import os, re

SIZE_UNITS = dict(
    b = 1024**0,
    k = 1024**1,
    m = 1024**2,
    g = 1024**3,
    t = 1024**4,
)


class MemBool:
    """
        Truth-checking with a memory, for use in chained if statements.
    """
    def __init__(self):
        self.v = None

    def __call__(self, v):
        self.v = v
        return bool(v)


def parse_size(s):
    try:
        return int(s)
    except ValueError:
        pass
    for i in SIZE_UNITS.keys():
        if s.endswith(i):
            try:
                return int(s[:-1]) * SIZE_UNITS[i]
            except ValueError:
                break
    raise ValueError("Invalid size specification.")


def get_header(val, headers):
    """
        Header keys may be Values, so we have to "generate" them as we try the match.
    """
    for h in headers:
        k = h.key.get_generator({})
        if len(k) == len(val) and k[:].lower() == val.lower():
            return h
    return None


def parse_anchor_spec(s):
    """
        Return a tuple, or None on error.
    """
    if not "=" in s:
        return None
    return tuple(s.split("=", 1))


def xrepr(s):
    return repr(s)[1:-1]


def inner_repr(s):
    """
        Returns the inner portion of a string or unicode repr (i.e. without the
        quotes)
    """
    if isinstance(s, unicode):
        return repr(s)[2:-1]
    else:
        return repr(s)[1:-1]


def escape_unprintables(s):
    """
        Like inner_repr, but preserves line breaks.
    """
    s = s.replace("\r\n", "PATHOD_MARKER_RN")
    s = s.replace("\n", "PATHOD_MARKER_N")
    s = inner_repr(s)
    s = s.replace("PATHOD_MARKER_RN", "\n")
    s = s.replace("PATHOD_MARKER_N", "\n")
    return s


class Data:
    def __init__(self, name):
        m = __import__(name)
        dirname, _ = os.path.split(m.__file__)
        self.dirname = os.path.abspath(dirname)

    def path(self, path):
        """
            Returns a path to the package data housed at 'path' under this
            module.Path can be a path to a file, or to a directory.

            This function will raise ValueError if the path does not exist.
        """
        fullpath = os.path.join(self.dirname, path)
        if not os.path.exists(fullpath):
            raise ValueError, "dataPath: %s does not exist."%fullpath
        return fullpath


data = Data(__name__)