websocket.py

"""The websocket proxy lib."""

import logging
import warnings
from collections import deque
from contextlib import AsyncExitStack
from textwrap import dedent
from typing import (
    TYPE_CHECKING,
    Any,
    List,
    NoReturn,
    Optional,
    Union,
)

import anyio
import anyio.abc
import httpx
import httpx_ws
import starlette.websockets as starlette_ws
import wsproto
from starlette import status as starlette_status
from starlette.background import BackgroundTask
from starlette.responses import Response
from starlette.types import Scope
from typing_extensions import override
from wsproto.events import BytesMessage as WsprotoBytesMessage
from wsproto.events import TextMessage as WsprotoTextMessage

from ._model import BaseProxyModel
from ._tool import (
    change_necessary_client_header_for_httpx,
    check_base_url,
)

# XXX: because these variables are private, we have to use try-except to avoid errors
try:
    from httpx_ws._api import (
        DEFAULT_KEEPALIVE_PING_INTERVAL_SECONDS,
        DEFAULT_KEEPALIVE_PING_TIMEOUT_SECONDS,
        DEFAULT_MAX_MESSAGE_SIZE_BYTES,
        DEFAULT_QUEUE_SIZE,
    )
except ImportError:  # pragma: no cover
    # ref: https://github.com/frankie567/httpx-ws/blob/b2135792141b71551b022ff0d76542a0263a890c/httpx_ws/_api.py#L31-L34
    DEFAULT_KEEPALIVE_PING_TIMEOUT_SECONDS = (  # pyright: ignore[reportConstantRedefinition]
        20.0
    )
    DEFAULT_KEEPALIVE_PING_INTERVAL_SECONDS = (  # pyright: ignore[reportConstantRedefinition]
        20.0
    )
    DEFAULT_MAX_MESSAGE_SIZE_BYTES = (  # pyright: ignore[reportConstantRedefinition]
        65_536
    )
    DEFAULT_QUEUE_SIZE = 512  # pyright: ignore[reportConstantRedefinition]

    warnings.warn(
        dedent(
            """\
            Can not import the default httpx_ws arguments, please open an issue on:
            https://github.com/WSH032/fastapi-proxy-lib\
            """
        ),
        RuntimeWarning,
        stacklevel=1,
    )


__all__ = (
    "BaseWebSocketProxy",
    "ReverseWebSocketProxy",
)

if TYPE_CHECKING:
    # 这些是私有模块，无法确定以后版本是否会改变，为了保证运行时不会出错，我们使用TYPE_CHECKING
    from httpx._types import HeaderTypes, QueryParamTypes


#################### Data Model ####################


_WsDisconnectType = Union[
    starlette_ws.WebSocketDisconnect, httpx_ws.WebSocketDisconnect
]

_WsDisconnectDequqType = Union[
    _WsDisconnectType,  # Exception that contains closing info
    Exception,  # other Exception
]

#################### Constant ####################


#################### Error ####################


#################### Tools function ####################


_change_client_header = change_necessary_client_header_for_httpx


def _get_client_request_subprotocols(ws_scope: Scope) -> Union[List[str], None]:
    """Get client request subprotocols.

    Args:
        ws_scope: client websocket scope.

    Returns:
        If the `ws_scope` has subprotocols, return the subprotocols `List[str]`.
        Else return `None`.
    """
    # https://asgi.readthedocs.io/en/latest/specs/www.html#websocket-connection-scope
    subprotocols: List[str] = ws_scope.get("subprotocols", [])
    if not subprotocols:  # 即为 []
        return None
    return subprotocols


# TODO: 等待starlette官方的支持
# 为什么使用这个函数而不是直接使用starlette_WebSocket.receive_text()
# 请看: https://github.com/encode/starlette/discussions/2310
async def _starlette_ws_receive_bytes_or_str(
    websocket: starlette_ws.WebSocket,
) -> Union[str, bytes]:
    """Receive bytes or str from starlette WebSocket.

