import os, pwd, regex

def expand_tilde(path):
    if not path.startswith('~'):
        return path
    parts = path.split('/', 1)
    if parts[0] == '~':
        parts[0] = os.getenv('HOME')
    elif parts[0].startswith('~'):
        users = [x[0] for x in pwd.getpwall()]
        if parts[0][1:] in users:
            home = pwd.getpwnam(parts[0][1:])[5]
            parts[0] = home
    if len(parts) > 1:
        s = os.path.join(parts[0], parts[1])
    else:
        s = parts[0]
    s = os.path.realpath(s)
    if os.path.isdir(s):
        s += '/'
    return s
        

def cleanse(s):
    s2 = s.replace("\n", "")
    return s2

def padtrunc(s, i, c=' '):
    assert i >= 0
    assert len(c) == 1

    l = len(s)
    if l < i:
        return s + c * (i - l)
    elif l > i:
        return s[0:i]
    else:
        return s

def pad(s, i, c=' '):
    assert len(c) == 1

    l = len(s)
    if len(s) < i:
        return s + c * (i - l)
    else:
        return s

def count_leading_whitespace(s):
    m = regex.leading_whitespace.match(s)
    assert m, "count leading whitespace failed somehow"
    return m.end() - m.start()