content: from __future__ import annotations
  
  import asyncio
  import os
  import re
  
  from ..datastructures import Headers
  from ..exceptions import SecurityError
  
  
  __all__ = ["read_request", "read_response"]
  
  MAX_NUM_HEADERS = int(os.environ.get("WEBSOCKETS_MAX_NUM_HEADERS", "128"))
  MAX_LINE_LENGTH = int(os.environ.get("WEBSOCKETS_MAX_LINE_LENGTH", "8192"))
  
  
  def d(value: bytes) -> str:
      """
      Decode a bytestring for interpolating into an error message.
  
      """
      return value.decode(errors="backslashreplace")
  
  
  # See https://datatracker.ietf.org/doc/html/rfc7230#appendix-B.
  
  # Regex for validating header names.
  
  _token_re = re.compile(rb"[-!#$%&\'*+.^_`|~0-9a-zA-Z]+")
  
  # Regex for validating header values.
  
  # We don't attempt to support obsolete line folding.
  
  # Include HTAB (\x09), SP (\x20), VCHAR (\x21-\x7e), obs-text (\x80-\xff).
  
  # The ABNF is complicated because it attempts to express that optional
  # whitespace is ignored. We strip whitespace and don't revalidate that.
  
  # See also https://www.rfc-editor.org/errata_search.php?rfc=7230&eid=4189
  
  _value_re = re.compile(rb"[\x09\x20-\x7e\x80-\xff]*")
  
  
  async def read_request(stream: asyncio.StreamReader) -> tuple[str, Headers]:
      """
      Read an HTTP/1.1 GET request and return ``(path, headers)``.
  
      ``path`` isn't URL-decoded or validated in any way.
  
      ``path`` and ``headers`` are expected to contain only ASCII characters.
      Other characters are represented with surrogate escapes.
  
      :func:`read_request` doesn't attempt to read the request body because
      WebSocket handshake requests don't have one. If the request contains a
      body, it may be read from ``stream`` after this coroutine returns.
  
      Args:
          stream: Input to read the request from.
  
      Raises:
          EOFError: If the connection is closed without a full HTTP request.
          SecurityError: If the request exceeds a security limit.
          ValueError: If the request isn't well formatted.
  
      """
      # https://datatracker.ietf.org/doc/html/rfc7230#section-3.1.1
  
      # Parsing is simple because fixed values are expected for method and
      # version and because path isn't checked. Since WebSocket software tends
      # to implement HTTP/1.1 strictly, there's little need for lenient parsing.
  
      try:
          request_line = await read_line(stream)
      except EOFError as exc:
          raise EOFError("connection closed while reading HTTP request line") from exc
  
      try:
          method, raw_path, version = request_line.split(b" ", 2)
      except ValueError:  # not enough values to unpack (expected 3, got 1-2)
          raise ValueError(f"invalid HTTP request line: {d(request_line)}") from None
  
      if method != b"GET":
          raise ValueError(f"unsupported HTTP method: {d(method)}")
      if version != b"HTTP/1.1":
          raise ValueError(f"unsupported HTTP version: {d(version)}")
      path = raw_path.decode("ascii", "surrogateescape")
  
      headers = await read_headers(stream)
  
      return path, headers
  
  
  async def read_response(stream: asyncio.StreamReader) -> tuple[int, str, Headers]:
      """
      Read an HTTP/1.1 response and return ``(status_code, reason, headers)``.
  
      ``reason`` and ``headers`` are expected to contain only ASCII characters.
      Other characters are represented with surrogate escapes.
  
      :func:`read_request` doesn't attempt to read the response body because
      WebSocket handshake responses don't have one. If the response contains a
      body, it may be read from ``stream`` after this coroutine returns.
  
      Args:
          stream: Input to read the response from.
  
      Raises:
          EOFError: If the connection is closed without a full HTTP response.
          SecurityError: If the response exceeds a security limit.
          ValueError: If the response isn't well formatted.
  
      """
      # https://datatracker.ietf.org/doc/html/rfc7230#section-3.1.2
  
      # As in read_request, parsing is simple because a fixed value is expected
      # for version, status_code is a 3-digit number, and reason can be ignored.
  
      try:
          status_line = await read_line(stream)
      except EOFError as exc:
          raise EOFError("connection closed while reading HTTP status line") from exc
  
      try:
          version, raw_status_code, raw_reason = status_line.split(b" ", 2)
      except ValueError:  # not enough values to unpack (expected 3, got 1-2)
          raise ValueError(f"invalid HTTP status line: {d(status_line)}") from None
  
      if version != b"HTTP/1.1":
          raise ValueError(f"unsupported HTTP version: {d(version)}")
      try:
          status_code = int(raw_status_code)
      except ValueError:  # invalid literal for int() with base 10
          raise ValueError(f"invalid HTTP status code: {d(raw_status_code)}") from None
      if not 100 <= status_code < 1000:
          raise ValueError(f"unsupported HTTP status code: {d(raw_status_code)}")
      if not _value_re.fullmatch(raw_reason):
          raise ValueError(f"invalid HTTP reason phrase: {d(raw_reason)}")
      reason = raw_reason.decode()
  
      headers = await read_headers(stream)
  
      return status_code, reason, headers
  
  
  async def read_headers(stream: asyncio.StreamReader) -> Headers:
      """
      Read HTTP headers from ``stream``.
  
      Non-ASCII characters are represented with surrogate escapes.
  
      """
      # https://datatracker.ietf.org/doc/html/rfc7230#section-3.2
  
      # We don't attempt to support obsolete line folding.
  
      headers = Headers()
      for _ in range(MAX_NUM_HEADERS + 1):
          try:
              line = await read_line(stream)
          except EOFError as exc:
              raise EOFError("connection closed while reading HTTP headers") from exc
          if line == b"":
              break
  
          try:
              raw_name, raw_value = line.split(b":", 1)
          except ValueError:  # not enough values to unpack (expected 2, got 1)
              raise ValueError(f"invalid HTTP header line: {d(line)}") from None
          if not _token_re.fullmatch(raw_name):
              raise ValueError(f"invalid HTTP header name: {d(raw_name)}")
          raw_value = raw_value.strip(b" \t")
          if not _value_re.fullmatch(raw_value):
              raise ValueError(f"invalid HTTP header value: {d(raw_value)}")
  
          name = raw_name.decode("ascii")  # guaranteed to be ASCII at this point
          value = raw_value.decode("ascii", "surrogateescape")
          headers[name] = value
  
      else:
          raise SecurityError("too many HTTP headers")
  
      return headers
  
  
  async def read_line(stream: asyncio.StreamReader) -> bytes:
      """
      Read a single line from ``stream``.
  
      CRLF is stripped from the return value.
  
      """
      # Security: this is bounded by the StreamReader's limit (default = 32 KiB).
      line = await stream.readline()
      # Security: this guarantees header values are small (hard-coded = 8 KiB)
      if len(line) > MAX_LINE_LENGTH:
          raise SecurityError("line too long")
      # Not mandatory but safe - https://datatracker.ietf.org/doc/html/rfc7230#section-3.5
      if not line.endswith(b"\r\n"):
          raise EOFError("line without CRLF")
      return line[:-2]
  