#include <cmath>
#include <limits>
#include <memory>
#include <type_traits>
#include <utility>

#include <catch2/catch_test_macros.hpp>

import mean_field;
import test_helpers;

namespace {
    struct StellarModelExtensionTracker final {
        int structureValidationCount{0};
        int surfaceValidationCount{0};
        int surfaceResolutionCount{0};

        const mean_field::eos::EquationOfState *structureEquationOfState{nullptr};

        const mean_field::eos::EquationOfState *surfaceValidationEquationOfState{nullptr};

        const mean_field::eos::EquationOfState *surfaceResolutionEquationOfState{nullptr};
    };

    class StellarModelTestStructure final : public mean_field::models::structure::StructureBase {
    public:
        explicit StellarModelTestStructure(std::shared_ptr<StellarModelExtensionTracker> tracker)
            : m_tracker(std::move(tracker)),
              m_equationOfState(
                  3.0,
                  0.25
              ) {
        }

        [[nodiscard]] const mean_field::eos::EquationOfState &equationOfState() const noexcept override {
            m_tracker->structureEquationOfState = &m_equationOfState;
            return m_equationOfState;
        }

        [[nodiscard]] double targetMass() const noexcept override {
            return 2.5;
        }

        [[nodiscard]] mean_field::models::structure::StructureSeed
        makeInitialSeed(const mean_field::models::structure::StructureSeedRequest &request) const override {
            mean_field::models::structure::StructureSeed seed;

            seed.radius.SetSize(2);
            seed.density.SetSize(2);
            seed.enthalpy.SetSize(2);

            seed.radius(0)       = 0.0;
            seed.radius(1)       = 1.0;

            seed.density(0)      = request.centralDensity;
            seed.density(1)      = 0.0;

            seed.enthalpy(0)     = 1.0;
            seed.enthalpy(1)     = 0.0;

            seed.stellarRadius   = 1.0;
            seed.centralDensity  = request.centralDensity;
            seed.centralEnthalpy = 1.0;

            return seed;
        }

        void validate() const override {
            ++m_tracker->structureValidationCount;
        }

    private:
        std::shared_ptr<StellarModelExtensionTracker> m_tracker;
        mean_field::eos::Polytrope m_equationOfState;
    };

    class StellarModelTestSurface final : public mean_field::surface::SurfaceBase {
    public:
        explicit StellarModelTestSurface(std::shared_ptr<StellarModelExtensionTracker> tracker)
            : m_tracker(std::move(tracker)) {
        }

        [[nodiscard]]
        mean_field::surface::ResolvedSurfaceCondition
        resolve(const mean_field::eos::EquationOfState &equationOfState) const override {
            ++m_tracker->surfaceResolutionCount;

            m_tracker->surfaceResolutionEquationOfState = &equationOfState;

            return mean_field::surface::ResolvedSurfaceCondition{0.375};
        }

        void validate(const mean_field::eos::EquationOfState &equationOfState) const override {
            ++m_tracker->surfaceValidationCount;

            m_tracker->surfaceValidationEquationOfState = &equationOfState;
        }

    private:
        std::shared_ptr<StellarModelExtensionTracker> m_tracker;
    };
} // namespace

TEST_CASE(
    "Stellar Model Owns Structure And Surface Prescriptions",
    tags::barotrope &tags::unit &tags::model
) {
    STATIC_REQUIRE_FALSE(std::is_copy_constructible_v<mean_field::models::StellarModel>);

    STATIC_REQUIRE_FALSE(std::is_copy_assignable_v<mean_field::models::StellarModel>);

    STATIC_REQUIRE(std::is_nothrow_move_constructible_v<mean_field::models::StellarModel>);

    STATIC_REQUIRE(std::is_nothrow_move_assignable_v<mean_field::models::StellarModel>);

    mean_field::models::StellarModel model{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{3.0, 0.25}, 1.0},
        mean_field::surface::Isobaric{0.0}
    };

    CHECK(model.targetMass() == 1.0);
    CHECK(model.resolvedSurfaceCondition().targetEnthalpy == 0.0);

    CHECK(
        dynamic_cast<const mean_field::models::structure::PolytropicStructure *>(&model.structurePrescription()) !=
        nullptr
    );

    CHECK(dynamic_cast<const mean_field::surface::Isobaric *>(&model.surfacePrescription()) != nullptr);
}

TEST_CASE(
    "Stellar Model Delegates Seed Construction To Its Structure",
    tags::barotrope &tags::unit &tags::model
) {
    mean_field::models::StellarModel model{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{3.0, 0.25}, 1.0},
        mean_field::surface::Isobaric{}
    };

    const mean_field::models::structure::StructureSeed seed =
        model.makeInitialSeed({.centralDensity = 2.0, .radialSampleCount = 64});

