/*
 * 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.nemo.common.ir;

import org.apache.commons.lang.mutable.MutableObject;
import org.apache.nemo.common.KeyRange;
import org.apache.nemo.common.Pair;
import org.apache.nemo.common.Util;
import org.apache.nemo.common.dag.DAG;
import org.apache.nemo.common.dag.DAGInterface;
import org.apache.nemo.common.ir.edge.IREdge;
import org.apache.nemo.common.ir.edge.executionproperty.*;
import org.apache.nemo.common.ir.executionproperty.EdgeExecutionProperty;
import org.apache.nemo.common.ir.executionproperty.VertexExecutionProperty;
import org.apache.nemo.common.ir.vertex.IRVertex;
import org.apache.nemo.common.ir.vertex.SourceVertex;
import org.apache.nemo.common.ir.vertex.executionproperty.*;
import org.apache.nemo.common.ir.vertex.utility.MessageAggregatorVertex;
import org.apache.nemo.common.ir.vertex.utility.RelayVertex;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.Serializable;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.IntSupplier;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 * Checks the integrity of an IR DAG.
 */
public final class IRDAGChecker {
  private static final Logger LOG = LoggerFactory.getLogger(IRDAGChecker.class.getName());

  private static final IRDAGChecker SINGLETON = new IRDAGChecker();

  private final List<SingleVertexChecker> singleVertexCheckerList;
  private final List<SingleEdgeChecker> singleEdgeCheckerList;
  private final List<NeighborChecker> neighborCheckerList;
  private final List<GlobalDAGChecker> globalDAGCheckerList;

  public static IRDAGChecker get() {
    return SINGLETON;
  }

  private IRDAGChecker() {
    this.singleVertexCheckerList = new ArrayList<>();
    this.singleEdgeCheckerList = new ArrayList<>();
    this.neighborCheckerList = new ArrayList<>();
    this.globalDAGCheckerList = new ArrayList<>();

    addParallelismCheckers();
    addShuffleEdgeCheckers();
    addPartitioningCheckers();
    addEncodingCompressionCheckers();
    addTriggerVertexCheckers();
    addStreamVertexCheckers();
    addLoopVertexCheckers();
    addScheduleGroupCheckers();
    addCacheCheckers();
  }

  /**
   * Applies all of the checkers on the DAG.
   *
   * @param underlyingDAG to check
   * @return the result.
   */
  public CheckerResult doCheck(final DAG<IRVertex, IREdge> underlyingDAG) {
    // Traverse the DAG once to run all local checkers
    for (final IRVertex v : underlyingDAG.getTopologicalSort()) {
      // Run per-vertex checkers
      for (final SingleVertexChecker checker : singleVertexCheckerList) {
        final CheckerResult result = checker.check(v);
        if (!result.isPassed()) {
          return result;
        }
      }

      final List<IREdge> inEdges = underlyingDAG.getIncomingEdgesOf(v);
      final List<IREdge> outEdges = underlyingDAG.getOutgoingEdgesOf(v);

      // Run per-edge checkers
      for (final IREdge inEdge : inEdges) {
        for (final SingleEdgeChecker checker : singleEdgeCheckerList) {
          final CheckerResult result = checker.check(inEdge);
          if (!result.isPassed()) {
            return result;
          }
        }
      }

      // Run neighbor checkers
      for (final NeighborChecker checker : neighborCheckerList) {
        final CheckerResult result = checker.check(v, inEdges, outEdges);
        if (!result.isPassed()) {
          return result;
        }
      }
    }

    // Run global checkers
    for (final GlobalDAGChecker checker : globalDAGCheckerList) {
      final CheckerResult result = checker.check(underlyingDAG);
      if (!result.isPassed()) {
        return result;
      }
    }

    return success();
  }

  ///////////////////////////// Checker interfaces

  /**
   * Checks each single vertex.
   */
  private interface SingleVertexChecker {
    CheckerResult check(IRVertex irVertex);
  }

  /**
   * Checks each single edge.
   */
  private interface SingleEdgeChecker {
    CheckerResult check(IREdge irEdge);
  }

  /**
   * Checks each vertex and its neighbor edges.
   */
  private interface NeighborChecker {
    CheckerResult check(IRVertex irVertex,
                        List<IREdge> inEdges,
                        List<IREdge> outEdges);
  }

  /**
   * Checks the entire DAG.
   */
  public interface GlobalDAGChecker {
    CheckerResult check(DAG<IRVertex, IREdge> irdag);
  }

