httputil.py

#
# Copyright 2009 Facebook
#
# 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.

"""HTTP utility code shared by clients and servers.

This module also defines the `HTTPServerRequest` class which is exposed
via `tornado.web.RequestHandler.request`.
"""

import calendar
import collections
import copy
import datetime
import email.utils
from http.client import responses
import http.cookies
import re
from ssl import SSLError
import time
import unicodedata
from urllib.parse import urlencode, urlparse, urlunparse, parse_qsl

from tornado.escape import native_str, parse_qs_bytes, utf8
from tornado.log import gen_log
from tornado.util import ObjectDict, unicode_type


# responses is unused in this file, but we re-export it to other files.
# Reference it so pyflakes doesn't complain.
responses

import typing
from typing import (
    Tuple,
    Iterable,
    List,
    Mapping,
    Iterator,
    Dict,
    Union,
    Optional,
    Awaitable,
    Generator,
    AnyStr,
)

if typing.TYPE_CHECKING:
    from typing import Deque  # noqa: F401
    from asyncio import Future  # noqa: F401
    import unittest  # noqa: F401


# RFC 7230 section 3.5: a recipient MAY recognize a single LF as a line
# terminator and ignore any preceding CR.
_CRLF_RE = re.compile(r"\r?\n")


class _NormalizedHeaderCache(dict):
    """Dynamic cached mapping of header names to Http-Header-Case.

    Implemented as a dict subclass so that cache hits are as fast as a
    normal dict lookup, without the overhead of a python function
    call.

    >>> normalized_headers = _NormalizedHeaderCache(10)
    >>> normalized_headers["coNtent-TYPE"]
    'Content-Type'
    """

    def __init__(self, size: int) -> None:
        super(_NormalizedHeaderCache, self).__init__()
        self.size = size
        self.queue = collections.deque()  # type: Deque[str]

    def __missing__(self, key: str) -> str:
        normalized = "-".join([w.capitalize() for w in key.split("-")])
        self[key] = normalized
        self.queue.append(key)
        if len(self.queue) > self.size:
            # Limit the size of the cache.  LRU would be better, but this
            # simpler approach should be fine.  In Python 2.7+ we could
            # use OrderedDict (or in 3.2+, @functools.lru_cache).
            old_key = self.queue.popleft()
            del self[old_key]
        return normalized


_normalized_headers = _NormalizedHeaderCache(1000)


class HTTPHeaders(collections.abc.MutableMapping):
    """A dictionary that maintains ``Http-Header-Case`` for all keys.

    Supports multiple values per key via a pair of new methods,
    `add()` and `get_list()`.  The regular dictionary interface
    returns a single value per key, with multiple values joined by a
    comma.

    >>> h = HTTPHeaders({"content-type": "text/html"})
    >>> list(h.keys())
    ['Content-Type']
    >>> h["Content-Type"]
    'text/html'

    >>> h.add("Set-Cookie", "A=B")
    >>> h.add("Set-Cookie", "C=D")
    >>> h["set-cookie"]
    'A=B,C=D'
    >>> h.get_list("set-cookie")
    ['A=B', 'C=D']

    >>> for (k,v) in sorted(h.get_all()):
    ...    print('%s: %s' % (k,v))
    ...
    Content-Type: text/html
    Set-Cookie: A=B
    Set-Cookie: C=D
    """

    @typing.overload
    def __init__(self, __arg: Mapping[str, List[str]]) -> None:
        pass

    @typing.overload  # noqa: F811
    def __init__(self, __arg: Mapping[str, str]) -> None:
        pass

    @typing.overload  # noqa: F811
    def __init__(self, *args: Tuple[str, str]) -> None:
        pass

    @typing.overload  # noqa: F811
    def __init__(self, **kwargs: str) -> None:
        pass

    def __init__(self, *args: typing.Any, **kwargs: str) -> None:  # noqa: F811
        self._dict = {}  # type: typing.Dict[str, str]
        self._as_list = {}  # type: typing.Dict[str, typing.List[str]]
        self._last_key = None
        if len(args) == 1 and len(kwargs) == 0 and isinstance(args[0], HTTPHeaders):
            # Copy constructor
            for k, v in args[0].get_all():
                self.add(k, v)
        else:
            # Dict-style initialization
            self.update(*args, **kwargs)

