{% ifthis FOO isoneof BAR BAZ ... %}

class IfThisNode(template.Node):
    '''
    Like {% if %} but checks if the first value is equal to any of the rest.

    Example:

        {% ifthis username isoneof 'steve' 'nick' var_with_other_username %}
            ...
        {% else %}
            ...
        {% endifthis %}
    '''
    def __init__(self, var, items, nodelist_true, nodelist_false, case_sensitive):
        self.var, self.items = var, items
        self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
        self.case_sensitive = case_sensitive

    def __str__(self):
        return "<IfNode>"

    def render(self, context):
        def _parse_var(var):
            if var.startswith('\'"'):
                return var[1:-1]
            else:
                return template.resolve_variable(var, context)

        var = _parse_var(self.var)
        items = map(_parse_var, self.items)

        if not self.case_sensitive:
            try:
                var = var.lower()
            except AttributeError:
                pass
            
            for n, item in enumerate(items):
                try:
                    items[n] = item.lower()
                except AttributeError:
                    pass

        if var in items:
            return self.nodelist_true.render(context)
        else:
            return self.nodelist_false.render(context)

def ifthis(parser, token, case_sensitive=True):
    bits = token.split_contents()
    if len(bits) < 4:
        raise template.TemplateSyntaxError, (
            "%r takes at least two arguments" % bits[0]
        )

    if bits[2] != 'isoneof':
        raise template.TemplateSyntaxError, (
            "%r must be of the format {% %r FOO isoneof BAR BAZ ... %}"
            % (bits[0], bits[0])
        )

    end_tag = 'end' + bits[0]
    nodelist_true = parser.parse(('else', end_tag))
    token = parser.next_token()

    if token.contents == 'else':
        nodelist_false = parser.parse((end_tag,))
        parser.delete_first_token()
    else:
        nodelist_false = template.NodeList()

    return IfThisNode(
        bits[1], bits[3:],
        nodelist_true, nodelist_false, case_sensitive
    )

register.tag('ifthis', ifthis)
register.tag('insensitiveifthis', lambda p, t: ifthis(p, t, False))