import java.util.Scanner;

public class CalculatorClient {
    public static void main(String args []){
        boolean exit = false;
        double number, number2;
        String operation, input;

        Scanner in = new Scanner(System.in);
        System.out.println("ENTER INITIAL NUMBER:");
        number = in.nextDouble();
        in.nextLine(); // skip \n from initial input (nextDouble method would cause the later inputs to be skipped)
        System.out.print(number);
        Calculator calc = new Calculator(number);

        while(exit!=true){
            input = in.nextLine();
            operation =  input.substring(0, 1);

            try{
                number2 = Double.parseDouble(input.substring(1, input.length()));
            }
            catch(Exception ex) {
                number2 = 0; //set a default number2 to avoid errors
                if(input.toLowerCase().equals("c")) {
                    operation = "C";
                }
                else if (input.toLowerCase().equals("exit")){
                    operation = "exit";
                }
                else {
                    System.out.print("\nUnknown operation...\n" + number);
                    continue; //skip while loop iteration
                }
            }

            switch(operation) {
                case "+":
                    System.out.print("=\n");
                    System.out.print(calc.add(number2));
                    break;
                case "-":
                    System.out.print(calc.subtract(number2));
                    break;
                case "/":
                    System.out.print(calc.divide(number2));
                    break;
                case "*":
                    System.out.print(calc.multiply(number2));
                    break;
                case "C":
                    calc.clear();
                    System.out.print("0");
                    break;
                case "exit":
                    System.out.println("EXIT");
                    exit = true;
                    break;
                default:
                    System.out.println("Unknown operation...\n" + number);
                    break;

            }
        }
    }
}