    - There is already a queue inside to store the received data
    - Even if `AssertionError` is raised, the `WebSocket` would **not** be closed automatically,
        you should close it manually,

    Args:
        websocket: The starlette WebSocket that has been connected.
            "has been connected" means that you have called "websocket.accept" first.

    Raises:
        starlette.websockets.WebSocketDisconnect: If the WebSocket is disconnected.
            WebSocketDisconnect.code is the close code.
            WebSocketDisconnect.reason is the close reason.
            - **This is normal behavior that you should catch**
        AssertionError:
            - If receive a invalid message type which is neither bytes nor str.
            - RuntimeError: If the WebSocket is not connected. Need to call "accept" first.
                If the `websocket` argument passed in is correct, this error will never be raised, just for assertion.

    Returns:
        bytes | str: The received data.
    """
    # Implement reference:
    # https://github.com/encode/starlette/blob/657e7e7b728e13dc66cc3f77dffd00a42545e171/starlette/websockets.py#L107C1-L115C1
    assert (
        websocket.application_state == starlette_ws.WebSocketState.CONNECTED
    ), """WebSocket is not connected. Need to call "accept" first."""

    message = await websocket.receive()

    if message["type"] == "websocket.disconnect":
        raise starlette_ws.WebSocketDisconnect(message["code"], message.get("reason"))

    # https://asgi.readthedocs.io/en/latest/specs/www.html#receive-receive-event
    if message.get("bytes") is not None:
        return message["bytes"]
    elif message.get("text") is not None:
        return message["text"]
    else:
        # It should never happen, because of the ASGI spec
        raise AssertionError("message should have 'bytes' or 'text' key")


# 为什么使用这个函数而不是直接使用httpx_ws_AsyncWebSocketSession.receive_text()
# 请看: https://github.com/frankie567/httpx-ws/discussions/52
async def _httpx_ws_receive_bytes_or_str(
    websocket: httpx_ws.AsyncWebSocketSession,
) -> Union[str, bytes]:
    """Receive bytes or str from httpx_ws AsyncWebSocketSession .

    - There is already a queue inside to store the received data
    - Even if `AssertionError` or `httpx_ws.WebSocketNetworkError` is raised, the `WebSocket` would **not** be closed automatically,
        you should close it manually,

    Args:
        websocket: The httpx_ws AsyncWebSocketSession that has been connected.

    Raises:
        httpx_ws.WebSocketDisconnect: If the WebSocket is disconnected.
            WebSocketDisconnect.code is the close code.
            WebSocketDisconnect.reason is the close reason.
            - **This is normal behavior that you should catch**
        httpx_ws.WebSocketNetworkError: A network error occurred.
        AssertionError: If receive a invalid message type which is neither bytes nor str.
            Usually it will never be raised, just for assertion

    Returns:
        bytes | str: The received data.
    """
    # 实现参考:
    # https://github.com/frankie567/httpx-ws/blob/1e1c252c2b678f8cc475e1c1546980a784f19702/httpx_ws/_api.py#L296C1-L334C1
    event = await websocket.receive()  # maybe raise httpx_ws.WebSocketNetworkError
    if isinstance(event, WsprotoTextMessage):
        return event.data
    elif isinstance(event, WsprotoBytesMessage):
        if isinstance(
            event.data, bytes
        ):  # pyright: ignore [reportUnnecessaryIsInstance]
            return event.data
        # FIXME: bytes 的类型注解是有问题的，实际上可能是 bytearray
        # https://github.com/frankie567/httpx-ws/discussions/38
        # http://python-hyper.org/projects/wsproto/en/stable/api.html#wsproto.events.TextMessage
        else:
            # 强制保证是bytes
            # FIXME, HACK, XXX: 注意，这是有性能损耗的，调查bytearray是否可以直接用
            return bytes(event.data)
    else:  # pragma: no cover # 无法测试这个分支，因为无法发送这种消息，正常来说也不会被执行，所以我们这里记录critical
        msg = f"Invalid message type received: {type(event)}"
        logging.critical(msg)
        raise AssertionError(event)


async def _httpx_ws_send_bytes_or_str(
    websocket: httpx_ws.AsyncWebSocketSession,
    data: Union[str, bytes],
) -> None:
    """Send bytes or str to WebSocket.

