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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 inspect import getcallargs
from typing import Any, Callable, DefaultDict, List, NoReturn, Optional, Type
from decorator import decorator
from requests import Response
class FormatterNotFound(Exception):
pass
class Formatter:
format: Optional[str] = None
mimetypes: List[str] = []
def __init__(self, request_mimetype: Optional[str] = None) -> 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) -> None:
pass
def render(self, obj: Any) -> bytes:
raise NotImplementedError(
"render() should be implemented by Formatter subclasses"
)
def __call__(self, obj: Any) -> Response:
return self._make_response(
self.render(obj), content_type=self.response_mimetype
)
def _make_response(self, body: bytes, content_type: str) -> Response:
raise NotImplementedError(
"_make_response() should be implemented by "
"framework-specific subclasses of Formatter"
)
class Negotiator:
def __init__(self, func: Callable[..., Any]) -> None:
self.func = func
self._formatters: List[Type[Formatter]] = []
self._formatters_by_format: DefaultDict = defaultdict(list)
self._formatters_by_mimetype: DefaultDict = defaultdict(list)
def __call__(self, *args, **kwargs) -> Response:
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: Type[Formatter], *args, **kwargs) -> None:
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: Optional[str] = None, mimetype: Optional[str] = None
) -> Formatter:
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) -> List[str]:
return [m for f in self._formatters for m in f.mimetypes]
def best_mimetype(self) -> str:
raise NotImplementedError(
"best_mimetype() should be implemented in "
"framework-specific subclasses of Negotiator"
)
def _abort(self, status_code: int, err: Optional[str] = None) -> NoReturn:
raise NotImplementedError(
"_abort() should be implemented in framework-specific "
"subclasses of Negotiator"
)
def negotiate(
negotiator_cls: Type[Negotiator], formatter_cls: Type[Formatter], *args, **kwargs
) -> Callable:
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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