Implement most of Connection

yaboli/connection.py

@@ -1,3 +1,14 @@
+import asyncio
+import logging
+from typing import Any, Awaitable, Callable
+
+import websockets
+
+from .events import Events
+from .exceptions import *
+
+logger = logging.getLogger(__name__)
+
 __all__ = ["Connection"]
 
 class Connection:
@@ -19,7 +30,7 @@ class Connection:
     2. call connect()
     3. send and receive packets, reconnecting automatically when connection is
     lost
-    4. call disconnect(), return to 2.
+    4. call disconnect()
 
 
     IN PHASE 1, parameters such as the url the Connection should connect to are
@@ -62,6 +73,197 @@ class Connection:
     "on_part-event" and "on_ping".
     """
 
-    def __init__(self,
-            url: str):
+    PING_TIMEOUT = 60 # seconds
+
+    _NOT_RUNNING = "not running"
+    _CONNECTING = "connecting"
+    _RUNNING = "running"
+    _RECONNECTING = "reconnecting"
+    _DISCONNECTING = "disconnecting"
+
+    # Initialising
+
+    def __init__(self, url: str) -> None:
         self._url = url
+
+        self._events = Events()
+
+        # This is the current status of the connection. It can be set to one of
+        # _NOT_RUNNING, _CONNECTING, _RUNNING, _RECONNECTING, or
+        # _DISCONNECTING.
+        #
+        # Always be careful to set any state-dependent variables.
+        self._status = _NOT_RUNNING
+        self._connected_event = asyncio.Event()
+        self._disconnected_event = asyncio.Event()
+
+        self._event_loop = None
+
+        # These must always be (re)set together. If one of them is None, all
+        # must be None.
+        self._ws = None
+        self._awaiting_replies = None
+        self._ping_check = None
+
+    def register_event(self,
+            event: str,
+            callback: Callable[..., Awaitable[None]]
+            ) -> None:
+        self._events.register(event, callback)
+
+    # Connecting and disconnecting
+
+    async def _disconnect(self) -> None:
+        """
+        Disconnect _ws and clean up _ws, _awaiting_replies and _ping_check.
+
+        Important: The caller must ensure that this function is called in valid
+        circumstances and not called twice at the same time. _disconnect() does
+        not check or manipulate _state.
+        """
+
+        if self._ws is None:
+            # This indicates that _ws, _awaiting_replies and _ping_check are
+            # cleaned up
+            return
+
+        await self._ws.close()
+
+        for tasks in self._awaiting_replies.values():
+            for task in tasks:
+                task.cancel()
+
+        self._ping_check.cancel()
+
+        self._ws = None
+        self._awaiting_replies = None
+        self._ping_check = None
+
+    async def _connect(self) -> bool:
+        """
+        Attempts once to create a ws connection.
+
+        Important: The caller must ensure that this function is called in valid
+        circumstances and not called twice at the same time. _connect() does
+        not check or manipulate _state, nor does it perform cleanup on
+        _awaiting_replies or _ping_check.
+        """
+
+        try:
+            ws = await websockets.connect(self._url)
+
+            self._ws = ws
+            self._awaiting_replies = {}
+            self._ping_check = asyncio.create_task(
+                    self._disconnect_in(self.PING_TIMEOUT))
+
+            return True
+
+        # TODO list all of the ways that creating a connection can go wrong
+        except websockets.InvalidStatusCode:
+            return False
+
+    async def _disconnect_in(self, delay):
+        await asyncio.sleep(delay)
+        await self._disconnect()
+
+    async def connect(self) -> bool:
+        # Special exception message for _CONNECTING.
+        if self._state == self._CONNECTING:
+            raise IncorrectStateException(("connect() may not be called"
+                " multiple times."))
+
+        if self._state != self._NOT_RUNNING:
+            raise IncorrectStateException(("disconnect() must complete before"
+                " connect() may be called again."))
+
+        # Now we're sure we're in the _NOT_RUNNING state, we can set our state.
+        # Important: No await-ing has occurred between checking the state and
+        # setting it.
+        self._state = self._CONNECTING
+
+        if await self._connect():
+            self._event_loop = asyncio.create_task(self._run())
+            self._state = self._RUNNING
+            return True
+        else:
+            self._state = self._NOT_RUNNING
+            return False
+
+    async def _reconnect(self) -> bool:
+        """
+        This function should only be called from the event loop while the
+        _state is _RUNNING.
+        """
+
+        if self._state != self._RUNNING:
+            raise IncorrectStateException()
+
+        self._state = self._RECONNECTING
+
+        await self._disconnect()
+        success =  await self._connect()
+
+        self._state = self._RUNNING
+
+        return success
+
+    async def disconnect(self) -> None:
+        # This function is kinda complex. The comments make it harder to read,
+        # but hopefully easier to understand.
+
+        # Possible states left: _NOT_RUNNING, _CONNECTING, _RUNNING,
+        # _RECONNECTING, _DISCONNECTING
+
+        # Waiting until the current connection attempt is finished.
+        if self._state in [self._CONNECTING, self._RECONNECTING]:
+            # After _CONNECTING, the state can either be _NOT_RUNNING or
+            # _RUNNING. After _RECONNECTING, the state must be _RUNNING.
+            await self._connected_event.wait()
+            # The state is now either _NOT_RUNNING or _RUNNING.
+
+        # Possible states left: _NOT_RUNNING, _RUNNING, _DISCONNECTING
+
+        if self._state == self._NOT_RUNNING:
+            # No need to do anything since we're already disconnected
+            return
+
+        # Possible states left: _RUNNING, _DISCONNECTING
+
+        if self._state == self._DISCONNECTING:
+            # Wait until the disconnecting currently going on is complete. This
+            # is to prevent the disconnect() function from ever returning
+            # without the disconnecting process being finished.
+            await self._disconnected_event.wait()
+            return
+
+        # Possible states left: _RUNNING
+
+        # By principle of exclusion, the only state left is _RUNNING. Doing an
+        # explicit check though, just to make sure.
+        if self._state != self._RUNNING:
+            raise IncorrectStateException("This should never happen.")
+
+        # Now, we can properly disconnect ^^
+        await self._disconnect()
+
+        await self._event_loop
+        self._event_loop = None
+
+        self._state = self._NOT_RUNNING
+
+        # Notify all other disconnect()s waiting
+        self._disconnected_event.set()
+        self._disconnected_event.clear()
+
+    # Running
+
+    async def _run(self) -> None:
+        """
+        The main loop that runs during phase 3
+        """
+
+        # TODO
+
+    async def send(self, packet: Any) -> Any:
+        pass # TODO