    - Usually, when Exception is raised, the `WebSocket` is already closed.

    Args:
        websocket: The `httpx_ws.AsyncWebSocketSession` that has been connected.
        data: The data to send.

    Raises:
        httpx_ws.WebSocketNetworkError: A network error occurred.
        wsproto.utilities.LocalProtocolError:
            This is raised when the connection is asked to do something
            that is either incompatible with the state or the websocket standard.
            - Mostly it will be raised when the WebSocket has already been disconnected or closed.
    """
    # HACK: make pyright happy
    # 这里有一个pyright问题，需要先判断str
    # 因为 bytes 历史上暗示了 bytes | bytearray | memoryview
    # https://github.com/microsoft/pyright/issues/6227
    if isinstance(data, str):
        await websocket.send_text(data)
    else:
        await websocket.send_bytes(data)


async def _starlette_ws_send_bytes_or_str(
    websocket: starlette_ws.WebSocket,
    data: Union[str, bytes],
) -> None:
    """Send bytes or str to WebSocket.

    - Even if Exception is raised, the `WebSocket` would **not** be closed automatically, you should close it manually

    Args:
        websocket: The starlette_ws.WebSocket that has been connected.
        data: The data to send.

    Raises:
        When websocket has been disconnected, will raise `starlette_ws.WebSocketDisconnect(1006)`.

    """
    # HACK: make pyright happy
    # 这里有一个pyright问题，需要先判断str
    # 因为 bytes 历史上暗示了 bytes | bytearray | memoryview
    # https://github.com/microsoft/pyright/issues/6227
    if isinstance(data, str):
        await websocket.send_text(data)
    else:
        await websocket.send_bytes(data)


async def _wait_client_then_send_to_server(
    client_ws: starlette_ws.WebSocket,
    server_ws: httpx_ws.AsyncWebSocketSession,
    ws_disconnect_deque: "deque[_WsDisconnectDequqType]",
    task_group: anyio.abc.TaskGroup,
) -> None:
    """Receive data from client, then send to target server.

    Args:
        client_ws: The websocket which receive data of client.
        server_ws: The websocket which send data to target server.
        ws_disconnect_deque: A deque to store Exception.
        task_group: The task group which run this task.
            if catch a Exception, will cancel the task group.

    Returns:
        None: Always run forever, except encounter Exception.

    Raises:
        error for receiving: refer to `_starlette_ws_receive_bytes_or_str`.
        error for sending: refer to `_httpx_ws_send_bytes_or_str`.
    """
    try:
        while True:
            receive = await _starlette_ws_receive_bytes_or_str(client_ws)
            await _httpx_ws_send_bytes_or_str(server_ws, receive)
    except Exception as ws_disconnect:
        task_group.cancel_scope.cancel()
        ws_disconnect_deque.append(ws_disconnect)


async def _wait_server_then_send_to_client(
    client_ws: starlette_ws.WebSocket,
    server_ws: httpx_ws.AsyncWebSocketSession,
    ws_disconnect_deque: "deque[_WsDisconnectDequqType]",
    task_group: anyio.abc.TaskGroup,
) -> None:
    """Receive data from target server, then send to client.

    Args:
        client_ws: The websocket which receive data of client.
        server_ws: The websocket which send data to target server.
        ws_disconnect_deque: A deque to store Exception.
        task_group: The task group which run this task.
            if catch a Exception, will cancel the task group.

    Returns:
        None: Always run forever, except encounter Exception.

