#include <catch2/catch_approx.hpp>
#include <catch2/catch_test_macros.hpp>
#include <catch2/matchers/catch_matchers_all.hpp>

#include <utils/PugsAssert.hpp>

#include <mesh/Mesh.hpp>
#include <mesh/NamedBoundaryDescriptor.hpp>
#include <scheme/DiscreteFunctionDPkVariant.hpp>
#include <scheme/DiscreteFunctionP0.hpp>
#include <scheme/DiscreteFunctionVariant.hpp>
#include <scheme/PolynomialReconstruction.hpp>

#include <DiscreteFunctionDPkForTests.hpp>
#include <MeshDataBaseForTests.hpp>

// clazy:excludeall=non-pod-global-static

TEST_CASE("PolynomialReconstruction_degree_2", "[scheme]")
{
  constexpr size_t degree = 2;

  SECTION("without symmetries")
  {
    std::vector<PolynomialReconstructionDescriptor> descriptor_list =
      {PolynomialReconstructionDescriptor{IntegrationMethodType::element, degree},
       PolynomialReconstructionDescriptor{IntegrationMethodType::boundary, degree}};

    for (auto descriptor : descriptor_list) {
      SECTION(name(descriptor.integrationMethodType()))
      {
        SECTION("1D")
        {
          using R1 = TinyVector<1>;

          SECTION("R data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;

                auto R_exact = [](const R1& x) { return 2.3 + 1.7 * x[0] - 1.4 * x[0] * x[0]; };

                DiscreteFunctionP0 fh = test_only::exact_projection(mesh, degree, std::function(R_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(fh);

                auto dpk_fh = reconstructions[0]->get<DiscreteFunctionDPk<1, const double>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_fh, std::function(R_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
              }
            }
          }

          SECTION("R^3 data")
          {
            using R3 = TinyVector<3>;

            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;

                auto R3_exact = [](const R1& x) -> R3 {
                  return R3{+2.3 + 1.7 * x[0] - x[0] * x[0],       //
                            +1.4 - 0.6 * x[0] + 2 * x[0] * x[0],   //
                            -0.2 + 3.1 * x[0] + 1.4 * x[0] * x[0]};
                };

                DiscreteFunctionP0 uh = test_only::exact_projection(mesh, degree, std::function(R3_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(uh);

                auto dpk_uh = reconstructions[0]->get<DiscreteFunctionDPk<1, const R3>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R3_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
              }
            }
          }

          SECTION("R^3x3 data")
          {
            using R3x3 = TinyMatrix<3, 3>;

            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;

                auto R3x3_exact = [](const R1& x) -> R3x3 {
                  return R3x3{+2.3 + 1.7 * x[0] - 2.3 * x[0] * x[0],   //
                              -1.7 + 2.1 * x[0] + 1.2 * x[0] * x[0],   //
                              +1.4 - 0.6 * x[0] - 2.0 * x[0] * x[0],   //
                                                                       //
                              +2.4 - 2.3 * x[0] + 1.1 * x[0] * x[0],   //
                              -0.2 + 3.1 * x[0] - 0.7 * x[0] * x[0],   //
                              -3.2 - 3.6 * x[0] + 0.1 * x[0] * x[0],   //
                              //
                              -4.1 + 3.1 * x[0] - 0.2 * x[0] * x[0],   //
                              +0.8 + 2.9 * x[0] + 4.1 * x[0] * x[0],   //
                              -1.6 + 2.3 * x[0] - 1.7 * x[0] * x[0]};
                };

                DiscreteFunctionP0 Ah = test_only::exact_projection(mesh, degree, std::function(R3x3_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(Ah);

                auto dpk_Ah = reconstructions[0]->get<DiscreteFunctionDPk<1, const R3x3>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_Ah, std::function(R3x3_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
              }
            }
          }