    # new public methods

    def add(self, name: str, value: str) -> None:
        """Adds a new value for the given key."""
        norm_name = _normalized_headers[name]
        self._last_key = norm_name
        if norm_name in self:
            self._dict[norm_name] = (
                native_str(self[norm_name]) + "," + native_str(value)
            )
            self._as_list[norm_name].append(value)
        else:
            self[norm_name] = value

    def get_list(self, name: str) -> List[str]:
        """Returns all values for the given header as a list."""
        norm_name = _normalized_headers[name]
        return self._as_list.get(norm_name, [])

    def get_all(self) -> Iterable[Tuple[str, str]]:
        """Returns an iterable of all (name, value) pairs.

        If a header has multiple values, multiple pairs will be
        returned with the same name.
        """
        for name, values in self._as_list.items():
            for value in values:
                yield (name, value)

    def parse_line(self, line: str) -> None:
        """Updates the dictionary with a single header line.

        >>> h = HTTPHeaders()
        >>> h.parse_line("Content-Type: text/html")
        >>> h.get('content-type')
        'text/html'
        """
        if line[0].isspace():
            # continuation of a multi-line header
            if self._last_key is None:
                raise HTTPInputError("first header line cannot start with whitespace")
            new_part = " " + line.lstrip()
            self._as_list[self._last_key][-1] += new_part
            self._dict[self._last_key] += new_part
        else:
            try:
                name, value = line.split(":", 1)
            except ValueError:
                raise HTTPInputError("no colon in header line")
            self.add(name, value.strip())

    @classmethod
    def parse(cls, headers: str) -> "HTTPHeaders":
        """Returns a dictionary from HTTP header text.

        >>> h = HTTPHeaders.parse("Content-Type: text/html\\r\\nContent-Length: 42\\r\\n")
        >>> sorted(h.items())
        [('Content-Length', '42'), ('Content-Type', 'text/html')]

        .. versionchanged:: 5.1

           Raises `HTTPInputError` on malformed headers instead of a
           mix of `KeyError`, and `ValueError`.

        """
        h = cls()
        for line in _CRLF_RE.split(headers):
            if line:
                h.parse_line(line)
        return h

    # MutableMapping abstract method implementations.

    def __setitem__(self, name: str, value: str) -> None:
        norm_name = _normalized_headers[name]
        self._dict[norm_name] = value
        self._as_list[norm_name] = [value]

    def __getitem__(self, name: str) -> str:
        return self._dict[_normalized_headers[name]]

    def __delitem__(self, name: str) -> None:
        norm_name = _normalized_headers[name]
        del self._dict[norm_name]
        del self._as_list[norm_name]

    def __len__(self) -> int:
        return len(self._dict)

    def __iter__(self) -> Iterator[typing.Any]:
        return iter(self._dict)

    def copy(self) -> "HTTPHeaders":
        # defined in dict but not in MutableMapping.
        return HTTPHeaders(self)

    # Use our overridden copy method for the copy.copy module.
    # This makes shallow copies one level deeper, but preserves
    # the appearance that HTTPHeaders is a single container.
    __copy__ = copy

    def __str__(self) -> str:
        lines = []
        for name, value in self.get_all():
            lines.append("%s: %s\n" % (name, value))
        return "".join(lines)

    __unicode__ = __str__


class HTTPServerRequest(object):
    """A single HTTP request.

    All attributes are type `str` unless otherwise noted.

    .. attribute:: method

       HTTP request method, e.g. "GET" or "POST"

    .. attribute:: uri

       The requested uri.

    .. attribute:: path

       The path portion of `uri`

    .. attribute:: query

       The query portion of `uri`

    .. attribute:: version

       HTTP version specified in request, e.g. "HTTP/1.1"

    .. attribute:: headers

       `.HTTPHeaders` dictionary-like object for request headers.  Acts like
       a case-insensitive dictionary with additional methods for repeated
       headers.

    .. attribute:: body

       Request body, if present, as a byte string.

    .. attribute:: remote_ip

       Client's IP address as a string.  If ``HTTPServer.xheaders`` is set,
       will pass along the real IP address provided by a load balancer
       in the ``X-Real-Ip`` or ``X-Forwarded-For`` header.

