Protocol muxing (#82)

* Implement protocol muxing

* Integrate protocol muxing into new stream and listen's conn handler

* Fix bugs in protocol muxing

* Remove blank line

* Add comments and fix linting issues

* Fix order of parameters to select_one_of to match interface

* Use array of protocol ids in new stream instead of protocol id

* Add basic protocol muxer tests

* Add todo

* Modify new stream to take in protocol ids

* Add check to all tests to ensure protocol id is saved to net stream properly

* Lint tests

* Fix lint issues

* Add todo

* Modify port numbers in tests

* Fix linting issues

* Add more documentation to functions

* Add docs describing classes and fix indent error

protocol_muxer/multiselect.py

@@ -0,0 +1,92 @@
+from .multiselect_muxer_interface import IMultiselectMuxer
+from .multiselect_communicator import MultiselectCommunicator
+
+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
+    """
+
+    def __init__(self):
+        self.handlers = {}
+
+    def add_handler(self, protocol, handler):
+        """
+        Store the handler with the given protocol
+        :param protocol: protocol name
+        :param handler: handler function
+        """
+        self.handlers[protocol] = handler
+
+    async def negotiate(self, stream):
+        """
+        Negotiate performs protocol selection
+        :param stream: stream to negotiate on
+        :return: selected protocol name, handler function
+        :raise Exception: negotiation failed exception
+        """
+
+        # Create a communicator to handle all communication across the stream
+        communicator = MultiselectCommunicator(stream)
+
+        # 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_stream_until_eof()
+
+            # Command is ls or a protocol
+            if command == "ls":
+                # TODO: handle ls command
+                pass
+            else:
+                protocol = 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):
+        """
+        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_stream_until_eof()
+
+        # Confirm that the protocols are the same
+        if not self.validate_handshake(handshake_contents):
+            raise MultiselectError("multiselect protocol ID mismatch")
+
+        # Handshake succeeded if this point is reached
+
+    def validate_handshake(self, handshake_contents):
+        """
+        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
+
+class MultiselectError(ValueError):
+    """Raised when an error occurs in multiselect process"""

protocol_muxer/multiselect_client.py

@@ -0,0 +1,121 @@
+from .multiselect_client_interface import IMultiselectClient
+from .multiselect_communicator import MultiselectCommunicator
+
+MULTISELECT_PROTOCOL_ID = "/multistream/1.0.0"
+PROTOCOL_NOT_FOUND_MSG = "na"
+
+class MultiselectClient(IMultiselectClient):
+    """
+    Client for communicating with receiver's multiselect
+    module in order to select a protocol id to communicate over
+    """
+    
+    def __init__(self):
+        pass
+
+    async def handshake(self, communicator):
+        """
+        Ensure that the client and multiselect
+        are both using the same multiselect protocol
+        :param stream: stream to communicate with multiselect over
+        :raise Exception: multiselect protocol ID mismatch
+        """
+
+        # TODO: Use format used by go repo for messages
+
+        # Send our MULTISELECT_PROTOCOL_ID to counterparty
+        await communicator.write(MULTISELECT_PROTOCOL_ID)
+
+        # Read in the protocol ID from other party
+        handshake_contents = await communicator.read_stream_until_eof()
+
+        # Confirm that the protocols are the same
+        if not self.validate_handshake(handshake_contents):
+            raise MultiselectClientError("multiselect protocol ID mismatch")
+
+        # Handshake succeeded if this point is reached
+
+    def validate_handshake(self, handshake_contents):
+        """
+        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
+
+    async def select_protocol_or_fail(self, protocol, stream):
+        """
+        Send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """
+
+        # Create a communicator to handle all communication across the stream
+        communicator = MultiselectCommunicator(stream)
+
+        # Perform handshake to ensure multiselect protocol IDs match
+        await self.handshake(communicator)
+
+        # Try to select the given protocol
+        selected_protocol = await self.try_select(communicator, protocol)
+
+        return selected_protocol
+
+    async def select_one_of(self, protocols, stream):
+        """
+        For each protocol, send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol. Returns first
+        protocol that multiselect agrees on (i.e. that multiselect selects)
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """
+
+        # Create a communicator to handle all communication across the stream
+        communicator = MultiselectCommunicator(stream)
+
+        # Perform handshake to ensure multiselect protocol IDs match
+        await self.handshake(communicator)
+
+        # For each protocol, attempt to select that protocol
+        # and return the first protocol selected
+        for protocol in protocols:
+            try:
+                selected_protocol = await self.try_select(communicator, protocol)
+                return selected_protocol
+            except MultiselectClientError:
+                pass
+
+        # No protocols were found, so return no protocols supported error
+        raise MultiselectClientError("protocols not supported")
+
+    async def try_select(self, communicator, protocol):
+        """
+        Try to select the given protocol or raise exception if fails
+        :param communicator: communicator to use to communicate with counterparty
+        :param protocol: protocol to select
+        :raise Exception: error in protocol selection
+        :return: selected protocol
+        """
+
+        # Tell counterparty we want to use protocol
+        await communicator.write(protocol)
+
+        # Get what counterparty says in response
+        response = await communicator.read_stream_until_eof()
+
+        # Return protocol if response is equal to protocol or raise error
+        if response == protocol:
+            return protocol
+        if response == PROTOCOL_NOT_FOUND_MSG:
+            raise MultiselectClientError("protocol not supported")
+        else:
+            raise MultiselectClientError("unrecognized response: " + response)
+
+class MultiselectClientError(ValueError):
+    """Raised when an error occurs in protocol selection process"""

