package epam.roman;
   
   import java.util.HashMap;
   import java.util.Map;
   import java.util.function.ToIntFunction;
   
   /**
    * A converter that converts Roman numerals to Arabic integers.
    */
  public final class RomanToArabicConverter implements ToIntFunction<String> {
  
      private static final Map<Character, Integer> ROMAN_TO_ARABIC_MAP = new HashMap<>();
  
      static {
          ROMAN_TO_ARABIC_MAP.put('I', 1);
          ROMAN_TO_ARABIC_MAP.put('V', 5);
          ROMAN_TO_ARABIC_MAP.put('X', 10);
          ROMAN_TO_ARABIC_MAP.put('L', 50);
          ROMAN_TO_ARABIC_MAP.put('C', 100);
          ROMAN_TO_ARABIC_MAP.put('D', 500);
          ROMAN_TO_ARABIC_MAP.put('M', 1000);
      }
  
      /**
       * Converts a Roman numeral string to an Arabic integer.
       *
       * @param roman the Roman numeral string to be converted
       * @return the Arabic integer representation of the Roman numeral
       */
      @Override
      public int applyAsInt(String roman) {
          int result = 0;
          int prevValue = 0;
  
          for (int i = roman.length() - 1; i >= 0; i--) {
              char currentChar = roman.charAt(i);
              int currentValue = ROMAN_TO_ARABIC_MAP.get(currentChar);
  
              if (currentValue < prevValue) {
                  result -= currentValue;
              } else {
                  result += currentValue;
              }
  
              prevValue = currentValue;
          }
  
          return result;
      }
  }