"""
advent1.py

 adventofcode.com 2017 day 1

"""

def list2sum(the_list):
    """ convert list of character digits to its sum 
        >>> list2sum(['1', '2', '3'])
        6
        >>> list2sum([])
        0
    """
    result = 0
    for x in the_list:
        result = result + int(x)
    return result

def part1(text):
    """ return sum of digits where next matches, with wrap 
        >>> part1('1122')
        3
        >>> part1('1111')
        4
        >>> part1('1234')
        0
    """
    n = len(text)
    keepers = []
    for i in range(n):
        if i + 1 == n:
            if text[i] == text[0]:
                keepers.append(text[i])
        else:
            if text[i] == text[i+1]:
                keepers.append(text[i])
    # print(keepers)
    return list2sum(keepers)

def part2(text):
    """ return sum of halfway around 
        >>> part2('1212')
        6
        >>> part2('123123')
        12
    """
    result = 0
    n = len(text)
    for i in range(n):
        if text[i] == text[(i + int(n/2)) % n]:
            result = result + int(text[i])
    return result

def process_file(filename = 'input_1.txt'):
    text = open(filename).read().strip()
    answer1 = part1(text)
    print("The answer to part 1 is ", answer1)
    answer2 = part2(text)
    print("The answer to part 2 is ", answer2)

if __name__ == '__main__':
    import doctest
    doctest.testmod()
    process_file()