def gravatar(email_address, cls='', size=30):

    """return html element of the gravatar

    This method will return an <img> with the resolution double the size (for

    retina screens) of the image. If the url returned from gravatar_url is

    empty then we fallback to using an icon.

    """

    from tg import tmpl_context as c

    if not c.visual.use_gravatar:

        return ''

    src = gravatar_url(email_address, size * 2)

    if src:

        # here it makes sense to use style="width: ..." (instead of, say, a

        # stylesheet) because we using this to generate a high-res (retina) size

        html = ('<i class="icon-gravatar {cls}"'

                ' style="font-size: {size}px;background-size: {size}px;background-image: url(\'{src}\')"'

                '></i>').format(cls=cls, size=size, src=src)

    else:

        # if src is empty then there was no gravatar, so we use a font icon

        html = ("""<i class="icon-user {cls}" style="font-size: {size}px;"></i>"""

    return literal(html)

def gravatar_url(email_address, size=30, default=''):

    # doh, we need to re-import those to mock it later

    from kallithea.config.routing import url

    from kallithea.model.db import User

    from tg import tmpl_context as c

    if not c.visual.use_gravatar:

        return ""

    _def = 'anonymous@kallithea-scm.org'  # default gravatar

    email_address = email_address or _def

    if email_address == _def:

        return default

    parsed_url = urllib.parse.urlparse(url.current(qualified=True))

    url = (c.visual.gravatar_url or User.DEFAULT_GRAVATAR_URL) \

               .replace('{email}', email_address) \

               .replace('{md5email}', hashlib.md5(safe_bytes(email_address).lower()).hexdigest()) \

               .replace('{netloc}', parsed_url.netloc) \

               .replace('{scheme}', parsed_url.scheme) \