#pragma once
#include <cstdint>
#include <memory>

namespace fluidsim::port {
// Rotational quantities use SI: rad, rad/s, N m, kg m2, J and W.
enum class DriveMode {Torque,Speed};
struct ShaftParameters {
    double inertia{.15},initial_speed{},initial_angle{};
    double friction_constant{},friction_viscous{},friction_quadratic{};
    bool forward_only{};
};
struct DriveParameters {DriveMode mode{DriveMode::Torque};double command{};bool enabled{true};};
struct BrakeParameters {double constant{},viscous{},quadratic{};bool enabled{true};};
struct ShaftState {
    std::uint32_t id{};
    double angle{},previous_angle{},speed{},inertia{},kinetic_energy{};
    double net_torque{},source_torque{},external_torque{},friction_torque{},brake_torque{},constraint_torque{};
    double external_work{},drive_work{},friction_loss{},brake_loss{},initial_energy{};
    // initial_energy + external_work + drive_work = kinetic_energy + losses.
};
struct DriveState {
    std::uint32_t id{},shaft{};
    double torque{},power{},work{};
};
struct BrakeState {
    std::uint32_t id{},shaft{};
    double torque{},power{},loss{}; // Torque on shaft signed; absorbed power >= 0.
};
// Independent rigid shaft nodes. Gears and clutches will couple these nodes;
// direct attachment adds torque or inertia to one named node exactly once.
class MechanicalSystem {
public:
    MechanicalSystem();
    ~MechanicalSystem();
    MechanicalSystem(const MechanicalSystem&)=delete;
    MechanicalSystem& operator=(const MechanicalSystem&)=delete;
    void add_shaft(std::uint32_t,const ShaftParameters&);
    void add_flywheel(std::uint32_t id,std::uint32_t shaft,double inertia);
    void add_drive(std::uint32_t id,std::uint32_t shaft,const DriveParameters&);
    void add_brake(std::uint32_t id,std::uint32_t shaft,const BrakeParameters&);
    void set_drive(std::uint32_t,const DriveParameters&);
    void set_brake(std::uint32_t,const BrakeParameters&);
    void set_friction(std::uint32_t shaft,double constant,double viscous,double quadratic);
    void add_torque(std::uint32_t shaft,double torque);
    void step(double dt);
    const ShaftState& shaft(std::uint32_t)const;
    const DriveState& drive(std::uint32_t)const;
    const BrakeState& brake(std::uint32_t)const;
private:
    struct Impl;
    std::unique_ptr<Impl> impl_;
};
}