from django.template import Library, Node
from django.db.models import get_model
from django.db.models import Q
from datetime import datetime

register = Library()

class UpcommingContentNode(Node):
    def __init__(self, model, fieldnames, num, varname):
        self.num, self.varname = num, varname
        self.fieldnames = fieldnames.split('|')
        self.model = get_model(*model.split('.'))

    def render(self, context):
        now = datetime.now()
        # do an OR lookup with the given fieldnames
        query = Q(**{'%s__gte' % self.fieldnames.pop(0): now})
        for fieldname in self.fieldnames:
            query = query | Q(**{'%s__gte' % fieldname: now})
        context[self.varname] = self.model._default_manager.filter(query)[:self.num]
        return''

def get_upcoming(parser, token):
    """
    Usage:
    {% get_upcoming app.Model fieldname(s) howmeny as variablename %}
    {% get_upcoming events.Event start_date 5 as upcoming_events %}
    {% get_upcoming events.Event start_date|end_date 5 as upcoming_events %}
    """
    bits = token.contents.split()
    if len(bits) != 6:
        raise TemplateSyntaxError, "'%s' tag takes exactly four arguments" % bits[0]
    if bits[4] != 'as':
        raise TemplateSyntaxError, "Second last argument to '%s' tag must be 'as'" % bits[0]
    return UpcommingContentNode(bits[1], bits[2], bits[3], bits[5])
get_upcoming = register.tag(get_upcoming)