From 0c8a30e61d494b2ec7ee75e5928f6f9d72a31ae4 Mon Sep 17 00:00:00 2001
From: Nathan Yergler <nathan@yergler.net>
Date: Sun, 4 Sep 2011 18:15:32 -0700
Subject: [PATCH] Issue 569: Initial framework for application middleware.

---
 mediagoblin/app.py                 | 28 +++++++++++++++++++++++-----
 mediagoblin/middleware/__init__.py | 19 +++++++++++++++++++
 mediagoblin/middleware/noop.py     | 26 ++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 5 deletions(-)
 create mode 100644 mediagoblin/middleware/__init__.py
 create mode 100644 mediagoblin/middleware/noop.py

diff --git a/mediagoblin/app.py b/mediagoblin/app.py
index dff61750..45b5e3ce 100644
--- a/mediagoblin/app.py
+++ b/mediagoblin/app.py
@@ -20,7 +20,7 @@ import urllib
 import routes
 from webob import Request, exc
 
-from mediagoblin import routing, util
+from mediagoblin import routing, util, middleware
 from mediagoblin.mg_globals import setup_globals
 from mediagoblin.init.celery import setup_celery_from_config
 from mediagoblin.init import (get_jinja_loader, get_staticdirector,
@@ -61,7 +61,7 @@ class MediaGoblinApp(object):
         # Get the template environment
         self.template_loader = get_jinja_loader(
             app_config.get('user_template_path'))
-        
+
         # Set up storage systems
         self.public_store, self.queue_store = setup_storage()
 
@@ -94,11 +94,22 @@ class MediaGoblinApp(object):
         # matters in always eager mode :)
         setup_workbench()
 
+        # instantiate application middleware
+        self.middleware = [util.import_component(m)(self)
+                           for m in middleware.ENABLED_MIDDLEWARE]
+
+
     def __call__(self, environ, start_response):
         request = Request(environ)
-        path_info = request.path_info
+
+        # pass the request through our middleware classes
+        for m in self.middleware:
+            response = m.process_request(request)
+            if response is not None:
+                return response(environ, start_response)
 
         ## Routing / controller loading stuff
+        path_info = request.path_info
         route_match = self.routing.match(path_info)
 
         ## Attach utilities to the request object
@@ -110,7 +121,7 @@ class MediaGoblinApp(object):
         # Also attach a few utilities from request.app for convenience?
         request.app = self
         request.locale = util.get_locale_from_request(request)
-            
+
         request.template_env = util.get_jinja_env(
             self.template_loader, request.locale)
         request.db = self.db
@@ -139,7 +150,14 @@ class MediaGoblinApp(object):
         controller = util.import_component(route_match['controller'])
         request.start_response = start_response
 
-        return controller(request)(environ, start_response)
+        # get the response from the controller
+        response = controller(request)
+
+        # pass the response through the middleware
+        for m in self.middleware[::-1]:
+            m.process_response(request, response)
+
+        return response(environ, start_response)
 
 
 def paste_app_factory(global_config, **app_config):
diff --git a/mediagoblin/middleware/__init__.py b/mediagoblin/middleware/__init__.py
new file mode 100644
index 00000000..586debbf
--- /dev/null
+++ b/mediagoblin/middleware/__init__.py
@@ -0,0 +1,19 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+ENABLED_MIDDLEWARE = (
+    'mediagoblin.middleware.noop:NoOpMiddleware',
+    )
diff --git a/mediagoblin/middleware/noop.py b/mediagoblin/middleware/noop.py
new file mode 100644
index 00000000..28380232
--- /dev/null
+++ b/mediagoblin/middleware/noop.py
@@ -0,0 +1,26 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+class NoOpMiddleware(object):
+
+    def __init__(self, mg_app):
+        self.app = mg_app
+
+    def process_request(self, request):
+        pass
+
+    def process_response(self, request, response):
+        pass
-- 
2.25.1