95 lines
3.3 KiB
Python
95 lines
3.3 KiB
Python
from typing import Dict, Tuple
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from libp2p.typing import StreamHandlerFn, TProtocol
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from .exceptions import MultiselectCommunicatorError, MultiselectError
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from .multiselect_communicator_interface import IMultiselectCommunicator
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from .multiselect_muxer_interface import IMultiselectMuxer
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MULTISELECT_PROTOCOL_ID = "/multistream/1.0.0"
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PROTOCOL_NOT_FOUND_MSG = "na"
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class Multiselect(IMultiselectMuxer):
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"""Multiselect module that is responsible for responding to a multiselect
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client and deciding on a specific protocol and handler pair to use for
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communication."""
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handlers: Dict[TProtocol, StreamHandlerFn]
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def __init__(self) -> None:
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self.handlers = {}
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def add_handler(self, protocol: TProtocol, handler: StreamHandlerFn) -> None:
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"""Store the handler with the given protocol.
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:param protocol: protocol name
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:param handler: handler function
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"""
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self.handlers[protocol] = handler
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async def negotiate(
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self, communicator: IMultiselectCommunicator
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) -> Tuple[TProtocol, StreamHandlerFn]:
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"""Negotiate performs protocol selection.
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:param stream: stream to negotiate on
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:return: selected protocol name, handler function
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:raise MultiselectError: raised when negotiation failed
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"""
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await self.handshake(communicator)
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while True:
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try:
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command = await communicator.read()
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except MultiselectCommunicatorError as error:
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raise MultiselectError(error)
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if command == "ls":
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# TODO: handle ls command
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pass
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else:
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protocol = TProtocol(command)
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if protocol in self.handlers:
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try:
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await communicator.write(protocol)
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except MultiselectCommunicatorError as error:
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raise MultiselectError(error)
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return protocol, self.handlers[protocol]
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try:
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await communicator.write(PROTOCOL_NOT_FOUND_MSG)
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except MultiselectCommunicatorError as error:
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raise MultiselectError(error)
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async def handshake(self, communicator: IMultiselectCommunicator) -> None:
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"""Perform handshake to agree on multiselect protocol.
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:param communicator: communicator to use
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:raise MultiselectError: raised when handshake failed
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"""
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try:
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await communicator.write(MULTISELECT_PROTOCOL_ID)
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except MultiselectCommunicatorError as error:
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raise MultiselectError(error)
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try:
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handshake_contents = await communicator.read()
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except MultiselectCommunicatorError as error:
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raise MultiselectError(error)
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if not validate_handshake(handshake_contents):
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raise MultiselectError(
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"multiselect protocol ID mismatch: "
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f"received handshake_contents={handshake_contents}"
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)
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def validate_handshake(handshake_contents: str) -> bool:
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"""Determine if handshake is valid and should be confirmed.
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:param handshake_contents: contents of handshake message
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:return: true if handshake is complete, false otherwise
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"""
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return handshake_contents == MULTISELECT_PROTOCOL_ID
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