          SECTION("R vector data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;
                std::array<std::function<double(const R1&)>, 3> vector_exact =
                  {[](const R1& x) -> double { return +2.3 + 1.7 * x[0] + 1.2 * x[0] * x[0]; },
                   [](const R1& x) -> double { return -1.7 + 2.1 * x[0] + 2.1 * x[0] * x[0]; },
                   [](const R1& x) -> double { return +1.4 - 0.6 * x[0] - 1.3 * x[0] * x[0]; }};

                DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

                auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);
                auto dpk_Vh          = reconstructions[0]->get<DiscreteFunctionDPkVector<1, const double>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
              }
            }
          }

          SECTION("R3 vector data")
          {
            using R3 = TinyVector<3>;

            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;

                std::array<std::function<R3(const R1&)>, 2> vector_exact =
                  {[](const R1& x) -> R3 {
                     return R3{+2.3 + 1.7 * x[0] + 0.8 * x[0] * x[0],   //
                               -1.7 + 2.1 * x[0] - 0.7 * x[0] * x[0],   //
                               +1.4 - 0.6 * x[0] + 1.9 * x[0] * x[0]};
                   },
                   [](const R1& x) -> R3 {
                     return R3{+1.6 + 0.7 * x[0], -2.1 + 1.2 * x[0], +1.1 - 0.3 * x[0]};
                   }};

                DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

                auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

                auto dpk_Vh = reconstructions[0]->get<DiscreteFunctionDPkVector<1, const R3>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
              }
            }
          }

          SECTION("list of various types")
          {
            using R3x3 = TinyMatrix<3>;
            using R3   = TinyVector<3>;

            for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
                auto& mesh  = *p_mesh;

                auto R_exact = [](const R1& x) { return 2.3 + 1.7 * x[0]; };

                auto R3_exact = [](const R1& x) -> R3 {
                  return R3{+2.3 + 1.7 * x[0] + 2.3 * x[0] * x[0],   //
                            +1.4 - 0.6 * x[0] - 1.5 * x[0] * x[0],   //
                            -0.2 + 3.1 * x[0] + 2.9 * x[0] * x[0]};
                };

                auto R3x3_exact = [](const R1& x) -> R3x3 {
                  return R3x3{
                    +2.3 + 1.7 * x[0] - 0.3 * x[0] * x[0],
                    -1.7 + 2.1 * x[0] + 1.4 * x[0] * x[0],
                    +1.4 - 0.6 * x[0] - 2.3 * x[0] * x[0],
                    //
                    +2.4 - 2.3 * x[0] + 1.8 * x[0] * x[0],
                    -0.2 + 3.1 * x[0] - 1.7 * x[0] * x[0],
                    -3.2 - 3.6 * x[0] + 0.7 * x[0] * x[0],
                    //
                    -4.1 + 3.1 * x[0] - 1.9 * x[0] * x[0],
                    +0.8 + 2.9 * x[0] + 2.2 * x[0] * x[0],
                    -1.6 + 2.3 * x[0] - 1.3 * x[0] * x[0],
                  };
                };

                std::array<std::function<double(const R1&)>, 3> vector_exact =
                  {[](const R1& x) -> double { return +2.3 + 1.7 * x[0] + 2.2 * x[0] * x[0]; },
                   [](const R1& x) -> double { return -1.7 + 2.1 * x[0] - 1.9 * x[0] * x[0]; },
                   [](const R1& x) -> double { return +1.4 - 0.6 * x[0] + 3.1 * x[0] * x[0]; }};

                DiscreteFunctionP0 fh       = test_only::exact_projection(mesh, degree, std::function(R_exact));
                DiscreteFunctionP0 uh       = test_only::exact_projection(mesh, degree, std::function(R3_exact));
                DiscreteFunctionP0 Ah       = test_only::exact_projection(mesh, degree, std::function(R3x3_exact));
                DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

                auto reconstructions =
                  PolynomialReconstruction{descriptor}.build(std::make_shared<DiscreteFunctionVariant>(fh), uh,
                                                             std::make_shared<DiscreteFunctionP0<R3x3>>(Ah),
                                                             DiscreteFunctionVariant(Vh));