    Raises:
        error for receiving: refer to `_httpx_ws_receive_bytes_or_str`.
        error for sending: refer to `_starlette_ws_send_bytes_or_str`.
    """
    try:
        while True:
            receive = await _httpx_ws_receive_bytes_or_str(server_ws)
            await _starlette_ws_send_bytes_or_str(client_ws, receive)
    except Exception as ws_disconnect:
        task_group.cancel_scope.cancel()
        ws_disconnect_deque.append(ws_disconnect)


async def _close_ws(  # noqa: C901, PLR0912
    client_ws: starlette_ws.WebSocket,
    server_ws: httpx_ws.AsyncWebSocketSession,
    ws_disconnect_deque: "deque[_WsDisconnectDequqType]",
    caught_tg_exc: Optional[BaseException],
):
    ws_disconnect_tuple = tuple(ws_disconnect_deque)

    client_disc_errs: List[starlette_ws.WebSocketDisconnect] = []
    not_client_disc_errs: List[Exception] = []
    for e in ws_disconnect_tuple:
        if isinstance(e, starlette_ws.WebSocketDisconnect):
            client_disc_errs.append(e)
        else:
            not_client_disc_errs.append(e)

    server_disc_errs: List[httpx_ws.WebSocketDisconnect] = []
    not_server_disc_errs: List[Exception] = []
    for e in ws_disconnect_tuple:
        if isinstance(e, httpx_ws.WebSocketDisconnect):
            server_disc_errs.append(e)
        else:
            not_server_disc_errs.append(e)

    is_canceled = isinstance(caught_tg_exc, anyio.get_cancelled_exc_class())

    client_host, client_port = (
        (client_ws.client.host, client_ws.client.port)
        if client_ws.client is not None
        else (None, None)
    )

    # Implement reference:
    # https://github.com/encode/starlette/blob/4e453ce91940cc7c995e6c728e3fdf341c039056/starlette/websockets.py#L64-L112
    client_ws_closed_state = {
        starlette_ws.WebSocketState.DISCONNECTED,
        starlette_ws.WebSocketState.RESPONSE,
    }
    if (
        client_ws.application_state not in client_ws_closed_state
        and client_ws.client_state not in client_ws_closed_state
    ):
        if server_disc_errs:
            server_disc = server_disc_errs[0]
            await client_ws.close(server_disc.code, server_disc.reason)
        elif is_canceled:
            await client_ws.close(starlette_status.WS_1001_GOING_AWAY)
        else:
            await client_ws.close(starlette_status.WS_1011_INTERNAL_ERROR)
            logging.warning(
                f"[{client_host}:{client_port}] Client websocket closed abnormally during proxying. "
                f"Catch tasks exceptions: {not_server_disc_errs!r} "
                f"Catch task group exceptions: {caught_tg_exc!r}"
            )

    # Implement reference:
    # https://github.com/frankie567/httpx-ws/blob/940c9adb3afee9dd7c8b95514bdf6444673e4820/httpx_ws/_api.py#L928-L931
    if server_ws.connection.state not in {
        wsproto.connection.ConnectionState.CLOSED,
        wsproto.connection.ConnectionState.LOCAL_CLOSING,
    }:
        if client_disc_errs:
            client_disc = client_disc_errs[0]
            await server_ws.close(client_disc.code, client_disc.reason)
        elif is_canceled:
            await server_ws.close(starlette_status.WS_1001_GOING_AWAY)
        else:
            # If remote server has closed normally, here we just close local ws.
            # It's normal, so we don't need warning.
            if (
                server_ws.connection.state
                != wsproto.connection.ConnectionState.REMOTE_CLOSING
            ):
                logging.warning(
                    f"[{client_host}:{client_port}] Server websocket closed abnormally during proxying. "
                    f"Catch tasks exceptions: {not_client_disc_errs!r} "
                    f"Catch task group exceptions: {caught_tg_exc!r}"
                )
            await server_ws.close(starlette_status.WS_1011_INTERNAL_ERROR)


