from django.core.exceptions import ObjectDoesNotExist

from django.template import Context, RequestContext, loader

from django.contrib.contenttypes.models import ContentType

from django.contrib.sites.models import Site

from django import http

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 = ContentType.objects.get(pk=content_type_id)

        obj = content_type.get_object_for_this_type(pk=object_id)

    except ObjectDoesNotExist:

        raise http.Http404, "Content type %s object %s doesn't exist" % (content_type_id, object_id)

    try:

        absurl = obj.get_absolute_url()

    except AttributeError:

        raise http.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://') or absurl.startswith('https://'):

        return http.HttpResponseRedirect(absurl)

    object_domain = None

    # Otherwise, we need to introspect the object's relationships for a

    # relation to the Site object

    opts = obj._meta

    # First, look for an many-to-many relationship to sites

    for field in opts.many_to_many:

        if field.rel.to is Site:

            try:

                object_domain = getattr(obj, field.name).all()[0].domain

            except IndexError:

                pass

            if object_domain is not None:

                break

    # Next look for a many-to-one relationship to site

    if object_domain is None:

        for field in obj._meta.fields:

            if field.rel and field.rel.to is Site:

                try:

                    object_domain = getattr(obj, field.name).domain

                except Site.DoesNotExist:

                    pass

                if object_domain is not None:

                    break

    # Fall back to the current site (if possible)

    if object_domain is None:

        try:

            object_domain = Site.objects.get_current().domain

        except Site.DoesNotExist:

            pass

    # If all that malarkey found an object domain, use it; otherwise fall back

    # to whatever get_absolute_url() returned.

    if object_domain is not None:

        protocol = request.is_secure() and 'https' or 'http'

        return http.HttpResponseRedirect('%s://%s%s' % (protocol, object_domain, absurl))

    else:

        return http.HttpResponseRedirect(absurl)

def page_not_found(request, template_name='404.html'):

    """

    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.html`

    Context:

        request_path

            The path of the requested URL (e.g., '/app/pages/bad_page/')

    """

    t = loader.get_template(template_name) # You need to create a 404.html template.

    return http.HttpResponseNotFound(t.render(RequestContext(request, {'request_path': request.path})))

def server_error(request, template_name='500.html'):

    """

    500 error handler.

    Templates: `500.html`

    Context: None

    """

    t = loader.get_template(template_name) # You need to create a 500.html template.

    return http.HttpResponseServerError(t.render(Context({})))