Car-Simulation/Car simulation/Core/Components/Engine.cs

using Car_simulation.Core.Physics;

namespace Car_simulation.Core.Components
{
    public class Engine : ICarComponent
    {
        // Energy state
        public float FlywheelEnergy { get; set; }

        // Physical properties
        public float MomentOfInertia { get; set; } = 0.25f;
        public float IdleRPM { get; set; } = 800f;
        public float RevLimit { get; set; } = 7000;
        public float StallSpeed { get; set; } = 200f;
        public float Throttle { get; set; } = 0f;
        public bool IsRunning => RPM > StallSpeed;

        private float _cutoffUntil = 0;
        private bool _cutoff = false;

        // Torque curve
        private TorqueCurve _torqueCurve;

        public Engine()
        {
            FlywheelEnergy = GetEnergyFromRPM(IdleRPM);
            _torqueCurve = new TorqueCurve();
            InitializeDefaultCurve();
        }

        private void InitializeDefaultCurve()
        {
            _torqueCurve.AddPoint(0f, 0f);
            _torqueCurve.AddPoint(800f, 95f);
            _torqueCurve.AddPoint(1500f, 160f);
            _torqueCurve.AddPoint(2500f, 200f);
            _torqueCurve.AddPoint(4000f, 235f);
            _torqueCurve.AddPoint(5000f, 230f);
            _torqueCurve.AddPoint(6000f, 210f);
            _torqueCurve.AddPoint(6800f, 185f);
            _torqueCurve.AddPoint(7200f, 170f);
        }

        public float RPM => GetRPM();
        public float AngularVelocity => GetOmega();
        public float CurrentPower { get; private set; }

        public void Update(float deltaTime)
        {
            // Engine updates are now handled through Car with totalTime parameter
        }

        public void UpdateWithTime(float deltaTime, float totalTime)
        {
            UpdateRevLimiter(totalTime);

            float combustionEnergy = CalculateCombustionPower(deltaTime);
            float frictionLoss = CalculateFrictionLoss(deltaTime);
            float netEnergy = combustionEnergy - frictionLoss;

            CurrentPower = netEnergy / deltaTime;
            FlywheelEnergy += netEnergy;

            // Stall protection
            float stallEnergy = GetEnergyFromRPM(StallSpeed);
            if (FlywheelEnergy < stallEnergy && Throttle > 0.1f)
            {
                FlywheelEnergy = stallEnergy * 1.2f;
            }

            FlywheelEnergy = Math.Max(FlywheelEnergy, 0);
        }

        private void UpdateRevLimiter(float totalTime)
        {
            if (RPM > RevLimit)
            {
                _cutoffUntil = totalTime + 0.01f;
            }
            _cutoff = (totalTime < _cutoffUntil);
        }

        private float CalculateFrictionLoss(float deltaTime)
        {
            float frictionTorque = GetFrictionTorque();
            float frictionPower = frictionTorque * AngularVelocity;
            return frictionPower * deltaTime;
        }

        private float GetFrictionTorque()
        {
            return RPM switch
            {
                < 500 => 15f,
                < 1000 => 14f,
                < 2000 => 16f,
                < 3000 => 18f,
                < 4000 => 21f,
                < 5000 => 25f,
                < 6000 => 30f,
                < 7000 => 36f,
                _ => 44f
            };
        }

        private float CalculateCombustionPower(float deltaTime)
        {
            float throttle = GetActualThrottle();
            if (_cutoff) throttle = 0;
            float torque = GetTorqueOutput() * throttle;
            return torque * AngularVelocity * deltaTime;
        }

        public float GetActualThrottle()
        {
            if (RPM < IdleRPM && Throttle < 0.1f)
            {
                float idleThrottle = (IdleRPM - RPM) / 200f;
                return Math.Clamp(idleThrottle, 0.1f, 0.3f);
            }
            return Throttle;
        }

        public float GetOmega() => MathF.Sqrt(2f * FlywheelEnergy / MomentOfInertia);
        public float GetRPM() => GetOmega() * PhysicsUtil.RAD_PER_SEC_TO_RPM;

        public float GetEnergyFromRPM(float rpm)
        {
            float omega = rpm * PhysicsUtil.RPM_TO_RAD_PER_SEC;
            return 0.5f * MomentOfInertia * omega * omega;
        }

        public float GetTorqueOutput() => _torqueCurve.GetTorqueAtRPM(RPM);
    }

    public class TorqueCurve
    {
        private List<(float RPM, float Torque)> _points = new List<(float, float)>();

        public void AddPoint(float rpm, float torque) => _points.Add((rpm, torque));

        public float GetTorqueAtRPM(float rpm)
        {
            if (rpm <= 400) return 0;
            if (_points.Count == 0) return 0;

            var orderedPoints = _points.OrderBy(p => p.RPM).ToList();
            if (rpm <= orderedPoints.First().RPM) return orderedPoints.First().Torque;
            if (rpm >= orderedPoints.Last().RPM) return orderedPoints.Last().Torque;

            for (int i = 0; i < orderedPoints.Count - 1; i++)
            {
                if (rpm >= orderedPoints[i].RPM && rpm <= orderedPoints[i + 1].RPM)
                {
                    float t = (rpm - orderedPoints[i].RPM) / (orderedPoints[i + 1].RPM - orderedPoints[i].RPM);
                    return PhysicsUtil.Lerp(orderedPoints[i].Torque, orderedPoints[i + 1].Torque, t);
                }
            }

            return 0f;
        }
    }
}