async def _handle_ws_upgrade_error(
    client_ws: starlette_ws.WebSocket,
    background: BackgroundTask,
    ws_upgrade_exc: httpx_ws.WebSocketUpgradeError,
) -> None:
    proxy_res = ws_upgrade_exc.response
    # https://asgi.readthedocs.io/en/latest/extensions.html#websocket-denial-response
    # https://github.com/encode/starlette/blob/4e453ce91940cc7c995e6c728e3fdf341c039056/starlette/websockets.py#L207-L214
    is_able_to_send_denial_response = "websocket.http.response" in client_ws.scope.get(
        "extensions", {}
    )

    if is_able_to_send_denial_response:
        # # XXX: Can not use send_denial_response with StreamingResponse
        # # See: https://github.com/encode/starlette/discussions/2566
        # denial_response = StreamingResponse(
        #     content=proxy_res.aiter_raw(),
        #     status_code=proxy_res.status_code,
        #     headers=proxy_res.headers,
        #     background=background,
        # )

        # # XXX: Unable to read the content of WebSocketUpgradeError.response
        # # See: https://github.com/frankie567/httpx-ws/discussions/69
        # content = await proxy_res.aread()

        denial_response = Response(
            content="",
            status_code=proxy_res.status_code,
            headers=proxy_res.headers,
            background=background,
        )
        await client_ws.send_denial_response(denial_response)
    else:
        msg = (
            "Proxy websocket handshake failed, "
            "but your ASGI server does not support sending denial response.\n"
            f"Denial response: {proxy_res!r}"
        )
        logging.warning(msg)
        # we close before accept, then ASGI will send 403 to client
        await client_ws.close()
        await background()


#################### # ####################


class BaseWebSocketProxy(BaseProxyModel):
    """Websocket proxy base class.

    Attributes:
        client: The [`httpx.AsyncClient`](https://www.python-httpx.org/api/#asyncclient) to establish websocket connection.
        follow_redirects: Whether follow redirects of target server.
        max_message_size_bytes: refer to [httpx_ws.aconnect_ws][]
        queue_size: refer to [httpx_ws.aconnect_ws][]
        keepalive_ping_interval_seconds: refer to [httpx_ws.aconnect_ws][]
        keepalive_ping_timeout_seconds: refer to [httpx_ws.aconnect_ws][]

    Tip:
        [`httpx_ws.aconnect_ws`](https://frankie567.github.io/httpx-ws/reference/httpx_ws/#httpx_ws.aconnect_ws)
    """

    client: httpx.AsyncClient
    follow_redirects: bool
    max_message_size_bytes: int
    queue_size: int
    keepalive_ping_interval_seconds: Union[float, None]
    keepalive_ping_timeout_seconds: Union[float, None]

    @override
    def __init__(
        self,
        client: Optional[httpx.AsyncClient] = None,
        *,
        follow_redirects: bool = False,
        max_message_size_bytes: int = DEFAULT_MAX_MESSAGE_SIZE_BYTES,
        queue_size: int = DEFAULT_QUEUE_SIZE,
        keepalive_ping_interval_seconds: Union[
            float, None
        ] = DEFAULT_KEEPALIVE_PING_INTERVAL_SECONDS,
        keepalive_ping_timeout_seconds: Union[
            float, None
        ] = DEFAULT_KEEPALIVE_PING_TIMEOUT_SECONDS,
    ) -> None:
        """Http proxy base class.

        Args:
            client: The `httpx.AsyncClient` to establish websocket connection. Defaults to None.<br>
                If None, will create a new `httpx.AsyncClient`,
                else will use the given `httpx.AsyncClient`.
            follow_redirects: Whether follow redirects of target server. Defaults to False.

            max_message_size_bytes: refer to [httpx_ws.aconnect_ws][]
            queue_size: refer to [httpx_ws.aconnect_ws][]
            keepalive_ping_interval_seconds: refer to [httpx_ws.aconnect_ws][]
            keepalive_ping_timeout_seconds: refer to [httpx_ws.aconnect_ws][]

