MooseMeshUtils.C

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//* This file is part of the MOOSE framework
//* https://mooseframework.inl.gov
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html

// MOOSE includes
#include "MooseMeshUtils.h"

#include "libmesh/elem.h"
#include "libmesh/boundary_info.h"
#include "libmesh/id_types.h"
#include "libmesh/int_range.h"
#include "libmesh/parallel.h"
#include "libmesh/parallel_algebra.h"
#include "libmesh/utility.h"

#include "libmesh/distributed_mesh.h"
#include "libmesh/parallel_elem.h"
#include "libmesh/parallel_node.h"
#include "libmesh/compare_elems_by_level.h"
#include "libmesh/mesh_communication.h"
#include "libmesh/edge_edge3.h"
#include "libmesh/enum_to_string.h"
#include "libmesh/unstructured_mesh.h"

#include "timpi/parallel_sync.h"

using namespace libMesh;

namespace MooseMeshUtils
{

void
mergeBoundaryIDsWithSameName(MeshBase & mesh)
{
  // We check if we have the same boundary name with different IDs. If we do, we assign the
  // first ID to every occurrence.
  const auto & side_bd_name_map = mesh.get_boundary_info().get_sideset_name_map();
  const auto & node_bd_name_map = mesh.get_boundary_info().get_nodeset_name_map();
  std::map<boundary_id_type, boundary_id_type> same_name_ids;

  auto populate_map = [](const std::map<boundary_id_type, std::string> & map,
                         std::map<boundary_id_type, boundary_id_type> & same_ids)
  {
    for (const auto & pair_outer : map)
      for (const auto & pair_inner : map)
        // The last condition is needed to make sure we only store one combination
        if (pair_outer.second == pair_inner.second && pair_outer.first != pair_inner.first &&
            same_ids.find(pair_inner.first) == same_ids.end())
          same_ids[pair_outer.first] = pair_inner.first;
  };

  populate_map(side_bd_name_map, same_name_ids);
  populate_map(node_bd_name_map, same_name_ids);

  for (const auto & [id1, id2] : same_name_ids)
    mesh.get_boundary_info().renumber_id(id2, id1);
}

void
changeBoundaryId(MeshBase & mesh,
                 const boundary_id_type old_id,
                 const boundary_id_type new_id,
                 bool delete_prev)
{
  // Get a reference to our BoundaryInfo object, we will use it several times below...
  BoundaryInfo & boundary_info = mesh.get_boundary_info();

  // Container to catch ids passed back from BoundaryInfo
  std::vector<boundary_id_type> old_ids;

  // Only level-0 elements store BCs.  Loop over them.
  for (auto & elem : as_range(mesh.level_elements_begin(0), mesh.level_elements_end(0)))
  {
    unsigned int n_sides = elem->n_sides();
    for (const auto s : make_range(n_sides))
    {
      boundary_info.boundary_ids(elem, s, old_ids);
      if (std::find(old_ids.begin(), old_ids.end(), old_id) != old_ids.end())
      {
        std::vector<boundary_id_type> new_ids(old_ids);
        std::replace(new_ids.begin(), new_ids.end(), old_id, new_id);
        if (delete_prev)
        {
          boundary_info.remove_side(elem, s);
          boundary_info.add_side(elem, s, new_ids);
        }
        else
          boundary_info.add_side(elem, s, new_ids);
      }
    }
  }

  // Remove any remaining references to the old ID from the
  // BoundaryInfo object.  This prevents things like empty sidesets
  // from showing up when printing information, etc.
  if (delete_prev)
    boundary_info.remove_id(old_id);

  // global information may now be out of sync
  mesh.unset_is_prepared();
}

std::vector<boundary_id_type>
getBoundaryIDs(const MeshBase & mesh,
               const std::vector<BoundaryName> & boundary_name,
               bool generate_unknown)
{
  return getBoundaryIDs(
      mesh, boundary_name, generate_unknown, mesh.get_boundary_info().get_boundary_ids());
}

std::vector<boundary_id_type>
getBoundaryIDs(const MeshBase & mesh,
               const std::vector<BoundaryName> & boundary_name,
               bool generate_unknown,
               const std::set<BoundaryID> & mesh_boundary_ids)
{
  const BoundaryInfo & boundary_info = mesh.get_boundary_info();
  const std::map<BoundaryID, std::string> & sideset_map = boundary_info.get_sideset_name_map();
  const std::map<BoundaryID, std::string> & nodeset_map = boundary_info.get_nodeset_name_map();

  BoundaryID max_boundary_local_id = 0;
  /* It is required to generate a new ID for a given name. It is used often in mesh modifiers such
   * as SideSetsBetweenSubdomains. Then we need to check the current boundary ids since they are
   * changing during "mesh modify()", and figure out the right max boundary ID. Most of mesh
   * modifiers are running in serial, and we won't involve a global communication.
   */
  if (generate_unknown)
  {
    const auto & bids = mesh.is_prepared() ? mesh.get_boundary_info().get_global_boundary_ids()
                                           : mesh.get_boundary_info().get_boundary_ids();
    max_boundary_local_id = bids.empty() ? 0 : *(bids.rbegin());
    /* We should not hit this often */
    if (!mesh.is_prepared() && !mesh.is_serial())
      mesh.comm().max(max_boundary_local_id);
  }

  BoundaryID max_boundary_id = mesh_boundary_ids.empty() ? 0 : *(mesh_boundary_ids.rbegin());

  max_boundary_id =
      max_boundary_id > max_boundary_local_id ? max_boundary_id : max_boundary_local_id;

  std::vector<BoundaryID> ids(boundary_name.size());
  for (const auto i : index_range(boundary_name))
  {
    if (boundary_name[i] == "ANY_BOUNDARY_ID")
    {
      ids.assign(mesh_boundary_ids.begin(), mesh_boundary_ids.end());
      if (i)
        mooseWarning("You passed \"ANY_BOUNDARY_ID\" in addition to other boundary_names.  This "
                     "may be a logic error.");
      break;
    }

    if (boundary_name[i].empty() && !generate_unknown)
      mooseError("Incoming boundary name is empty and we are not generating unknown boundary IDs. "
                 "This is invalid.");

    BoundaryID id;

    if (boundary_name[i].empty() || !MooseUtils::isDigits(boundary_name[i]))
    {
      if (generate_unknown &&
          !MooseUtils::doesMapContainValue(sideset_map, std::string(boundary_name[i])) &&
          !MooseUtils::doesMapContainValue(nodeset_map, std::string(boundary_name[i])))
        id = ++max_boundary_id;
      else
        id = boundary_info.get_id_by_name(boundary_name[i]);
    }
    else
      id = getIDFromName<BoundaryName, BoundaryID>(boundary_name[i]);

    ids[i] = id;
  }

  return ids;
}

std::set<BoundaryID>
getBoundaryIDSet(const MeshBase & mesh,
                 const std::vector<BoundaryName> & boundary_name,
                 bool generate_unknown)
{
  auto boundaries = getBoundaryIDs(mesh, boundary_name, generate_unknown);
  return std::set<BoundaryID>(boundaries.begin(), boundaries.end());
}

std::vector<subdomain_id_type>
getSubdomainIDs(const MeshBase & mesh, const std::vector<SubdomainName> & subdomain_names)
{
  std::vector<subdomain_id_type> ids;

