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# Copyright 2020 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Implementation of the metadata abstraction for gRPC Asyncio Python."""
from collections import OrderedDict
from collections import abc
from typing import Any, Iterator, List, Tuple, Union
MetadataKey = str
MetadataValue = Union[str, bytes]
class Metadata(abc.Mapping):
"""Metadata abstraction for the asynchronous calls and interceptors.
The metadata is a mapping from str -> List[str]
Traits
* Multiple entries are allowed for the same key
* The order of the values by key is preserved
* Getting by an element by key, retrieves the first mapped value
* Supports an immutable view of the data
* Allows partial mutation on the data without recreating the new object from scratch.
"""
def __init__(self, *args: Tuple[MetadataKey, MetadataValue]) -> None:
self._metadata = OrderedDict()
for md_key, md_value in args:
self.add(md_key, md_value)
@classmethod
def from_tuple(cls, raw_metadata: tuple):
if raw_metadata:
return cls(*raw_metadata)
return cls()
def add(self, key: MetadataKey, value: MetadataValue) -> None:
self._metadata.setdefault(key, [])
self._metadata[key].append(value)
def __len__(self) -> int:
"""Return the total number of elements that there are in the metadata,
including multiple values for the same key.
"""
return sum(map(len, self._metadata.values()))
def __getitem__(self, key: MetadataKey) -> MetadataValue:
"""When calling <metadata>[<key>], the first element of all those
mapped for <key> is returned.
"""
try:
return self._metadata[key][0]
except (ValueError, IndexError) as e:
raise KeyError("{0!r}".format(key)) from e
def __setitem__(self, key: MetadataKey, value: MetadataValue) -> None:
"""Calling metadata[<key>] = <value>
Maps <value> to the first instance of <key>.
"""
if key not in self:
self._metadata[key] = [value]
else:
current_values = self.get_all(key)
self._metadata[key] = [value, *current_values[1:]]
def __delitem__(self, key: MetadataKey) -> None:
"""``del metadata[<key>]`` deletes the first mapping for <key>."""
current_values = self.get_all(key)
if not current_values:
raise KeyError(repr(key))
self._metadata[key] = current_values[1:]
def delete_all(self, key: MetadataKey) -> None:
"""Delete all mappings for <key>."""
del self._metadata[key]
def __iter__(self) -> Iterator[Tuple[MetadataKey, MetadataValue]]:
for key, values in self._metadata.items():
for value in values:
yield (key, value)
def get_all(self, key: MetadataKey) -> List[MetadataValue]:
"""For compatibility with other Metadata abstraction objects (like in Java),
this would return all items under the desired <key>.
"""
return self._metadata.get(key, [])
def set_all(self, key: MetadataKey, values: List[MetadataValue]) -> None:
self._metadata[key] = values
def __contains__(self, key: MetadataKey) -> bool:
return key in self._metadata
def __eq__(self, other: Any) -> bool:
if isinstance(other, self.__class__):
return self._metadata == other._metadata
if isinstance(other, tuple):
return tuple(self) == other
return NotImplemented # pytype: disable=bad-return-type
def __add__(self, other: Any) -> 'Metadata':
if isinstance(other, self.__class__):
return Metadata(*(tuple(self) + tuple(other)))
if isinstance(other, tuple):
return Metadata(*(tuple(self) + other))
return NotImplemented # pytype: disable=bad-return-type
def __repr__(self) -> str:
view = tuple(self)
return "{0}({1!r})".format(self.__class__.__name__, view)
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