  ///////////////////////////// Checker implementations

  /**
   * Parallelism-related checkers.
   */
  void addParallelismCheckers() {
    final SingleVertexChecker parallelismWithOtherEPsInSingleVertex = (v -> {
      final Optional<Integer> parallelism = v.getPropertyValue(ParallelismProperty.class);
      if (!parallelism.isPresent()) {
        return success(); // No need to check, if the parallelism is not set yet
      }

      final Optional<Integer> resourceSiteSize = v.getPropertyValue(ResourceSiteProperty.class)
        .map(rs -> rs.values().stream().mapToInt(Integer::intValue).sum());
      if (resourceSiteSize.isPresent() && !parallelism.equals(resourceSiteSize)) {
        return failure("Parallelism must equal to sum of site nums",
          v, ParallelismProperty.class, ResourceSiteProperty.class);
      }

      final Optional<HashSet<Integer>> antiAffinitySet = v.getPropertyValue(ResourceAntiAffinityProperty.class);
      if (antiAffinitySet.isPresent()
        && !getZeroToNSet(parallelism.get()).containsAll(antiAffinitySet.get())) {
        return failure("Offsets must be within parallelism",
          v, ParallelismProperty.class, ResourceAntiAffinityProperty.class);
      }

      return success();
    });
    singleVertexCheckerList.add(parallelismWithOtherEPsInSingleVertex);

    final SingleVertexChecker parallelismOfSourceVertex = (v -> {
      final Optional<Integer> parallelism = v.getPropertyValue(ParallelismProperty.class);
      try {
        if (parallelism.isPresent() && v instanceof SourceVertex) {
          final int numOfReadables = ((SourceVertex) v).getReadables(parallelism.get()).size();
          if (parallelism.get() != numOfReadables) {
            return failure(String.format("(Parallelism %d) != (Number of SourceVertex %s Readables %d)",
              parallelism.get(), v.getId(), numOfReadables));
          }
        }
      } catch (Exception e) {
        return failure(e.getMessage());
      }

      return success();
    });
    singleVertexCheckerList.add(parallelismOfSourceVertex);

    final NeighborChecker parallelismWithCommPattern = ((v, inEdges, outEdges) -> {
      // Just look at incoming (edges, as this checker will be applied on every vertex
      for (final IREdge inEdge : inEdges) {
        if (CommunicationPatternProperty.Value.ONE_TO_ONE
          .equals(inEdge.getPropertyValue(CommunicationPatternProperty.class).get())) {
          if (v.getPropertyValue(ParallelismProperty.class).isPresent()
            && inEdge.getSrc().getPropertyValue(ParallelismProperty.class).isPresent()
            && !inEdge.getSrc().getPropertyValue(ParallelismProperty.class)
            .equals(v.getPropertyValue(ParallelismProperty.class))) {
            return failure("OneToOne edges must have the same parallelism",
              inEdge.getSrc(), ParallelismProperty.class, v, ParallelismProperty.class);
          }
        }
      }

      return success();
    });
    neighborCheckerList.add(parallelismWithCommPattern);

    final NeighborChecker parallelismWithPartitionSet = ((v, inEdges, outEdges) -> {
      final Optional<Integer> parallelism = v.getPropertyValue(ParallelismProperty.class);
      for (final IREdge inEdge : inEdges) {
        final Optional<Integer> keyRangeListSize = inEdge.getPropertyValue(PartitionSetProperty.class)
          .map(List::size);
        if (parallelism.isPresent() && keyRangeListSize.isPresent() && !parallelism.equals(keyRangeListSize)) {
          return failure("PartitionSet must contain all task offsets required for the dst parallelism",
            v, ParallelismProperty.class, inEdge, PartitionSetProperty.class);
        }
      }

      return success();
    });
    neighborCheckerList.add(parallelismWithPartitionSet);
  }

