import logging
import argparse
import re
import grp
import pwd

def memoize(function):
    cache = {}
    def decorated_function(*args):
        try:
            return cache[args]
        except KeyError:
            val = function(*args)
            cache[args] = val
            return val
    return decorated_function

@memoize
def uid2user(uid):
    try:
        return pwd.getpwuid(uid).pw_name
    except KeyError:
        return None

@memoize
def user2uid(user):
    try:
        return pwd.getpwnam(user).pw_uid
    except KeyError:
        return None

@memoize
def gid2group(gid):
    try:
        return grp.getgrgid(gid).gr_name
    except KeyError:
        return None

@memoize
def group2gid(group):
    try:
        return grp.getgrnam(group).gr_gid
    except KeyError:
        return None

class LevelFilter(logging.Filter):
    """Filter that counts record levels
    """
    def __init__(self, *args, **kwargs):
        logging.Filter.__init__(self, *args, **kwargs)
        self.count = {}

    def filter(self, record):
        self.count.setdefault(record.levelname, 0)
        self.count[record.levelname] += 1
        return record


class Location(object):

    loc_re = re.compile(r'^((?:(?P<user>[^@]+)@)?(?P<host>[^:]+):)?'
                        r'(?P<path>[^:]*)(?:::(?P<archive>[^:]+))?$')

    def __init__(self, text):
        loc = self.loc_re.match(text)
        loc = loc and loc.groupdict()
        if not loc:
            raise ValueError
        self.user = loc['user']
        self.host = loc['host']
        self.path = loc['path']
        if not self.host and not self.path:
            raise ValueError
        self.archive = loc['archive']

    def __str__(self):
        text = ''
        if self.user:
            text += '%s@' % self.user
        if self.host:
            text += '%s::' % self.host
        if self.path:
            text += self.path
        if self.archive:
            text += ':%s' % self.archive
        return text

    def __repr__(self):
        return "Location('%s')" % self


def location_validator(archive=None):
    def validator(text):
        try:
            loc = Location(text)
        except ValueError:
            raise argparse.ArgumentTypeError('Invalid location format: "%s"' % text)
        if archive is True and not loc.archive:
            raise argparse.ArgumentTypeError('"%s": No archive specified' % text)
        elif archive is False and loc.archive:
            raise argparse.ArgumentTypeError('"%s" No archive can be specified' % text)
        return loc
    return validator


def pretty_size(v):
    if v > 1024 * 1024 * 1024:
        return '%.2f GB' % (v / 1024. / 1024. / 1024.)
    elif v > 1024 * 1024:
        return '%.2f MB' % (v / 1024. / 1024.)
    elif v > 1024:
        return '%.2f kB' % (v / 1024.)
    else:
        return str(v)