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 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 approximate 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

    # In short version, we want nicer handling of ages of more than a year

    if show_short_version:

        if deltas['year'] == 1:

            # ages between 1 and 2 years: show as months

            deltas['month'] += 12

            deltas['year'] = 0

        if deltas['year'] >= 2:

            # ages 2+ years: round

            if deltas['month'] > 6:

                deltas['year'] += 1

                deltas['month'] = 0

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

            else:

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

        if future:

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

                fmt_funcs[sub_part](sub_value))

        else:

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

                fmt_funcs[sub_part](sub_value))

    return _('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://', 'git://'):

        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(clone_uri_tmpl, prefix_url, repo_name, repo_id, username=None):

    parsed_url = urlobject.URLObject(prefix_url)

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

    args = {

        'scheme': parsed_url.scheme,

        'user': safe_unicode(urllib.quote(safe_str(username or ''))),

        'netloc': parsed_url.netloc + prefix,  # like "hostname:port/prefix" (with optional ":port" and "/prefix")

        'prefix': prefix, # undocumented, empty or starting with /

        'repo': repo_name,

        'repoid': str(repo_id),

    }

    url = re.sub('{([^{}]+)}', lambda m: args.get(m.group(1), m.group(0)), clone_uri_tmpl)

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

    url_obj = urlobject.URLObject(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)

# Must match regexp in kallithea/public/js/base.js MentionsAutoComplete()

# Check char before @ - it must not look like we are in an email addresses.

# Matching is greedy so we don't have to look beyond the end.

MENTIONS_REGEX = re.compile(r'(?:^|(?<=[^a-zA-Z0-9]))@([a-zA-Z0-9][-_.a-zA-Z0-9]*[a-zA-Z0-9])')

def extract_mentioned_usernames(text):

    r"""

    Returns list of (possible) usernames @mentioned in given text.

    >>> extract_mentioned_usernames('@1-2.a_X,@1234 not@not @ddd@not @n @ee @ff @gg, @gg;@hh @n\n@zz,')

    ['1-2.a_X', '1234', 'ddd', 'ee', 'ff', 'gg', 'gg', 'hh', 'zz']

    """

    return MENTIONS_REGEX.findall(text)

def extract_mentioned_users(text):

    """ Returns set of actual database Users @mentioned in given text. """

    from kallithea.model.db import User

    result = set()

    for name in extract_mentioned_usernames(text):

        user = User.get_by_username(name, case_insensitive=True)

        if user is not None and not user.is_default_user:

            result.add(user)

    return result

class AttributeDict(dict):

    def __getattr__(self, attr):

        return self.get(attr, None)

    __setattr__ = dict.__setitem__

    __delattr__ = dict.__delitem__

def obfuscate_url_pw(engine):

    from sqlalchemy.engine import url as sa_url

    from sqlalchemy.exc import ArgumentError

    try:

        _url = sa_url.make_url(engine or '')

    except ArgumentError:

        return engine

    if _url.password:

        _url.password = 'XXXXX'

    return str(_url)

def get_hook_environment():

    """

    Get hook context by deserializing the global KALLITHEA_EXTRAS environment

    variable.

    Called early in Git out-of-process hooks to get .ini config path so the

    basic environment can be configured properly. Also used in all hooks to get

    information about the action that triggered it.

    """

    try:

        extras = json.loads(os.environ['KALLITHEA_EXTRAS'])

    except KeyError:

        raise Exception("Environment variable KALLITHEA_EXTRAS not found")

    try:

        for k in ['username', 'repository', 'scm', 'action', 'ip']:

            extras[k]

    except KeyError:

        raise Exception('Missing key %s in KALLITHEA_EXTRAS %s' % (k, extras))

    return AttributeDict(extras)

def set_hook_environment(username, ip_addr, repo_name, repo_alias, action=None):

    """Prepare global context for running hooks by serializing data in the

    global KALLITHEA_EXTRAS environment variable.

    Most importantly, this allow Git hooks to do proper logging and updating of

    caches after pushes.

    Must always be called before anything with hooks are invoked.

    """

    from kallithea import CONFIG

    extras = {

        'ip': ip_addr, # used in log_push/pull_action action_logger

        'username': username,

        'action': action or 'push_local', # used in log_push_action_raw_ids action_logger

        'repository': repo_name,

        'scm': repo_alias, # used to pick hack in log_push_action_raw_ids

        'config': CONFIG['__file__'], # used by git hook to read config

    }

    os.environ['KALLITHEA_EXTRAS'] = json.dumps(extras)

def get_current_authuser():

    """

    Gets kallithea user from threadlocal tmpl_context variable if it's

    defined, else returns None.

    """

    from tg 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

        """