  void addPartitioningCheckers() {
    final NeighborChecker partitionerAndPartitionSet = ((v, inEdges, outEdges) -> {
      for (final IREdge inEdge : inEdges) {
        final Optional<Pair<PartitionerProperty.Type, Integer>> partitioner =
          inEdge.getPropertyValue(PartitionerProperty.class);
        final Optional<ArrayList<KeyRange>> partitionSet = inEdge.getPropertyValue(PartitionSetProperty.class);
        // Shuffle edge
        if (partitioner.isPresent() && partitionSet.isPresent()) {
          final Set<Integer> flattenedPartitionOffsets = partitionSet.get()
            .stream()
            .flatMap(keyRange -> IntStream.range(
              (int) keyRange.rangeBeginInclusive(), (int) keyRange.rangeEndExclusive()).boxed())
            .collect(Collectors.toSet());
          if (partitioner.get().right() == PartitionerProperty.NUM_EQUAL_TO_DST_PARALLELISM) {
            final Optional<Integer> parallelism = v.getPropertyValue(ParallelismProperty.class);
            if (parallelism.isPresent()
              && !getZeroToNSet(parallelism.get()).equals(flattenedPartitionOffsets)) {
              return failure("PartitionSet must contain all partition offsets required for dst parallelism",
                v, ParallelismProperty.class, inEdge, PartitionSetProperty.class);
            }
          } else {
            if (!getZeroToNSet(partitioner.get().right()).equals(flattenedPartitionOffsets)) {
              return failure("PartitionSet must contain all partition offsets required for the partitioner",
                inEdge, PartitionerProperty.class, PartitionSetProperty.class);
            }
          }
        }
      }

      return success();
    });
    neighborCheckerList.add(partitionerAndPartitionSet);
  }

  void addShuffleEdgeCheckers() {
    final NeighborChecker shuffleChecker = ((v, inEdges, outEdges) -> {
      for (final IREdge inEdge : inEdges) {
        if (CommunicationPatternProperty.Value.SHUFFLE
          .equals(inEdge.getPropertyValue(CommunicationPatternProperty.class).get())) {
          // Shuffle edges must have the following properties
          if (!inEdge.getPropertyValue(KeyExtractorProperty.class).isPresent()
            || !inEdge.getPropertyValue(KeyEncoderProperty.class).isPresent()
            || !inEdge.getPropertyValue(KeyDecoderProperty.class).isPresent()) {
            return failure("Shuffle edge does not have a Key-related property: " + inEdge.getId());
          }
        } else {
          // Non-shuffle edges must not have the following properties
          final Optional<Pair<PartitionerProperty.Type, Integer>> partitioner =
            inEdge.getPropertyValue(PartitionerProperty.class);
          if (partitioner.isPresent() && partitioner.get().left().equals(PartitionerProperty.Type.HASH)) {
            return failure("Only shuffle can have the hash partitioner",
              inEdge, CommunicationPatternProperty.class, PartitionerProperty.class);
          }
          if (inEdge.getPropertyValue(PartitionSetProperty.class).isPresent()) {
            return failure("Only shuffle can select partition sets",
              inEdge, CommunicationPatternProperty.class, PartitionSetProperty.class);
          }
        }
      }

      return success();
    });
    neighborCheckerList.add(shuffleChecker);
  }

  void addTriggerVertexCheckers() {
    final GlobalDAGChecker messageIds = (dag -> {
      final long numMessageAggregatorVertices = dag.getVertices()
        .stream()
        .filter(v -> v instanceof MessageAggregatorVertex)
        .count();

      // Triggering ids, must be unique
      final List<Integer> vertexMessageIds = dag.getVertices()
        .stream()
        .filter(v -> v.getPropertyValue(MessageIdVertexProperty.class).isPresent())
        .map(v -> v.getPropertyValue(MessageIdVertexProperty.class).get())
        .collect(Collectors.toList());

      // Target ids
      final Set<Integer> edgeMessageIds = dag.getEdges()
        .stream()
        .filter(e -> e.getPropertyValue(MessageIdEdgeProperty.class).isPresent())
        .flatMap(e -> e.getPropertyValue(MessageIdEdgeProperty.class).get().stream())
        .collect(Collectors.toSet());

      if (numMessageAggregatorVertices != vertexMessageIds.size()) {
        return failure("Num vertex-messageId mismatch: "
          + numMessageAggregatorVertices + " != " + vertexMessageIds.size());
      }
      if (vertexMessageIds.stream().distinct().count() != vertexMessageIds.size()) {
        return failure("Duplicate vertex message ids: " + vertexMessageIds.toString());
      }
      if (!new HashSet<>(vertexMessageIds).equals(edgeMessageIds)) {
        return failure("Vertex and edge message id mismatch: "
          + vertexMessageIds.toString() + " / " + edgeMessageIds.toString());
      }

      return success();
    });
    globalDAGCheckerList.add(messageIds);
  }

  void addStreamVertexCheckers() {
    // TODO #342: Check Encoder/Decoder symmetry
  }