    .. versionchanged:: 3.1
       The list format of ``X-Forwarded-For`` is now supported.

    .. attribute:: protocol

       The protocol used, either "http" or "https".  If ``HTTPServer.xheaders``
       is set, will pass along the protocol used by a load balancer if
       reported via an ``X-Scheme`` header.

    .. attribute:: host

       The requested hostname, usually taken from the ``Host`` header.

    .. attribute:: arguments

       GET/POST arguments are available in the arguments property, which
       maps arguments names to lists of values (to support multiple values
       for individual names). Names are of type `str`, while arguments
       are byte strings.  Note that this is different from
       `.RequestHandler.get_argument`, which returns argument values as
       unicode strings.

    .. attribute:: query_arguments

       Same format as ``arguments``, but contains only arguments extracted
       from the query string.

       .. versionadded:: 3.2

    .. attribute:: body_arguments

       Same format as ``arguments``, but contains only arguments extracted
       from the request body.

       .. versionadded:: 3.2

    .. attribute:: files

       File uploads are available in the files property, which maps file
       names to lists of `.HTTPFile`.

    .. attribute:: connection

       An HTTP request is attached to a single HTTP connection, which can
       be accessed through the "connection" attribute. Since connections
       are typically kept open in HTTP/1.1, multiple requests can be handled
       sequentially on a single connection.

    .. versionchanged:: 4.0
       Moved from ``tornado.httpserver.HTTPRequest``.
    """

    path = None  # type: str
    query = None  # type: str

    # HACK: Used for stream_request_body
    _body_future = None  # type: Future[None]

    def __init__(
        self,
        method: str = None,
        uri: str = None,
        version: str = "HTTP/1.0",
        headers: HTTPHeaders = None,
        body: bytes = None,
        host: str = None,
        files: Dict[str, List["HTTPFile"]] = None,
        connection: "HTTPConnection" = None,
        start_line: "RequestStartLine" = None,
        server_connection: object = None,
    ) -> None:
        if start_line is not None:
            method, uri, version = start_line
        self.method = method
        self.uri = uri
        self.version = version
        self.headers = headers or HTTPHeaders()
        self.body = body or b""

        # set remote IP and protocol
        context = getattr(connection, "context", None)
        self.remote_ip = getattr(context, "remote_ip", None)
        self.protocol = getattr(context, "protocol", "http")

        self.host = host or self.headers.get("Host") or "127.0.0.1"
        self.host_name = split_host_and_port(self.host.lower())[0]
        self.files = files or {}
        self.connection = connection
        self.server_connection = server_connection
        self._start_time = time.time()
        self._finish_time = None

        if uri is not None:
            self.path, sep, self.query = uri.partition("?")
        self.arguments = parse_qs_bytes(self.query, keep_blank_values=True)
        self.query_arguments = copy.deepcopy(self.arguments)
        self.body_arguments = {}  # type: Dict[str, List[bytes]]

    @property
    def cookies(self) -> Dict[str, http.cookies.Morsel]:
        """A dictionary of ``http.cookies.Morsel`` objects."""
        if not hasattr(self, "_cookies"):
            self._cookies = http.cookies.SimpleCookie()
            if "Cookie" in self.headers:
                try:
                    parsed = parse_cookie(self.headers["Cookie"])
                except Exception:
                    pass
                else:
                    for k, v in parsed.items():
                        try:
                            self._cookies[k] = v
                        except Exception:
                            # SimpleCookie imposes some restrictions on keys;
                            # parse_cookie does not. Discard any cookies
                            # with disallowed keys.
                            pass
        return self._cookies

    def full_url(self) -> str:
        """Reconstructs the full URL for this request."""
        return self.protocol + "://" + self.host + self.uri

    def request_time(self) -> float:
        """Returns the amount of time it took for this request to execute."""
        if self._finish_time is None:
            return time.time() - self._start_time
        else:
            return self._finish_time - self._start_time

    def get_ssl_certificate(
        self, binary_form: bool = False
    ) -> Union[None, Dict, bytes]:
        """Returns the client's SSL certificate, if any.

