import sys


BASE_LABELS = {
    2: "Binary",
    3: "Ternary",
    4: "Quaternary",
    5: "Quinary",
    6: "Senary",
    7: "Septenary",
    8: "Octal",
    9: "Nonary",
    10: "Decimal",
    11: "Undecimal",
    12: "Duodecimal",
    13: "Tridecimal",
    14: "Tetradecimal",
    15: "Pentadecimal",
    16: "Hexadecimal",
}
DIGIT_VALUES = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"


def char_to_value(char: str) -> int:
    return DIGIT_VALUES.index(char.upper())


def value_to_char(value: int) -> str:
    return DIGIT_VALUES[value]


def is_valid_number(number: str, base: int) -> bool:
    valid_digits = DIGIT_VALUES[:base]
    return all(char.upper() in valid_digits for char in number)


def convert(number: str, orig_base: int, new_base: int) -> str:
    if new_base == orig_base:  # if base is the same, just return the original number
        return number

    if not is_valid_number(number, orig_base):
        raise ValueError(f"{number} is not valid in {BASE_LABELS[orig_base]}.")

    result = 0
    result_str = ""

    if orig_base != 10:  # convert the original number to base 10 before converting
        # `enumerate` gives the index AND value in an iterable (in our case a string)
        # `[::-1]` reverses an iterable using "slice notation"
        for place, digit in enumerate(number[::-1]):
            result += (orig_base**place) * char_to_value(digit)
    else:
        result = int(number)

    if new_base == 10:  # if the new base is already 10, the process is done
        return str(result)

    while result > 0:
        result, remainder = divmod(result, new_base)
        result_str = value_to_char(remainder) + result_str

    return result_str or "0"


if __name__ == "__main__":
    print("=" * 32)
    print(f"{'Base Converter':^32}")
    print("=" * 32)

    orig_base = int(input("Input the original base: "))
    new_base = int(input("Input the new base: "))
    if any(base < 2 or base > 36 for base in (orig_base, new_base)):
        print("Bases must be between 2 and 36!")
        sys.exit(1)

    number = input("Input your number: ")

    try:
        converted = convert(number, orig_base, new_base)
        print(
            f"{number} ({BASE_LABELS.get(orig_base, f'Base {orig_base}')})"
            " = "
            f"{converted} ({BASE_LABELS.get(new_base, f'Base {new_base}')})"
        )
    except ValueError as ve:
        print(ve)