#coding=utf-8
import re
import cgi

re_string = re.compile(r'(?P<htmlchars>[<&>])|(?P<space>^[ \t]+)|(?P<lineend>\r\n|\r|\n)|(?P<protocal>(^|\s*)((http|ftp)://.*?))(\s|$)', re.S|re.M|re.I)
def text2html(text, tabstop=4):
    def do_sub(m):
        c = m.groupdict()
        if c['htmlchars']:
            return cgi.escape(c['htmlchars'])
        if c['lineend']:
            return '<br>'
        elif c['space']:
            t = m.group().replace('\t', '&nbsp;'*tabstop)
            t = t.replace(' ', '&nbsp;')
            return t
        elif c['space'] == '\t':
            return ' '*tabstop;
        else:
            url = m.group('protocal')
            if url.startswith(' '):
                prefix = ' '
                url = url[1:]
            else:
                prefix = ''
            last = m.groups()[-1]
            if last in ['\n', '\r', '\r\n']:
                last = '<br>'
            return '%s<a href="%s">%s</a>%s' % (prefix, url, url, last)
    return re.sub(re_string, do_sub, text)

if __name__ == '__main__':
    text="""
  http://groups.google.com/group/python-cn/pending
"""
    print text2html(text)