        To use client certificates, the HTTPServer's
        `ssl.SSLContext.verify_mode` field must be set, e.g.::

            ssl_ctx = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
            ssl_ctx.load_cert_chain("foo.crt", "foo.key")
            ssl_ctx.load_verify_locations("cacerts.pem")
            ssl_ctx.verify_mode = ssl.CERT_REQUIRED
            server = HTTPServer(app, ssl_options=ssl_ctx)

        By default, the return value is a dictionary (or None, if no
        client certificate is present).  If ``binary_form`` is true, a
        DER-encoded form of the certificate is returned instead.  See
        SSLSocket.getpeercert() in the standard library for more
        details.
        http://docs.python.org/library/ssl.html#sslsocket-objects
        """
        try:
            if self.connection is None:
                return None
            # TODO: add a method to HTTPConnection for this so it can work with HTTP/2
            return self.connection.stream.socket.getpeercert(  # type: ignore
                binary_form=binary_form
            )
        except SSLError:
            return None

    def _parse_body(self) -> None:
        parse_body_arguments(
            self.headers.get("Content-Type", ""),
            self.body,
            self.body_arguments,
            self.files,
            self.headers,
        )

        for k, v in self.body_arguments.items():
            self.arguments.setdefault(k, []).extend(v)

    def __repr__(self) -> str:
        attrs = ("protocol", "host", "method", "uri", "version", "remote_ip")
        args = ", ".join(["%s=%r" % (n, getattr(self, n)) for n in attrs])
        return "%s(%s)" % (self.__class__.__name__, args)


class HTTPInputError(Exception):
    """Exception class for malformed HTTP requests or responses
    from remote sources.

    .. versionadded:: 4.0
    """

    pass


class HTTPOutputError(Exception):
    """Exception class for errors in HTTP output.

    .. versionadded:: 4.0
    """

    pass


class HTTPServerConnectionDelegate(object):
    """Implement this interface to handle requests from `.HTTPServer`.

    .. versionadded:: 4.0
    """

    def start_request(
        self, server_conn: object, request_conn: "HTTPConnection"
    ) -> "HTTPMessageDelegate":
        """This method is called by the server when a new request has started.

        :arg server_conn: is an opaque object representing the long-lived
            (e.g. tcp-level) connection.
        :arg request_conn: is a `.HTTPConnection` object for a single
            request/response exchange.

        This method should return a `.HTTPMessageDelegate`.
        """
        raise NotImplementedError()

    def on_close(self, server_conn: object) -> None:
        """This method is called when a connection has been closed.

        :arg server_conn: is a server connection that has previously been
            passed to ``start_request``.
        """
        pass


class HTTPMessageDelegate(object):
    """Implement this interface to handle an HTTP request or response.

    .. versionadded:: 4.0
    """

    # TODO: genericize this class to avoid exposing the Union.
    def headers_received(
        self,
        start_line: Union["RequestStartLine", "ResponseStartLine"],
        headers: HTTPHeaders,
    ) -> Optional[Awaitable[None]]:
        """Called when the HTTP headers have been received and parsed.

        :arg start_line: a `.RequestStartLine` or `.ResponseStartLine`
            depending on whether this is a client or server message.
        :arg headers: a `.HTTPHeaders` instance.

        Some `.HTTPConnection` methods can only be called during
        ``headers_received``.

        May return a `.Future`; if it does the body will not be read
        until it is done.
        """
        pass

    def data_received(self, chunk: bytes) -> Optional[Awaitable[None]]:
        """Called when a chunk of data has been received.

        May return a `.Future` for flow control.
        """
        pass

    def finish(self) -> None:
        """Called after the last chunk of data has been received."""
        pass

    def on_connection_close(self) -> None:
        """Called if the connection is closed without finishing the request.

        If ``headers_received`` is called, either ``finish`` or
        ``on_connection_close`` will be called, but not both.
        """
        pass


class HTTPConnection(object):
    """Applications use this interface to write their responses.

    .. versionadded:: 4.0
    """

    def write_headers(
        self,
        start_line: Union["RequestStartLine", "ResponseStartLine"],
        headers: HTTPHeaders,
        chunk: bytes = None,
    ) -> "Future[None]":
        """Write an HTTP header block.

        :arg start_line: a `.RequestStartLine` or `.ResponseStartLine`.
        :arg headers: a `.HTTPHeaders` instance.
        :arg chunk: the first (optional) chunk of data.  This is an optimization
            so that small responses can be written in the same call as their
            headers.

