import re


def convert_column_name_to_display_name(column_name: str) -> str:
    """
    Add method to convert from column style names to human readable display names. Column style names should be
    snake_case with a double underscore before the units (if units are relevant). The display name will have the
    first letter capitalized, spaces between words, and the units in parentheses at the end.
    Example: `transit_duration__days` -> `Transit duration (days)`

    :param column_name: The column whose name should be converted.
    :return: The display version of the name.
    """
    display_name = re.sub(r'__(.*)', r' (\g<1>)', column_name)  # Move units into parentheses.
    display_name = display_name.replace('_', ' ')
    specific_replacements = {
        r'tic id': 'TIC ID',
        r'\(btjd\)': '(BTJD)',
        r'\(bjd\)': '(BJD)',
        r'\(jd\)': '(JD)',
        r'pdcsap': 'PDCSAP',
        r'(^|\s)sap($|\s)': r'\g<1>SAP\g<2>',  # SAP avoiding possible cases where `sap` is part of a real word.
    }
    for pattern, replacement in specific_replacements.items():
        display_name = re.sub(pattern, replacement, display_name)
    display_name = display_name[0].upper() + display_name[1:]  # Make first letter uppercase.
    return display_name