web_ws.py

import asyncio
import base64
import binascii
import hashlib
import json
from typing import Any, Iterable, Optional, Tuple, cast

import async_timeout
import attr
from multidict import CIMultiDict

from . import hdrs
from .abc import AbstractStreamWriter
from .helpers import call_later, set_result
from .http import (
    WS_CLOSED_MESSAGE,
    WS_CLOSING_MESSAGE,
    WS_KEY,
    WebSocketError,
    WebSocketReader,
    WebSocketWriter,
    WSCloseCode,
    WSMessage,
    WSMsgType as WSMsgType,
    ws_ext_gen,
    ws_ext_parse,
)
from .log import ws_logger
from .streams import EofStream, FlowControlDataQueue
from .typedefs import Final, JSONDecoder, JSONEncoder
from .web_exceptions import HTTPBadRequest, HTTPException
from .web_request import BaseRequest
from .web_response import StreamResponse

__all__ = (
    "WebSocketResponse",
    "WebSocketReady",
    "WSMsgType",
)

THRESHOLD_CONNLOST_ACCESS: Final[int] = 5


@attr.s(auto_attribs=True, frozen=True, slots=True)
class WebSocketReady:
    ok: bool
    protocol: Optional[str]

    def __bool__(self) -> bool:
        return self.ok


class WebSocketResponse(StreamResponse):

    _length_check = False

    def __init__(
        self,
        *,
        timeout: float = 10.0,
        receive_timeout: Optional[float] = None,
        autoclose: bool = True,
        autoping: bool = True,
        heartbeat: Optional[float] = None,
        protocols: Iterable[str] = (),
        compress: bool = True,
        max_msg_size: int = 4 * 1024 * 1024,
    ) -> None:
        super().__init__(status=101)
        self._protocols = protocols
        self._ws_protocol: Optional[str] = None
        self._writer: Optional[WebSocketWriter] = None
        self._reader: Optional[FlowControlDataQueue[WSMessage]] = None
        self._closed = False
        self._closing = False
        self._conn_lost = 0
        self._close_code: Optional[int] = None
        self._loop: Optional[asyncio.AbstractEventLoop] = None
        self._waiting: Optional[asyncio.Future[bool]] = None
        self._exception: Optional[BaseException] = None
        self._timeout = timeout
        self._receive_timeout = receive_timeout
        self._autoclose = autoclose
        self._autoping = autoping
        self._heartbeat = heartbeat
        self._heartbeat_cb: Optional[asyncio.TimerHandle] = None
        if heartbeat is not None:
            self._pong_heartbeat = heartbeat / 2.0
        self._pong_response_cb: Optional[asyncio.TimerHandle] = None
        self._compress = compress
        self._max_msg_size = max_msg_size

    def _cancel_heartbeat(self) -> None:
        if self._pong_response_cb is not None:
            self._pong_response_cb.cancel()
            self._pong_response_cb = None

        if self._heartbeat_cb is not None:
            self._heartbeat_cb.cancel()
            self._heartbeat_cb = None

    def _reset_heartbeat(self) -> None:
        self._cancel_heartbeat()

        if self._heartbeat is not None:
            assert self._loop is not None
            self._heartbeat_cb = call_later(
                self._send_heartbeat, self._heartbeat, self._loop
            )

    def _send_heartbeat(self) -> None:
        if self._heartbeat is not None and not self._closed:
            assert self._loop is not None
            # fire-and-forget a task is not perfect but maybe ok for
            # sending ping. Otherwise we need a long-living heartbeat
            # task in the class.
            self._loop.create_task(self._writer.ping())  # type: ignore[union-attr]

            if self._pong_response_cb is not None:
                self._pong_response_cb.cancel()
            self._pong_response_cb = call_later(
                self._pong_not_received, self._pong_heartbeat, self._loop
            )

    def _pong_not_received(self) -> None:
        if self._req is not None and self._req.transport is not None:
            self._closed = True
            self._close_code = WSCloseCode.ABNORMAL_CLOSURE
            self._exception = asyncio.TimeoutError()
            self._req.transport.close()

    async def prepare(self, request: BaseRequest) -> AbstractStreamWriter:
        # make pre-check to don't hide it by do_handshake() exceptions
        if self._payload_writer is not None:
            return self._payload_writer

        protocol, writer = self._pre_start(request)
        payload_writer = await super().prepare(request)
        assert payload_writer is not None
        self._post_start(request, protocol, writer)
        await payload_writer.drain()
        return payload_writer

    def _handshake(
        self, request: BaseRequest
    ) -> Tuple["CIMultiDict[str]", str, bool, bool]:
        headers = request.headers
        if "websocket" != headers.get(hdrs.UPGRADE, "").lower().strip():
            raise HTTPBadRequest(
                text=(
                    "No WebSocket UPGRADE hdr: {}\n Can "
                    '"Upgrade" only to "WebSocket".'
                ).format(headers.get(hdrs.UPGRADE))
            )

        if "upgrade" not in headers.get(hdrs.CONNECTION, "").lower():
            raise HTTPBadRequest(
                text="No CONNECTION upgrade hdr: {}".format(
                    headers.get(hdrs.CONNECTION)
                )
            )