        The ``version`` field of ``start_line`` is ignored.

        Returns a future for flow control.

        .. versionchanged:: 6.0

           The ``callback`` argument was removed.
        """
        raise NotImplementedError()

    def write(self, chunk: bytes) -> "Future[None]":
        """Writes a chunk of body data.

        Returns a future for flow control.

        .. versionchanged:: 6.0

           The ``callback`` argument was removed.
        """
        raise NotImplementedError()

    def finish(self) -> None:
        """Indicates that the last body data has been written.
        """
        raise NotImplementedError()


def url_concat(
    url: str,
    args: Union[
        None, Dict[str, str], List[Tuple[str, str]], Tuple[Tuple[str, str], ...]
    ],
) -> str:
    """Concatenate url and arguments regardless of whether
    url has existing query parameters.

    ``args`` may be either a dictionary or a list of key-value pairs
    (the latter allows for multiple values with the same key.

    >>> url_concat("http://example.com/foo", dict(c="d"))
    'http://example.com/foo?c=d'
    >>> url_concat("http://example.com/foo?a=b", dict(c="d"))
    'http://example.com/foo?a=b&c=d'
    >>> url_concat("http://example.com/foo?a=b", [("c", "d"), ("c", "d2")])
    'http://example.com/foo?a=b&c=d&c=d2'
    """
    if args is None:
        return url
    parsed_url = urlparse(url)
    if isinstance(args, dict):
        parsed_query = parse_qsl(parsed_url.query, keep_blank_values=True)
        parsed_query.extend(args.items())
    elif isinstance(args, list) or isinstance(args, tuple):
        parsed_query = parse_qsl(parsed_url.query, keep_blank_values=True)
        parsed_query.extend(args)
    else:
        err = "'args' parameter should be dict, list or tuple. Not {0}".format(
            type(args)
        )
        raise TypeError(err)
    final_query = urlencode(parsed_query)
    url = urlunparse(
        (
            parsed_url[0],
            parsed_url[1],
            parsed_url[2],
            parsed_url[3],
            final_query,
            parsed_url[5],
        )
    )
    return url


class HTTPFile(ObjectDict):
    """Represents a file uploaded via a form.

    For backwards compatibility, its instance attributes are also
    accessible as dictionary keys.

    * ``filename``
    * ``body``
    * ``content_type``
    """

    pass


def _parse_request_range(
    range_header: str
) -> Optional[Tuple[Optional[int], Optional[int]]]:
    """Parses a Range header.

    Returns either ``None`` or tuple ``(start, end)``.
    Note that while the HTTP headers use inclusive byte positions,
    this method returns indexes suitable for use in slices.

    >>> start, end = _parse_request_range("bytes=1-2")
    >>> start, end
    (1, 3)
    >>> [0, 1, 2, 3, 4][start:end]
    [1, 2]
    >>> _parse_request_range("bytes=6-")
    (6, None)
    >>> _parse_request_range("bytes=-6")
    (-6, None)
    >>> _parse_request_range("bytes=-0")
    (None, 0)
    >>> _parse_request_range("bytes=")
    (None, None)
    >>> _parse_request_range("foo=42")
    >>> _parse_request_range("bytes=1-2,6-10")

    Note: only supports one range (ex, ``bytes=1-2,6-10`` is not allowed).

    See [0] for the details of the range header.

    [0]: http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p5-range-latest.html#byte.ranges
    """
    unit, _, value = range_header.partition("=")
    unit, value = unit.strip(), value.strip()
    if unit != "bytes":
        return None
    start_b, _, end_b = value.partition("-")
    try:
        start = _int_or_none(start_b)
        end = _int_or_none(end_b)
    except ValueError:
        return None
    if end is not None:
        if start is None:
            if end != 0:
                start = -end
                end = None
        else:
            end += 1
    return (start, end)


def _get_content_range(start: Optional[int], end: Optional[int], total: int) -> str:
    """Returns a suitable Content-Range header:

    >>> print(_get_content_range(None, 1, 4))
    bytes 0-0/4
    >>> print(_get_content_range(1, 3, 4))
    bytes 1-2/4
    >>> print(_get_content_range(None, None, 4))
    bytes 0-3/4
    """
    start = start or 0
    end = (end or total) - 1
    return "bytes %s-%s/%s" % (start, end, total)


def _int_or_none(val: str) -> Optional[int]:
    val = val.strip()
    if val == "":
        return None
    return int(val)


def parse_body_arguments(
    content_type: str,
    body: bytes,
    arguments: Dict[str, List[bytes]],
    files: Dict[str, List[HTTPFile]],
    headers: HTTPHeaders = None,
) -> None:
    """Parses a form request body.

