Add implementations for ExceptionChannel

Co-authored-by: Jan Beinke <git@janbeinke.com>

src/Quasar/Exceptions/ExceptionChannel.hs

+module Quasar.Exception.ExceptionChannel (
+  panicChannel,
+  loggingExceptionChannel,
+) where
+
+import Control.Concurrent (forkIO)
+import Control.Concurrent.STM
+import Control.Exception (BlockedIndefinitelyOnSTM(..))
+import Control.Monad.Catch
+import Debug.Trace qualified as Trace
+import GHC.IO (unsafePerformIO)
+import Quasar.Async.STMHelper
+import Quasar.Exceptions
+import Quasar.Prelude
+import Quasar.Utils.ShortIO
+import System.Exit (die)
+
+
+{-# NOINLINE panicChannel #-}
+panicChannel :: ExceptionChannel
+panicChannel = unsafePerformIO newPanicChannel
+
+newPanicChannel :: IO ExceptionChannel
+newPanicChannel = do
+  var <- newEmptyTMVarIO
+  void $ forkIO $ handle (\BlockedIndefinitelyOnSTM -> pure ()) do
+    ex <- atomically $ readTMVar var
+    die $ "Panic: " <> displayException ex
+  pure $ ExceptionChannel $ void . tryPutTMVar var
+
+
+loggingExceptionChannel :: TIOWorker -> ExceptionChannel
+loggingExceptionChannel worker =
+  -- Logging an exception should never fail - so if it does this panics the application
+  ExceptionChannel \ex -> startShortIOSTM_ (logFn ex) worker panicChannel
+  where
+    logFn :: SomeException -> ShortIO ()
+    logFn ex = unsafeShortIO $ Trace.traceIO $ displayException ex