  // shortcut for "ANY_BLOCK_ID"
  if (subdomain_names.size() == 1 && subdomain_names[0] == "ANY_BLOCK_ID")
  {
    // since get_mesh_subdomains() requires a prepared mesh, we need to check that here
    mooseAssert(mesh.is_prepared(),
                "getSubdomainIDs() should only be called on a prepared mesh if ANY_BLOCK_ID is "
                "used to query all block IDs");
    ids.assign(mesh.get_mesh_subdomains().begin(), mesh.get_mesh_subdomains().end());
    return ids;
  }

  // loop through subdomain names and get IDs (this preserves the order of subdomain_names)
  ids.resize(subdomain_names.size());
  for (auto i : index_range(subdomain_names))
  {
    if (subdomain_names[i] == "ANY_BLOCK_ID")
      mooseError("getSubdomainIDs() accepts \"ANY_BLOCK_ID\" if and only if it is the only "
                 "subdomain name being queried.");
    ids[i] = MooseMeshUtils::getSubdomainID(subdomain_names[i], mesh);
  }

  return ids;
}

std::set<subdomain_id_type>
getSubdomainIDs(const MeshBase & mesh, const std::set<SubdomainName> & subdomain_names)
{
  const auto blk_ids = getSubdomainIDs(
      mesh, std::vector<SubdomainName>(subdomain_names.begin(), subdomain_names.end()));
  return {blk_ids.begin(), blk_ids.end()};
}

BoundaryID
getBoundaryID(const BoundaryName & boundary_name, const MeshBase & mesh)
{
  BoundaryID id = Moose::INVALID_BOUNDARY_ID;
  if (boundary_name.empty())
    return id;

  if (!MooseUtils::isDigits(boundary_name))
    id = mesh.get_boundary_info().get_id_by_name(boundary_name);
  else
    id = getIDFromName<BoundaryName, BoundaryID>(boundary_name);

  return id;
}

SubdomainID
getSubdomainID(const SubdomainName & subdomain_name, const MeshBase & mesh)
{
  if (subdomain_name == "ANY_BLOCK_ID")
    mooseError("getSubdomainID() does not work with \"ANY_BLOCK_ID\"");

  SubdomainID id = Moose::INVALID_BLOCK_ID;
  if (subdomain_name.empty())
    return id;

  if (!MooseUtils::isDigits(subdomain_name))
    id = mesh.get_id_by_name(subdomain_name);
  else
    id = getIDFromName<SubdomainName, SubdomainID>(subdomain_name);

  return id;
}

void
changeSubdomainId(MeshBase & mesh, const subdomain_id_type old_id, const subdomain_id_type new_id)
{
  for (const auto & elem : mesh.element_ptr_range())
    if (elem->subdomain_id() == old_id)
      elem->subdomain_id() = new_id;

  // global cached information may now be out of sync
  mesh.unset_is_prepared();
}

Point
meshCentroidCalculator(const MeshBase & mesh)
{
  Point centroid_pt = Point(0.0, 0.0, 0.0);
  Real vol_tmp = 0.0;
  for (const auto & elem : mesh.active_local_element_ptr_range())
  {
    Real elem_vol = elem->volume();
    centroid_pt += (elem->true_centroid()) * elem_vol;
    vol_tmp += elem_vol;
  }
  mesh.comm().sum(centroid_pt);
  mesh.comm().sum(vol_tmp);
  centroid_pt /= vol_tmp;
  return centroid_pt;
}

Point
boundaryCentroidCalculator(const BoundaryName & boundary, MeshBase & mesh)
{
  // Need boundaries to be synchronized
  if (!mesh.preparation().has_boundary_id_sets)
    mesh.get_boundary_info().synchronize_global_id_set();
  BoundaryInfo & mesh_boundary_info = mesh.get_boundary_info();
  boundary_id_type boundary_id = mesh_boundary_info.get_id_by_name(boundary);
  const auto side_list = mesh_boundary_info.build_side_list();

  // Initialize sums
  Real volume_sum = 0;
  Point volume_weighted_centroid_sum(0, 0, 0);

  for (const auto & [eid, side_i, bid] : side_list)
  {
    if (bid != boundary_id)
      continue;

    // Get the side
    const auto elem = mesh.elem_ptr(eid);
    const auto side = elem->side_ptr(side_i);

    volume_sum += side->volume();
    volume_weighted_centroid_sum += side->volume() * side->true_centroid();
  }
  // Sum across processes
  mesh.comm().sum(volume_weighted_centroid_sum);
  mesh.comm().sum(volume_sum);

  return volume_weighted_centroid_sum / volume_sum;
}

RealVectorValue
boundaryWeightedNormal(const BoundaryName & boundary, MeshBase & mesh)
{
  // Need boundaries to be synchronized
  if (!mesh.preparation().has_boundary_id_sets)
    mesh.get_boundary_info().synchronize_global_id_set();
  BoundaryInfo & mesh_boundary_info = mesh.get_boundary_info();
  boundary_id_type boundary_id = mesh_boundary_info.get_id_by_name(boundary);
  const auto side_list = mesh_boundary_info.build_side_list();

  // Initialize sums
  Real volume_sum = 0;
  RealVectorValue volume_weighted_normal_sum(0, 0, 0);

  for (const auto & [eid, side_i, bid] : side_list)
  {
    if (bid != boundary_id)
      continue;

    // Get the side
    const auto elem = mesh.elem_ptr(eid);
    const auto side = elem->side_ptr(side_i);

    volume_sum += side->volume();
    volume_weighted_normal_sum += side->volume() * elem->side_vertex_average_normal(side_i);
  }
  // Sum across processes
  mesh.comm().sum(volume_weighted_normal_sum);
  mesh.comm().sum(volume_sum);

  return volume_weighted_normal_sum / volume_sum;
}

Real
computeMaxDistanceToAxis(const MeshBase & mesh,
                         const Point & origin,
                         const RealVectorValue & direction)
{
  Real distance = 0;
  mooseAssert(MooseUtils::absoluteFuzzyEqual(direction.norm_sq(), 1),
              "Direction should be normalized");
  for (const auto & node : mesh.node_ptr_range())
    if (const auto dist_node = (*node - origin).cross(direction).norm(); dist_node > distance)
      distance = dist_node;
  mesh.comm().max(distance);
  return distance;
}

std::unordered_map<dof_id_type, dof_id_type>
getExtraIDUniqueCombinationMap(const MeshBase & mesh,
                               const std::set<SubdomainID> & block_ids,
                               std::vector<ExtraElementIDName> extra_ids)
{
  // check block restriction
  const bool block_restricted = !block_ids.empty();
  // get element id name of interest in recursive parsing algorithm
  ExtraElementIDName id_name = extra_ids.back();
  extra_ids.pop_back();
  const auto id_index = mesh.get_elem_integer_index(id_name);

  // create base parsed id set
  if (extra_ids.empty())
  {
    // get set of extra id values;
    std::vector<dof_id_type> ids;
    {
      std::set<dof_id_type> ids_set;
      for (const auto & elem : mesh.active_element_ptr_range())
      {
        if (block_restricted && block_ids.find(elem->subdomain_id()) == block_ids.end())
          continue;
        const auto id = elem->get_extra_integer(id_index);
        ids_set.insert(id);
      }
      mesh.comm().set_union(ids_set);
      ids.assign(ids_set.begin(), ids_set.end());
    }

    // determine new extra id values;
    std::unordered_map<dof_id_type, dof_id_type> parsed_ids;
    for (auto & elem : mesh.active_element_ptr_range())
    {
      if (block_restricted && block_ids.find(elem->subdomain_id()) == block_ids.end())
        continue;
      parsed_ids[elem->id()] = std::distance(
          ids.begin(), std::lower_bound(ids.begin(), ids.end(), elem->get_extra_integer(id_index)));
    }
    return parsed_ids;
  }

