#include <utils/ParMETISPartitioner.hpp>

#include <utils/pugs_config.hpp>

#ifdef PUGS_HAS_PARMETIS

#include <utils/Exceptions.hpp>
#include <utils/Messenger.hpp>

#include <parmetis.h>

#include <iostream>
#include <vector>

Array<int>
ParMETISPartitioner::partition(const CRSGraph& graph)
{
  std::cout << "Partitioning graph into " << rang::style::bold << parallel::size() << rang::style::reset
            << " parts using " << rang::fgB::green << "ParMETIS" << rang::fg::reset << '\n';

  MPI_Group world_group;
  MPI_Comm_group(parallel::Messenger::getInstance().comm(), &world_group);

  MPI_Group mesh_group;
  std::vector<int> group_ranks = [&]() {
    Array<int> graph_node_owners = parallel::allGather(static_cast<int>(graph.numberOfNodes()));
    std::vector<int> grp_ranks;
    grp_ranks.reserve(graph_node_owners.size());
    for (size_t i = 0; i < graph_node_owners.size(); ++i) {
      if (graph_node_owners[i] > 0) {
        grp_ranks.push_back(i);
      }
    }
    return grp_ranks;
  }();

  MPI_Group_incl(world_group, group_ranks.size(), &(group_ranks[0]), &mesh_group);

  MPI_Comm partitioning_comm;
  MPI_Comm_create_group(parallel::Messenger::getInstance().comm(), mesh_group, 1, &partitioning_comm);

  Array<int> partition;
  if (graph.numberOfNodes() > 0) {
    int wgtflag = 0;
    int numflag = 0;
    int ncon    = 1;
    int npart   = parallel::size();
    std::vector<float> tpwgts(npart, 1. / npart);

    std::vector<float> ubvec{1.05};
    std::vector<int> options{1, 0, 0};
    int edgecut = 0;

    int local_number_of_nodes = graph.numberOfNodes();

    partition = Array<int>(local_number_of_nodes);
    std::vector<int> vtxdist{0, local_number_of_nodes};

    const Array<const int>& entries   = graph.entries();
    const Array<const int>& neighbors = graph.neighbors();

    int* entries_ptr   = const_cast<int*>(&(entries[0]));
    int* neighbors_ptr = const_cast<int*>(&(neighbors[0]));

    int result =
      ParMETIS_V3_PartKway(&(vtxdist[0]), entries_ptr, neighbors_ptr, NULL, NULL, &wgtflag, &numflag, &ncon, &npart,
                           &(tpwgts[0]), &(ubvec[0]), &(options[0]), &edgecut, &(partition[0]), &partitioning_comm);
    // LCOV_EXCL_START
    if (result == METIS_ERROR) {
      throw UnexpectedError("Metis Error");
    }
    // LCOV_EXCL_STOP
  }

  MPI_Comm_free(&partitioning_comm);
  MPI_Group_free(&mesh_group);
  MPI_Group_free(&world_group);

  return partition;
}

#else   // PUGS_HAS_PARMETIS

Array<int>
ParMETISPartitioner::partition(const CRSGraph& graph)
{
  Array<int> partition{graph.entries().size() - 1};
  partition.fill(0);
  return partition;
}

#endif   // PUGS_HAS_PARMETIS