#include <vector>
#include <catch2/catch_test_macros.hpp>

#include "serif/discretization/domain/mesh/topology.hpp"
#include "serif/discretization/domain/schema/schemas.hpp"
#include "serif/discretization/domain/schema/validation/all.hpp"

namespace {
    namespace domain = serif::discretization::domain;

    /** @brief Represent the core, envelope, vacuum and their interfaces without a finite-element backend. */
    [[nodiscard]] domain::mesh::MeshTopologyData layered_topology() {
        return {
            .elementDomainIDs = {1, 2, 3},
            .faceElements = {{.firstElementID = 0, .secondElementID = 1}, {.firstElementID = 1, .secondElementID = 2}, {.firstElementID = 2}},
            .boundaryElementBoundaryIDs = {1, 2},
            .boundaryElementFaceIDs = {1, 2}
        };
    }
}

TEST_CASE("Physical schema validation uses backend-independent mesh connectivity", "[unit][discretization][domain]") {
    const domain::mesh::MeshTopology topology(layered_topology());
    const auto result = domain::schema::validation::validate_schema<domain::schema::CoreEnvelopeVacuumDomainSchema>(topology);
    REQUIRE(result);
    CHECK(result.relation_count() == 7);
    CHECK(topology.element_neighbors(0) == std::vector<int>{1});
    CHECK((topology.element_neighbors(1) == std::vector<int>{0, 2}));
    CHECK(topology.boundary_elements_on_face(1) == std::vector<int>{0});
    CHECK(topology.boundary_element_face(1) == 2);
    CHECK(topology.face_elements(2).secondElementID == -1);
}

TEST_CASE("Neutral topology rejects invalid indexing before deriving adjacency", "[unit][discretization][domain]") {
    domain::mesh::MeshTopologyData data = layered_topology();
    SECTION("A face names an absent volume element") {
        data.faceElements.front().firstElementID = 3;
    }
    SECTION("Boundary labels and faces have different counts") {
        data.boundaryElementFaceIDs.pop_back();
    }
    SECTION("A boundary names an absent face") {
        data.boundaryElementFaceIDs.front() = 3;
    }
    CHECK_THROWS(domain::mesh::MeshTopology(data));
}

TEST_CASE("Neutral topology retains unresolved and multiply labelled boundary faces", "[unit][discretization][domain]") {
    domain::mesh::MeshTopologyData data = layered_topology();
    data.boundaryElementBoundaryIDs.insert(data.boundaryElementBoundaryIDs.end(), {7, 8});
    data.boundaryElementFaceIDs.insert(data.boundaryElementFaceIDs.end(), {1, -1});
    const domain::mesh::MeshTopology topology(data);
    CHECK((topology.boundary_elements_on_face(1) == std::vector<int>{0, 2}));
    CHECK(topology.boundary_element_face(3) == -1);
    CHECK(topology.boundary_element_boundary_id(3) == 8);
    CHECK(topology.element_neighbors(-1).empty());
    CHECK(topology.boundary_elements_on_face(100).empty());
    CHECK(topology.element_domain_id(100) == 0);
}