"""
 advent9.py

 advent of code day 9
"""

import re

def dump_exclamation(stream):
    """ Remove !. from stream. Return new version 
        >>> dump_exclamation('!!abc!abbb')
        'abcbbb'
        >>> dump_exclamation('--!a!!!b,')
        '--,'
        >>> dump_exclamation('{{<!>},{<!>},{<!>},{<a>}}')
        '{{<},{<},{<},{<a>}}'
    """
    return re.sub(r'!.', '', stream)

def dump_angles(stream):
    """ Remove <....> from stream; return new version.
        >>> dump_angles('a<<<<>b')
        'ab'
        >>> dump_angles('<>')
        ''
        >>> dump_angles('ab<c')
        'ab<c'
    """
    return re.sub(r'<[^>]*>', '', stream)

def angles_to_dashes(stream):
    """ count number of garbage characters
        >>> len('<>') - len(angles_to_dashes('<>'))
        0
        >>> len('<<<<>') - len(angles_to_dashes('<<<<>'))
        3
    """
    return re.sub(r'<[^>]*>', '--', stream)

# test regular expression in python :
# print re.sub(r'^(.*)(ab)(cd)(.*)$', 
#             r'\1\3\2\4', "__abcde__")

def score_groups(stream):
    """ Return score for embedded curlies 
        >>> score_groups('{}')
        1
        >>> score_groups('{{{}}}')
        6
        >>> score_groups('{{},{}}')
        5
        >>> score_groups('{{{},{},{{}}}}')
        16
    """
    depth = 0
    total = 0
    for ch in stream:
        if ch == '{':
            depth = depth + 1
        if ch == '}':
            total = total + depth
            depth = depth - 1
    return total

def remove_exclaims(stream):
    result = ''
    last_was_exclaim = False
    for i in range(len(stream)):
        if last_was_exclaim:
            last_was_exclaim = False
        elif stream[i] == '!':
            last_was_exclaim = True
        else:
            result = result + stream[i]
    return result

def main():
    data = open("day9_input.txt").read()
    data_dumped = dump_exclamation(data)
    data_dump_squared = dump_angles(data_dumped)
    score = score_groups(data_dump_squared)
    print "answer to part 1 is ", score
    #
    length1 = len(data_dumped)
    length2 = len(angles_to_dashes(data_dumped))
    print "answer to part 2 is ", length1 - length2

if __name__ == "__main__":
    import doctest
    doctest.testmod()
    main()