import chardet

        encoding = chardet.detect(str_)['encoding']

        if encoding is None:

            raise Exception()

        return str_.decode(encoding)

    except (ImportError, UnicodeDecodeError, Exception):

        return unicode(str_, from_encoding[0], 'replace')

def safe_str(unicode_, to_encoding=None):

    """

    safe str function. Does few trick to turn unicode_ into string

    In case of UnicodeEncodeError we try to return it with encoding detected

    by chardet library if it fails fallback to string with errors replaced

    :param unicode_: unicode to encode

    :rtype: str

    :returns: str object

    """

    # if it's not basestr cast to str

    if not isinstance(unicode_, basestring):

        return str(unicode_)

    if isinstance(unicode_, str):

        return unicode_

    if not to_encoding:

        import kallithea

        DEFAULT_ENCODINGS = aslist(kallithea.CONFIG.get('default_encoding',

                                                        'utf8'), sep=',')

        to_encoding = DEFAULT_ENCODINGS

    if not isinstance(to_encoding, (list, tuple)):

        to_encoding = [to_encoding]

    for enc in to_encoding:

        try:

            return unicode_.encode(enc)

        except UnicodeEncodeError:

            pass

    try:

        import chardet

        encoding = chardet.detect(unicode_)['encoding']

        if encoding is None:

            raise UnicodeEncodeError()

        return unicode_.encode(encoding)

    except (ImportError, UnicodeEncodeError):

        return unicode_.encode(to_encoding[0], 'replace')

def remove_suffix(s, suffix):

    if s.endswith(suffix):

        s = s[:-1 * len(suffix)]

    return s

def remove_prefix(s, prefix):

    if s.startswith(prefix):

        s = s[len(prefix):]

    return s

def engine_from_config(configuration, prefix='sqlalchemy.', **kwargs):

    """

    Custom engine_from_config functions that makes sure we use NullPool for

    file based sqlite databases. This prevents errors on sqlite. This only

    applies to sqlalchemy versions < 0.7.0

    """

    import sqlalchemy

    from sqlalchemy import engine_from_config as efc

    import logging

    if int(sqlalchemy.__version__.split('.')[1]) < 7:

        # This solution should work for sqlalchemy < 0.7.0, and should use

        # proxy=TimerProxy() for execution time profiling

        from sqlalchemy.pool import NullPool

        url = configuration[prefix + 'url']

        if url.startswith('sqlite'):

            kwargs.update({'poolclass': NullPool})

        return efc(configuration, prefix, **kwargs)

    else:

        import time

        from sqlalchemy import event

        from sqlalchemy.engine import Engine

        log = logging.getLogger('sqlalchemy.engine')

        BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = xrange(30, 38)

        engine = efc(configuration, prefix, **kwargs)

        def color_sql(sql):

            COLOR_SEQ = "\033[1;%dm"

            COLOR_SQL = YELLOW

            normal = '\x1b[0m'

            return ''.join([COLOR_SEQ % COLOR_SQL, sql, normal])

        if configuration['debug']:

            #attach events only for debug configuration

            def before_cursor_execute(conn, cursor, statement,

                                    parameters, context, executemany):

                context._query_start_time = time.time()

                log.info(color_sql(">>>>> STARTING QUERY >>>>>"))

            def after_cursor_execute(conn, cursor, statement,

                                    parameters, context, executemany):

                total = time.time() - context._query_start_time

                log.info(color_sql("<<<<< TOTAL TIME: %f <<<<<" % total))

            event.listen(engine, "before_cursor_execute",

                         before_cursor_execute)

            event.listen(engine, "after_cursor_execute",

                         after_cursor_execute)

    return engine

def age(prevdate, show_short_version=False, now=None):

    """

    turns a datetime into an age string.

    If show_short_version is True, then it will generate a not so accurate but shorter string,

    example: 2days ago, instead of 2 days and 23 hours ago.

    :param prevdate: datetime object

    :param show_short_version: if it should aproximate the date and return a shorter string

    :rtype: unicode

    :returns: unicode words describing age

    """

    now = now or datetime.datetime.now()

    order = ['year', 'month', 'day', 'hour', 'minute', 'second']

    deltas = {}

    future = False

    if prevdate > now:

        now, prevdate = prevdate, now

        future = True

    if future:

        prevdate = prevdate.replace(microsecond=0)

    # Get date parts deltas

    from dateutil import relativedelta

    for part in order:

        d = relativedelta.relativedelta(now, prevdate)

        deltas[part] = getattr(d, part + 's')