  // if extra_ids is not empty, recursively call getExtraIDUniqueCombinationMap
  const auto base_parsed_ids =
      MooseMeshUtils::getExtraIDUniqueCombinationMap(mesh, block_ids, extra_ids);
  // parsing extra ids based on ref_parsed_ids
  std::vector<std::pair<dof_id_type, dof_id_type>> unique_ids;
  {
    std::set<std::pair<dof_id_type, dof_id_type>> unique_ids_set;
    for (const auto & elem : mesh.active_element_ptr_range())
    {
      if (block_restricted && block_ids.find(elem->subdomain_id()) == block_ids.end())
        continue;
      const dof_id_type id1 = libmesh_map_find(base_parsed_ids, elem->id());
      const dof_id_type id2 = elem->get_extra_integer(id_index);
      const std::pair<dof_id_type, dof_id_type> ids = std::make_pair(id1, id2);
      unique_ids_set.insert(ids);
    }
    mesh.comm().set_union(unique_ids_set);
    unique_ids.assign(unique_ids_set.begin(), unique_ids_set.end());
  }

  std::unordered_map<dof_id_type, dof_id_type> parsed_ids;

  for (const auto & elem : mesh.active_element_ptr_range())
  {
    if (block_restricted && block_ids.find(elem->subdomain_id()) == block_ids.end())
      continue;
    const dof_id_type id1 = libmesh_map_find(base_parsed_ids, elem->id());
    const dof_id_type id2 = elem->get_extra_integer(id_index);
    const dof_id_type new_id = std::distance(
        unique_ids.begin(),
        std::lower_bound(unique_ids.begin(), unique_ids.end(), std::make_pair(id1, id2)));
    parsed_ids[elem->id()] = new_id;
  }

  return parsed_ids;
}

bool
isCoPlanar(const std::vector<Point> & vec_pts, const Point plane_nvec, const Point fixed_pt)
{
  for (const auto & pt : vec_pts)
    if (!MooseUtils::absoluteFuzzyEqual((pt - fixed_pt) * plane_nvec, 0.0))
      return false;
  return true;
}

bool
isCoPlanar(const std::vector<Point> & vec_pts, const Point plane_nvec)
{
  return isCoPlanar(vec_pts, plane_nvec, vec_pts.front());
}

bool
isCoPlanar(const std::vector<Point> & vec_pts)
{
  // Assuming that overlapped Points are allowed, the Points that are overlapped with vec_pts[0] are
  // removed before further calculation.
  std::vector<Point> vec_pts_nonzero{vec_pts[0]};
  for (const auto i : index_range(vec_pts))
    if (!MooseUtils::absoluteFuzzyEqual((vec_pts[i] - vec_pts[0]).norm(), 0.0))
      vec_pts_nonzero.push_back(vec_pts[i]);
  // 3 or fewer points are always coplanar
  if (vec_pts_nonzero.size() <= 3)
    return true;
  else
  {
    for (const auto i : make_range(vec_pts_nonzero.size() - 1))
    {
      const Point tmp_pt = (vec_pts_nonzero[i] - vec_pts_nonzero[0])
                               .cross(vec_pts_nonzero[i + 1] - vec_pts_nonzero[0]);
      // if the three points are not collinear, use cross product as the normal vector of the plane
      if (!MooseUtils::absoluteFuzzyEqual(tmp_pt.norm(), 0.0))
        return isCoPlanar(vec_pts_nonzero, tmp_pt.unit());
    }
  }
  // If all the points are collinear, they are also coplanar
  return true;
}

SubdomainID
getNextFreeSubdomainID(MeshBase & input_mesh)
{
  // Call this to get most up to date block id information
  input_mesh.cache_elem_data();

  std::set<SubdomainID> preexisting_subdomain_ids;
  input_mesh.subdomain_ids(preexisting_subdomain_ids);
  if (preexisting_subdomain_ids.empty())
    return 0;
  else
  {
    const auto highest_subdomain_id =
        *std::max_element(preexisting_subdomain_ids.begin(), preexisting_subdomain_ids.end());
    mooseAssert(highest_subdomain_id < std::numeric_limits<SubdomainID>::max(),
                "A SubdomainID with max possible value was found");
    return highest_subdomain_id + 1;
  }
}

BoundaryID
getNextFreeBoundaryID(MeshBase & input_mesh)
{
  if (!input_mesh.preparation().has_boundary_id_sets)
    input_mesh.get_boundary_info().regenerate_id_sets();

  auto boundary_ids = input_mesh.get_boundary_info().get_boundary_ids();
  if (boundary_ids.empty())
    return 0;
  return (*boundary_ids.rbegin() + 1);
}

bool
hasSubdomainID(const MeshBase & input_mesh, const SubdomainID & id)
{
  std::set<SubdomainID> mesh_blocks;
  input_mesh.subdomain_ids(mesh_blocks);

  // On a distributed mesh we may have sideset IDs that only exist on
  // other processors
  if (!input_mesh.is_replicated())
    input_mesh.comm().set_union(mesh_blocks);

  return mesh_blocks.count(id) && (id != Moose::INVALID_BLOCK_ID);
}

bool
hasSubdomainName(const MeshBase & input_mesh, const SubdomainName & name)
{
  const auto id = getSubdomainID(name, input_mesh);
  return hasSubdomainID(input_mesh, id);
}

bool
hasBoundaryID(const MeshBase & input_mesh, const BoundaryID id)
{
  const BoundaryInfo & boundary_info = input_mesh.get_boundary_info();
  std::set<boundary_id_type> boundary_ids = boundary_info.get_boundary_ids();

  // On a distributed mesh we may have boundary IDs that only exist on
  // other processors
  if (!input_mesh.is_replicated())
    input_mesh.comm().set_union(boundary_ids);

  return boundary_ids.count(id) && (id != Moose::INVALID_BOUNDARY_ID);
}

bool
hasBoundaryName(const MeshBase & input_mesh, const BoundaryName & name)
{
  const auto id = getBoundaryID(name, input_mesh);
  return hasBoundaryID(input_mesh, id);
}

