using System;

namespace BWR_simulator
{
    public class PressureVessel
    {
        public readonly double TOTAL_VOLUME; // Liters
        private const double VESSEL_COOLING_COEFF = 1000;
        private const double ROD_HEATING_COEFF = 2000;

        // fluid density coeffcients to calculate fluid density at different pressures and temps
        private readonly double[] FDC = 
        [
            999.83311,
            0.0752,
            0.0089,
            7.36413e-5,
            4.74639e-7,
            1.34888e-9,
            1.36e-11
        ];
        public double HotwellTemp { get; private set; }

        public double GasMass { get; private set; }
        public double GasVolume { get; private set; }
        public double GasDensity { get; private set; }
        public double Pressure { get; private set; }

        public double FluidMass { get; private set; }
        public double FluidDensity { get; private set; }
        public double FluidVolume { get; private set; }
        public double FluidTemp { get; private set; }
        public double FluidBoilingPoint { get; private set; }
        
        public double FeedwaterFlow { get; private set; }
        public double ReliefValvePos { get; private set; }
        public double InputEnergy { get; private set; }

        public PressureVessel(double totalVolume = 9500,
                              double fluidTemp = 300, 
                              double fluidMass = 6200, 
                              double gasMass = 0)
        {
            TOTAL_VOLUME = totalVolume;
            FluidTemp = fluidTemp;
            FluidMass = fluidMass;
            GasMass = gasMass;

            InputEnergy = 0;
            ReliefValvePos = 0;
            FeedwaterFlow = 0;
            Pressure = 1; // calcualte initial pressure
            FluidBoilingPoint = Constants.WATER_BOILING_POINT_NORM; // calculate boiling point givien initial pressure
            FluidDensity = 1;

            HotwellTemp = 300;
            CalculateDensity();

        }
        private void CalculateDensity()
        {
            FluidVolume = FluidMass / FluidDensity;
            GasVolume = TOTAL_VOLUME - FluidVolume;
            GasDensity = GasMass / GasVolume;
        }
        private void CalculateEnergyInput(double dt)
        {
            InputEnergy -= VESSEL_COOLING_COEFF * (HotwellTemp - FluidTemp) * dt;
            InputEnergy += ROD_HEATING_COEFF * (600 - FluidTemp) * dt;
            InputEnergy /= 1e6;
        }
        public void Step(double dt)
        {
            CalculateEnergyInput(dt);
            FluidVolume += FeedwaterFlow * dt;
            FluidBoilingPoint = Math.Pow((1/Constants.WATER_BOILING_POINT_NORM - (8.314 * Math.Log(Pressure))/40700), -1);

            FluidTemp += (InputEnergy * 1e6) / (FluidMass * Constants.WATER_HEAT_CAPACITY);
            if (FluidTemp > FluidBoilingPoint)
            {
                InputEnergy = FluidMass * Constants.WATER_HEAT_CAPACITY * FluidTemp - FluidBoilingPoint;
                FluidTemp = FluidBoilingPoint;
                double d_vapour = InputEnergy / Constants.WATER_LATENT_HEAT;
                FluidMass -= d_vapour;
                GasMass += d_vapour;

                CalculateDensity();
            }

            Pressure = 1 + ((GasMass/Constants.WATER_MOLAR_MASS) * (Constants.IDEAL_GAS_CONSTANT * FluidTemp / TOTAL_VOLUME - FluidVolume));
            if (Pressure < 1) {Pressure = 1;}

            GasMass -= (Pressure - 1) * ReliefValvePos * dt;
            if (GasMass < 0) {GasMass = 0;}
        }
    }
}