Add Paystack fees in CSharp

PaystackFees.cs

using System;
					
public class PaystackFees
{
    const Double DEFAULT_PERCENTAGE = 0.015;
    const Double DEFAULT_ADDITIONAL_CHARGE = 10000;
    const Double DEFAULT_THRESHOLD = 250000;
    const Double DEFAULT_CAP = 200000;
    
    private Double percentage;
    private Double additional_charge;
    private Double threshold;
    private Double cap;

    private Double chargeDivider;
    private Double crossover;
    private Double flatlinePlusCharge;
    private Double flatline;
    
    public PaystackFees()
    {
        this.percentage = PaystackFees.DEFAULT_ADDITIONAL_CHARGE;
        this.additional_charge = PaystackFees.DEFAULT_ADDITIONAL_CHARGE;
        this.threshold = PaystackFees.DEFAULT_THRESHOLD;
        this.cap = PaystackFees.DEFAULT_CAP;
        this.__setup();
    }
 
    public PaystackFees withPercentage(Double percentage)
    {
        this.percentage = percentage;
        this.__setup();
        return this;
    }

    public PaystackFees withAdditionalCharge(Double additional_charge)
    {
        this.additional_charge = additional_charge;
        this.__setup();
        return this;
    }

    public PaystackFees withThreshold(Double threshold)
    {
        this.threshold = threshold;
        this.__setup();
        return this;
    }

    public PaystackFees withCap(Double cap)
    {
        this.cap = cap;
        this.__setup();
        return this;
    }

    private void __setup()
    {
        this.chargeDivider = this.__chargeDivider();
        this.crossover = this.__crossover();
        this.flatlinePlusCharge = this.__flatlinePlusCharge();
        this.flatline = this.__flatline();
    }

    private Double __chargeDivider()
    {
        return 1 - this.percentage;
    }

    private Double __crossover()
    {
        return (this.threshold * this.chargeDivider) - this.additional_charge;
    }

    private Double __flatlinePlusCharge()
    {
        return (this.cap - this.additional_charge) / this.percentage;
    }

    private Double __flatline()
    {
        return this.flatlinePlusCharge - this.cap;
    }

    public int addFeeFor(int amountinkobo)
    {
        if (amountinkobo > this.flatline) {
            return Convert.ToInt32(Math.Ceiling(amountinkobo + this.cap));
        } else if (amountinkobo > this.crossover) {
            return Convert.ToInt32(Math.Ceiling((amountinkobo + this.additional_charge) / this.chargeDivider));
        } else {
            return Convert.ToInt32(Math.Ceiling(amountinkobo / this.chargeDivider));
        }
    }

    public int calculateFeeFor(int amountinkobo)
    {
        Double fee = this.percentage * amountinkobo;
        if (amountinkobo >= this.threshold) {
            fee += this.additional_charge;
        }
        if (fee > this.cap) {
            fee = this.cap;
        }
        return Convert.ToInt32(Math.Ceiling(fee));
    }
}

PaystackFeesSample.cs

	
using System;
// import PaystackFees somehow;
					
public class PaystackFeesSample;
{
    public static void Main()
    {
        PaystackFees p = new PaystackFees();
		
        // you can configure to use default charge (1.5% with a additional 100ngn if above 2500)
        // or a negotiated charge
        int calc = p.withPercentage(0.015) // 0.015 (1.5%)
            .withThreshold(250000) // 250000 (2,500 naira)
            .withAdditionalCharge(10000) // 10000 (100 naira)
            .withCap(200000)
            .addFeeFor(10000);
        Console.WriteLine(calc);
    }
}