.ApexStateBackend();
  }

  static class InputPortInfo {
    InputPort port;
    AppliedPTransform transform;

    public InputPortInfo(InputPort port, AppliedPTransform transform) {
      this.port = port;
      this.transform = transform;
    }
  }

  static class OutputPortInfo {
    OutputPort port;
    AppliedPTransform transform;

    public OutputPortInfo(OutputPort port, AppliedPTransform transform) {
      this.port = port;
      this.transform = transform;
    }
  }
}