  void addLoopVertexCheckers() {
    final NeighborChecker duplicateEdgeGroupId = ((v, inEdges, outEdges) -> {
      // In loop vertices, different edges with empty output tag must be distinguished separately.
      for (final List<IREdge> sameTagOutEdges : groupOutEdgesByAdditionalOutputTag(outEdges, true)) {
        if (sameTagOutEdges.stream()
          .map(e -> e.getPropertyValue(DuplicateEdgeGroupProperty.class)
            .map(DuplicateEdgeGroupPropertyValue::getGroupId))
          .distinct().count() > 1) {
          return failure("Different duplicate edge group ids in: " + Util.stringifyIREdgeIds(sameTagOutEdges));
        }
      }
      return success();
    });
    neighborCheckerList.add(duplicateEdgeGroupId);
  }

  void addCacheCheckers() {
    final SingleEdgeChecker cachedEdge = (edge -> {
      if (edge.getPropertyValue(CacheIDProperty.class).isPresent()) {
        if (!edge.getDst().getPropertyValue(IgnoreSchedulingTempDataReceiverProperty.class).isPresent()) {
          return failure("Cache edge should point to a IgnoreSchedulingTempDataReceiver",
            edge, CacheIDProperty.class);
        }
      }
      return success();
    });
    singleEdgeCheckerList.add(cachedEdge);
  }

  void addScheduleGroupCheckers() {
    final GlobalDAGChecker scheduleGroupTopoOrdering = (irdag -> {
      int lastSeenScheduleGroup = Integer.MIN_VALUE;

      for (final IRVertex v : irdag.getVertices()) {
        final MutableObject violatingReachableVertex = new MutableObject();
        v.getPropertyValue(ScheduleGroupProperty.class).ifPresent(startingScheduleGroup ->
          irdag.dfsDo(
            v,
            visited -> {
              if (visited.getPropertyValue(ScheduleGroupProperty.class).isPresent()
                && visited.getPropertyValue(ScheduleGroupProperty.class).get() < startingScheduleGroup) {
                violatingReachableVertex.setValue(visited);
              }
            },
            DAGInterface.TraversalOrder.PreOrder,
            new HashSet<>()));
        if (violatingReachableVertex.getValue() != null) {
          return failure(
            "A reachable vertex with a smaller schedule group ",
            v,
            ScheduleGroupProperty.class,
            violatingReachableVertex.getValue(),
            ScheduleGroupProperty.class);
        }
      }
      return success();
    });
    globalDAGCheckerList.add(scheduleGroupTopoOrdering);

    final SingleEdgeChecker splitByPull = (edge -> {
      if (Util.isControlEdge(edge)) {
        return success();
      }

      if (Optional.of(DataFlowProperty.Value.PULL).equals(edge.getPropertyValue(DataFlowProperty.class))) {
        final Optional<Integer> srcSG = edge.getSrc().getPropertyValue(ScheduleGroupProperty.class);
        final Optional<Integer> dstSG = edge.getDst().getPropertyValue(ScheduleGroupProperty.class);
        if (srcSG.isPresent() && dstSG.isPresent()) {
          if (srcSG.get().equals(dstSG.get())) {
            return failure("Schedule group must split by Pull",
              edge.getSrc(), ScheduleGroupProperty.class, edge.getDst(), ScheduleGroupProperty.class);
          }
        }
      }
      return success();
    });
    singleEdgeCheckerList.add(splitByPull);
  }

  void addEncodingCompressionCheckers() {
    final NeighborChecker additionalOutputEncoder = ((irVertex, inEdges, outEdges) -> {
      for (final List<IREdge> sameTagOutEdges : groupOutEdgesByAdditionalOutputTag(outEdges, false)) {
        final List<IREdge> nonStreamVertexEdge = sameTagOutEdges.stream()
          .filter(stoe -> !isConnectedToStreamVertex(stoe))
          .collect(Collectors.toList());

        if (!nonStreamVertexEdge.isEmpty()) {
          if (1 != nonStreamVertexEdge.stream()
            .map(e -> e.getPropertyValue(EncoderProperty.class).get().getClass()).distinct().count()) {
            return failure("Incompatible encoders in " + Util.stringifyIREdgeIds(nonStreamVertexEdge));
          }
          if (1 != nonStreamVertexEdge.stream()
            .map(e -> e.getPropertyValue(DecoderProperty.class).get().getClass()).distinct().count()) {
            return failure("Incompatible decoders in " + Util.stringifyIREdgeIds(nonStreamVertexEdge));
          }
        }
      }
      return success();
    });
    neighborCheckerList.add(additionalOutputEncoder);

