text: # Copyright 2014-2016 OpenMarket Ltd
  # Copyright 2018 New Vector Ltd
  #
  # 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.
  import re
  from typing import Union
  
  from twisted.internet import address, task
  from twisted.web.client import FileBodyProducer
  from twisted.web.iweb import IRequest
  
  from synapse.api.errors import SynapseError
  
  
  class RequestTimedOutError(SynapseError):
      """Exception representing timeout of an outbound request"""
  
      def __init__(self, msg):
          super().__init__(504, msg)
  
  
  ACCESS_TOKEN_RE = re.compile(r"(\?.*access(_|%5[Ff])token=)[^&]*(.*)$")
  CLIENT_SECRET_RE = re.compile(r"(\?.*client(_|%5[Ff])secret=)[^&]*(.*)$")
  
  
  def redact_uri(uri):
      """Strips sensitive information from the uri replaces with <redacted>"""
      uri = ACCESS_TOKEN_RE.sub(r"\1<redacted>\3", uri)
      return CLIENT_SECRET_RE.sub(r"\1<redacted>\3", uri)
  
  
  class QuieterFileBodyProducer(FileBodyProducer):
      """Wrapper for FileBodyProducer that avoids CRITICAL errors when the connection drops.
  
      Workaround for https://github.com/matrix-org/synapse/issues/4003 /
      https://twistedmatrix.com/trac/ticket/6528
      """
  
      def stopProducing(self):
          try:
              FileBodyProducer.stopProducing(self)
          except task.TaskStopped:
              pass
  
  
  def get_request_uri(request: IRequest) -> bytes:
      """Return the full URI that was requested by the client"""
      return b"%s://%s%s" % (
          b"https" if request.isSecure() else b"http",
          _get_requested_host(request),
          # despite its name, "request.uri" is only the path and query-string.
          request.uri,
      )
  
  
  def _get_requested_host(request: IRequest) -> bytes:
      hostname = request.getHeader(b"host")
      if hostname:
          return hostname
  
      # no Host header, use the address/port that the request arrived on
      host: Union[address.IPv4Address, address.IPv6Address] = request.getHost()
  
      hostname = host.host.encode("ascii")
  
      if request.isSecure() and host.port == 443:
          # default port for https
          return hostname
  
      if not request.isSecure() and host.port == 80:
          # default port for http
          return hostname
  
      return b"%s:%i" % (
          hostname,
          host.port,
      )
  
  
  def get_request_user_agent(request: IRequest, default: str = "") -> str:
      """Return the last User-Agent header, or the given default."""
      # There could be raw utf-8 bytes in the User-Agent header.
  
      # N.B. if you don't do this, the logger explodes cryptically
      # with maximum recursion trying to log errors about
      # the charset problem.
      # c.f. https://github.com/matrix-org/synapse/issues/3471
  
      h = request.getHeader(b"User-Agent")
      return h.decode("ascii", "replace") if h else default
  