        Tip:
            [`httpx_ws.aconnect_ws`](https://frankie567.github.io/httpx-ws/reference/httpx_ws/#httpx_ws.aconnect_ws)
        """
        self.max_message_size_bytes = max_message_size_bytes
        self.queue_size = queue_size
        self.keepalive_ping_interval_seconds = keepalive_ping_interval_seconds
        self.keepalive_ping_timeout_seconds = keepalive_ping_timeout_seconds
        super().__init__(client, follow_redirects=follow_redirects)

    @override
    async def send_request_to_target(  # pyright: ignore [reportIncompatibleMethodOverride]
        self,
        *,
        websocket: starlette_ws.WebSocket,
        target_url: httpx.URL,
    ) -> bool:
        """Establish websocket connection for both client and target_url, then pass messages between them.

        Args:
            websocket: The client websocket requests.
            target_url: The url of target websocket server.

        Returns:
            bool: If handshake failed, return True. Else return False.
        """
        client = self.client
        follow_redirects = self.follow_redirects
        max_message_size_bytes = self.max_message_size_bytes
        queue_size = self.queue_size
        keepalive_ping_interval_seconds = self.keepalive_ping_interval_seconds
        keepalive_ping_timeout_seconds = self.keepalive_ping_timeout_seconds

        client_request_subprotocols: Union[List[str], None] = (
            _get_client_request_subprotocols(websocket.scope)
        )

        # httpx.stream()
        # refer to: https://www.python-httpx.org/api/#helper-functions
        client_request_headers: "HeaderTypes" = _change_client_header(
            headers=websocket.headers, target_url=target_url
        )
        client_request_params: "QueryParamTypes" = websocket.query_params

        # DEBUG: 用于调试的记录
        logging.debug(
            "WS: client:%s ; url:%s ; params:%s ; headers:%s",
            websocket.client,
            target_url,
            client_request_params,
            client_request_headers,
        )

        # https://github.com/frankie567/httpx-ws/discussions/11
        # https://docs.python.org/3.12/library/contextlib.html?highlight=asyncexitstack#catching-exceptions-from-enter-methods
        stack = AsyncExitStack()
        try:
            # FIX: https://github.com/WSH032/fastapi-proxy-lib/security/advisories/GHSA-7vwr-g6pm-9hc8
            # time cost: 396 ns ± 3.39 ns
            # 由于这不是原子性的操作，所以不保证一定阻止cookie泄漏
            # 一定能保证修复的方法是通过`_tool.change_necessary_client_header_for_httpx`强制指定优先级最高的cookie头
            client.cookies.clear()

            proxy_ws = await stack.enter_async_context(
                httpx_ws.aconnect_ws(
                    # XXX: 这个是httpx_ws类型注解的问题，其实是可以使用httpx.URL的
                    url=target_url,  # pyright: ignore [reportArgumentType]
                    client=client,
                    max_message_size_bytes=max_message_size_bytes,
                    queue_size=queue_size,
                    keepalive_ping_interval_seconds=keepalive_ping_interval_seconds,
                    keepalive_ping_timeout_seconds=keepalive_ping_timeout_seconds,
                    subprotocols=client_request_subprotocols,
                    # httpx.stream() params
                    # refer to: https://www.python-httpx.org/api/#helper-functions
                    headers=client_request_headers,
                    params=client_request_params,
                    follow_redirects=follow_redirects,
                )
            )
        except httpx_ws.WebSocketUpgradeError as ws_upgrade_exc:
            await _handle_ws_upgrade_error(
                client_ws=websocket,
                background=BackgroundTask(stack.aclose),
                ws_upgrade_exc=ws_upgrade_exc,
            )
            return True

