"""

        runs detection of what renderer should be used for generating html

        from a markup language

        filename can be also explicitly a renderer name

        :param source:

        :param filename:

        """

        if self.MARKDOWN_PAT.findall(filename):

            return self.markdown

        elif self.RST_PAT.findall(filename):

            return self.rst

        elif self.PLAIN_PAT.findall(filename):

            return self.rst

        return self.plain

    @classmethod

    def _flavored_markdown(cls, text):

        """

        Github style flavored markdown

        :param text:

        """

        from hashlib import md5

        # Extract pre blocks.

        extractions = {}

        def pre_extraction_callback(matchobj):

            digest = md5(matchobj.group(0)).hexdigest()

            extractions[digest] = matchobj.group(0)

            return "{gfm-extraction-%s}" % digest

        pattern = re.compile(r'<pre>.*?</pre>', re.MULTILINE | re.DOTALL)

        text = re.sub(pattern, pre_extraction_callback, text)

        # Prevent foo_bar_baz from ending up with an italic word in the middle.

        def italic_callback(matchobj):

            s = matchobj.group(0)

            if list(s).count('_') >= 2:

                return s.replace('_', '\_')

            return s

        text = re.sub(r'^(?! {4}|\t)\w+_\w+_\w[\w_]*', italic_callback, text)

        # In very clear cases, let newlines become <br /> tags.

        def newline_callback(matchobj):

            if len(matchobj.group(1)) == 1:

                return matchobj.group(0).rstrip() + '  \n'

            else:

                return matchobj.group(0)

        pattern = re.compile(r'^[\w\<][^\n]*(\n+)', re.MULTILINE)

        text = re.sub(pattern, newline_callback, text)

        # Insert pre block extractions.

        def pre_insert_callback(matchobj):

            return '\n\n' + extractions[matchobj.group(1)]

        text = re.sub(r'{gfm-extraction-([0-9a-f]{32})\}',

                      pre_insert_callback, text)

        return text

    def render(self, source, filename=None):

        """

        Renders a given filename using detected renderer

        it detects renderers based on file extension or mimetype.

        At last it will just do a simple html replacing new lines with <br/>

        :param file_name:

        :param source:

        """

        renderer = self._detect_renderer(source, filename)

        readme_data = renderer(source)

        return readme_data

    @classmethod

    def plain(cls, source, universal_newline=True):

        source = safe_unicode(source)

        if universal_newline:

            newline = '\n'

            source = newline.join(source.splitlines())

        def url_func(match_obj):

            url_full = match_obj.group(0)

            return '<a href="%(url)s">%(url)s</a>' % ({'url': url_full})

        source = url_re.sub(url_func, source)

        return '<br />' + source.replace("\n", '<br />')

    @classmethod

    def markdown(cls, source, safe=True, flavored=False):

        source = safe_unicode(source)

        try:

            import markdown as __markdown

            if flavored:

                source = cls._flavored_markdown(source)

        except ImportError:

            log.warning('Install markdown to use this function')

            return cls.plain(source)

        except Exception:

            log.error(traceback.format_exc())

            if safe:

                log.debug('Falling back to render in plain mode')

                return cls.plain(source)

            else:

                raise

    @classmethod

    def rst(cls, source, safe=True):

        source = safe_unicode(source)

        try:

            from docutils.core import publish_parts

            from docutils.parsers.rst import directives

            docutils_settings = dict([(alias, None) for alias in

                                cls.RESTRUCTUREDTEXT_DISALLOWED_DIRECTIVES])

            docutils_settings.update({'input_encoding': 'unicode',

                                      'report_level': 4})

            for k, v in docutils_settings.iteritems():

                directives.register_directive(k, v)

            parts = publish_parts(source=source,

                                  writer_name="html4css1",

                                  settings_overrides=docutils_settings)

            return parts['html_title'] + parts["fragment"]

        except ImportError:

            log.warning('Install docutils to use this function')

            return cls.plain(source)

        except Exception:

            log.error(traceback.format_exc())

            if safe:

                log.debug('Falling back to render in plain mode')

                return cls.plain(source)

            else:

                raise

    @classmethod

    def rst_with_mentions(cls, source):

        def wrapp(match_obj):

            uname = match_obj.groups()[0]

            return '\ **@%(uname)s**\ ' % {'uname': uname}

        mention_hl = MENTIONS_REGEX.sub(wrapp, source).strip()

        return cls.rst(mention_hl)