/*
 * Kulajda.java
 *
 * Created on 11. červenec 2002, 17:00
 */

/**
 *
 * @author  Petr
 */
public class Kulajda {

	protected class Oper {
		public static final int MULT = 0;
		public static final int DIV = 1;
		public static final int PLUS = 2;
		public static final int MINUS = 3;
		public static final int ID = 4;
	};

	protected String EDIV = "Error - divided by zero";

	protected int op = Oper.ID;
	protected boolean delete = true;

	public String display = "0";

	protected double register = 0;
	protected double onDisp = 0;

	protected boolean isInteger = true;

	public String toString() {
		return display;
	}

	public String addNum(int Num) {
		if (delete == false) {
			display += Num;
			onDisp = Double.parseDouble(display);
		} else {
			onDisp = Num;
			display = String.valueOf(Num);
			delete = false;
		}
		return display;
	}

	public String times() {
		return eval(Oper.MULT);
	}

	public String divide() {
		return eval(Oper.DIV);
	}

	public String minus() {
		return eval(Oper.MINUS);
	}

	public String plus() {
		return eval(Oper.PLUS);
	}

	public String is() {
		String retVal;
		retVal = eval(Oper.ID);
		onDisp = register;
		return retVal;
	}

	protected String eval(int newOp) {
		double retVal;
		boolean err = false;

		switch (op) {
			case Oper.PLUS :
				retVal = register + onDisp;
				break;
			case Oper.MINUS :
				retVal = register - onDisp;
				break;
			case Oper.MULT :
				retVal = register * onDisp;
				break;
			case Oper.DIV :
				if (onDisp == 0) {
					err = true;
					retVal = 0;
					break;
				}
				retVal = register / onDisp;
				break;
			case Oper.ID :
				retVal = onDisp;
				break;
			default :
				retVal = 0; //Debug error
		}
		
		op = newOp;
		register = retVal;
		delete = true;
		isInteger = true;

		if (err == true) {
			return (display = EDIV);
		} else {
			return (display = String.valueOf(retVal));
		}
	}

	public String dot() {
		if (isInteger == false) { //already float number
			return display;
		}
		isInteger = false;
		if (delete == true) {
			display = "0.";
			onDisp = 0;
		} else {
			display += ".";
		}
		delete = false;
		return display;
	}
	
	public String plusminus() {
		if (display == EDIV) {
			return EDIV;
		}
		onDisp = -onDisp;
		if (display.charAt(0) == '-') {
			display = display.substring(1);
		}
		else {
			display = '-' + display;
		}
		return display;
	}
	
	public String clear() {
		onDisp = 0;
		display = "0";
		isInteger = true;
		delete = true;
		return display;
	}
	
	public String allClear() {
		clear();
		register = 0;
		op = Oper.ID;
		return display;
	}
}