    CHECK(seed.radius.Size() == 64);
    CHECK(seed.density.Size() == 64);
    CHECK(seed.enthalpy.Size() == 64);
    CHECK(seed.centralDensity == 2.0);
    CHECK(seed.stellarRadius > 0.0);
    CHECK(seed.density(0) == 2.0);
    CHECK(seed.density(63) == 0.0);
    CHECK(seed.enthalpy(63) == 0.0);
}

TEST_CASE(
    "Moving A Stellar Model Preserves Stable Prescription Addresses",
    tags::barotrope &tags::unit &tags::model
) {
    mean_field::models::StellarModel originalModel{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{3.0, 0.25}, 1.0},
        mean_field::surface::Isobaric{}
    };

    const mean_field::models::structure::StructureBase *structureAddress = &originalModel.structurePrescription();

    const mean_field::surface::SurfaceBase *surfaceAddress               = &originalModel.surfacePrescription();

    const mean_field::eos::EquationOfState *equationOfStateAddress       = &originalModel.equationOfState();

    mean_field::models::StellarModel movedModel{std::move(originalModel)};

    CHECK(&movedModel.structurePrescription() == structureAddress);
    CHECK(&movedModel.surfacePrescription() == surfaceAddress);
    CHECK(&movedModel.equationOfState() == equationOfStateAddress);
    CHECK(movedModel.targetMass() == 1.0);
}

TEST_CASE(
    "Stellar Model Resolves A Positive Isobaric Surface",
    tags::barotrope &tags::unit &tags::model
) {
    constexpr double targetPressure = 0.03125;

    mean_field::models::StellarModel model{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{3.0, 0.25}, 1.0},
        mean_field::surface::Isobaric{targetPressure}
    };

    const double targetEnthalpy = model.resolvedSurfaceCondition().targetEnthalpy;

    CHECK(targetEnthalpy > 0.0);
    CHECK(
        std::abs(model.equationOfState().pressure_from_enthalpy(targetEnthalpy) - targetPressure) <
        64.0 * std::numeric_limits<double>::epsilon()
    );
}

TEST_CASE(
    "Stellar Model Supports Custom Structure And Surface Prescriptions",
    tags::barotrope &tags::unit &tags::model
) {
    const auto tracker = std::make_shared<StellarModelExtensionTracker>();

    mean_field::models::StellarModel model{StellarModelTestStructure{tracker}, StellarModelTestSurface{tracker}};

    REQUIRE(tracker->structureValidationCount == 1);
    REQUIRE(tracker->surfaceValidationCount == 1);
    REQUIRE(tracker->surfaceResolutionCount == 1);

    CHECK(dynamic_cast<const StellarModelTestStructure *>(&model.structurePrescription()) != nullptr);

    CHECK(dynamic_cast<const StellarModelTestSurface *>(&model.surfacePrescription()) != nullptr);

    const mean_field::eos::EquationOfState *ownedEquationOfState = &model.equationOfState();

    CHECK(tracker->structureEquationOfState == ownedEquationOfState);

    CHECK(tracker->surfaceValidationEquationOfState == ownedEquationOfState);

    CHECK(tracker->surfaceResolutionEquationOfState == ownedEquationOfState);

    CHECK(model.targetMass() == 2.5);

    CHECK(model.resolvedSurfaceCondition().targetEnthalpy == 0.375);
}

TEST_CASE(
    "Move Assignment Preserves Stellar Model Prescription Addresses",
    tags::barotrope &tags::unit &tags::model
) {
    mean_field::models::StellarModel sourceModel{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{3.0, 0.25}, 1.25},
        mean_field::surface::Isobaric{0.0}
    };

    mean_field::models::StellarModel destinationModel{
        mean_field::models::structure::PolytropicStructure{mean_field::eos::Polytrope{2.0, 0.5}, 4.0},
        mean_field::surface::Isobaric{0.02}
    };

    const mean_field::models::structure::StructureBase *sourceStructureAddress = &sourceModel.structurePrescription();

    const mean_field::surface::SurfaceBase *sourceSurfaceAddress               = &sourceModel.surfacePrescription();

    const mean_field::eos::EquationOfState *sourceEquationOfStateAddress       = &sourceModel.equationOfState();

    const double sourceTargetEnthalpy = sourceModel.resolvedSurfaceCondition().targetEnthalpy;

    destinationModel                  = std::move(sourceModel);

    CHECK(&destinationModel.structurePrescription() == sourceStructureAddress);

    CHECK(&destinationModel.surfacePrescription() == sourceSurfaceAddress);

    CHECK(&destinationModel.equationOfState() == sourceEquationOfStateAddress);

    CHECK(destinationModel.targetMass() == 1.25);

    CHECK(destinationModel.resolvedSurfaceCondition().targetEnthalpy == sourceTargetEnthalpy);
}