import java.util.Scanner;

public class RomanNumerals
{
	public static void main(String []args)
	{
		//Declarations
		Scanner sc = new Scanner(System.in);
		String strRoman;
		int strValue;
		String again = "y";

		while(again.equalsIgnoreCase("y"))
		{
			strRoman = "";
			strValue = 0;

			System.out.println("Roman Numeral Converter");
			System.out.print("Please Enter a roman numeral number to convert to arabic number format: ");
			strRoman = sc.nextLine();
			if(isValid(strRoman))
			{
				strValue = getValueOfRoman(strRoman);
				System.out.println(strValue);
			}
			else
			{
				System.out.println("Your Value is not Valid.");
			}
			System.out.println("Restart Program?(y or n)");
			again = sc.nextLine();
		}
	}

	// Takes the String in and returns the actual value
	// This method will call both assignValueArray and evaluateArray
	// to do it's work.
	public static int getValueOfRoman(String strRoman)
	{
		int[] valueArray = assignValueArray(strRoman);
		int answer = evaluateArray(valueArray);

		return answer;
	}

	// Returns the value of individual 'Roman' letters
	// ie V returns 5, X returns 10 etc.
	// Hint: might be a good place for a switch
	public static int getValue(char ch)
	{
		int value = 0;
		switch(ch)
		{
			case 'I': value = 1; break;
			case 'V': value = 5; break;
			case 'X': value = 10; break;
			case 'L': value = 50; break;
			case 'C': value = 100; break;
			case 'D': value = 500; break;
			case 'M': value = 1000; break;
		}
		return value;
	}

	// Goes thru the String (for loop) and builds an int[] valueArray based on
	// the value of each letter.
	// Hint: use getValue() in your for loop
	public static int[] assignValueArray(String roman)
	{
		int [] foo = new int[roman.length()];

		for(int i = 0; i < roman.length(); i++)
		{
			foo[i] = getValue(roman.charAt(i));
		}
		return foo;
	}

	// Goes thru the valueArray and evaluates based on 1 of 2 algorithms
	public static int evaluateArray(int[]valueArray)
	{
		int answer = 0;
		for(int i = 0; i < valueArray.length; i++) //3 0-2
		{
			if(i == valueArray.length-1) //to check for last index to avoid overflow //2
							{
				answer += valueArray[i];
			}
			else if(valueArray[i+1] > valueArray[i])
			{
				answer += -(valueArray[i]);
			}
			else
			{
				answer += valueArray[i];
			}
		}

		return answer;
	}

	// Goes thru the String and checks to make sure that each char is a valid
	// roman letter/digit.  If any char is not valid returns false; otherwise true.
	public static boolean isValid(String roman)
	{
		roman = roman.toUpperCase();
		for(int i=0; i<roman.length(); i++)
		{
			switch(roman.charAt(i))
			{
				case 'M':
				case 'D':
				case 'C':
				case 'L':
				case 'X':
				case 'V':
				case 'I':break;
				default: return false;
			}
		}
		return true;
	}
}
/*
=====Test Cases=====
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: XIV
14
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: CMI
901
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: XXIX
29
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: XLIX
49
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: MMDCCCLX
IV
2864
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: M4IVX
Your Value is not Valid.
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: MQLXI
Your Value is not Valid.
Restart Program?(y or n)
y
Roman Numeral Converter
Please Enter a roman numeral number to convert to arabic number format: XVIII
18
Restart Program?(y or n)
n
Press any key to continue . . .
*/