yaboli/events.py

@@ -0,0 +1,25 @@
+import asyncio
+import logging
+from typing import Any, Awaitable, Callable, Dict, List
+
+logger = logging.getLogger(__name__)
+
+__all__ = ["Events"]
+
+class Events:
+    def __init__(self) -> None:
+        self._callbacks: Dict[str, List[Callable[..., Awaitable[None]]]] = {}
+
+    def register(self,
+            event: str,
+            callback: Callable[..., Awaitable[None]]
+            ) -> None:
+        callback_list = self._callbacks.get(event, [])
+        callback_list.append(callback)
+        self._callbacks[event] = callback_list
+        logger.debug(f"Registered callback for event {event!r}")
+
+    async def fire(self, event: str, *args: Any, **kwargs: Any) -> None:
+        logger.debug(f"Calling callbacks for event {event!r}")
+        for callback in self._callbacks.get(event, []):
+            asyncio.create_task(callback(*args, **kwargs))

yaboli/exceptions.py

@@ -5,6 +5,21 @@ __all__ = ["EuphException", "JoinException", "CouldNotConnectException",
 class EuphException(Exception):
     pass
 
+# Connection stuff
+
+class IncorrectStateException(EuphException):
+    """
+    A Connection function was called while the Connection was in the incorrect
+    state.
+    """
+    pass
+
+class ConnectionClosedException(EuphException):
+    """
+    The connection was closed unexpectedly.
+    """
+    pass
+
 # Joining a room
 
 class JoinException(EuphException):