                {
                  auto dpk_fh      = reconstructions[0]->get<DiscreteFunctionDPk<1, const double>>();
                  double max_error = test_only::max_reconstruction_error(mesh, dpk_fh, std::function(R_exact));
                  REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
                }

                {
                  auto dpk_uh      = reconstructions[1]->get<DiscreteFunctionDPk<1, const R3>>();
                  double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R3_exact));
                  REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
                }

                {
                  auto dpk_Ah      = reconstructions[2]->get<DiscreteFunctionDPk<1, const R3x3>>();
                  double max_error = test_only::max_reconstruction_error(mesh, dpk_Ah, std::function(R3x3_exact));
                  REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
                }

                {
                  auto dpk_Vh      = reconstructions[3]->get<DiscreteFunctionDPkVector<1, const double>>();
                  double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
                  REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-14));
                }
              }
            }
          }
        }

        SECTION("2D")
        {
          using R2 = TinyVector<2>;

          SECTION("R data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all2DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<2>>();
                auto& mesh  = *p_mesh;

                auto R_exact = [](const R2& x) {
                  return 2.3 + 1.7 * x[0] - 1.3 * x[1]   //
                         + 1.2 * x[0] * x[0] + 1.3 * x[0] * x[1] - 3.2 * x[1] * x[1];
                };

                DiscreteFunctionP0 fh = test_only::exact_projection(mesh, degree, std::function(R_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(fh);

                auto dpk_fh = reconstructions[0]->get<DiscreteFunctionDPk<2, const double>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_fh, std::function(R_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("R^3 data")
          {
            using R3 = TinyVector<3>;

            for (auto named_mesh : MeshDataBaseForTests::get().all2DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<2>>();
                auto& mesh  = *p_mesh;

                auto R3_exact = [](const R2& x) -> R3 {
                  return R3{+2.3 + 1.7 * x[0] - 2.2 * x[1]                                   //
                              - 2.1 * x[0] * x[0] - 2.3 * x[0] * x[1] - 3.2 * x[1] * x[1],   //
                            +1.4 - 0.6 * x[0] + 1.3 * x[1]                                   //
                              + 2.3 * x[0] * x[0] - 1.3 * x[0] * x[1] + 1.2 * x[1] * x[1],   //
                            -0.2 + 3.1 * x[0] - 1.1 * x[1]                                   //
                              - 2.1 * x[0] * x[0] + 1.3 * x[0] * x[1] - 1.1 * x[1] * x[1]};
                };

                DiscreteFunctionP0 uh = test_only::exact_projection(mesh, degree, std::function(R3_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(uh);

                auto dpk_uh = reconstructions[0]->get<DiscreteFunctionDPk<2, const R3>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R3_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("R^2x2 data")
          {
            using R2x2 = TinyMatrix<2, 2>;

            for (auto named_mesh : MeshDataBaseForTests::get().all2DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<2>>();
                auto& mesh  = *p_mesh;

                auto R2x2_exact = [](const R2& x) -> R2x2 {
                  return R2x2{+2.3 + 1.7 * x[0] + 1.2 * x[1]                                   //
                                - 2.1 * x[0] * x[0] + 1.3 * x[0] * x[1] + 1.2 * x[1] * x[1],   //
                              -1.7 + 2.1 * x[0] - 2.2 * x[1]                                   //
                                - 1.2 * x[0] * x[0] + 2.1 * x[0] * x[1] - 1.3 * x[1] * x[1],   //
                              +1.4 - 0.6 * x[0] - 2.1 * x[1]                                   //
                                - 1.1 * x[0] * x[0] - 2.3 * x[0] * x[1] + 2.1 * x[1] * x[1],
                              +2.4 - 2.3 * x[0] + 1.3 * x[1]   //
                                + 2.7 * x[0] * x[0] + 2.1 * x[0] * x[1] - 2.7 * x[1] * x[1]};
                };

