module;

#include <array>
#include <utility>

export module mean_field_extension_example.rotating_stellar_model;

export import mean_field_extension_example.ideal_gas_radiation;
import mean_field;

/*
 * This file is the physics-facing composition layer.  It contains no block
 * matrices, generated residual types, Jacobian indices, or preconditioner
 * plumbing.  StellarModel infers those structural types from the four
 * physical specifications passed to it.
 */
export namespace mean_field::extension_example {
    struct RotatingStellarModelParameters final {
        IdealGasRadiation::Parameters equationOfState;
        mean_field::dimensions::PressureValue surfacePressure;
        mean_field::dimensions::MassValue totalMass;
        mean_field::dimensions::AngularMomentumValue totalAngularMomentum;
        std::array<double, 3> rotationAxis{0.0, 0.0, 1.0};
        std::array<double, 3> rotationCenter{0.0, 0.0, 0.0};
    };

    [[nodiscard]] auto makeRotatingStellarModel(const RotatingStellarModelParameters &parameters) {
        return mean_field::model::StellarModel(
            IdealGasRadiation(parameters.equationOfState),
            mean_field::surface::Isobaric({.Psurf = parameters.surfacePressure}),
            mean_field::integral::FixedTotalMass({.Mtotal = parameters.totalMass}),
            mean_field::integral::FixedAngularMomentum({
                .Jtotal = parameters.totalAngularMomentum,
                .axis = parameters.rotationAxis,
                .center = parameters.rotationCenter
            })
        );
    }

    using RotatingStellarModel = decltype(
        makeRotatingStellarModel(std::declval<const RotatingStellarModelParameters &>())
    );

    static_assert(mean_field::model::StellarModelType<RotatingStellarModel>);
    static_assert(RotatingStellarModel::symbolicallySquare);

    /*
     * Deliberate capability boundary:
     *
     * The specification above is a valid, strongly typed stellar model.  The
     * current numerical equilibrium core, however, closes density through a
     * barotropic relation rho(h).  This EOS instead needs an independent
     * temperature or entropy field and its governing equation.  Keeping this
     * assertion false prevents an example from suggesting that discretize()
     * already implements thermal equilibrium when it does not.
     */
    inline constexpr bool currentEquilibriumBackendSupportsIdealGasRadiation =
        mean_field::equilibrium::StellarEquilibriumModel<RotatingStellarModel>;

    static_assert(!currentEquilibriumBackendSupportsIdealGasRadiation);
} // namespace mean_field::extension_example