    Supports ``application/x-www-form-urlencoded`` and
    ``multipart/form-data``.  The ``content_type`` parameter should be
    a string and ``body`` should be a byte string.  The ``arguments``
    and ``files`` parameters are dictionaries that will be updated
    with the parsed contents.
    """
    if headers and "Content-Encoding" in headers:
        gen_log.warning("Unsupported Content-Encoding: %s", headers["Content-Encoding"])
        return
    if content_type.startswith("application/x-www-form-urlencoded"):
        try:
            uri_arguments = parse_qs_bytes(native_str(body), keep_blank_values=True)
        except Exception as e:
            gen_log.warning("Invalid x-www-form-urlencoded body: %s", e)
            uri_arguments = {}
        for name, values in uri_arguments.items():
            if values:
                arguments.setdefault(name, []).extend(values)
    elif content_type.startswith("multipart/form-data"):
        try:
            fields = content_type.split(";")
            for field in fields:
                k, sep, v = field.strip().partition("=")
                if k == "boundary" and v:
                    parse_multipart_form_data(utf8(v), body, arguments, files)
                    break
            else:
                raise ValueError("multipart boundary not found")
        except Exception as e:
            gen_log.warning("Invalid multipart/form-data: %s", e)


def parse_multipart_form_data(
    boundary: bytes,
    data: bytes,
    arguments: Dict[str, List[bytes]],
    files: Dict[str, List[HTTPFile]],
) -> None:
    """Parses a ``multipart/form-data`` body.

    The ``boundary`` and ``data`` parameters are both byte strings.
    The dictionaries given in the arguments and files parameters
    will be updated with the contents of the body.

    .. versionchanged:: 5.1

       Now recognizes non-ASCII filenames in RFC 2231/5987
       (``filename*=``) format.
    """
    # The standard allows for the boundary to be quoted in the header,
    # although it's rare (it happens at least for google app engine
    # xmpp).  I think we're also supposed to handle backslash-escapes
    # here but I'll save that until we see a client that uses them
    # in the wild.
    if boundary.startswith(b'"') and boundary.endswith(b'"'):
        boundary = boundary[1:-1]
    final_boundary_index = data.rfind(b"--" + boundary + b"--")
    if final_boundary_index == -1:
        gen_log.warning("Invalid multipart/form-data: no final boundary")
        return
    parts = data[:final_boundary_index].split(b"--" + boundary + b"\r\n")
    for part in parts:
        if not part:
            continue
        eoh = part.find(b"\r\n\r\n")
        if eoh == -1:
            gen_log.warning("multipart/form-data missing headers")
            continue
        headers = HTTPHeaders.parse(part[:eoh].decode("utf-8"))
        disp_header = headers.get("Content-Disposition", "")
        disposition, disp_params = _parse_header(disp_header)
        if disposition != "form-data" or not part.endswith(b"\r\n"):
            gen_log.warning("Invalid multipart/form-data")
            continue
        value = part[eoh + 4 : -2]
        if not disp_params.get("name"):
            gen_log.warning("multipart/form-data value missing name")
            continue
        name = disp_params["name"]
        if disp_params.get("filename"):
            ctype = headers.get("Content-Type", "application/unknown")
            files.setdefault(name, []).append(
                HTTPFile(
                    filename=disp_params["filename"], body=value, content_type=ctype
                )
            )
        else:
            arguments.setdefault(name, []).append(value)


def format_timestamp(
    ts: Union[int, float, tuple, time.struct_time, datetime.datetime]
) -> str:
    """Formats a timestamp in the format used by HTTP.

    The argument may be a numeric timestamp as returned by `time.time`,
    a time tuple as returned by `time.gmtime`, or a `datetime.datetime`
    object.

