ROMANOP : UN UTILITAIRE POUR LES NOMBRES ROMAINS (CONVERSION ROMAN -> ENTIERS, ENTIERS -> ROMAINS, CALCULS...)

package romanop;

import java.util.*;

/**
 * @author Delache Michaël
 */
public class RomanOp {
	private static final List<String> keys = new ArrayList<String>();
	private static final List<Integer> values = new ArrayList<Integer>();
	
	/**
	 * Constructor of the RomanCalc class, initializes the two tables
	 */
	public RomanOp() {
		keys.add("M");
		values.add(1000);
		keys.add("CM");
		values.add(900);
		keys.add("D");
		values.add(500);
		keys.add("CD");
		values.add(400);
		keys.add("C");
		values.add(100);
		keys.add("XC");
		values.add(90);
		keys.add("L");
		values.add(50);
		keys.add("XL");
		values.add(40);
		keys.add("X");
		values.add(10);
		keys.add("IX");
		values.add(9);
		keys.add("V");
		values.add(5);
		keys.add("IV");
		values.add(4);
		keys.add("I");
		values.add(1);
	}
	/**
	 * Convert Roman to int
	 * @param s Roman number
	 * @return An int representing the roman number
	 */
	
	public int toInt(final String s) {
		int res = 0;
		int size = s.length();
		String tmp = "";
		if (size == 1) {
			res = this.getInt(s);
		}
		if (size == 2) {
			if (keys.contains(s)) {
				res = this.getInt(s);
			}
			else {
				res += this.toInt(s.substring(0,1));
				res += this.toInt(s.substring(1,2));
			}
		}
		if (size > 2) {
			if (keys.contains(tmp = s.substring(size-2, size))) {
				res += this.getInt(tmp);
				res += this.toInt(s.substring(0, size-2));
			}
			else {
				tmp = s.substring(size-1, size);
				res += this.getInt(tmp);
				res += this.toInt(s.substring(0, size-1));
			}
		}
		return res;
	}
	
	/**
	 * Returns the integer value of the roman value given by <i>s</i> or 0 if <i>s</i> is not in the table
	 */
	public int getInt(final String s) {
		int res = 0;
		for (String str : keys) {
			if (str.equals(s)) {
				int index = keys.indexOf(str);
				res = values.get(index);
			}
		}
		return res;
	}
	
	/**
	 * Converts integer value into roman value
	 * @param i the integer to convert
	 * @return a string representing the roman value
	 */
	public String toRoman(final int i) {
		int cpt = i;
		String res = "";
		while (cpt > 0) {
			for (int j : values) {
				if ((cpt/j) >= 1) {
					int index = values.indexOf(j);
					res += keys.get(index);
					cpt -= j;
					break;
				}
			}
		}
		return res;
	}
	
	/**
	 * Calculates the result of the operation determined by the two operands and the operator
	 * @param x operand 1
	 * @param y operand 2
	 * @param op operator
	 * @return the result
	 */
	public String calc (final String x, final String y, final char op) {
		if (this.isOk(x) && this.isOk(y)) {
			int x1 = this.toInt(x);
			int y1 = this.toInt(y);
			switch (op) {
				case '+' :
					return this.toRoman(x1 + y1);
				case '-' :
					return this.toRoman(x1 - y1);
				case '*' :
					return this.toRoman(x1 * y1);
				case '/' :
					return this.toRoman(x1 / y1);
				default :
					break;
			}
		}
		return null;
	}
	
	/**
	 * Says if the roman value given by <i>s</i> respect the roman value syntax
	 * @param s the roman value to verify
	 * @return true if <i>s</i> is correctly formed according to the roman value syntax (ie IV for 4 and not IIII), false else
	 */
	public Boolean isOk(final String s) {
		int i = this.toInt(s);
		String str = this.toRoman(i);
		return s.equals(str);
	}
	
}