                DiscreteFunctionP0 Ah = test_only::exact_projection(mesh, degree, std::function(R2x2_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(Ah);

                auto dpk_Ah      = reconstructions[0]->get<DiscreteFunctionDPk<2, const R2x2>>();
                double max_error = test_only::max_reconstruction_error(mesh, dpk_Ah, std::function(R2x2_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("vector data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all2DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<2>>();
                auto& mesh  = *p_mesh;

                std::array<std::function<double(const R2&)>, 4> vector_exact =
                  {[](const R2& x) -> double {
                     return +2.3 + 1.7 * x[0] + 1.2 * x[1] + 1.2 * x[0] * x[0] - 2.1 * x[0] * x[1] + 3.1 * x[1] * x[1];
                   },
                   [](const R2& x) -> double {
                     return -1.7 + 2.1 * x[0] - 2.2 * x[1] - 0.7 * x[0] * x[0] + 2.2 * x[0] * x[1] - 1.6 * x[1] * x[1];
                   },
                   [](const R2& x) -> double {
                     return +1.4 - 0.6 * x[0] - 2.1 * x[1] + 2.3 * x[0] * x[0] + 2.3 * x[0] * x[1] - 2.9 * x[1] * x[1];
                   },
                   [](const R2& x) -> double {
                     return +2.4 - 2.3 * x[0] + 1.3 * x[1] - 2.7 * x[0] * x[0] - 1.2 * x[0] * x[1] - 0.7 * x[1] * x[1];
                   }};

                DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

                auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

                auto dpk_Vh      = reconstructions[0]->get<DiscreteFunctionDPkVector<2, const double>>();
                double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }
        }

        SECTION("3D")
        {
          using R3 = TinyVector<3>;

          SECTION("R data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all3DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<3>>();
                auto& mesh  = *p_mesh;

                auto R_exact = [](const R3& x) {
                  return 2.3 + 1.7 * x[0] - 1.3 * x[1] + 2.1 * x[2]                    //
                         + 1.7 * x[0] * x[0] + 1.4 * x[1] * x[1] + 1.7 * x[2] * x[2]   //
                         - 2.3 * x[0] * x[1] + 1.6 * x[0] * x[2] - 1.9 * x[1] * x[2];
                };

                DiscreteFunctionP0 fh = test_only::exact_projection(mesh, degree, std::function(R_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(fh);

                auto dpk_fh = reconstructions[0]->get<DiscreteFunctionDPk<3, const double>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_fh, std::function(R_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("R^3 data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all3DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<3>>();
                auto& mesh  = *p_mesh;

                auto R3_exact = [](const R3& x) -> R3 {
                  return R3{+2.3 + 1.7 * x[0] - 2.2 * x[1] + 1.8 * x[2]                      //
                              + 1.7 * x[0] * x[0] - 2.4 * x[1] * x[1] - 2.3 * x[2] * x[2]    //
                              - 2.1 * x[0] * x[1] + 2.6 * x[0] * x[2] + 1.6 * x[1] * x[2],   //
                            +1.4 - 0.6 * x[0] + 1.3 * x[1] - 3.7 * x[2]                      //
                              + 3.1 * x[0] * x[0] - 1.1 * x[1] * x[1] + 1.7 * x[2] * x[2]    //
                              - 2.3 * x[0] * x[1] - 2.6 * x[0] * x[2] - 1.9 * x[1] * x[2],   //
                            -0.2 + 3.1 * x[0] - 1.1 * x[1] + 1.9 * x[2]                      //
                              - 1.5 * x[0] * x[0] + 1.4 * x[1] * x[1] - 1.2 * x[2] * x[2]    //
                              - 1.7 * x[0] * x[1] - 1.3 * x[0] * x[2] + 2.1 * x[1] * x[2]};
                };

