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"""
Content negotiation deals with selecting an appropriate renderer given the
incoming request. Typically this will be based on the request's Accept header.
"""
from __future__ import unicode_literals
from django.http import Http404
from rest_framework import HTTP_HEADER_ENCODING, exceptions
from rest_framework.settings import api_settings
from rest_framework.utils.mediatypes import (
_MediaType, media_type_matches, order_by_precedence
)
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.query_params.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.
media_type_wrapper = _MediaType(media_type)
if (
_MediaType(renderer.media_type).precedence >
media_type_wrapper.precedence
):
# Eg client requests '*/*'
# Accepted media type is 'application/json'
full_media_type = ';'.join(
(renderer.media_type,) +
tuple('{0}={1}'.format(
key, value.decode(HTTP_HEADER_ENCODING))
for key, value in media_type_wrapper.params.items()))
return renderer, full_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 tokenized list of media
type strings.
"""
header = request.META.get('HTTP_ACCEPT', '*/*')
return [token.strip() for token in header.split(',')]