    >>> format_timestamp(1359312200)
    'Sun, 27 Jan 2013 18:43:20 GMT'
    """
    if isinstance(ts, (int, float)):
        time_num = ts
    elif isinstance(ts, (tuple, time.struct_time)):
        time_num = calendar.timegm(ts)
    elif isinstance(ts, datetime.datetime):
        time_num = calendar.timegm(ts.utctimetuple())
    else:
        raise TypeError("unknown timestamp type: %r" % ts)
    return email.utils.formatdate(time_num, usegmt=True)


RequestStartLine = collections.namedtuple(
    "RequestStartLine", ["method", "path", "version"]
)


def parse_request_start_line(line: str) -> RequestStartLine:
    """Returns a (method, path, version) tuple for an HTTP 1.x request line.

    The response is a `collections.namedtuple`.

    >>> parse_request_start_line("GET /foo HTTP/1.1")
    RequestStartLine(method='GET', path='/foo', version='HTTP/1.1')
    """
    try:
        method, path, version = line.split(" ")
    except ValueError:
        # https://tools.ietf.org/html/rfc7230#section-3.1.1
        # invalid request-line SHOULD respond with a 400 (Bad Request)
        raise HTTPInputError("Malformed HTTP request line")
    if not re.match(r"^HTTP/1\.[0-9]$", version):
        raise HTTPInputError(
            "Malformed HTTP version in HTTP Request-Line: %r" % version
        )
    return RequestStartLine(method, path, version)


ResponseStartLine = collections.namedtuple(
    "ResponseStartLine", ["version", "code", "reason"]
)


def parse_response_start_line(line: str) -> ResponseStartLine:
    """Returns a (version, code, reason) tuple for an HTTP 1.x response line.

    The response is a `collections.namedtuple`.

    >>> parse_response_start_line("HTTP/1.1 200 OK")
    ResponseStartLine(version='HTTP/1.1', code=200, reason='OK')
    """
    line = native_str(line)
    match = re.match("(HTTP/1.[0-9]) ([0-9]+) ([^\r]*)", line)
    if not match:
        raise HTTPInputError("Error parsing response start line")
    return ResponseStartLine(match.group(1), int(match.group(2)), match.group(3))


# _parseparam and _parse_header are copied and modified from python2.7's cgi.py
# The original 2.7 version of this code did not correctly support some
# combinations of semicolons and double quotes.
# It has also been modified to support valueless parameters as seen in
# websocket extension negotiations, and to support non-ascii values in
# RFC 2231/5987 format.


def _parseparam(s: str) -> Generator[str, None, None]:
    while s[:1] == ";":
        s = s[1:]
        end = s.find(";")
        while end > 0 and (s.count('"', 0, end) - s.count('\\"', 0, end)) % 2:
            end = s.find(";", end + 1)
        if end < 0:
            end = len(s)
        f = s[:end]
        yield f.strip()
        s = s[end:]


def _parse_header(line: str) -> Tuple[str, Dict[str, str]]:
    r"""Parse a Content-type like header.

    Return the main content-type and a dictionary of options.

    >>> d = "form-data; foo=\"b\\\\a\\\"r\"; file*=utf-8''T%C3%A4st"
    >>> ct, d = _parse_header(d)
    >>> ct
    'form-data'
    >>> d['file'] == r'T\u00e4st'.encode('ascii').decode('unicode_escape')
    True
    >>> d['foo']
    'b\\a"r'
    """
    parts = _parseparam(";" + line)
    key = next(parts)
    # decode_params treats first argument special, but we already stripped key
    params = [("Dummy", "value")]
    for p in parts:
        i = p.find("=")
        if i >= 0:
            name = p[:i].strip().lower()
            value = p[i + 1 :].strip()
            params.append((name, native_str(value)))
    decoded_params = email.utils.decode_params(params)
    decoded_params.pop(0)  # get rid of the dummy again
    pdict = {}
    for name, decoded_value in decoded_params:
        value = email.utils.collapse_rfc2231_value(decoded_value)
        if len(value) >= 2 and value[0] == '"' and value[-1] == '"':
            value = value[1:-1]
        pdict[name] = value
    return key, pdict


def _encode_header(key: str, pdict: Dict[str, str]) -> str:
    """Inverse of _parse_header.