    # Fix negative offsets (there is 1 second between 10:59:59 and 11:00:00,

    # not 1 hour, -59 minutes and -59 seconds)

    for num, length in [(5, 60), (4, 60), (3, 24)]:  # seconds, minutes, hours

        part = order[num]

        carry_part = order[num - 1]

        if deltas[part] < 0:

            deltas[part] += length

            deltas[carry_part] -= 1

    # Same thing for days except that the increment depends on the (variable)

    # number of days in the month

    month_lengths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

    if deltas['day'] < 0:

        if prevdate.month == 2 and (prevdate.year % 4 == 0 and

            (prevdate.year % 100 != 0 or prevdate.year % 400 == 0)):

            deltas['day'] += 29

        else:

            deltas['day'] += month_lengths[prevdate.month - 1]

        deltas['month'] -= 1

    if deltas['month'] < 0:

        deltas['month'] += 12

        deltas['year'] -= 1

    # Format the result

    fmt_funcs = {

        'year': lambda d: ungettext(u'%d year', '%d years', d) % d,

        'month': lambda d: ungettext(u'%d month', '%d months', d) % d,

        'day': lambda d: ungettext(u'%d day', '%d days', d) % d,

        'hour': lambda d: ungettext(u'%d hour', '%d hours', d) % d,

        'minute': lambda d: ungettext(u'%d minute', '%d minutes', d) % d,

        'second': lambda d: ungettext(u'%d second', '%d seconds', d) % d,

    }

    for i, part in enumerate(order):

        value = deltas[part]

        if value == 0:

            continue

        if i < 5:

            sub_part = order[i + 1]

            sub_value = deltas[sub_part]

        else:

            sub_value = 0

        if sub_value == 0 or show_short_version:

            if future:

                return _(u'in %s') % fmt_funcs[part](value)

            else:

                return _(u'%s ago') % fmt_funcs[part](value)

        if future:

            return _(u'in %s and %s') % (fmt_funcs[part](value),

                fmt_funcs[sub_part](sub_value))

        else:

            return _(u'%s and %s ago') % (fmt_funcs[part](value),

                fmt_funcs[sub_part](sub_value))

    return _(u'just now')

def uri_filter(uri):

    """

    Removes user:password from given url string

    :param uri:

    :rtype: unicode

    :returns: filtered list of strings

    """

    if not uri:

        return ''

    proto = ''

    for pat in ('https://', 'http://'):

        if uri.startswith(pat):

            uri = uri[len(pat):]

            proto = pat

            break

    # remove passwords and username

    uri = uri[uri.find('@') + 1:]

    # get the port

    cred_pos = uri.find(':')

    if cred_pos == -1:

        host, port = uri, None

    else:

        host, port = uri[:cred_pos], uri[cred_pos + 1:]

    return filter(None, [proto, host, port])

def credentials_filter(uri):

    """

    Returns a url with removed credentials

    :param uri:

    """

    uri = uri_filter(uri)

    #check if we have port

    if len(uri) > 2 and uri[2]:

        uri[2] = ':' + uri[2]

    return ''.join(uri)

def get_clone_url(uri_tmpl, qualifed_home_url, repo_name, repo_id, **override):

    parsed_url = urlobject.URLObject(qualifed_home_url)

    decoded_path = safe_unicode(urllib.unquote(parsed_url.path.rstrip('/')))

    args = {

        'scheme': parsed_url.scheme,

        'user': '',

        'netloc': parsed_url.netloc+decoded_path,  # path if we use proxy-prefix

        'prefix': decoded_path,

        'repo': repo_name,

        'repoid': str(repo_id)

    }

    args.update(override)

    args['user'] = urllib.quote(safe_str(args['user']))

    for k, v in args.items():

        uri_tmpl = uri_tmpl.replace('{%s}' % k, v)

    # remove leading @ sign if it's present. Case of empty user

    url_obj = urlobject.URLObject(uri_tmpl)

    url = url_obj.with_netloc(url_obj.netloc.lstrip('@'))

    return safe_unicode(url)

def get_changeset_safe(repo, rev):

    """

    Safe version of get_changeset if this changeset doesn't exists for a

    repo it returns a Dummy one instead

    :param repo:

    :param rev:

    """

    from kallithea.lib.vcs.backends.base import BaseRepository

    from kallithea.lib.vcs.exceptions import RepositoryError

    from kallithea.lib.vcs.backends.base import EmptyChangeset

    if not isinstance(repo, BaseRepository):

        raise Exception('You must pass an Repository '

                        'object as first argument got %s', type(repo))

    try:

        cs = repo.get_changeset(rev)

    except (RepositoryError, LookupError):

        cs = EmptyChangeset(requested_revision=rev)

    return cs

def datetime_to_time(dt):

    if dt:

        return time.mktime(dt.timetuple())

def time_to_datetime(tm):

    if tm:

        if isinstance(tm, basestring):

            try:

                tm = float(tm)

            except ValueError:

                return

        return datetime.datetime.fromtimestamp(tm)

