import os
import pwd
import re
import regex

# character buffers use sequences like [r:d]foo[d:d] to indicate that foo
# should be fg=red,bg=default. as such, we have to escape \, [ and ].
cbuf_re = re.compile(r'[\[\]\\]')
def cbuf_escape(s):
    '''escape characters which have special meaning in color buffers'''
    return cbuf_re.sub(lambda m: '\\' + m.group(0), s)

def flatzip(a, b):
    '''interleave two lists, e.g. ((a,b),(1,2)) -> (a,1,b,2)'''
    l = []
    for x, y in zip(a, b):
        l.append(x)
        l.append(y)
    return l

def should_ignore_path(path, suffixes):
    '''whether file (or any parent) should be ignored based on suffixes '''
    for name in path.split('/'):
        for suffix in suffixes:
            if name.endswith(suffix):
                return True
    return False

def literal_path(path):
    '''return the system path for the given user path'''
    path = os.path.realpath(expand_tilde(path))
    return os.path.abspath(path)

def normal_path(path):
    '''return the user path for the given system path '''
    path  = os.path.normpath(path)
    home  = os.getenv('HOME')
    isdir = os.path.isdir(path)
    if path.startswith(home):
        path = path.replace(home, '~', 1)
    if isdir and not path.endswith('/'):
        path += '/'
    return path

def expand_tilde(path):
    '''correctly expand the tilde in the provided path'''
    isdir = path.endswith('/')
    if not path.startswith('~'):
        return path
    parts = path.split('/', 1)
    if parts[0] == '~':
        parts[0] = os.getenv('HOME')
    elif parts[0].startswith('~'):
        try:
            parts[0] = pwd.getpwnam(parts[0][1:])[5]
        except KeyError:
            pass
    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) and isdir:
        s += '/'
    return s

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

def make_name(name, testf):
    '''generate a new name, using testf() to see which names are taken'''
    if testf(name):
        i = 1
        auxname = '%s/%d' % (name, i)
        while testf(auxname):
            i += 1
            auxname = '%s/%d' % (name, i)
        name = auxname
    return name

# TODO: move these somewhere more sensible. they aren't really utilities.
def get_margin_limit(w, def_limit=80):
    lname = '%s.margin' % w.mode.name.lower()
    if lname in w.application.config:
        return w.application.config[lname]
    else:
        return w.application.config.get('margin', def_limit)

def get_margin_color(w, def_color='blue'):
    lname = '%s.margin_color' % w.mode.name.lower()
    if lname in w.application.config:
        return w.application.config[lname]
    else:
        return w.application.config.get('margin_color', def_color)

# emulate defaultdict for 2.4
try:
    from collections import defaultdict
except:
    class defaultdict(dict):
        def __init__(self, default_factory=None, *a, **kw):
            if (default_factory is not None and
                not hasattr(default_factory, '__call__')):
                raise TypeError('first argument must be callable')
            dict.__init__(self, *a, **kw)
            self.default_factory = default_factory
        def __getitem__(self, key):
            try:
                return dict.__getitem__(self, key)
            except KeyError:
                return self.__missing__(key)
        def __missing__(self, key):
            if self.default_factory is None:
                raise KeyError(key)
            self[key] = value = self.default_factory()
            return value
        def __reduce__(self):
            if self.default_factory is None:
                args = tuple()
            else:
                args = self.default_factory,
            return type(self), args, None, None, self.items()
        def copy(self):
            return self.__copy__()
        def __copy__(self):
            return type(self)(self.default_factory, self)
        def __deepcopy__(self, memo):
            import copy
            return type(self)(self.default_factory,
                              copy.deepcopy(self.items()))
        def __repr__(self):
            return 'defaultdict(%s, %s)' % (self.default_factory,
                                            dict.__repr__(self))