from typing import Dict, Tuple from libp2p.typing import StreamHandlerFn, TProtocol from .exceptions import MultiselectError from .multiselect_communicator_interface import IMultiselectCommunicator from .multiselect_muxer_interface import IMultiselectMuxer MULTISELECT_PROTOCOL_ID = "/multistream/1.0.0" PROTOCOL_NOT_FOUND_MSG = "na" class Multiselect(IMultiselectMuxer): """ Multiselect module that is responsible for responding to a multiselect client and deciding on a specific protocol and handler pair to use for communication """ handlers: Dict[TProtocol, StreamHandlerFn] def __init__(self) -> None: self.handlers = {} def add_handler(self, protocol: TProtocol, handler: StreamHandlerFn) -> None: """ Store the handler with the given protocol :param protocol: protocol name :param handler: handler function """ self.handlers[protocol] = handler async def negotiate( self, communicator: IMultiselectCommunicator ) -> Tuple[TProtocol, StreamHandlerFn]: """ Negotiate performs protocol selection :param stream: stream to negotiate on :return: selected protocol name, handler function :raise Exception: negotiation failed exception """ # Perform handshake to ensure multiselect protocol IDs match await self.handshake(communicator) # Read and respond to commands until a valid protocol ID is sent while True: # Read message command = await communicator.read() # Command is ls or a protocol if command == "ls": # TODO: handle ls command pass else: protocol = TProtocol(command) if protocol in self.handlers: # Tell counterparty we have decided on a protocol await communicator.write(protocol) # Return the decided on protocol return protocol, self.handlers[protocol] # Tell counterparty this protocol was not found await communicator.write(PROTOCOL_NOT_FOUND_MSG) async def handshake(self, communicator: IMultiselectCommunicator) -> None: """ Perform handshake to agree on multiselect protocol :param communicator: communicator to use :raise Exception: error in handshake """ # TODO: Use format used by go repo for messages # Send our MULTISELECT_PROTOCOL_ID to other party await communicator.write(MULTISELECT_PROTOCOL_ID) # Read in the protocol ID from other party handshake_contents = await communicator.read() # Confirm that the protocols are the same if not validate_handshake(handshake_contents): raise MultiselectError( "multiselect protocol ID mismatch: " f"received handshake_contents={handshake_contents}" ) # Handshake succeeded if this point is reached def validate_handshake(handshake_contents: str) -> bool: """ Determine if handshake is valid and should be confirmed :param handshake_contents: contents of handshake message :return: true if handshake is complete, false otherwise """ # TODO: Modify this when format used by go repo for messages # is added return handshake_contents == MULTISELECT_PROTOCOL_ID