void
makeOrderedNodeList(std::vector<std::pair<dof_id_type, dof_id_type>> & node_assm,
                    std::vector<dof_id_type> & elem_id_list,
                    std::vector<dof_id_type> & midpoint_node_list,
                    std::vector<dof_id_type> & ordered_node_list,
                    std::vector<dof_id_type> & ordered_elem_id_list)
{
  // a flag to indicate if the ordered_node_list has been reversed
  bool is_flipped = false;
  // Start from the first element, try to find a chain of nodes
  mooseAssert(node_assm.size(), "Node list must not be empty");
  ordered_node_list.push_back(node_assm.front().first);
  if (midpoint_node_list.front() != DofObject::invalid_id)
    ordered_node_list.push_back(midpoint_node_list.front());
  ordered_node_list.push_back(node_assm.front().second);
  ordered_elem_id_list.push_back(elem_id_list.front());
  // Remove the element that has just been added to ordered_node_list
  node_assm.erase(node_assm.begin());
  midpoint_node_list.erase(midpoint_node_list.begin());
  elem_id_list.erase(elem_id_list.begin());
  const unsigned int node_assm_size_0 = node_assm.size();
  for (unsigned int i = 0; i < node_assm_size_0; i++)
  {
    // Find nodes to expand the chain
    dof_id_type end_node_id = ordered_node_list.back();
    auto isMatch1 = [end_node_id](std::pair<dof_id_type, dof_id_type> old_id_pair)
    { return old_id_pair.first == end_node_id; };
    auto isMatch2 = [end_node_id](std::pair<dof_id_type, dof_id_type> old_id_pair)
    { return old_id_pair.second == end_node_id; };
    auto result = std::find_if(node_assm.begin(), node_assm.end(), isMatch1);
    bool match_first;
    if (result == node_assm.end())
    {
      match_first = false;
      result = std::find_if(node_assm.begin(), node_assm.end(), isMatch2);
    }
    else
    {
      match_first = true;
    }
    // If found, add the node to boundary_ordered_node_list
    if (result != node_assm.end())
    {
      const auto elem_index = std::distance(node_assm.begin(), result);
      if (midpoint_node_list[elem_index] != DofObject::invalid_id)
        ordered_node_list.push_back(midpoint_node_list[elem_index]);
      ordered_node_list.push_back(match_first ? (*result).second : (*result).first);
      node_assm.erase(result);
      midpoint_node_list.erase(midpoint_node_list.begin() + elem_index);
      ordered_elem_id_list.push_back(elem_id_list[elem_index]);
      elem_id_list.erase(elem_id_list.begin() + elem_index);
    }
    // If there are still elements in node_assm and result ==
    // node_assm.end(), this means the curve is not a loop, the
    // ordered_node_list is flipped and try the other direction that has not
    // been examined yet.
    else
    {
      if (is_flipped)
        // Flipped twice; this means the node list has at least two segments.
        throw MooseException("The node list provided has more than one segments.");

      // mark the first flip event.
      is_flipped = true;
      std::reverse(ordered_node_list.begin(), ordered_node_list.end());
      std::reverse(midpoint_node_list.begin(), midpoint_node_list.end());
      std::reverse(ordered_elem_id_list.begin(), ordered_elem_id_list.end());
      // As this iteration is wasted, set the iterator backward
      i--;
    }
  }
}

void
makeOrderedNodeList(std::vector<std::pair<dof_id_type, dof_id_type>> & node_assm,
                    std::vector<dof_id_type> & elem_id_list,
                    std::vector<dof_id_type> & ordered_node_list,
                    std::vector<dof_id_type> & ordered_elem_id_list)
{
  std::vector<dof_id_type> dummy_midpoint_node_list(node_assm.size(), DofObject::invalid_id);
  makeOrderedNodeList(
      node_assm, elem_id_list, dummy_midpoint_node_list, ordered_node_list, ordered_elem_id_list);
}

void
swapNodesInElem(Elem & elem, const unsigned int nd1, const unsigned int nd2)
{
  Node * n_temp = elem.node_ptr(nd1);
  elem.set_node(nd1, elem.node_ptr(nd2));
  elem.set_node(nd2, n_temp);
}

void
extraElemIntegerSwapParametersProcessor(
    const std::string & class_name,
    const unsigned int num_sections,
    const unsigned int num_integers,
    const std::vector<std::vector<std::vector<dof_id_type>>> & elem_integers_swaps,
    std::vector<std::unordered_map<dof_id_type, dof_id_type>> & elem_integers_swap_pairs)
{
  elem_integers_swap_pairs.reserve(num_sections * num_integers);
  for (const auto i : make_range(num_integers))
  {
    const auto & elem_integer_swaps = elem_integers_swaps[i];
    std::vector<std::unordered_map<dof_id_type, dof_id_type>> elem_integer_swap_pairs;
    try
    {
      MooseMeshUtils::idSwapParametersProcessor(class_name,
                                                "elem_integers_swaps",
                                                elem_integer_swaps,
                                                elem_integer_swap_pairs,
                                                i * num_sections);
    }
    catch (const MooseException & e)
    {
      throw MooseException(e.what());
    }

    elem_integers_swap_pairs.insert(elem_integers_swap_pairs.end(),
                                    elem_integer_swap_pairs.begin(),
                                    elem_integer_swap_pairs.end());
  }
}

std::unique_ptr<ReplicatedMesh>
buildBoundaryMesh(const MeshBase & input_mesh, const boundary_id_type boundary_id)
{
  if (!input_mesh.is_serial())
    ::mooseError("Input mesh should be serialized for extracting the boundary mesh.\nInput mesh:" +
                 input_mesh.get_info());
  auto poly_mesh = std::make_unique<ReplicatedMesh>(input_mesh.comm());

  auto side_list = input_mesh.get_boundary_info().build_side_list();

  std::unordered_map<dof_id_type, dof_id_type> old_new_node_map;
  for (const auto & [eid, side_i, bid] : side_list)
  {
    if (bid != boundary_id)
      continue;

    // Get the side
    const auto elem = input_mesh.elem_ptr(eid);
    const auto side = elem->side_ptr(side_i);
    auto side_elem = elem->build_side_ptr(side_i);
    auto copy = side_elem->build(side_elem->type());

    for (const auto i : side_elem->node_index_range())
    {
      auto & n = side_elem->node_ref(i);

      if (old_new_node_map.count(n.id()))
        copy->set_node(i, poly_mesh->node_ptr(old_new_node_map[n.id()]));
      else
      {
        Node * node = poly_mesh->add_point(side_elem->point(i));
        copy->set_node(i, node);
        old_new_node_map[n.id()] = node->id();
      }
    }
    poly_mesh->add_elem(copy.release());
  }
  poly_mesh->skip_partitioning(true);
  poly_mesh->prepare_for_use();
  if (poly_mesh->n_elem() == 0)
    mooseError("The input mesh to extract the boundary from does not have a boundary with id ",
               boundary_id,
               ".\n",
               input_mesh);

  return poly_mesh;
}

std::unique_ptr<ReplicatedMesh>
buildLoopBoundaryOf2DMesh(const MeshBase & input_mesh, const boundary_id_type boundary_id)
{
  if (!input_mesh.is_serial())
    ::mooseError(
        "Input 2D mesh should be serialized for extracting the loop boundary mesh.\nInput mesh:" +
        input_mesh.get_info());
  auto edge_mesh = std::make_unique<ReplicatedMesh>(input_mesh.comm());
  auto side_list = input_mesh.get_boundary_info().build_side_list();
  std::set<BoundaryInfo::BCTuple> visited;
  bool already_seen_this_side_tuple = false;
  BoundaryInfo::BCTuple first_side_visited = {libMesh::invalid_uint, 0, 0};

  // Helps move elem to elem at a given node
  const auto node_to_elem_map = buildBoundaryNodeToElemMap(input_mesh, boundary_id);
  // Helps check if a node is part of a boundary
  const auto & node_to_bids = input_mesh.get_boundary_info().get_nodeset_map();

  // Traverse from the first side (edge) in the side_list that matches the boundary_id
  for (const auto & bside : side_list)
  {
    if (std::get<2>(bside) != boundary_id)
      continue;

    // Check that we are not starting 'another' loop
    if (bside != first_side_visited)
    {
      if (visited.size() && !visited.count(bside))
        mooseWarning(
            "Boundary " + std::to_string(boundary_id) +
            " is not a (contiguous) loop. Boundary side: (" + Moose::stringify(bside) +
            ") was not visited after a single pass around the boundary. Boundary sides visited: " +
            Moose::stringify(visited));
      else if (visited.empty())
        first_side_visited = bside;
      else
        continue;
    }

    // Form the element to be able to find the side
    // These three variables will be updated while traversing the loop boundary
    const Elem * elem = input_mesh.elem_ptr(std::get<0>(bside));
    auto current_side = std::get<1>(bside);
    auto side_elem = elem->build_side_ptr(current_side);