        # find common sub-protocol between client and server
        protocol = None
        if hdrs.SEC_WEBSOCKET_PROTOCOL in headers:
            req_protocols = [
                str(proto.strip())
                for proto in headers[hdrs.SEC_WEBSOCKET_PROTOCOL].split(",")
            ]

            for proto in req_protocols:
                if proto in self._protocols:
                    protocol = proto
                    break
            else:
                # No overlap found: Return no protocol as per spec
                ws_logger.warning(
                    "Client protocols %r don’t overlap server-known ones %r",
                    req_protocols,
                    self._protocols,
                )

        # check supported version
        version = headers.get(hdrs.SEC_WEBSOCKET_VERSION, "")
        if version not in ("13", "8", "7"):
            raise HTTPBadRequest(text=f"Unsupported version: {version}")

        # check client handshake for validity
        key = headers.get(hdrs.SEC_WEBSOCKET_KEY)
        try:
            if not key or len(base64.b64decode(key)) != 16:
                raise HTTPBadRequest(text=f"Handshake error: {key!r}")
        except binascii.Error:
            raise HTTPBadRequest(text=f"Handshake error: {key!r}") from None

        accept_val = base64.b64encode(
            hashlib.sha1(key.encode() + WS_KEY).digest()
        ).decode()
        response_headers = CIMultiDict(
            {
                hdrs.UPGRADE: "websocket",
                hdrs.CONNECTION: "upgrade",
                hdrs.SEC_WEBSOCKET_ACCEPT: accept_val,
            }
        )

        notakeover = False
        compress = 0
        if self._compress:
            extensions = headers.get(hdrs.SEC_WEBSOCKET_EXTENSIONS)
            # Server side always get return with no exception.
            # If something happened, just drop compress extension
            compress, notakeover = ws_ext_parse(extensions, isserver=True)
            if compress:
                enabledext = ws_ext_gen(
                    compress=compress, isserver=True, server_notakeover=notakeover
                )
                response_headers[hdrs.SEC_WEBSOCKET_EXTENSIONS] = enabledext

        if protocol:
            response_headers[hdrs.SEC_WEBSOCKET_PROTOCOL] = protocol
        return (
            response_headers,
            protocol,
            compress,
            notakeover,
        )  # type: ignore[return-value]

    def _pre_start(self, request: BaseRequest) -> Tuple[str, WebSocketWriter]:
        self._loop = request._loop

        headers, protocol, compress, notakeover = self._handshake(request)

        self.set_status(101)
        self.headers.update(headers)
        self.force_close()
        self._compress = compress
        transport = request._protocol.transport
        assert transport is not None
        writer = WebSocketWriter(
            request._protocol, transport, compress=compress, notakeover=notakeover
        )

        return protocol, writer

    def _post_start(
        self, request: BaseRequest, protocol: str, writer: WebSocketWriter
    ) -> None:
        self._ws_protocol = protocol
        self._writer = writer

        self._reset_heartbeat()

        loop = self._loop
        assert loop is not None
        self._reader = FlowControlDataQueue(request._protocol, 2**16, loop=loop)
        request.protocol.set_parser(
            WebSocketReader(self._reader, self._max_msg_size, compress=self._compress)
        )
        # disable HTTP keepalive for WebSocket
        request.protocol.keep_alive(False)

    def can_prepare(self, request: BaseRequest) -> WebSocketReady:
        if self._writer is not None:
            raise RuntimeError("Already started")
        try:
            _, protocol, _, _ = self._handshake(request)
        except HTTPException:
            return WebSocketReady(False, None)
        else:
            return WebSocketReady(True, protocol)

    @property
    def closed(self) -> bool:
        return self._closed

    @property
    def close_code(self) -> Optional[int]:
        return self._close_code

    @property
    def ws_protocol(self) -> Optional[str]:
        return self._ws_protocol

    @property
    def compress(self) -> bool:
        return self._compress

    def exception(self) -> Optional[BaseException]:
        return self._exception

    async def ping(self, message: bytes = b"") -> None:
        if self._writer is None:
            raise RuntimeError("Call .prepare() first")
        await self._writer.ping(message)

    async def pong(self, message: bytes = b"") -> None:
        # unsolicited pong
        if self._writer is None:
            raise RuntimeError("Call .prepare() first")
        await self._writer.pong(message)

    async def send_str(self, data: str, compress: Optional[bool] = None) -> None:
        if self._writer is None:
            raise RuntimeError("Call .prepare() first")
        if not isinstance(data, str):
            raise TypeError("data argument must be str (%r)" % type(data))
        await self._writer.send(data, binary=False, compress=compress)

    async def send_bytes(self, data: bytes, compress: Optional[bool] = None) -> None:
        if self._writer is None:
            raise RuntimeError("Call .prepare() first")
        if not isinstance(data, (bytes, bytearray, memoryview)):
            raise TypeError("data argument must be byte-ish (%r)" % type(data))
        await self._writer.send(data, binary=True, compress=compress)

    async def send_json(
        self,
        data: Any,
        compress: Optional[bool] = None,
        *,
        dumps: JSONEncoder = json.dumps,
    ) -> None:
        await self.send_str(dumps(data), compress=compress)

    async def write_eof(self) -> None:  # type: ignore[override]
        if self._eof_sent:
            return
        if self._payload_writer is None:
            raise RuntimeError("Response has not been started")

        await self.close()
        self._eof_sent = True

    async def close(self, *, code: int = WSCloseCode.OK, message: bytes = b"") -> bool:
        if self._writer is None:
            raise RuntimeError("Call .prepare() first")

        self._cancel_heartbeat()
        reader = self._reader
        assert reader is not None

