from django.core.exceptions import Http404, ObjectDoesNotExist
from django.core.template import Context, loader
from django.models.core import sites, contenttypes
from django.utils import httpwrappers

def shortcut(request, content_type_id, object_id):
    """Redirect to an object's page based on a content-type ID and an object ID"""
    # Look up the object, making sure it's got a get_absolute_url() function.
    try:
        content_type = contenttypes.get_object(pk=content_type_id)
        obj = content_type.get_object_for_this_type(pk=object_id)
    except ObjectDoesNotExist:
        raise Http404, "Content type %s object %s doesn't exist" % (content_type_id, object_id)
    try:
        absurl = obj.get_absolute_url()
    except AttributeError:
        raise Http404, "%s objects don't have get_absolute_url() methods" % content_type.name
    
    # Try to figure out the object's domain so we can do a cross-site redirect
    # if necessary

    # If the object actually defines a domain, we're done.
    if absurl.startswith('http://'):
        return httpwrappers.HttpResponseRedirect(absurl)

    object_domain = None
    
    # Next, look for an many-to-many relationship to sites
    if hasattr(obj, 'get_site_list'):
        site_list = obj.get_site_list()
        if site_list:
            object_domain = site_list[0].domain
   
    # Next, look for a many-to-one relationship to sites 
    elif hasattr(obj, 'get_site'):
        try:
            object_domain = obj.get_site().domain
        except sites.SiteDoesNotExist:
            pass

    # Then, fall back to the current site (if possible)
    else:
        try:
            object_domain = sites.get_current().domain
        except sites.SiteDoesNotExist:
            # Finally, give up and use a URL without the domain name
            return httpwrappers.HttpResponseRedirect(obj.get_absolute_url())
    return httpwrappers.HttpResponseRedirect('http://%s%s' % (object_domain, obj.get_absolute_url()))

def page_not_found(request):
    """
    Default 404 handler, which looks for the requested URL in the redirects
    table, redirects if found, and displays 404 page if not redirected.

    Templates: `404`
    Context: None
    """
    from django.models.core import redirects
    from django.conf.settings import APPEND_SLASH, SITE_ID
    path = request.get_full_path()
    try:
        r = redirects.get_object(site__id__exact=SITE_ID, old_path__exact=path)
    except redirects.RedirectDoesNotExist:
        r = None
    if r is None and APPEND_SLASH:
        # Try removing the trailing slash.
        try:
            r = redirects.get_object(site__id__exact=SITE_ID, old_path__exact=path[:path.rfind('/')]+path[path.rfind('/')+1:])
        except redirects.RedirectDoesNotExist:
            pass
    if r is not None:
        if r == '':
            return httpwrappers.HttpResponseGone()
        return httpwrappers.HttpResponseRedirect(r.new_path)
    t = loader.get_template('404')
    c = Context()
    return httpwrappers.HttpResponseNotFound(t.render(c))

def server_error(request):
    """
    500 Error handler

    Templates: `500`
    Context: None
    """
    t = loader.get_template('500')
    c = Context()
    return httpwrappers.HttpResponseServerError(t.render(c))