protocol_muxer/multiselect_client_interface.py

@@ -0,0 +1,28 @@
+from abc import ABC, abstractmethod
+
+class IMultiselectClient(ABC):
+    """
+    Client for communicating with receiver's multiselect
+    module in order to select a protocol id to communicate over
+    """
+
+    @abstractmethod
+    def select_protocol_or_fail(self, protocol, stream):
+        """
+        Send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """
+
+    @abstractmethod
+    def select_one_of(self, protocols, stream):
+        """
+        For each protocol, send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol. Returns first
+        protocol that multiselect agrees on (i.e. that multiselect selects)
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """

protocol_muxer/multiselect_communicator.py

@@ -0,0 +1,25 @@
+from .multiselect_communicator_interface import IMultiselectCommunicator
+
+class MultiselectCommunicator(IMultiselectCommunicator):
+    """
+    Communicator helper class that ensures both the client
+    and multistream module will follow the same multistream protocol,
+    which is necessary for them to work
+    """
+    
+    def __init__(self, stream):
+        self.stream = stream
+
+    async def write(self, msg_str):
+        """
+        Write message to stream
+        :param msg_str: message to write
+        """
+        await self.stream.write(msg_str.encode())
+
+    async def read_stream_until_eof(self):
+        """
+        Reads message from stream until EOF
+        """
+        read_str = (await self.stream.read()).decode()
+        return read_str

protocol_muxer/multiselect_communicator_interface.py

@@ -0,0 +1,21 @@
+from abc import ABC, abstractmethod
+
+class IMultiselectCommunicator(ABC):
+    """
+    Communicator helper class that ensures both the client
+    and multistream module will follow the same multistream protocol,
+    which is necessary for them to work
+    """
+
+    @abstractmethod
+    def write(self, msg_str):
+        """
+        Write message to stream
+        :param msg_str: message to write
+        """
+
+    @abstractmethod
+    def read_stream_until_eof(self):
+        """
+        Reads message from stream until EOF
+        """

protocol_muxer/multiselect_muxer_interface.py

@@ -0,0 +1,25 @@
+from abc import ABC, abstractmethod
+
+class IMultiselectMuxer(ABC):
+    """
+    Multiselect module that is responsible for responding to
+    a multiselect client and deciding on
+    a specific protocol and handler pair to use for communication
+    """
+
+    @abstractmethod
+    def add_handler(self, protocol, handler):
+        """
+        Store the handler with the given protocol
+        :param protocol: protocol name
+        :param handler: handler function
+        """
+
+    @abstractmethod
+    def negotiate(self, stream):
+        """
+        Negotiate performs protocol selection
+        :param stream: stream to negotiate on
+        :return: selected protocol name, handler function
+        :raise Exception: negotiation failed exception
+        """