        # NOTE: 对于反向代理服务器，我们不返回 "任何" "具体的内部" 错误信息给客户端，因为这可能涉及到服务器内部的信息泄露

        # NOTE: 请使用 with 语句来 "保证关闭" AsyncWebSocketSession
        async with stack:
            proxy_ws_resp = proxy_ws.response
            # TODO: Here is a typing issue of `httpx_ws`, we have to use `assert` to make pyright happy
            # https://github.com/frankie567/httpx-ws/pull/54#pullrequestreview-1974062119
            assert proxy_ws_resp is not None
            headers = proxy_ws_resp.headers.copy()
            # ASGI not allow the headers contains `sec-websocket-protocol` field
            # https://asgi.readthedocs.io/en/latest/specs/www.html#accept-send-event
            headers.pop("sec-websocket-protocol", None)
            # XXX: uvicorn websockets implementation not allow contains multiple `Date` and `Server` field,
            # only wsporoto can do so.
            # https://github.com/encode/uvicorn/pull/1606
            # https://github.com/python-websockets/websockets/issues/1226
            headers.pop("Date", None)
            headers.pop("Server", None)
            await websocket.accept(
                subprotocol=proxy_ws.subprotocol, headers=headers.raw
            )

            ws_disconnect_deque: "deque[_WsDisconnectDequqType]" = deque()
            caught_tg_exc = None
            try:
                async with anyio.create_task_group() as tg:
                    tg.start_soon(
                        _wait_client_then_send_to_server,
                        websocket,
                        proxy_ws,
                        ws_disconnect_deque,
                        tg,
                        name="client_to_server_task",
                    )
                    tg.start_soon(
                        _wait_server_then_send_to_client,
                        websocket,
                        proxy_ws,
                        ws_disconnect_deque,
                        tg,
                        name="server_to_client_task",
                    )
            except BaseException as base_exc:
                caught_tg_exc = base_exc
                raise  # NOTE: must raise again
            finally:
                with anyio.CancelScope(shield=True):
                    await _close_ws(
                        websocket,
                        proxy_ws,
                        ws_disconnect_deque,
                        caught_tg_exc,
                    )

        return False

    @override
    async def proxy(*_: Any, **__: Any) -> NoReturn:
        """NotImplemented."""
        raise NotImplementedError()


# FIXME: 目前无法正确转发目标服务器的响应，包括握手成功的响应头和握手失败的整个响应
# 其中 握手成功的响应头 需要等待 httpx_ws 的支持: https://github.com/frankie567/httpx-ws/pull/54
# 握手失败的响应目前在uvicorn中无法实现
# FIXME: 意外关闭时候的关闭码无法确定
class ReverseWebSocketProxy(BaseWebSocketProxy):
    '''Reverse http proxy.

    Attributes:
        client: The `httpx.AsyncClient` to establish websocket connection.
        base_url: The target proxy server url.
        follow_redirects: Whether follow redirects of target server.
        max_message_size_bytes: refer to [httpx_ws.aconnect_ws][]
        queue_size: refer to [httpx_ws.aconnect_ws][]
        keepalive_ping_interval_seconds: refer to [httpx_ws.aconnect_ws][]
        keepalive_ping_timeout_seconds: refer to [httpx_ws.aconnect_ws][]

    Tip:
        [`httpx_ws.aconnect_ws`](https://frankie567.github.io/httpx-ws/reference/httpx_ws/#httpx_ws.aconnect_ws)

    Bug: There is a issue for handshake response:
        This WebSocket proxy can correctly forward request headers.
        But currently,
        it is unable to properly forward responses from the target service,
        including successful handshake response headers and
        the entire response in case of a handshake failure.

        **In most cases, you don't need to worry about this.**
        It only affects the HTTP handshake before establishing the WebSocket,
        and regular WebSocket messages will be forwarded correctly.