    // 3D elements should not be part of this boundary
    if (elem->dim() != 2)
      mooseError(
          "Finding the loop boundary of a 2D mesh cannot be done with non-2D elements such as ",
          *elem);

    // Start from node 0 of the side (on the boundary), set the next node as the other node
    // one that side, and keep going from tht next node
    bool looped_back = false;
    const Node * starting_node = side_elem->node_ptr(0);
    const auto new_mesh_starting_node = edge_mesh->add_point(side_elem->point(0));
    Node * new_first_node = new_mesh_starting_node;
    [[maybe_unused]] dof_id_type first_node_index = starting_node->id();
    dof_id_type second_node_index = input_mesh.node_ptr(side_elem->node_id(1))->id();

    while (!looped_back && !already_seen_this_side_tuple)
    {
      if (MooseUtils::absoluteFuzzyEqual(input_mesh.point(second_node_index),
                                         Point(*starting_node)))
        looped_back = true;

      // Get the opposite node (the next node) and add it to the edge mesh
      Node * new_second_node = looped_back
                                   ? new_mesh_starting_node
                                   : edge_mesh->add_point(input_mesh.point(second_node_index));

      // Add a copy of the edge side element to the mesh
      side_elem = elem->build_side_ptr(current_side);
      auto copy = side_elem->build(side_elem->type());
      copy->set_node(0, new_first_node);
      copy->set_node(1, new_second_node);
      edge_mesh->add_elem(copy.release());

      // Make this side as 'visited'
      std::tuple<dof_id_type, unsigned short int, boundary_id_type> bc_tuple = {
          elem->id(), current_side, boundary_id};
      const auto & visit_iter = visited.insert(bc_tuple);
      if (!looped_back && !visit_iter.second)
        already_seen_this_side_tuple = true;

      // Find the next element and side_elem
      auto & connected_elems = libmesh_map_find(node_to_elem_map, second_node_index);
      bool found_match = false;
      const auto current_eid = elem->id();

      for (const auto eid : connected_elems)
      {
        mooseAssert(!found_match,
                    "We should only find one node on a connected element on this boundary");
        if (eid != current_eid)
        {
          // Update the element (on the input mesh)
          elem = input_mesh.elem_ptr(eid);

          // Find the side and the opposite node index in that side
          for (const auto si : elem->side_index_range())
          {
            // Check that second node is on the side
            const auto local_second_node_index =
                elem->get_node_index(input_mesh.node_ptr(second_node_index));
            // 2 sides should match this
            if (elem->is_node_on_side(local_second_node_index, si))
            {
              // Only one side should be on the same boundary (node is connected to two elements)
              // Form a bc_tuple and check the list of boundary sides
              std::tuple<dof_id_type, unsigned short int, boundary_id_type> side_bc_tuple = {
                  elem->id(), si, boundary_id};

              if (std::find(side_list.begin(), side_list.end(), side_bc_tuple) == side_list.end())
                continue;

              // We are on the right boundary, just need to get the other node
              for (const auto local_side_node_id : elem->nodes_on_side(si))
              {
                const auto side_node_id = elem->node_id(local_side_node_id);

                // Skip current node (use global index to compare)
                if (side_node_id == second_node_index)
                  continue;
                mooseAssert(side_node_id != first_node_index,
                            "Somehow looped back in a single element");

                current_side = si;
                second_node_index = side_node_id;
                found_match = true;
                break;
              }
            }
            // No need to examine more sides
            if (found_match)
              break;
          }

          // No need to examine more elements
          if (found_match)
            break;
        }
        // next node could be on the same element, just moving on to the next side
        else if (connected_elems.size() == 1)
        {
          elem = input_mesh.elem_ptr(eid);
          const auto local_second_node_index =
              elem->get_node_index(input_mesh.node_ptr(second_node_index));

          // Move on to the next side
          for (const auto si : elem->side_index_range())
            if (si != current_side && elem->is_node_on_side(local_second_node_index, si))
            {
              // Check all nodes on that next side
              for (const auto local_side_node_id : elem->nodes_on_side(si))
              {
                const auto side_node_id = elem->node_id(local_side_node_id);
                // Skip current node
                if (side_node_id == second_node_index)
                  continue;
                mooseAssert((side_node_id != first_node_index) ||
                                (side_list.size() == elem->n_sides()),
                            "Somehow looped back in a single element");

                // Check all the boundaries the other node (on the edge side) is part of
                const auto bids_range = node_to_bids.equal_range(input_mesh.node_ptr(side_node_id));

                for (auto iter = bids_range.first; iter != bids_range.second; iter++)
                  if (iter->second == boundary_id)
                  {
                    current_side = si;
                    second_node_index = side_node_id;
                    found_match = true;
                  }
              }

              // no need to examine other sides
              if (found_match)
                break;
            }
        }
      }

      // Set current node to opposite node of new element
      // NOTE: do not use new_first_node or new_second_node to search in the input mesh!
      new_first_node = new_second_node;
      first_node_index = second_node_index;

      // Handle loop ending criterion
      if (!found_match)
      {
        mooseWarning("Search for next element in loop boundary failed. Is boundary '" +
                         std::to_string(boundary_id) + "' of mesh ",
                     input_mesh,
                     " a loop boundary?");
        break;
      }
    }
  }

  if (already_seen_this_side_tuple)
    mooseWarning("Boundary " + std::to_string(boundary_id) +
                 " seems to have cycles. A single-cycle loop should be used");

  edge_mesh->skip_partitioning(true);
  edge_mesh->prepare_for_use();
  if (edge_mesh->n_elem() == 0)
    mooseError("The input mesh to extract the boundary from does not have a boundary with id ",
               boundary_id,
               "\n",
               input_mesh);

  return edge_mesh;
}

std::unordered_map<dof_id_type, std::unordered_set<dof_id_type>>
buildBoundaryNodeToElemMap(const MeshBase & input_mesh, const boundary_id_type boundary_id)
{
  if (!input_mesh.is_serial())
    ::mooseError(
        "Input 2D mesh should be serialized for extracting the loop boundary mesh.\nInput mesh:" +
        input_mesh.get_info());

  // Get all nodes on that boundary
  // Boundary ID might be a sideset or a nodeset, get nodes regardless
  const auto particular_node_ids = getBoundaryNodes(input_mesh, boundary_id);

  std::unordered_map<dof_id_type, std::unordered_set<dof_id_type>> nid_to_eids_map;
  // Fill the map from looping over elements
  for (const auto & elem :
       as_range(input_mesh.active_elements_begin(), input_mesh.active_elements_end()))
  {
    for (const auto & nd : elem->node_ref_range())
    {
      // Only add the element id if the node is on the boundary
      if (!particular_node_ids.count(nd.id()))
        continue;

      auto & elem_ids = nid_to_eids_map[nd.id()];
      elem_ids.insert(elem->id());
    }
  }
  return nid_to_eids_map;
}

std::set<dof_id_type>
getBoundaryNodes(const MeshBase & mesh, const BoundaryID boundary_id)
{
  std::set<dof_id_type> boundary_node_ids;
  const BoundaryInfo & boundary_info = mesh.get_boundary_info();

  // Get all nodes from the sideset with ID of boundary_id
  const auto & bc_sides =
      boundary_info.build_side_list(libMesh::BoundaryInfo::BCTupleSortBy::BOUNDARY_ID);
  for (const auto & [elem_id, side, bc_id] : bc_sides)
  {
    if (bc_id == boundary_id)
    {
      const auto elem = mesh.elem_ptr(elem_id);
      for (const auto ni : elem->nodes_on_side(side))
        boundary_node_ids.insert(elem->node_id(ni));
    }
  }

