import java.util.Scanner;
import java.util.regex.Pattern;
//import java.util.*;
import java.lang.Math;
public class snellslaw {

	public static void main(String[] args) {
	    double taDouble = 0;
		double tbDouble = 0;
		double n1Double = 0;
		double n2Double = 0;
		//Ta = teta1 1=a
		//Tb = teta2 2=b
		//n1 = denisty of teta1
		//n2 denisty of teta2
		Scanner input = new Scanner(System.in);
		//double Tb;
		//double Ta;
		//double n2;
		System.out.println("Snell's Law Calculator + Features");
		System.out.println("What kind of action do you want to make?");
		System.out.println("A - Snell's Law Calculator");
        System.out.println("B- Critical Angle Calculator");
        String choice = input.next();
        int x = 1;
        do {
        if(choice.equalsIgnoreCase("A")) {
        	x = 2;

            }
        else if (choice.equalsIgnoreCase("B")) {
        	x = 2;
        }
        else {
        	System.out.println("\"" + choice + "\"" + " Is not a valid option! Try again: ");
            choice = input.next();
        }
        }while(x==1);
		System.out.println("Enter n1: ");
		//double n1 = input.nextDouble();
		String n1String = input.next();
		System.out.println("Enter θ1: ");
		String taString = input.next();
	/*	if(TaS.contentEquals("x")) {
			double TbN = Math.toRadians(Tb);
			double snella = n2 * Math.sin(TbN);
			double DivA = snella / n1;
			double ASin = Math.asin(DivA);
			double snellf = Math.toDegrees(ASin);
			System.out.println(snellf);
		}
		else {
			// Not done yet.
		double Tb = input.nextDouble();
        double snella = n1 * Math.toRadians(Ta);
        double snellb = n2 * Math.toRadians(Tb);
        System.out.println(snella = snellb);
	}*/
		System.out.println("Enter n2: ");
		//double n2 = input.nextDouble();
		String n2String = input.next();
		// Calculate Critical Angle, If user writes Critical.
	/*	if(Double.parseDouble(n1String) > Double.parseDouble(n2String) && input.equals("Critical")) {
			double div = Double.parseDouble(n2String) / Double.parseDouble(n1String);
			double critic = Math.asin(div);
			System.out.println(Math.toDegrees(critic));
			input.close();
}
		else if (Double.parseDouble(n2String) > Double.parseDouble(n1String) && input.equals("Critical") ) {
			double div = Double.parseDouble(n1String) / Double.parseDouble(n2String);
			double critic = Math.asin(div);
			System.out.println(Math.toDegrees(critic));
}*/
		System.out.println("Enter θ2: ");
		String tbString = input.next();

		if(tbString.contentEquals("x")) {
			// If θ2 is a variable - Calculate it.
			double taN = Math.toRadians(Double.parseDouble(taString));
			double snella = Double.parseDouble(n1String) * Math.sin(taN);
			double divA = snella / Double.parseDouble(n2String);
			double aSin = Math.asin(divA);
			double snellfa = Math.toDegrees(aSin);
			System.out.println(tbString + " Is equal to: " + snellfa);
}
		else {
			 tbDouble = Double.parseDouble(tbString);
}
		if(calc(Double a)) {
			//if θ1 is a variable - Calculate it.
			double tbN = Math.toRadians(tbDouble);
			double snella = Double.parseDouble(n2String) * Math.sin(tbN);
			double divA = snella / Double.parseDouble(n1String);
			double aSin = Math.asin(divA);
			double snellfb = Math.toDegrees(aSin);
			System.out.println(taString + " Is equal to: " + snellfb);
}
			else{
				//If θ1 is a normal number, Continue as normal.
				  taDouble = Double.parseDouble(taString);
}
	 if(n2String.contentEquals("x")) {
		 //If n2 is a variable - Calculate it.
		 double taN = Math.toRadians(taDouble);
		 double tbN = Math.toRadians(tbDouble);
		 double snella = Double.parseDouble(n1String) * Math.sin(taN);
		 double sinTb = Math.sin(tbN);
		 double divA = snella / sinTb;
		 double snellfc = divA;
		 System.out.println(n2String + " Is equal to: " + snellfc);
	 }
	 else {
		 //If n2 is a normal number, Continue as normal.
		 n2Double = Double.parseDouble(n2String);
	 }
	 if(n1String.contentEquals("x")) {
		 //If n1 is a variable - Calculate it.
		 double taN = Math.toRadians(taDouble);
		 double tbN = Math.toRadians(tbDouble);
         double snella = Double.parseDouble(n2String) * Math.sin(tbN);
         double sinTa = Math.sin(taN);
         double divA = snella / sinTa;
         double snellfd = divA;
         System.out.println(n1String + " Is equal to: " + snellfd);
	 }
	 else {
		 //If n1 is a normal number, Continue as normal.
		 n1Double = Double.parseDouble(n1String);
	 }
}
	public static void calc(String n1String, String taString, String n2String, String tbString) {
	    // Parse the inputs
	    Pattern varName = Pattern.compile("[A-Za-z]\\w*");
	    Double a = (varName.matcher(n1String).matches() ? null : Double.valueOf(n1String));
	    Double b = (varName.matcher(taString).matches() ? null : Double.valueOf(taString));
	    Double c = (varName.matcher(n2String).matches() ? null : Double.valueOf(n2String));
	    Double d = (varName.matcher(tbString).matches() ? null : Double.valueOf(tbString));
	}
	/*public static void calc(String taDouble, String tbDouble, String n1Double, String n2Double, double snellfa, double snellfb, double snellfc, double snellfd) {
   	 if (1 != (taDouble == null ? 1 : 0) + (tbDouble == null ? 1 : 0) +
                (n1Double == null ? 1 : 0) + (n2Double == null ? 1 : 0)) {
           throw new IllegalArgumentException("Warning! Exactly 3 of the input must be number! Try again:");
   	 }
 	if (taDouble == null) {
        System.out.println(taDouble + " = " + snellfa);
    } else if (tbDouble == null) {
        System.out.println(tbDouble + " = " + snellfb);
    } else if (n1Double == null) {
        System.out.println(n1Double + " = " + snellfc);
    } else {
        System.out.println(n2Double + " = " + snellfd);
    }

	}



private static Double parse(String s) {
    try {
        return Double.valueOf(s);
    } catch (NumberFormatException e) {
        return null;
    }
}*/


	}