diff -r 57b4279d8c4e -r 03e267d67478 app/django/middleware/common.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/middleware/common.py	Fri Jul 18 18:22:23 2008 +0000
@@ -0,0 +1,134 @@
+import md5
+import re
+
+from django.conf import settings
+from django import http
+from django.core.mail import mail_managers
+from django.utils.http import urlquote
+from django.core import urlresolvers
+
+class CommonMiddleware(object):
+    """
+    "Common" middleware for taking care of some basic operations:
+
+        - Forbids access to User-Agents in settings.DISALLOWED_USER_AGENTS
+
+        - URL rewriting: Based on the APPEND_SLASH and PREPEND_WWW settings,
+          this middleware appends missing slashes and/or prepends missing
+          "www."s.
+
+            - If APPEND_SLASH is set and the initial URL doesn't end with a
+              slash, and it is not found in urlpatterns, a new URL is formed by
+              appending a slash at the end. If this new URL is found in
+              urlpatterns, then an HTTP-redirect is returned to this new URL;
+              otherwise the initial URL is processed as usual. 
+
+        - ETags: If the USE_ETAGS setting is set, ETags will be calculated from
+          the entire page content and Not Modified responses will be returned
+          appropriately.
+    """
+
+    def process_request(self, request):
+        """
+        Check for denied User-Agents and rewrite the URL based on
+        settings.APPEND_SLASH and settings.PREPEND_WWW
+        """
+
+        # Check for denied User-Agents
+        if 'HTTP_USER_AGENT' in request.META:
+            for user_agent_regex in settings.DISALLOWED_USER_AGENTS:
+                if user_agent_regex.search(request.META['HTTP_USER_AGENT']):
+                    return http.HttpResponseForbidden('<h1>Forbidden</h1>')
+
+        # Check for a redirect based on settings.APPEND_SLASH
+        # and settings.PREPEND_WWW
+        host = request.get_host()
+        old_url = [host, request.path]
+        new_url = old_url[:]
+
+        if (settings.PREPEND_WWW and old_url[0] and
+                not old_url[0].startswith('www.')):
+            new_url[0] = 'www.' + old_url[0]
+
+        # Append a slash if APPEND_SLASH is set and the URL doesn't have a
+        # trailing slash and there is no pattern for the current path
+        if settings.APPEND_SLASH and (not old_url[1].endswith('/')):
+            try:
+                urlresolvers.resolve(request.path)
+            except urlresolvers.Resolver404:
+                new_url[1] = new_url[1] + '/'
+                if settings.DEBUG and request.method == 'POST':
+                    raise RuntimeError, (""
+                    "You called this URL via POST, but the URL doesn't end "
+                    "in a slash and you have APPEND_SLASH set. Django can't "
+                    "redirect to the slash URL while maintaining POST data. "
+                    "Change your form to point to %s%s (note the trailing "
+                    "slash), or set APPEND_SLASH=False in your Django "
+                    "settings.") % (new_url[0], new_url[1])
+
+        if new_url != old_url:
+            # Redirect if the target url exists
+            try:
+                urlresolvers.resolve(new_url[1])
+            except urlresolvers.Resolver404:
+                pass
+            else:
+                if new_url[0]:
+                    newurl = "%s://%s%s" % (
+                        request.is_secure() and 'https' or 'http',
+                        new_url[0], urlquote(new_url[1]))
+                else:
+                    newurl = urlquote(new_url[1])
+                if request.GET:
+                    newurl += '?' + request.GET.urlencode()
+                return http.HttpResponsePermanentRedirect(newurl)
+
+        return None
+
+    def process_response(self, request, response):
+        "Check for a flat page (for 404s) and calculate the Etag, if needed."
+        if response.status_code == 404:
+            if settings.SEND_BROKEN_LINK_EMAILS:
+                # If the referrer was from an internal link or a non-search-engine site,
+                # send a note to the managers.
+                domain = request.get_host()
+                referer = request.META.get('HTTP_REFERER', None)
+                is_internal = _is_internal_request(domain, referer)
+                path = request.get_full_path()
+                if referer and not _is_ignorable_404(path) and (is_internal or '?' not in referer):
+                    ua = request.META.get('HTTP_USER_AGENT', '<none>')
+                    ip = request.META.get('REMOTE_ADDR', '<none>')
+                    mail_managers("Broken %slink on %s" % ((is_internal and 'INTERNAL ' or ''), domain),
+                        "Referrer: %s\nRequested URL: %s\nUser agent: %s\nIP address: %s\n" \
+                                  % (referer, request.get_full_path(), ua, ip))
+                return response
+
+        # Use ETags, if requested.
+        if settings.USE_ETAGS:
+            if response.has_header('ETag'):
+                etag = response['ETag']
+            else:
+                etag = md5.new(response.content).hexdigest()
+            if response.status_code >= 200 and response.status_code < 300 and request.META.get('HTTP_IF_NONE_MATCH') == etag:
+                cookies = response.cookies
+                response = http.HttpResponseNotModified()
+                response.cookies = cookies
+            else:
+                response['ETag'] = etag
+
+        return response
+
+def _is_ignorable_404(uri):
+    "Returns True if a 404 at the given URL *shouldn't* notify the site managers"
+    for start in settings.IGNORABLE_404_STARTS:
+        if uri.startswith(start):
+            return True
+    for end in settings.IGNORABLE_404_ENDS:
+        if uri.endswith(end):
+            return True
+    return False
+
+def _is_internal_request(domain, referer):
+    "Return true if the referring URL is the same domain as the current request"
+    # Different subdomains are treated as different domains.
+    return referer is not None and re.match("^https?://%s/" % re.escape(domain), referer)