pyssb/ssb/packet_stream.py

"""Packet streams"""

from asyncio import Event, Queue
from enum import Enum
import logging
from math import ceil
import struct
from time import time
from typing import Any, AsyncIterator, Dict, Optional, Union

from secret_handshake.network import SHSDuplexStream
import simplejson

logger = logging.getLogger("packet_stream")

PSMessageData = Union[bytes, bool, Dict[str, Any], str]


class PSMessageType(Enum):
    """Available message types"""

    BUFFER = 0
    TEXT = 1
    JSON = 2


class PSStreamHandler:
    """Packet stream handler"""

    def __init__(self, req: int):
        self.req = req
        self.queue: Queue[Optional["PSMessage"]] = Queue()

    async def process(self, msg):
        """Process a pending message"""

        await self.queue.put(msg)

    async def stop(self):
        """Stop a pending request"""

        await self.queue.put(None)

    def __aiter__(self) -> AsyncIterator[Optional["PSMessage"]]:
        return self

    async def __anext__(self) -> Optional["PSMessage"]:
        elem = await self.queue.get()

        if not elem:
            raise StopAsyncIteration()

        return elem


class PSRequestHandler:
    """Packet stream request handler"""

    def __init__(self, req: int):
        self.req = req
        self.event = Event()
        self._msg = None

    async def process(self, msg):
        """Process a message request"""

        self._msg = msg
        self.event.set()

    async def stop(self):
        """Stop a pending event request"""

        if not self.event.is_set():
            self.event.set()

    def __aiter__(self):
        return self

    async def __anext__(self) -> Optional["PSMessage"]:
        # wait until 'process' is called
        await self.event.wait()

        return self._msg


class PSMessage:
    """Packet Stream message"""

    @classmethod
    def from_header_body(cls, flags, req, body):
        """Parse a raw message"""
        type_ = PSMessageType(flags & 0x03)

        if type_ == PSMessageType.TEXT:
            body = body.decode("utf-8")
        elif type_ == PSMessageType.JSON:
            body = simplejson.loads(body)

        return cls(type_, body, bool(flags & 0x08), bool(flags & 0x04), req=req)

    @property
    def data(self) -> bytes:
        """The raw message data"""

        if self.type == PSMessageType.TEXT:
            return self.body.encode("utf-8")

        if self.type == PSMessageType.JSON:
            return simplejson.dumps(self.body).encode("utf-8")

        return self.body

    def __init__(self, type_, body, stream, end_err, req=None):  # pylint: disable=too-many-arguments
        self.stream = stream
        self.end_err = end_err
        self.type = type_
        self.body = body
        self.req = req

    def __repr__(self):
        if self.type == PSMessageType.BUFFER:
            body = f"{len(self.body)} bytes"
        else:
            body = self.body

        req = "" if self.req is None else f" [{self.req}]"
        is_stream = "~" if self.stream else ""
        err = "!" if self.end_err else ""

        return f"<PSMessage ({self.type.name}): {body}{req} {is_stream}{err}>"


class PacketStream:
    """SSB Packet stream"""

    def __init__(self, connection: SHSDuplexStream):
        self.connection = connection
        self.req_counter = 1
        self._event_map = {}
        self._connected = False

    def register_handler(self, handler):
        """Register an RPC handler"""

        self._event_map[handler.req] = (time(), handler)

    @property
    def is_connected(self):
        """Check if the stream is connected"""

        return self.connection.is_connected

    def __aiter__(self) -> AsyncIterator[Optional[PSMessage]]:
        return self

    async def __anext__(self) -> Optional[PSMessage]:
        msg = await self.read()

        if not msg:
            raise StopAsyncIteration()

        if msg.req >= 0:
            return msg

        return None

    async def __await__(self):
        async for data in self:
            logger.info("RECV: %r", data)
            if data is None:
                return

    async def _read(self):
        try:
            header = await self.connection.read()
            if not header or header == b"\x00" * 9:
                return
            flags, length, req = struct.unpack(">BIi", header)

            n_packets = ceil(length / 4096)

            body = b""

            for _ in range(n_packets):
                body += await self.connection.read()

            logger.debug("READ %s %s", header, len(body))
            return PSMessage.from_header_body(flags, req, body)
        except StopAsyncIteration:
            logger.debug("DISCONNECT")
            self.connection.disconnect()
            return None

    async def read(self):
        """Read data from the packet stream"""

        msg = await self._read()
        if not msg:
            return None
        # check whether it's a reply and handle accordingly
        if msg.req < 0:
            _, handler = self._event_map[-msg.req]
            await handler.process(msg)
            logger.info("RESPONSE [%d]: %r", -msg.req, msg)
            if msg.end_err:
                await handler.stop()
                del self._event_map[-msg.req]
                logger.info("RESPONSE [%d]: EOS", -msg.req)
        return msg

    def _write(self, msg: PSMessage) -> None:
        logger.info("SEND [%d]: %r", msg.req, msg)
        header = struct.pack(
            ">BIi", (int(msg.stream) << 3) | (int(msg.end_err) << 2) | msg.type.value, len(msg.data), msg.req
        )
        self.connection.write(header)
        self.connection.write(msg.data)
        logger.debug("WRITE HDR: %s", header)
        logger.debug("WRITE DATA: %s", msg.data)

    def send(  # pylint: disable=too-many-arguments
        self,
        data: Any,
        msg_type: PSMessageType = PSMessageType.JSON,
        stream: bool = False,
        end_err: bool = False,
        req: Optional[int] = None,
    ):
        """Send data through the packet stream"""

        update_counter = False

        if req is None:
            update_counter = True
            req = self.req_counter

        msg = PSMessage(msg_type, data, stream=stream, end_err=end_err, req=req)

        # send request
        self._write(msg)

        if stream:
            handler = PSStreamHandler(self.req_counter)
        else:
            handler = PSRequestHandler(self.req_counter)

        self.register_handler(handler)

        if update_counter:
            self.req_counter += 1

        return handler

    def disconnect(self):
        """Disconnect the stream"""

        self._connected = False
        self.connection.disconnect()