Add SubscriptionAPI

And `TrioSubscriptionAPI`, to make subscription io-agnostic.

libp2p/pubsub/abc.py

@@ -0,0 +1,98 @@
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING, AsyncContextManager, AsyncIterable, List
+
+from libp2p.peer.id import ID
+from libp2p.typing import TProtocol
+
+from .pb import rpc_pb2
+
+if TYPE_CHECKING:
+    from .pubsub import Pubsub  # noqa: F401
+
+
+# TODO: Add interface for Pubsub
+class IPubsub(ABC):
+    pass
+
+
+class IPubsubRouter(ABC):
+    @abstractmethod
+    def get_protocols(self) -> List[TProtocol]:
+        """
+        :return: the list of protocols supported by the router
+        """
+
+    @abstractmethod
+    def attach(self, pubsub: "Pubsub") -> None:
+        """
+        Attach is invoked by the PubSub constructor to attach the router to a
+        freshly initialized PubSub instance.
+
+        :param pubsub: pubsub instance to attach to
+        """
+
+    @abstractmethod
+    def add_peer(self, peer_id: ID, protocol_id: TProtocol) -> None:
+        """
+        Notifies the router that a new peer has been connected.
+
+        :param peer_id: id of peer to add
+        """
+
+    @abstractmethod
+    def remove_peer(self, peer_id: ID) -> None:
+        """
+        Notifies the router that a peer has been disconnected.
+
+        :param peer_id: id of peer to remove
+        """
+
+    @abstractmethod
+    async def handle_rpc(self, rpc: rpc_pb2.RPC, sender_peer_id: ID) -> None:
+        """
+        Invoked to process control messages in the RPC envelope.
+        It is invoked after subscriptions and payload messages have been processed
+        TODO: Check if this interface is ok. It's not the exact same as the go code, but the go
+        code is really confusing with the msg origin, they specify `rpc.from` even when the rpc
+        shouldn't have a from
+        :param rpc: rpc message
+        """
+
+    @abstractmethod
+    async def publish(self, msg_forwarder: ID, pubsub_msg: rpc_pb2.Message) -> None:
+        """
+        Invoked to forward a new message that has been validated.
+
+        :param msg_forwarder: peer_id of message sender
+        :param pubsub_msg: pubsub message to forward
+        """
+
+    @abstractmethod
+    async def join(self, topic: str) -> None:
+        """
+        Join notifies the router that we want to receive and forward messages
+        in a topic. It is invoked after the subscription announcement.
+
+        :param topic: topic to join
+        """
+
+    @abstractmethod
+    async def leave(self, topic: str) -> None:
+        """
+        Leave notifies the router that we are no longer interested in a topic.
+        It is invoked after the unsubscription announcement.
+
+        :param topic: topic to leave
+        """
+
+
+class ISubscriptionAPI(
+    AsyncContextManager["ISubscriptionAPI"], AsyncIterable[rpc_pb2.Message]
+):
+    @abstractmethod
+    async def cancel(self) -> None:
+        ...
+
+    @abstractmethod
+    async def get(self) -> rpc_pb2.Message:
+        ...