    >>> _encode_header('permessage-deflate',
    ...     {'client_max_window_bits': 15, 'client_no_context_takeover': None})
    'permessage-deflate; client_max_window_bits=15; client_no_context_takeover'
    """
    if not pdict:
        return key
    out = [key]
    # Sort the parameters just to make it easy to test.
    for k, v in sorted(pdict.items()):
        if v is None:
            out.append(k)
        else:
            # TODO: quote if necessary.
            out.append("%s=%s" % (k, v))
    return "; ".join(out)


def encode_username_password(
    username: Union[str, bytes], password: Union[str, bytes]
) -> bytes:
    """Encodes a username/password pair in the format used by HTTP auth.

    The return value is a byte string in the form ``username:password``.

    .. versionadded:: 5.1
    """
    if isinstance(username, unicode_type):
        username = unicodedata.normalize("NFC", username)
    if isinstance(password, unicode_type):
        password = unicodedata.normalize("NFC", password)
    return utf8(username) + b":" + utf8(password)


def doctests():
    # type: () -> unittest.TestSuite
    import doctest

    return doctest.DocTestSuite()


def split_host_and_port(netloc: str) -> Tuple[str, Optional[int]]:
    """Returns ``(host, port)`` tuple from ``netloc``.

    Returned ``port`` will be ``None`` if not present.

    .. versionadded:: 4.1
    """
    match = re.match(r"^(.+):(\d+)$", netloc)
    if match:
        host = match.group(1)
        port = int(match.group(2))  # type: Optional[int]
    else:
        host = netloc
        port = None
    return (host, port)


def qs_to_qsl(qs: Dict[str, List[AnyStr]]) -> Iterable[Tuple[str, AnyStr]]:
    """Generator converting a result of ``parse_qs`` back to name-value pairs.

    .. versionadded:: 5.0
    """
    for k, vs in qs.items():
        for v in vs:
            yield (k, v)


_OctalPatt = re.compile(r"\\[0-3][0-7][0-7]")
_QuotePatt = re.compile(r"[\\].")
_nulljoin = "".join


def _unquote_cookie(s: str) -> str:
    """Handle double quotes and escaping in cookie values.

    This method is copied verbatim from the Python 3.5 standard
    library (http.cookies._unquote) so we don't have to depend on
    non-public interfaces.
    """
    # If there aren't any doublequotes,
    # then there can't be any special characters.  See RFC 2109.
    if s is None or len(s) < 2:
        return s
    if s[0] != '"' or s[-1] != '"':
        return s

    # We have to assume that we must decode this string.
    # Down to work.

    # Remove the "s
    s = s[1:-1]

    # Check for special sequences.  Examples:
    #    \012 --> \n
    #    \"   --> "
    #
    i = 0
    n = len(s)
    res = []
    while 0 <= i < n:
        o_match = _OctalPatt.search(s, i)
        q_match = _QuotePatt.search(s, i)
        if not o_match and not q_match:  # Neither matched
            res.append(s[i:])
            break
        # else:
        j = k = -1
        if o_match:
            j = o_match.start(0)
        if q_match:
            k = q_match.start(0)
        if q_match and (not o_match or k < j):  # QuotePatt matched
            res.append(s[i:k])
            res.append(s[k + 1])
            i = k + 2
        else:  # OctalPatt matched
            res.append(s[i:j])
            res.append(chr(int(s[j + 1 : j + 4], 8)))
            i = j + 4
    return _nulljoin(res)


def parse_cookie(cookie: str) -> Dict[str, str]:
    """Parse a ``Cookie`` HTTP header into a dict of name/value pairs.

    This function attempts to mimic browser cookie parsing behavior;
    it specifically does not follow any of the cookie-related RFCs
    (because browsers don't either).

    The algorithm used is identical to that used by Django version 1.9.10.

    .. versionadded:: 4.4.2
    """
    cookiedict = {}
    for chunk in cookie.split(str(";")):
        if str("=") in chunk:
            key, val = chunk.split(str("="), 1)
        else:
            # Assume an empty name per
            # https://bugzilla.mozilla.org/show_bug.cgi?id=169091
            key, val = str(""), chunk
        key, val = key.strip(), val.strip()
        if key or val:
            # unquote using Python's algorithm.
            cookiedict[key] = _unquote_cookie(val)
    return cookiedict