    // TODO #342: Check Encoder/Decoder symmetry

    final SingleEdgeChecker compressAndDecompress = (edge -> {
      if (!isConnectedToStreamVertex(edge)) {
        if (!edge.getPropertyValue(CompressionProperty.class)
          .equals(edge.getPropertyValue(DecompressionProperty.class))) {
          return failure("Compression and decompression must be symmetric",
            edge, CompressionProperty.class, DecompressionProperty.class);
        }
      }
      return success();
    });
    singleEdgeCheckerList.add(compressAndDecompress);
  }

  /**
   * Group outgoing edges by the additional output tag property.
   * @param outEdges the outedges to group.
   * @param distinguishEmpty whether or not to distinguish empty tags separately or not.
   * @return the edges grouped by the additional output tag property value.
   */
  private Collection<List<IREdge>> groupOutEdgesByAdditionalOutputTag(final List<IREdge> outEdges,
                                                                      final boolean distinguishEmpty) {
    final AtomicInteger distinctIntegerForEmptyOutputTag = new AtomicInteger(0);
    final IntSupplier tagValueSupplier = distinguishEmpty
      ? distinctIntegerForEmptyOutputTag::getAndIncrement : distinctIntegerForEmptyOutputTag::get;

    return outEdges.stream().collect(Collectors.groupingBy(
      outEdge -> outEdge.getPropertyValue(AdditionalOutputTagProperty.class)
        .orElse(String.valueOf(tagValueSupplier.getAsInt())),
      Collectors.toList())).values();
  }

  ///////////////////////////// Private helper methods

  private boolean isConnectedToStreamVertex(final IREdge irEdge) {
    return irEdge.getDst() instanceof RelayVertex || irEdge.getSrc() instanceof RelayVertex;
  }

  private Set<Integer> getZeroToNSet(final int n) {
    return IntStream.range(0, n)
      .boxed()
      .collect(Collectors.toSet());
  }

  ///////////////////////////// Successes and Failures

  private final CheckerResult success = new CheckerResult(true, "");

  /**
   * Result of a checker.
   */
  public class CheckerResult {
    private final boolean pass;
    private final String failReason; // empty string if pass = true

    CheckerResult(final boolean pass, final String failReason) {
      this.pass = pass;
      this.failReason = failReason;
    }

    public final boolean isPassed() {
      return pass;
    }

    public final String getFailReason() {
      return failReason;
    }
  }

  CheckerResult success() {
    return success;
  }

  CheckerResult failure(final String failReason) {
    return new CheckerResult(false, failReason);
  }

  CheckerResult failure(final String description,
                        final Object vertexOrEdgeOne, final Class epOne,
                        final Object vertexOrEdgeTwo, final Class epTwo) {
    final CheckerResult failureOne = vertexOrEdgeOne instanceof IRVertex
      ? failure("First", (IRVertex) vertexOrEdgeOne, epOne)
      : failure("First", (IREdge) vertexOrEdgeOne, epOne);
    final CheckerResult failureTwo = vertexOrEdgeTwo instanceof IRVertex
      ? failure("Second", (IRVertex) vertexOrEdgeTwo, epTwo)
      : failure("Second", (IREdge) vertexOrEdgeTwo, epTwo);
    return failure(description + " - ("
      + failureOne.failReason + ") incompatible with (" + failureTwo.failReason + ")");
  }

  CheckerResult failure(final String description,
                        final IRVertex v,
                        final Class... eps) {
    final List<Optional> epsList = Arrays.stream(eps)
      .map(ep -> (Class<VertexExecutionProperty<Serializable>>) ep)
      .map(v::getPropertyValue).collect(Collectors.toList());
    return failure(String.format("%s - [IRVertex %s: %s]", description, v.getId(), epsList.toString()));
  }

  CheckerResult failure(final String description,
                        final IREdge e,
                        final Class... eps) {
    final List<Optional> epsList = Arrays.stream(eps)
      .map(ep -> (Class<EdgeExecutionProperty<Serializable>>) ep)
      .map(e::getPropertyValue).collect(Collectors.toList());
    return failure(String.format("%s - [IREdge(%s->%s) %s: %s]",
      description, e.getSrc().getId(), e.getDst().getId(), e.getId(), epsList.toString()));
  }
}