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negotiation.py
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negotiation.py
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# This code is a partial and adapted copy of
# https://github.com/nickstenning/negotiate
#
# Copyright 2012-2013 Nick Stenning
# 2019 The Software Heritage developers
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
#
from collections import defaultdict
from decorator import decorator
from inspect import getcallargs
from typing import Any, List, Optional
class FormatterNotFound(Exception):
pass
class Formatter:
format = None # type: Optional[str]
mimetypes = [] # type: List[Any]
def __init__(self, request_mimetype=None):
if request_mimetype is None or request_mimetype not in self.mimetypes:
try:
self.response_mimetype = self.mimetypes[0]
except IndexError:
raise NotImplementedError(
"%s.mimetypes should be a non-empty list" %
self.__class__.__name__)
else:
self.response_mimetype = request_mimetype
def configure(self):
pass
def render(self, obj):
raise NotImplementedError(
"render() should be implemented by Formatter subclasses")
def __call__(self, obj):
return self._make_response(
self.render(obj), content_type=self.response_mimetype)
def _make_response(self, body, content_type):
raise NotImplementedError(
"_make_response() should be implemented by "
"framework-specific subclasses of Formatter"
)
class Negotiator:
def __init__(self, func):
self.func = func
self._formatters = []
self._formatters_by_format = defaultdict(list)
self._formatters_by_mimetype = defaultdict(list)
def __call__(self, *args, **kwargs):
result = self.func(*args, **kwargs)
format = getcallargs(self.func, *args, **kwargs).get('format')
mimetype = self.best_mimetype()
try:
formatter = self.get_formatter(format, mimetype)
except FormatterNotFound as e:
return self._abort(404, str(e))
return formatter(result)
def register_formatter(self, formatter, *args, **kwargs):
self._formatters.append(formatter)
self._formatters_by_format[formatter.format].append(
(formatter, args, kwargs))
for mimetype in formatter.mimetypes:
self._formatters_by_mimetype[mimetype].append(
(formatter, args, kwargs))
def get_formatter(self, format=None, mimetype=None):
if format is None and mimetype is None:
raise TypeError(
"get_formatter expects one of the 'format' or 'mimetype' "
"kwargs to be set")
if format is not None:
try:
# the first added will be the most specific
formatter_cls, args, kwargs = (
self._formatters_by_format[format][0])
except IndexError:
raise FormatterNotFound(
"Formatter for format '%s' not found!" % format)
elif mimetype is not None:
try:
# the first added will be the most specific
formatter_cls, args, kwargs = (
self._formatters_by_mimetype[mimetype][0])
except IndexError:
raise FormatterNotFound(
"Formatter for mimetype '%s' not found!" % mimetype)
formatter = formatter_cls(request_mimetype=mimetype)
formatter.configure(*args, **kwargs)
return formatter
@property
def accept_mimetypes(self):
return [m for f in self._formatters for m in f.mimetypes]
def best_mimetype(self):
raise NotImplementedError(
"best_mimetype() should be implemented in "
"framework-specific subclasses of Negotiator"
)
def _abort(self, status_code, err=None):
raise NotImplementedError(
"_abort() should be implemented in framework-specific "
"subclasses of Negotiator"
)
def negotiate(negotiator_cls, formatter_cls, *args, **kwargs):
def _negotiate(f, *args, **kwargs):
return f.negotiator(*args, **kwargs)
def decorate(f):
if not hasattr(f, 'negotiator'):
f.negotiator = negotiator_cls(f)
f.negotiator.register_formatter(formatter_cls, *args, **kwargs)
return decorator(_negotiate, f)
return decorate

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