###### arithmetic_arranger.py #####

import random, string

import operator

operator_functions = { '+': operator.add, '-': operator.sub, '*': operator.mul, '/': operator.truediv}

def arithmetic_arranger(problems, answer=None):
    opr1 = ''
    opr2 = ''    
    opr3 = ''
    opr4 = ''
    
    for i in range(len(problems)):
        
        problem = problems[i].split()
        
        if len(problem[0]) > 4 or len(problem[2]) > 4:
            return 'Error: Numbers cannot be more than four digits.'  
        
        elif any(c.isalpha() for c in problem[0]) == True or any(c.isalpha() for c in problem[2]) == True:
            return 'Error: Numbers must only contain digits.'    
   
        elif len(problems) > 5:  
            return 'Error: Too many problems.'
        
        elif problem[1] not in operator_functions or problem[1] == '*' or problem[1] == '/':
            return "Error: Operator must be '+' or '-'."  
        
        else:    
            nl = '\n'
            u = max(len(problem[0]), len(problem[2]))
            opr1 = opr1 + f'{problem[0].rjust(u + 2)}' + "    "
            opr2 = opr2 + f'{problem[1].ljust(u + 2 - len(problem[2]))}{problem[2].ljust(len(problem[2])+4)}'
            opr3 = opr3 + f'{("-" * (u + 2)).ljust(u+6)}'           
            if answer is True:
                if problem[1] == '+':
                    ans = int(problem[0]) + int(problem[2])
                elif problem[1] == '-':
                    ans = int(problem[0]) - int(problem[2])
                ans = str(ans)
                opr4 = opr4 + f'{ans.rjust(u + 2)}' + "    "
    return f'{opr1}{nl}{opr2}{nl}{opr3}{nl}{opr4}'
    return f'{opr1}{nl}{opr2}{nl}{opr3}'
    
print(arithmetic_arranger(["32 - 698", "1 - 3801", "45 + 43", "123 + 49"], True))

# This entrypoint file to be used in development. Start by reading README.md
import arithmetic_arranger
from unittest import main


print(arithmetic_arranger(["32 + 698", "3801 - 2", "45 + 43", "123 + 49"]))


# Run unit tests automatically
main(module='test_module', exit=False)