turner-townsend-backend-assessment/roman/roman.py

import readline


class RomanNumeralConverter:
    def __init__(self):
        self.valid_numerals = "IVXCM"
        self.values = {"I": 1, "V": 5, "X": 10, "C": 100, "M": 1000}

    def convert_to_number(self, numerals: str) -> str:
        filtered = self._filter_valid_numerals(numerals)
        if not filtered:
            return "ERROR: Invalid input"

        values = self._convert_numerals_to_values(filtered)
        return self._format_output(filtered, values)

    def _filter_valid_numerals(self, numerals: str) -> str:
        """Extract only valid Roman numerals from input."""
        filtered_chars = [
            char for char in numerals.upper() if char in self.valid_numerals
        ]
        return "".join(filtered_chars)

    def _convert_numerals_to_values(self, numerals: str) -> list[int]:
        """Convert Roman numeral characters to their integer values."""
        values = []
        for char in numerals:
            match char:
                case "I":
                    values.append(1)
                case "V":
                    values.append(5)
                case "X":
                    values.append(10)
                case "C":
                    values.append(100)
                case "M":
                    values.append(1000)
        return values

    def _format_output(self, numerals: str, values: list[int]) -> str:
        """Format the conversion result for display."""
        if len(values) == 1:
            return f"{numerals} = {values[0]}"
        else:
            values_str = " + ".join(str(v) for v in values)
            return f"{numerals} = {values_str} = {sum(values)}"


def main():
    converter = RomanNumeralConverter()
    while True:
        try:
            numerals = input("Please enter some Roman numerals: ")
            print(converter.convert_to_number(numerals))
        except (EOFError, KeyboardInterrupt):
            break


if __name__ == "__main__":
    main()