                DiscreteFunctionP0 uh = test_only::exact_projection(mesh, degree, std::function(R3_exact));

                auto reconstructions = PolynomialReconstruction{descriptor}.build(uh);

                auto dpk_uh = reconstructions[0]->get<DiscreteFunctionDPk<3, const R3>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R3_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("R^2x2 data")
          {
            using R2x2 = TinyMatrix<2, 2>;

            for (auto named_mesh : MeshDataBaseForTests::get().all3DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<3>>();
                auto& mesh  = *p_mesh;

                auto R2x2_exact = [](const R3& x) -> R2x2 {
                  return R2x2{
                    +2.3 + 1.7 * x[0] + 1.2 * x[1] - 1.3 * x[2]                      //
                      - 1.7 * x[0] * x[0] + 1.4 * x[1] * x[1] + 1.7 * x[2] * x[2]    //
                      - 1.3 * x[0] * x[1] + 1.6 * x[0] * x[2] - 1.9 * x[1] * x[2],   //
                    -1.7 + 2.1 * x[0] - 2.2 * x[1] - 2.4 * x[2]                      //
                      + 3.7 * x[0] * x[0] + 1.3 * x[1] * x[1] + 1.6 * x[2] * x[2]    //
                      - 2.1 * x[0] * x[1] - 1.5 * x[0] * x[2] - 1.7 * x[1] * x[2],   //
                    //
                    +2.4 - 2.3 * x[0] + 1.3 * x[1] + 1.4 * x[2]                      //
                      - 2.1 * x[0] * x[0] + 1.7 * x[1] * x[1] + 1.8 * x[2] * x[2]    //
                      - 1.4 * x[0] * x[1] + 1.3 * x[0] * x[2] - 2.9 * x[1] * x[2],   //
                    -0.2 + 3.1 * x[0] + 0.8 * x[1] - 1.8 * x[2]                      //
                      + 1.6 * x[0] * x[0] + 2.1 * x[1] * x[1] - 2.1 * x[2] * x[2]    //
                      - 1.1 * x[0] * x[1] - 1.3 * x[0] * x[2] + 1.6 * x[1] * x[2],   //
                  };
                };

                DiscreteFunctionP0 Ah = test_only::exact_projection(mesh, degree, std::function(R2x2_exact));

                descriptor.setRowWeighting(false);
                auto reconstructions = PolynomialReconstruction{descriptor}.build(Ah);

                auto dpk_Ah      = reconstructions[0]->get<DiscreteFunctionDPk<3, const R2x2>>();
                double max_error = test_only::max_reconstruction_error(mesh, dpk_Ah, std::function(R2x2_exact));
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }

          SECTION("vector data")
          {
            for (auto named_mesh : MeshDataBaseForTests::get().all3DMeshes()) {
              SECTION(named_mesh.name())
              {
                auto p_mesh = named_mesh.mesh()->get<Mesh<3>>();
                auto& mesh  = *p_mesh;
#warning continue here
                std::array<std::function<double(const R3&)>, 4> vector_exact =
                  {[](const R3& x) -> double { return +2.3 + 1.7 * x[0] + 1.2 * x[1] - 1.3 * x[2]; },
                   [](const R3& x) -> double { return -1.7 + 2.1 * x[0] - 2.2 * x[1] - 2.4 * x[2]; },
                   [](const R3& x) -> double { return +2.4 - 2.3 * x[0] + 1.3 * x[1] + 1.4 * x[2]; },
                   [](const R3& x) -> double { return -0.2 + 3.1 * x[0] + 0.8 * x[1] - 1.8 * x[2]; }};

                DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

                descriptor.setPreconditioning(false);
                auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

                auto dpk_Vh = reconstructions[0]->get<DiscreteFunctionDPkVector<3, const double>>();

                double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
                REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
              }
            }
          }
        }
      }
    }
  }

  SECTION("with symmetries")
  {
    // SECTION("1D")
    // {
    //   std::vector<PolynomialReconstructionDescriptor> descriptor_list =
    //     {PolynomialReconstructionDescriptor{IntegrationMethodType::element, degree,
    //                                         std::vector<std::shared_ptr<const IBoundaryDescriptor>>{
    //                                           std::make_shared<NamedBoundaryDescriptor>("XMIN")}},
    //      PolynomialReconstructionDescriptor{IntegrationMethodType::boundary, degree,
    //                                         std::vector<std::shared_ptr<const IBoundaryDescriptor>>{
    //                                           std::make_shared<NamedBoundaryDescriptor>("XMIN")}}};