  // Get all nodes from nodeset with ID of boundary_id
  const auto & bc_nodes = boundary_info.build_node_list();
  for (const auto & [n_id, bc_id] : bc_nodes)
    if (bc_id == boundary_id)
      boundary_node_ids.insert(n_id);

  return boundary_node_ids;
}

void
createSubdomainFromSidesets(MeshBase & mesh,
                            std::vector<BoundaryName> boundary_names,
                            const SubdomainID new_subdomain_id,
                            const SubdomainName new_subdomain_name,
                            const std::string type_name)
{
  // Generate a new block id if one isn't supplied.
  SubdomainID new_block_id = new_subdomain_id;

  // Make sure our boundary info and parallel counts are setup
  if (!mesh.is_prepared())
  {
    const bool allow_remote_element_removal = mesh.allow_remote_element_removal();
    // We want all of our boundary elements available, so avoid removing them if they haven't
    // already been so
    mesh.allow_remote_element_removal(false);
    mesh.prepare_for_use();
    mesh.allow_remote_element_removal(allow_remote_element_removal);
  }

  // Check that the sidesets are present in the mesh
  for (const auto & sideset : boundary_names)
    if (!MooseMeshUtils::hasBoundaryName(mesh, sideset))
      mooseException("The sideset '", sideset, "' was not found within the mesh");

  auto sideset_ids = MooseMeshUtils::getBoundaryIDs(mesh, boundary_names, true);
  std::set<boundary_id_type> sidesets(sideset_ids.begin(), sideset_ids.end());
  auto side_list = mesh.get_boundary_info().build_side_list();
  if (!mesh.is_serial() && mesh.comm().size() > 1)
  {
    std::vector<Elem *> elements_to_send;
    unsigned short i_need_boundary_elems = 0;
    for (const auto & [elem_id, side, bc_id] : side_list)
    {
      libmesh_ignore(side);
      if (sidesets.count(bc_id))
      {
        // Whether we have this boundary information through our locally owned element or a ghosted
        // element, we'll need the boundary elements for parallel consistent addition
        i_need_boundary_elems = 1;
        auto * elem = mesh.elem_ptr(elem_id);
        if (elem->processor_id() == mesh.processor_id())
          elements_to_send.push_back(elem);
      }
    }

    std::set<const Elem *, libMesh::CompareElemIdsByLevel> connected_elements(
        elements_to_send.begin(), elements_to_send.end());
    std::set<const Node *> connected_nodes;
    reconnect_nodes(connected_elements, connected_nodes);
    std::set<dof_id_type> connected_node_ids;
    for (auto * nd : connected_nodes)
      connected_node_ids.insert(nd->id());

    std::vector<unsigned short> need_boundary_elems(mesh.comm().size());
    mesh.comm().allgather(i_need_boundary_elems, need_boundary_elems);
    std::unordered_map<processor_id_type, decltype(elements_to_send)> push_element_data;
    std::unordered_map<processor_id_type, decltype(connected_nodes)> push_node_data;

    for (const auto pid : index_range(mesh.comm()))
      // Don't need to send to self
      if (pid != mesh.processor_id() && need_boundary_elems[pid])
      {
        if (elements_to_send.size())
          push_element_data[pid] = elements_to_send;
        if (connected_nodes.size())
          push_node_data[pid] = connected_nodes;
      }

    auto node_action_functor = [](processor_id_type, const auto &)
    {
      // Node packing specialization already has unpacked node into mesh, so nothing to do
    };
    Parallel::push_parallel_packed_range(mesh.comm(), push_node_data, &mesh, node_action_functor);
    auto elem_action_functor = [](processor_id_type, const auto &)
    {
      // Elem packing specialization already has unpacked elem into mesh, so nothing to do
    };
    TIMPI::push_parallel_packed_range(mesh.comm(), push_element_data, &mesh, elem_action_functor);

    // now that we've gathered everything, we need to rebuild the side list
    side_list = mesh.get_boundary_info().build_side_list();
  }

  std::vector<std::pair<dof_id_type, ElemSidePair>> element_sides_on_boundary;
  dof_id_type counter = 0;
  for (const auto & [eid, side, bid] : side_list)
    if (sidesets.count(bid))
    {
      if (auto elem = mesh.query_elem_ptr(eid))
      {
        if (!elem->active())
          mooseError(
              "Only active, level 0 elements can be made interior parents of new level 0 lower-d "
              "elements. Make sure that ",
              type_name,
              "s are run before any refinement generators");
        element_sides_on_boundary.push_back(std::make_pair(counter, ElemSidePair(elem, side)));
      }
      ++counter;
    }

  dof_id_type max_elem_id = mesh.max_elem_id();
  unique_id_type max_unique_id = mesh.parallel_max_unique_id();

  // Making an important assumption that at least our boundary elements are the same on all
  // processes even in distributed mesh mode (this is reliant on the correct ghosting functors
  // existing on the mesh)
  for (auto & [i, elem_side] : element_sides_on_boundary)
  {
    Elem * elem = elem_side.elem;

    const auto side = elem_side.side;

    // Build a non-proxy element from this side.
    std::unique_ptr<Elem> side_elem(elem->build_side_ptr(side));

    // The side will be added with the same processor id as the parent.
    side_elem->processor_id() = elem->processor_id();

    // Add subdomain ID
    side_elem->subdomain_id() = new_block_id;

    // Also assign the side's interior parent, so it is always
    // easy to figure out the Elem we came from.
    side_elem->set_interior_parent(elem);

    // Add id
    side_elem->set_id(max_elem_id + i);
    side_elem->set_unique_id(max_unique_id + i);

    // Finally, add the lower-dimensional element to the mesh.
    mesh.add_elem(side_elem.release());
  };

  // Assign block name, if provided
  if (new_subdomain_name.size())
    mesh.subdomain_name(new_block_id) = new_subdomain_name;

  const bool skip_partitioning_old = mesh.skip_partitioning();
  mesh.skip_partitioning(true);
  mesh.prepare_for_use();
  mesh.skip_partitioning(skip_partitioning_old);
}

void
convertBlockToMesh(MeshBase & source_mesh,
                   MeshBase & target_mesh,
                   const std::vector<SubdomainName> & target_blocks)
{
  if (!source_mesh.is_replicated())
    mooseError("This generator does not support distributed meshes.");

  const auto target_block_ids = MooseMeshUtils::getSubdomainIDs(source_mesh, target_blocks);

  // Check that the block ids/names exist in the mesh
  std::set<SubdomainID> mesh_blocks;
  source_mesh.subdomain_ids(mesh_blocks);

  for (const auto i : index_range(target_block_ids))
    if (target_block_ids[i] == Moose::INVALID_BLOCK_ID || !mesh_blocks.count(target_block_ids[i]))
    {
      mooseException("The target_block '", target_blocks[i], "' was not found within the mesh.");
    }

  // know which nodes have already been inserted, by tracking the old mesh's node's ids'
  std::unordered_map<dof_id_type, dof_id_type> old_new_node_map;

  for (const auto target_block_id : target_block_ids)
  {

    for (auto elem : source_mesh.active_subdomain_elements_ptr_range(target_block_id))
    {
      if (elem->level() != 0)
        mooseError("Refined blocks are not supported by this generator. "
                   "Can you re-organize mesh generators to refine after converting the block?");

