from django.template import Library
from django.utils.encoding import force_unicode
import re

register = Library()

re_widont = re.compile(r'\s+(\S+\s*)$')
def widont(value, count=1):
    """
    Adds an HTML non-breaking space between the final two words of the string to
    avoid "widowed" words.

    Examples:

    >>> print widont('Test   me   out')
    Test   me&nbsp;out

    >>> widont('It works with trailing spaces too  ')
    u'It works with trailing spaces&nbsp;too  '

    >>> print widont('NoEffect')
    NoEffect
    """
    def replace(matchobj):
        return u'&nbsp;%s' % matchobj.group(1)
    for i in range(count):
        value = re_widont.sub(replace, force_unicode(value))
    return value

re_widont_html = re.compile(r'([^<>\s])\s+([^<>\s]+\s*)(</?(?:address|blockquote|br|dd|div|dt|fieldset|form|h[1-6]|li|noscript|p|td|th)[^>]*>|$)', re.IGNORECASE)
def widont_html(value):
    """
    Adds an HTML non-breaking space between the final two words at the end of
    (and in sentences just outside of) block level tags to avoid "widowed"
    words.

    Examples:

    >>> print widont_html('<h2>Here is a simple  example  </h2> <p>Single</p>')
    <h2>Here is a simple&nbsp;example  </h2> <p>Single</p>

    >>> print widont_html('<p>test me<br /> out</p><h2>Ok?</h2>Not in a p<p title="test me">and this</p>')
    <p>test&nbsp;me<br /> out</p><h2>Ok?</h2>Not in a&nbsp;p<p title="test me">and&nbsp;this</p>

    >>> print widont_html('leading text  <p>test me out</p>  trailing text')
    leading&nbsp;text  <p>test me&nbsp;out</p>  trailing&nbsp;text
    """
    def replace(matchobj):
        return u'%s&nbsp;%s%s' % matchobj.groups()
    return re_widont_html.sub(replace, force_unicode(value))

register.filter(widont)
register.filter(widont_html)

def _test():
    import doctest
    doctest.testmod()

if __name__ == "__main__":
    _test()