MENTIONS_REGEX = r'(?:^@|\s@)([a-zA-Z0-9]{1}[a-zA-Z0-9\-\_\.]+)(?:\s{1})'

def extract_mentioned_users(s):

    """

    Returns unique usernames from given string s that have @mention

    :param s: string to get mentions

    """

    usrs = set()

    for username in re.findall(MENTIONS_REGEX, s):

        usrs.add(username)

    return sorted(list(usrs), key=lambda k: k.lower())

class AttributeDict(dict):

    def __getattr__(self, attr):

        return self.get(attr, None)

    __setattr__ = dict.__setitem__

    __delattr__ = dict.__delitem__

def fix_PATH(os_=None):

    """

    Get current active python path, and append it to PATH variable to fix issues

    of subprocess calls and different python versions

    """

    if os_ is None:

        import os

    else:

        os = os_

    cur_path = os.path.split(sys.executable)[0]

    if not os.environ['PATH'].startswith(cur_path):

        os.environ['PATH'] = '%s:%s' % (cur_path, os.environ['PATH'])

def obfuscate_url_pw(engine):

    _url = engine or ''

    from sqlalchemy.engine import url as sa_url

    try:

        _url = sa_url.make_url(engine)

        if _url.password:

            _url.password = 'XXXXX'

    except Exception:

        pass

    return str(_url)

def get_server_url(environ):

    req = webob.Request(environ)

    return req.host_url + req.script_name

def _extract_extras(env=None):

    """

    Extracts the rc extras data from os.environ, and wraps it into named

    AttributeDict object

    """

    if not env:

        env = os.environ

    try:

    except Exception:

        print os.environ

        print >> sys.stderr, traceback.format_exc()

        rc_extras = {}

    try:

        for k in ['username', 'repository', 'locked_by', 'scm', 'make_lock',

                  'action', 'ip']:

            rc_extras[k]

    except KeyError, e:

        raise Exception('Missing key %s in os.environ %s' % (e, rc_extras))

    return AttributeDict(rc_extras)

def _set_extras(extras):

def unique_id(hexlen=32):

    alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjklmnpqrstuvwxyz"

    return suuid(truncate_to=hexlen, alphabet=alphabet)

def suuid(url=None, truncate_to=22, alphabet=None):

    """

    Generate and return a short URL safe UUID.

    If the url parameter is provided, set the namespace to the provided

    URL and generate a UUID.

    :param url to get the uuid for

    :truncate_to: truncate the basic 22 UUID to shorter version

    The IDs won't be universally unique any longer, but the probability of

    a collision will still be very low.

    """

    # Define our alphabet.

    _ALPHABET = alphabet or "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"

    # If no URL is given, generate a random UUID.

    if url is None:

        unique_id = uuid.uuid4().int

    else:

        unique_id = uuid.uuid3(uuid.NAMESPACE_URL, url).int

    alphabet_length = len(_ALPHABET)

    output = []

    while unique_id > 0:

        digit = unique_id % alphabet_length

        output.append(_ALPHABET[digit])

        unique_id = int(unique_id / alphabet_length)

    return "".join(output)[:truncate_to]

def get_current_authuser():

    """

    Gets rhodecode user from threadlocal tmpl_context variable if it's

    defined, else returns None.

    """

    from pylons import tmpl_context

    if hasattr(tmpl_context, 'authuser'):

        return tmpl_context.authuser

    return None

class OptionalAttr(object):

    """

    Special Optional Option that defines other attribute. Example::

        def test(apiuser, userid=Optional(OAttr('apiuser')):

            user = Optional.extract(userid)

            # calls

    """

    def __init__(self, attr_name):

        self.attr_name = attr_name

    def __repr__(self):

        return '<OptionalAttr:%s>' % self.attr_name

    def __call__(self):

        return self

#alias

OAttr = OptionalAttr

class Optional(object):

    """

    Defines an optional parameter::

        param = param.getval() if isinstance(param, Optional) else param

        param = param() if isinstance(param, Optional) else param

    is equivalent of::

        param = Optional.extract(param)

    """

    def __init__(self, type_):

        self.type_ = type_

    def __repr__(self):

        return '<Optional:%s>' % self.type_.__repr__()

    def __call__(self):

        return self.getval()

    def getval(self):

        """

        returns value from this Optional instance

        """

        if isinstance(self.type_, OAttr):

            # use params name

            return self.type_.attr_name

        return self.type_

    @classmethod

    def extract(cls, val):

        """

        Extracts value from Optional() instance

        :param val:

        :return: original value if it's not Optional instance else

            value of instance

        """

        if isinstance(val, cls):

            return val.getval()

        return val