Move the code from Site.find_for_request() to separate module (#3500)

Create ``sites.get_site_for_hostname(hostname, port)`` for better
reusability.

Co-authored with @mikedingjan

wagtail/wagtailcore/models.py

@@ -15,7 +15,7 @@ from django.core.handlers.base import BaseHandler
 from django.core.handlers.wsgi import WSGIRequest
 from django.core.urlresolvers import reverse
 from django.db import connection, models, transaction
-from django.db.models import Case, IntegerField, Q, When
+from django.db.models import Q
 from django.http import Http404
 from django.template.response import TemplateResponse
 # Must be imported from Django so we get the new implementation of with_metaclass
@@ -32,6 +32,7 @@ from treebeard.mp_tree import MP_Node
 from wagtail.utils.compat import user_is_authenticated
 from wagtail.wagtailcore.query import PageQuerySet, TreeQuerySet
 from wagtail.wagtailcore.signals import page_published, page_unpublished
+from wagtail.wagtailcore.sites import get_site_for_hostname
 from wagtail.wagtailcore.url_routing import RouteResult
 from wagtail.wagtailcore.utils import (
     WAGTAIL_APPEND_SLASH, camelcase_to_underscore, resolve_model_string)
@@ -42,12 +43,6 @@ logger = logging.getLogger('wagtail.core')
 PAGE_TEMPLATE_VAR = 'page'
 
 
-MATCH_HOSTNAME_PORT = 0
-MATCH_HOSTNAME_DEFAULT = 1
-MATCH_DEFAULT = 2
-MATCH_HOSTNAME = 3
-
-
 class SiteManager(models.Manager):
     def get_by_natural_key(self, hostname, port):
         return self.get(hostname=hostname, port=port)
@@ -129,42 +124,7 @@ class Site(models.Model):
         except (AttributeError, KeyError):
             port = request.META.get('SERVER_PORT')
 
-        sites = list(Site.objects.annotate(match=Case(
-            # annotate the results by best choice descending
-
-            # put exact hostname+port match first
-            When(hostname=hostname, port=port, then=MATCH_HOSTNAME_PORT),
-
-            # then put hostname+default (better than just hostname or just default)
-            When(hostname=hostname, is_default_site=True, then=MATCH_HOSTNAME_DEFAULT),
-
-            # then match default with different hostname. there is only ever
-            # one default, so order it above (possibly multiple) hostname
-            # matches so we can use sites[0] below to access it
-            When(is_default_site=True, then=MATCH_DEFAULT),
-
-            # because of the filter below, if it's not default then its a hostname match
-            default=MATCH_HOSTNAME,
-
-            output_field=IntegerField(),
-        )).filter(Q(hostname=hostname) | Q(is_default_site=True)).order_by(
-            'match'
-        ).select_related(
-            'root_page'
-        ))
-
-        if sites:
-            # if theres a unique match or hostname (with port or default) match
-            if len(sites) == 1 or sites[0].match in (MATCH_HOSTNAME_PORT, MATCH_HOSTNAME_DEFAULT):
-                return sites[0]
-
-            # if there is a default match with a different hostname, see if
-            # there are many hostname matches. if only 1 then use that instead
-            # otherwise we use the default
-            if sites[0].match == MATCH_DEFAULT:
-                return sites[len(sites) == 2]
-
-        raise Site.DoesNotExist()
+        return get_site_for_hostname(hostname, port)
 
     @property
     def root_url(self):

wagtail/wagtailcore/sites.py

@@ -0,0 +1,52 @@
+from __future__ import absolute_import, unicode_literals
+
+from django.apps import apps
+from django.db.models import Case, IntegerField, Q, When
+
+
+MATCH_HOSTNAME_PORT = 0
+MATCH_HOSTNAME_DEFAULT = 1
+MATCH_DEFAULT = 2
+MATCH_HOSTNAME = 3
+
+
+def get_site_for_hostname(hostname, port):
+    """Return the wagtailcore.Site object for the given hostname and port."""
+    Site = apps.get_model('wagtailcore.Site')
+
+    sites = list(Site.objects.annotate(match=Case(
+        # annotate the results by best choice descending
+
+        # put exact hostname+port match first
+        When(hostname=hostname, port=port, then=MATCH_HOSTNAME_PORT),
+
+        # then put hostname+default (better than just hostname or just default)
+        When(hostname=hostname, is_default_site=True, then=MATCH_HOSTNAME_DEFAULT),
+
+        # then match default with different hostname. there is only ever
+        # one default, so order it above (possibly multiple) hostname
+        # matches so we can use sites[0] below to access it
+        When(is_default_site=True, then=MATCH_DEFAULT),
+
+        # because of the filter below, if it's not default then its a hostname match
+        default=MATCH_HOSTNAME,
+
+        output_field=IntegerField(),
+    )).filter(Q(hostname=hostname) | Q(is_default_site=True)).order_by(
+        'match'
+    ).select_related(
+        'root_page'
+    ))
+
+    if sites:
+        # if theres a unique match or hostname (with port or default) match
+        if len(sites) == 1 or sites[0].match in (MATCH_HOSTNAME_PORT, MATCH_HOSTNAME_DEFAULT):
+            return sites[0]
+
+        # if there is a default match with a different hostname, see if
+        # there are many hostname matches. if only 1 then use that instead
+        # otherwise we use the default
+        if sites[0].match == MATCH_DEFAULT:
+            return sites[len(sites) == 2]
+
+    raise Site.DoesNotExist()