      // make a deep copy so that mutiple meshes' destructors don't segfault at program termination
      auto copy = elem->build(elem->type());

      // Keep the subdomain id
      copy->subdomain_id() = elem->subdomain_id();

      // index of node in the copy element must be managed manually as there is no intelligent
      // insert method
      dof_id_type copy_n_index = 0;

      // correctly assign new copies of nodes, loop over nodes
      for (dof_id_type i : elem->node_index_range())
      {
        auto & n = elem->node_ref(i);

        if (old_new_node_map.count(n.id()))
        {
          // case where we have already inserted this particular point before
          // then we need to find the already-inserted one and hook it up right
          // to it's respective element
          copy->set_node(copy_n_index++, target_mesh.node_ptr(old_new_node_map[n.id()]));
        }
        else
        {
          // case where we've NEVER inserted this particular point before
          // add them both to the element and the mesh

          // Nodes' IDs are their indexes in the nodes' respective mesh
          // If we set them as invalid they are automatically assigned
          // Add to mesh, auto-assigning a new id.
          Node * node = target_mesh.add_point(elem->point(i));

          // Add to element copy (manually)
          copy->set_node(copy_n_index++, node);

          // remember the (old) ID
          old_new_node_map[n.id()] = node->id();
        }
      }

      // it is ok to release the copy element into the mesh because derived meshes class
      // (ReplicatedMesh, DistributedMesh) manage their own elements, will delete them
      target_mesh.add_elem(copy.release());
    }
  }

  // Move subdomain names
  for (const auto sbd_id : target_block_ids)
    target_mesh.subdomain_name(sbd_id) = source_mesh.subdomain_name(sbd_id);
}

void
copyIntoMesh(MeshGenerator & mg,
             UnstructuredMesh & destination,
             const UnstructuredMesh & source,
             const bool avoid_merging_subdomains,
             const bool avoid_merging_boundaries,
             const Parallel::Communicator & communicator)
{
  dof_id_type node_delta = destination.max_node_id();
  dof_id_type elem_delta = destination.max_elem_id();

  unique_id_type unique_delta =
#ifdef LIBMESH_ENABLE_UNIQUE_ID
      destination.parallel_max_unique_id();
#else
      0;
#endif

  // Prevent overlaps by offsetting the subdomains in
  std::unordered_map<subdomain_id_type, subdomain_id_type> id_remapping;
  unsigned int block_offset = 0;
  if (avoid_merging_subdomains)
  {
    // Note: if performance becomes an issue, this is overkill for just getting the max node id
    std::set<subdomain_id_type> source_ids;
    std::set<subdomain_id_type> dest_ids;

    // We need source subdomain ids already cached; libMesh will
    // scream otherwise
    source.subdomain_ids(source_ids, true);

    // Our destination is non-const, so we can fix any missing caches
    if (!destination.preparation().has_cached_elem_data)
      destination.cache_elem_data();

    destination.subdomain_ids(dest_ids, true);

    mooseAssert(source_ids.size(), "Should have a subdomain");
    mooseAssert(dest_ids.size(), "Should have a subdomain");
    unsigned int max_dest_bid = *dest_ids.rbegin();
    unsigned int min_source_bid = *source_ids.begin();
    communicator.max(max_dest_bid);
    communicator.min(min_source_bid);
    block_offset = 1 + max_dest_bid - min_source_bid;
    for (const auto bid : source_ids)
      id_remapping[bid] = block_offset + bid;
  }

  // Copy mesh data over from the other mesh
  destination.copy_nodes_and_elements(source,
                                      // Skipping this should cause the neighbors
                                      // to simply be copied from the other mesh
                                      // (which makes sense and is way faster)
                                      /*skip_find_neighbors = */ true,
                                      elem_delta,
                                      node_delta,
                                      unique_delta,
                                      avoid_merging_subdomains ? &id_remapping : nullptr);

  // Get an offset to prevent overlaps / wild merging between boundaries
  BoundaryInfo & boundary = destination.get_boundary_info();
  const BoundaryInfo & other_boundary = source.get_boundary_info();

  unsigned int bid_offset = 0;
  if (avoid_merging_boundaries)
  {
    const auto boundary_ids = boundary.get_boundary_ids();
    const auto other_boundary_ids = other_boundary.get_boundary_ids();
    unsigned int max_dest_bid = boundary_ids.size() ? *boundary_ids.rbegin() : 0;
    unsigned int min_source_bid = other_boundary_ids.size() ? *other_boundary_ids.begin() : 0;
    communicator.max(max_dest_bid);
    communicator.min(min_source_bid);
    bid_offset = 1 + max_dest_bid - min_source_bid;
  }

  // Note: the code below originally came from ReplicatedMesh::stitch_mesh_helper()
  // in libMesh replicated_mesh.C around line 1203

  // Copy BoundaryInfo from other_mesh too.  We do this via the
  // list APIs rather than element-by-element for speed.
  for (const auto & t : other_boundary.build_node_list())
    boundary.add_node(std::get<0>(t) + node_delta, bid_offset + std::get<1>(t));

  for (const auto & t : other_boundary.build_side_list())
    boundary.add_side(std::get<0>(t) + elem_delta, std::get<1>(t), bid_offset + std::get<2>(t));

  for (const auto & t : other_boundary.build_edge_list())
    boundary.add_edge(std::get<0>(t) + elem_delta, std::get<1>(t), bid_offset + std::get<2>(t));

  for (const auto & t : other_boundary.build_shellface_list())
    boundary.add_shellface(
        std::get<0>(t) + elem_delta, std::get<1>(t), bid_offset + std::get<2>(t));

  // Check for the case with two block ids sharing the same name
  if (avoid_merging_subdomains)
  {
    mooseAssert(mg.parameters().isParamDefined("avoid_merging_subdomains"),
                "Missing parameter in the mesh generator calling this function: "
                "avoid_merging_subdomains. Considering setting avoid_merging_subdomains to true.");
    for (const auto & [block_id, block_name] : destination.get_subdomain_name_map())
      for (const auto & [source_id, source_name] : source.get_subdomain_name_map())
        if (block_name == source_name)
          mg.paramWarning(
              "avoid_merging_subdomains",
              "Not merging subdomains is creating two subdomains with the same name '" +
                  block_name + "' but different ids: " + std::to_string(source_id) + " & " +
                  std::to_string(block_id + block_offset) +
                  ".\n We recommend using a RenameBlockGenerator to prevent this as you "
                  "will get errors reading the Exodus output later.");
  }

  for (const auto & [block_id, block_name] : source.get_subdomain_name_map())
    destination.set_subdomain_name_map().insert(
        std::make_pair<SubdomainID, SubdomainName>(block_id + block_offset, block_name));

