""" This module has utility methods related to Singapore NRIC number"""

def check_nric_sg(nric):
    """ check if a nric is valid or not"""
    list_m = [2, 7, 6, 5, 4, 3, 2]
    list_st = list('JZIHGFEDCBA')
    list_fg = list('XWUTRQPNMLK')

    if len(nric) != 9:
        return False

    nric = nric.upper()
    if nric[0] not in ['S', 'T', 'F', 'G']:
        return False

    list_nric = list(nric[1:8])
    result = sum([int(a)*b for a, b in zip(list_nric, list_m)])

    if nric[0] == 'T' or nric[0] == 'G':
        result += 4

    result_mod = result % 11

    if nric[0] == "S" or nric[0] == "T":
        checksum = list_st[result_mod]
    elif nric[0] == "F" or nric[0] == "G":
        checksum = list_fg[result_mod]

    return nric[8] == checksum

def fix_nric_sg(nric):
    """Fix the first char of the NRIC as many patients don't input that"""
    if not check_nric_sg(nric):
        for prefix in ['S', 'T', 'F', 'G']:
            nric_temp = prefix + nric
            if check_nric_sg(nric_temp):
                return nric_temp
        return False