From 27cb8550ba5aad45f4486f9893facf16b3923289 Mon Sep 17 00:00:00 2001
From: Orion Kindel <orionkindel@gmail.com>
Date: Wed, 22 Nov 2023 10:05:01 -0600
Subject: [PATCH] feat: isLocked

---
 src/Data.Async.Class.purs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/Data.Async.Class.purs b/src/Data.Async.Class.purs
index 2acb98d..9a8fea3 100644
--- a/src/Data.Async.Class.purs
+++ b/src/Data.Async.Class.purs
@@ -2,7 +2,8 @@ module Data.Async.Class where
 
 import Prelude
 
-import Data.Maybe (Maybe)
+import Data.Foldable (for_)
+import Data.Maybe (Maybe, isNothing)
 import Effect.Aff.Class (class MonadAff)
 
 -- | Acquire a lock that guarantees access to mutable state
@@ -32,6 +33,13 @@ class AsyncStateLock m lock | lock -> m where
   -- | `unlock` has been invoked.
   unlock :: forall async a. MonadAff async => m a -> lock a -> async Unit
 
+-- | Returns whether a lock is currently held
+isLocked :: forall async a l g. MonadAff async => AsyncStateLock l g => l a -> async Boolean
+isLocked l = do
+  guard :: Maybe (g a) <- tryLock l
+  for_ guard (unlock l)
+  pure $ isNothing guard
+
 -- | A lock type that supports writing data to the mutable state.
 -- |
 -- | Writable locks must also be Readable.