1 files changed, 82 insertions, 0 deletions
diff --git a/rest_framework/negotiation.py b/rest_framework/negotiation.py
new file mode 100644
index 00000000..dae38477
--- /dev/null
+++ b/rest_framework/negotiation.py
@@ -0,0 +1,82 @@
+from django.http import Http404
+from rest_framework import exceptions
+from rest_framework.settings import api_settings
+from rest_framework.utils.mediatypes import order_by_precedence, media_type_matches
+
+
+class BaseContentNegotiation(object):
+    def select_parser(self, request, parsers):
+        raise NotImplementedError('.select_parser() must be implemented')
+
+    def select_renderer(self, request, renderers, format_suffix=None):
+        raise NotImplementedError('.select_renderer() must be implemented')
+
+
+class DefaultContentNegotiation(BaseContentNegotiation):
+    settings = api_settings
+
+    def select_parser(self, request, parsers):
+        """
+        Given a list of parsers and a media type, return the appropriate
+        parser to handle the incoming request.
+        """
+        for parser in parsers:
+            if media_type_matches(parser.media_type, request.content_type):
+                return parser
+        return None
+
+    def select_renderer(self, request, renderers, format_suffix=None):
+        """
+        Given a request and a list of renderers, return a two-tuple of:
+        (renderer, media type).
+        """
+        # Allow URL style format override.  eg. "?format=json
+        format_query_param = self.settings.URL_FORMAT_OVERRIDE
+        format = format_suffix or request.GET.get(format_query_param)
+
+        if format:
+            renderers = self.filter_renderers(renderers, format)
+
+        accepts = self.get_accept_list(request)
+
+        # Check the acceptable media types against each renderer,
+        # attempting more specific media types first
+        # NB. The inner loop here isn't as bad as it first looks :)
+        #     Worst case is we're looping over len(accept_list) * len(self.renderers)
+        for media_type_set in order_by_precedence(accepts):
+            for renderer in renderers:
+                for media_type in media_type_set:
+                    if media_type_matches(renderer.media_type, media_type):
+                        # Return the most specific media type as accepted.
+                        if len(renderer.media_type) > len(media_type):
+                            # Eg client requests '*/*'
+                            # Accepted media type is 'application/json'
+                            return renderer, renderer.media_type
+                        else:
+                            # Eg client requests 'application/json; indent=8'
+                            # Accepted media type is 'application/json; indent=8'
+                            return renderer, media_type
+
+        raise exceptions.NotAcceptable(available_renderers=renderers)
+
+    def filter_renderers(self, renderers, format):
+        """
+        If there is a '.json' style format suffix, filter the renderers
+        so that we only negotiation against those that accept that format.
+        """
+        renderers = [renderer for renderer in renderers
+                     if renderer.format == format]
+        if not renderers:
+            raise Http404
+        return renderers
+
+    def get_accept_list(self, request):
+        """
+        Given the incoming request, return a tokenised list of media
+        type strings.
+
+        Allows URL style accept override.  eg. "?accept=application/json"
+        """
+        header = request.META.get('HTTP_ACCEPT', '*/*')
+        header = request.GET.get(self.settings.URL_ACCEPT_OVERRIDE, header)
+        return [token.strip() for token in header.split(',')]