        # we need to break `receive()` cycle first,
        # `close()` may be called from different task
        if self._waiting is not None and not self._closed:
            reader.feed_data(WS_CLOSING_MESSAGE, 0)
            await self._waiting

        if not self._closed:
            self._closed = True
            try:
                await self._writer.close(code, message)
                writer = self._payload_writer
                assert writer is not None
                await writer.drain()
            except (asyncio.CancelledError, asyncio.TimeoutError):
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                raise
            except Exception as exc:
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                self._exception = exc
                return True

            if self._closing:
                return True

            reader = self._reader
            assert reader is not None
            try:
                async with async_timeout.timeout(self._timeout):
                    msg = await reader.read()
            except asyncio.CancelledError:
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                raise
            except Exception as exc:
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                self._exception = exc
                return True

            if msg.type == WSMsgType.CLOSE:
                self._close_code = msg.data
                return True

            self._close_code = WSCloseCode.ABNORMAL_CLOSURE
            self._exception = asyncio.TimeoutError()
            return True
        else:
            return False

    async def receive(self, timeout: Optional[float] = None) -> WSMessage:
        if self._reader is None:
            raise RuntimeError("Call .prepare() first")

        loop = self._loop
        assert loop is not None
        while True:
            if self._waiting is not None:
                raise RuntimeError("Concurrent call to receive() is not allowed")

            if self._closed:
                self._conn_lost += 1
                if self._conn_lost >= THRESHOLD_CONNLOST_ACCESS:
                    raise RuntimeError("WebSocket connection is closed.")
                return WS_CLOSED_MESSAGE
            elif self._closing:
                return WS_CLOSING_MESSAGE

            try:
                self._waiting = loop.create_future()
                try:
                    async with async_timeout.timeout(timeout or self._receive_timeout):
                        msg = await self._reader.read()
                    self._reset_heartbeat()
                finally:
                    waiter = self._waiting
                    set_result(waiter, True)
                    self._waiting = None
            except (asyncio.CancelledError, asyncio.TimeoutError):
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                raise
            except EofStream:
                self._close_code = WSCloseCode.OK
                await self.close()
                return WSMessage(WSMsgType.CLOSED, None, None)
            except WebSocketError as exc:
                self._close_code = exc.code
                await self.close(code=exc.code)
                return WSMessage(WSMsgType.ERROR, exc, None)
            except Exception as exc:
                self._exception = exc
                self._closing = True
                self._close_code = WSCloseCode.ABNORMAL_CLOSURE
                await self.close()
                return WSMessage(WSMsgType.ERROR, exc, None)

            if msg.type == WSMsgType.CLOSE:
                self._closing = True
                self._close_code = msg.data
                if not self._closed and self._autoclose:
                    await self.close()
            elif msg.type == WSMsgType.CLOSING:
                self._closing = True
            elif msg.type == WSMsgType.PING and self._autoping:
                await self.pong(msg.data)
                continue
            elif msg.type == WSMsgType.PONG and self._autoping:
                continue

            return msg

    async def receive_str(self, *, timeout: Optional[float] = None) -> str:
        msg = await self.receive(timeout)
        if msg.type != WSMsgType.TEXT:
            raise TypeError(
                "Received message {}:{!r} is not WSMsgType.TEXT".format(
                    msg.type, msg.data
                )
            )
        return cast(str, msg.data)

    async def receive_bytes(self, *, timeout: Optional[float] = None) -> bytes:
        msg = await self.receive(timeout)
        if msg.type != WSMsgType.BINARY:
            raise TypeError(f"Received message {msg.type}:{msg.data!r} is not bytes")
        return cast(bytes, msg.data)

    async def receive_json(
        self, *, loads: JSONDecoder = json.loads, timeout: Optional[float] = None
    ) -> Any:
        data = await self.receive_str(timeout=timeout)
        return loads(data)

    async def write(self, data: bytes) -> None:
        raise RuntimeError("Cannot call .write() for websocket")

    def __aiter__(self) -> "WebSocketResponse":
        return self

    async def __anext__(self) -> WSMessage:
        msg = await self.receive()
        if msg.type in (WSMsgType.CLOSE, WSMsgType.CLOSING, WSMsgType.CLOSED):
            raise StopAsyncIteration
        return msg

    def _cancel(self, exc: BaseException) -> None:
        if self._reader is not None:
            self._reader.set_exception(exc)