    //   using R1 = TinyVector<1>;

    //   for (auto descriptor : descriptor_list) {
    //     SECTION(name(descriptor.integrationMethodType()))
    //     {
    //       SECTION("R^1 data")
    //       {
    //         auto p_mesh = MeshDataBaseForTests::get().unordered1DMesh()->get<Mesh<1>>();

    //         auto& mesh = *p_mesh;

    //         auto R1_exact = [](const R1& x) { return R1{1.7 * (x[0] + 1)}; };

    //         DiscreteFunctionP0 fh = test_only::exact_projection(mesh, degree, std::function(R1_exact));

    //         auto reconstructions = PolynomialReconstruction{descriptor}.build(fh);

    //         auto dpk_fh = reconstructions[0]->get<DiscreteFunctionDPk<1, const R1>>();

    //         double max_error = test_only::max_reconstruction_error(mesh, dpk_fh, std::function(R1_exact));
    //         REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //       }

    //       SECTION("R1 vector data")
    //       {
    //         for (auto named_mesh : MeshDataBaseForTests::get().all1DMeshes()) {
    //           SECTION(named_mesh.name())
    //           {
    //             auto p_mesh = named_mesh.mesh()->get<Mesh<1>>();
    //             auto& mesh  = *p_mesh;

    //             std::array<std::function<R1(const R1&)>, 2> vector_exact   //
    //               = {[](const R1& x) -> R1 { return R1{+1.7 * (x[0] + 1)}; },
    //                  [](const R1& x) -> R1 { return R1{-0.3 * (x[0] + 1)}; }};

    //             DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

    //             auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

    //             auto dpk_Vh = reconstructions[0]->get<DiscreteFunctionDPkVector<1, const R1>>();

    //             double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
    //             REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //           }
    //         }
    //       }
    //     }
    //   }
    // }

    // SECTION("2D")
    // {
    //   std::vector<PolynomialReconstructionDescriptor> descriptor_list =
    //     {PolynomialReconstructionDescriptor{IntegrationMethodType::element, degree,
    //                                         std::vector<std::shared_ptr<
    //                                           const IBoundaryDescriptor>>{std::
    //                                                                         make_shared<NamedBoundaryDescriptor>(
    //                                                                           "XMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "YMAX")}},
    //      PolynomialReconstructionDescriptor{IntegrationMethodType::boundary, degree,
    //                                         std::vector<std::shared_ptr<
    //                                           const IBoundaryDescriptor>>{std::
    //                                                                         make_shared<NamedBoundaryDescriptor>(
    //                                                                           "XMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "YMAX")}}};

    //   using R2 = TinyVector<2>;

    //   for (auto descriptor : descriptor_list) {
    //     SECTION(name(descriptor.integrationMethodType()))
    //     {
    //       SECTION("R^2 data")
    //       {
    //         auto p_mesh = MeshDataBaseForTests::get().hybrid2DMesh()->get<Mesh<2>>();
    //         auto& mesh  = *p_mesh;

    //         auto R2_exact = [](const R2& x) -> R2 { return R2{2.3 * (x[0] - 2), -1.3 * (x[1] - 1)}; };

    //         DiscreteFunctionP0 uh = test_only::exact_projection(mesh, degree, std::function(R2_exact));

    //         auto reconstructions = PolynomialReconstruction{descriptor}.build(uh);

    //         auto dpk_uh = reconstructions[0]->get<DiscreteFunctionDPk<2, const R2>>();

    //         double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R2_exact));
    //         REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //       }

