#!/usr/bin/env python3
import sys

# Creates an iterator that loops a list indefinitely
class LoopList:
    def __init__(self, ls):
        self.ls = ls
    def __iter__(self):
        self.i = 0
        return self
    def __next__(self):
        v = self.ls[self.i]
        self.i = (self.i + 1) % len(self.ls)
        return v

def splitAt(w,n):
    for i in range(0,len(w),n):
        yield w[i:i+n]

# computes checkdigit for invoice number
# https://www.pangaliit.ee/settlements-and-standards/reference-number-of-the-invoice
def checkdigit(ref):
    ref = str(ref)
    weights = [7,3,1]
    wref = [int(x[0])*int(x[1]) for x in zip(ref[::-1], LoopList(weights))]
    wsum = sum(wref)
    checkdigit = 10 - (wsum % 10)
    return str(checkdigit)[-1]

# https://github.com/terokallio/reference-numbers/blob/master/src/main/java/com/terokallio/referencenumbers/RFCreditorReference.java
def isocheckdigits(ref):
    #       ref + "RF"   + "00"
    #        |      |       |
    #        v      v       v
    magic = ref + '2715' + '00'
    mod = int(magic) % 97
    check = 98 - mod
    return '0' + str(check) if check < 10 else str(check)

def convert(ref):
    refc = ref + checkdigit(ref)
    print('Reference with checkdigit: \n\t', refc)

    refiso = 'RF' + isocheckdigits(refc) + refc
    refiso = " ".join(splitAt(refiso,4))
    print('ISO 11649 converted reference: \n\t', refiso)

if __name__ == '__main__':
    ref = sys.argv[1]
    convert(ref)