  // Check for the case with two boundary ids sharing the same name
  if (avoid_merging_boundaries)
  {
    mooseAssert(mg.parameters().isParamDefined("avoid_merging_boundaries"),
                "Missing parameter in the mesh generator calling this function: "
                "avoid_merging_boundaries. Considering setting avoid_merging_boundaries to true.");
    for (const auto & [b_id, b_name] : other_boundary.get_sideset_name_map())
      for (const auto & [source_id, source_name] : boundary.get_sideset_name_map())
        if (b_name == source_name)
          mg.paramWarning(
              "avoid_merging_boundaries",
              "Not merging boundaries is creating two sidesets with the same name '" + b_name +
                  "' but different ids: " + std::to_string(source_id) + " & " +
                  std::to_string(b_id + bid_offset) +
                  ".\n We recommend using a RenameBoundaryGenerator to prevent this as you "
                  "will get errors reading the Exodus output later.");
    for (const auto & [b_id, b_name] : other_boundary.get_nodeset_name_map())
      for (const auto & [source_id, source_name] : boundary.get_nodeset_name_map())
        if (b_name == source_name)
          mg.paramWarning(
              "avoid_merging_boundaries",
              "Not merging boundaries is creating two nodesets with the same name '" + b_name +
                  "' but different ids: " + std::to_string(source_id) + " & " +
                  std::to_string(b_id + bid_offset) +
                  ".\n We recommend using a RenameBoundaryGenerator to prevent this as you "
                  "will get errors reading the Exodus output later.");
  }

  for (const auto & [nodeset_id, nodeset_name] : other_boundary.get_nodeset_name_map())
    boundary.set_nodeset_name_map().insert(
        std::make_pair<BoundaryID, BoundaryName>(nodeset_id + bid_offset, nodeset_name));

  for (const auto & [sideset_id, sideset_name] : other_boundary.get_sideset_name_map())
    boundary.set_sideset_name_map().insert(
        std::make_pair<BoundaryID, BoundaryName>(sideset_id + bid_offset, sideset_name));

  for (const auto & [edgeset_id, edgeset_name] : other_boundary.get_edgeset_name_map())
    boundary.set_edgeset_name_map().insert(
        std::make_pair<BoundaryID, BoundaryName>(edgeset_id + bid_offset, edgeset_name));
}

void
buildPolyLineMesh(MeshBase & mesh,
                  const std::vector<Point> & points,
                  const std::vector<Point> & mid_points,
                  const bool loop,
                  const BoundaryName & start_boundary,
                  const BoundaryName & end_boundary,
                  const std::vector<unsigned int> & nums_edges_between_points)
{
  mooseAssert(nums_edges_between_points.size() == 1 ||
                  nums_edges_between_points.size() == points.size() - 1 + loop,
              "nums_edges_between_points must be either a single value or have the same number of "
              "entries as segments defined by the points.");
  mooseAssert(
      mid_points.size() == 0 || mid_points.size() == points.size() - (loop ? 0 : 1),
      "mid_points must be either empty or have the consistent number of entries as points.");
  mooseAssert(
      mid_points.size() == 0 ||
          (nums_edges_between_points.size() == 1 && nums_edges_between_points.front() == 1) ||
          (nums_edges_between_points.size() == points.size() - 1 + loop &&
           std::all_of(nums_edges_between_points.begin(),
                       nums_edges_between_points.end(),
                       [](unsigned int n) { return n == 1; })),
      "mid_points can only be provided if each segment has exactly one edge.");

  const auto n_points = points.size();
  for (auto i : make_range(n_points))
  {
    const auto & num_edges_between_points =
        (nums_edges_between_points.size() == 1)
            ? nums_edges_between_points[0]
            : (i == nums_edges_between_points.size() ? 0 : nums_edges_between_points[i]);

    Point p = points[i];
    const auto pt_counter = (nums_edges_between_points.size() == 1)
                                ? i
                                : std::accumulate(nums_edges_between_points.begin(),
                                                  nums_edges_between_points.begin() + i,
                                                  0);
    mesh.add_point(
        p, nums_edges_between_points.size() == 1 ? (i * num_edges_between_points) : pt_counter);

    if (num_edges_between_points > 1)
    {
      if (!loop && (i + 1) == n_points)
        break;

      const auto ip1 = (i + 1) % n_points;
      const Point pvec = (points[ip1] - p) / num_edges_between_points;

      for (auto j : make_range(1u, num_edges_between_points))
      {
        p += pvec;
        mesh.add_point(
            p,
            (nums_edges_between_points.size() == 1 ? (i * num_edges_between_points) : pt_counter) +
                j);
      }
    }
  }
  // Add mid points if applicable. When mid points are provided, each segment has exactly one edge,
  // so the midpoint node ids follow the vertex node ids.
  for (const auto & i : make_range(mid_points.size()))
    mesh.add_point(mid_points[i], n_points + i);

  const auto n_segments = loop ? n_points : (n_points - 1);
  const auto n_elem =
      nums_edges_between_points.size() == 1
          ? n_segments * nums_edges_between_points[0]
          : std::accumulate(nums_edges_between_points.begin(), nums_edges_between_points.end(), 0);
  const auto max_nodes =
      (nums_edges_between_points.size() == 1 ? n_segments * nums_edges_between_points[0]
                                             : std::accumulate(nums_edges_between_points.begin(),
                                                               nums_edges_between_points.end(),
                                                               0)) +
      (loop ? 0 : 1);
  for (auto i : make_range(n_elem))
  {
    std::unique_ptr<Elem> elem;
    if (mid_points.size())
    {
      elem = std::make_unique<Edge3>();
      elem->set_node(2, mesh.node_ptr(n_points + i));
    }
    else
      elem = Elem::build(EDGE2);
    const auto ip1 = (i + 1) % max_nodes;
    elem->set_node(0, mesh.node_ptr(i));
    elem->set_node(1, mesh.node_ptr(ip1));
    elem->set_id() = i;
    mesh.add_elem(std::move(elem));
  }

  if (!loop)
  {
    BoundaryInfo & bi = mesh.get_boundary_info();
    std::vector<BoundaryName> bdy_names{start_boundary, end_boundary};
    std::vector<boundary_id_type> ids = MooseMeshUtils::getBoundaryIDs(mesh, bdy_names, true);
    bi.add_side(mesh.elem_ptr(0), 0, ids[0]);
    bi.add_side(mesh.elem_ptr(n_elem - 1), 1, ids[1]);
  }
  else
    mooseAssert(start_boundary.empty() && end_boundary.empty(),
                "Cannot assign start/end boundaries on a looped polyline.");

  mesh.prepare_for_use();
}

void
buildPolyLineMesh(MeshBase & mesh,
                  const std::vector<Point> & points,
                  const bool loop,
                  const BoundaryName & start_boundary,
                  const BoundaryName & end_boundary,
                  const std::vector<unsigned int> & nums_edges_between_points)
{
  buildPolyLineMesh(
      mesh, points, {}, loop, start_boundary, end_boundary, nums_edges_between_points);
}

void
buildPolyLineMesh(MeshBase & mesh,
                  const std::vector<Point> & points,
                  const bool loop,
                  const BoundaryName & start_boundary,
                  const BoundaryName & end_boundary,
                  const Real max_elem_size)
{
  std::vector<unsigned int> nums_edges_between_points;
  const auto n_points = points.size();
  for (auto i : make_range(n_points))
  {
    if (!loop && (i + 1) == n_points)
      break;

    const auto ip1 = (i + 1) % n_points;
    const Real length = (points[ip1] - points[i]).norm();
    const unsigned int n_elems = std::max(
        static_cast<unsigned int>(std::ceil(length / max_elem_size)), static_cast<unsigned int>(1));
    nums_edges_between_points.push_back(n_elems);
  }

  buildPolyLineMesh(
      mesh, points, {}, loop, start_boundary, end_boundary, nums_edges_between_points);
}

void
addExternalBoundary(MeshBase & mesh, const BoundaryID extern_bid, bool & has_external_bid)
{
  auto & binfo = mesh.get_boundary_info();
  for (const auto & elem : mesh.active_element_ptr_range())
    for (const auto & i_side : elem->side_index_range())
      if (elem->neighbor_ptr(i_side) == nullptr)
      {
        has_external_bid = true;
        binfo.add_side(elem, i_side, extern_bid);
      }
}
}