    //       SECTION("vector of R2")
    //       {
    //         auto p_mesh = MeshDataBaseForTests::get().hybrid2DMesh()->get<Mesh<2>>();
    //         auto& mesh  = *p_mesh;

    //         std::array<std::function<R2(const R2&)>, 2> vector_exact   //
    //           = {[](const R2& x) -> R2 {
    //                return R2{+1.7 * (x[0] - 2), -0.6 * (x[1] - 1)};
    //              },
    //              [](const R2& x) -> R2 {
    //                return R2{-2.3 * (x[0] - 2), +1.1 * (x[1] - 1)};
    //              }};

    //         DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

    //         auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

    //         auto dpk_Vh = reconstructions[0]->get<DiscreteFunctionDPkVector<2, const R2>>();

    //         double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
    //         REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //       }
    //     }
    //   }
    // }

    // SECTION("3D")
    // {
    //   std::vector<PolynomialReconstructionDescriptor> descriptor_list =
    //     {PolynomialReconstructionDescriptor{IntegrationMethodType::element, degree,
    //                                         std::vector<std::shared_ptr<
    //                                           const IBoundaryDescriptor>>{std::
    //                                                                         make_shared<NamedBoundaryDescriptor>(
    //                                                                           "XMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "YMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "ZMAX")}},
    //      PolynomialReconstructionDescriptor{IntegrationMethodType::boundary, degree,
    //                                         std::vector<std::shared_ptr<
    //                                           const IBoundaryDescriptor>>{std::
    //                                                                         make_shared<NamedBoundaryDescriptor>(
    //                                                                           "XMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "YMAX"),
    //                                                                       std::make_shared<NamedBoundaryDescriptor>(
    //                                                                         "ZMAX")}}};

    //   using R3 = TinyVector<3>;

    //   for (auto descriptor : descriptor_list) {
    //     SECTION(name(descriptor.integrationMethodType()))
    //     {
    //       SECTION("R^3 data")
    //       {
    //         auto p_mesh = MeshDataBaseForTests::get().hybrid3DMesh()->get<Mesh<3>>();
    //         auto& mesh  = *p_mesh;

    //         auto R3_exact = [](const R3& x) -> R3 { return R3{2.3 * (x[0] - 2), -1.3 * (x[1] - 1), 1.4 * (x[2] - 1)};
    //         };

    //         DiscreteFunctionP0 uh = test_only::exact_projection(mesh, degree, std::function(R3_exact));

    //         auto reconstructions = PolynomialReconstruction{descriptor}.build(uh);

    //         auto dpk_uh = reconstructions[0]->get<DiscreteFunctionDPk<3, const R3>>();

    //         double max_error = test_only::max_reconstruction_error(mesh, dpk_uh, std::function(R3_exact));
    //         REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //       }

    //       SECTION("vector of R3")
    //       {
    //         auto p_mesh = MeshDataBaseForTests::get().hybrid3DMesh()->get<Mesh<3>>();
    //         auto& mesh  = *p_mesh;

    //         std::array<std::function<R3(const R3&)>, 2> vector_exact   //
    //           = {[](const R3& x) -> R3 {
    //                return R3{+1.7 * (x[0] - 2), -0.6 * (x[1] - 1), +1.2 * (x[2] - 1)};
    //              },
    //              [](const R3& x) -> R3 {
    //                return R3{-2.3 * (x[0] - 2), +1.1 * (x[1] - 1), -0.3 * (x[2] - 1)};
    //              }};

    //         DiscreteFunctionP0Vector Vh = test_only::exact_projection(mesh, degree, vector_exact);

    //         auto reconstructions = PolynomialReconstruction{descriptor}.build(Vh);

    //         auto dpk_Vh = reconstructions[0]->get<DiscreteFunctionDPkVector<3, const R3>>();

    //         double max_error = test_only::max_reconstruction_error(mesh, dpk_Vh, vector_exact);
    //         REQUIRE(parallel::allReduceMax(max_error) == Catch::Approx(0).margin(1E-12));
    //       }
    //     }
    //   }
    // }
  }
}