    # # Examples

    ```python
    from contextlib import asynccontextmanager
    from typing import AsyncIterator

    from fastapi import FastAPI
    from fastapi_proxy_lib.core.websocket import ReverseWebSocketProxy
    from httpx import AsyncClient
    from starlette.websockets import WebSocket

    proxy = ReverseWebSocketProxy(AsyncClient(), base_url="ws://echo.websocket.events/")

    @asynccontextmanager
    async def close_proxy_event(_: FastAPI) -> AsyncIterator[None]:
        """Close proxy."""
        yield
        await proxy.aclose()

    app = FastAPI(lifespan=close_proxy_event)

    @app.websocket("/{path:path}")
    async def _(websocket: WebSocket):
        return await proxy.proxy(websocket=websocket)

    # Then run shell: `uvicorn <your.py>:app --host http://127.0.0.1:8000 --port 8000`
    # visit the app: `ws://127.0.0.1:8000/`
    # you can establish websocket connection with `ws://echo.websocket.events`
    ```
    '''

    client: httpx.AsyncClient
    base_url: httpx.URL
    follow_redirects: bool
    max_message_size_bytes: int
    queue_size: int
    keepalive_ping_interval_seconds: Union[float, None]
    keepalive_ping_timeout_seconds: Union[float, None]

    @override
    def __init__(
        self,
        client: Optional[httpx.AsyncClient] = None,
        *,
        base_url: Union[httpx.URL, str],
        follow_redirects: bool = False,
        max_message_size_bytes: int = DEFAULT_MAX_MESSAGE_SIZE_BYTES,
        queue_size: int = DEFAULT_QUEUE_SIZE,
        keepalive_ping_interval_seconds: Union[
            float, None
        ] = DEFAULT_KEEPALIVE_PING_INTERVAL_SECONDS,
        keepalive_ping_timeout_seconds: Union[
            float, None
        ] = DEFAULT_KEEPALIVE_PING_TIMEOUT_SECONDS,
    ) -> None:
        """Reverse http proxy.

        Note: please make sure `base_url` is available.
            Because when an error occurs,
            we cannot distinguish whether it is a proxy server network error, or it is a error of `base_url`.

        Args:
            base_url: The target proxy server url.
            client: The `httpx.AsyncClient` to establish websocket connection. Defaults to None.<br>
                If None, will create a new `httpx.AsyncClient`,
                else will use the given `httpx.AsyncClient`.
            follow_redirects: Whether follow redirects of target server. Defaults to False.

            max_message_size_bytes: refer to [httpx_ws.aconnect_ws][]
            queue_size: refer to [httpx_ws.aconnect_ws][]
            keepalive_ping_interval_seconds: refer to [httpx_ws.aconnect_ws][]
            keepalive_ping_timeout_seconds: refer to [httpx_ws.aconnect_ws][]

        Tip:
            [`httpx_ws.aconnect_ws`](https://frankie567.github.io/httpx-ws/reference/httpx_ws/#httpx_ws.aconnect_ws)
        """
        self.base_url = check_base_url(base_url)
        super().__init__(
            client,
            follow_redirects=follow_redirects,
            max_message_size_bytes=max_message_size_bytes,
            queue_size=queue_size,
            keepalive_ping_interval_seconds=keepalive_ping_interval_seconds,
            keepalive_ping_timeout_seconds=keepalive_ping_timeout_seconds,
        )

    @override
    async def proxy(  # pyright: ignore [reportIncompatibleMethodOverride]
        self, *, websocket: starlette_ws.WebSocket
    ) -> bool:
        """Establish websocket connection for both client and target_url, then pass messages between them.

        Args:
            websocket: The client websocket requests.

        Returns:
            bool: If handshake failed, return True. Else return False.
        """
        base_url = self.base_url

        # 只取第一个路径参数。注意，我们允许没有路径参数，这代表直接请求
        path_param: str = next(iter(websocket.path_params.values()), "")

        # 将路径参数拼接到目标url上
        # e.g: "https://www.example.com/p0/" + "p1"
        # NOTE: 这里的 path_param 是不带查询参数的，且允许以 "/" 开头 (最终为/p0//p1)
        target_url = base_url.copy_with(
            path=(base_url.path + path_param)
        )  # 耗时: 18.4 µs ± 262 ns

        # self.send_request_to_target 内部会处理连接失败时，返回错误给客户端，所以这里不处理了
        return await self.send_request_to_target(
            websocket=websocket, target_url=target_url
        )