fix: use watchDir callback instead of watchTreeChan for reliable event delivery

src/Roux/Server.hs

@@ -9,10 +9,9 @@ module Roux.Server (
     app,
 ) where
 
-import Control.Concurrent (forkIO)
-import Control.Concurrent.Chan (Chan, newChan, readChan)
+import Control.Concurrent (forkIO, threadDelay)
 import Control.Exception (SomeException, catch)
-import Control.Monad (when)
+import Control.Monad (forever, when)
 import Data.ByteString.Lazy (ByteString)
 import Data.Char (toLower)
 import Data.IORef (IORef, atomicModifyIORef', newIORef, readIORef)
@@ -20,7 +19,7 @@ import Data.List (isSuffixOf)
 import Data.Map.Strict (Map)
 import qualified Data.Map.Strict as Map
 import Data.Text (Text)
-import Data.Time.Clock (UTCTime, diffUTCTime, getCurrentTime)
+
 import qualified Network.HTTP.Types as HTTP
 import qualified Network.Wai as Wai
 import System.Directory (doesFileExist, makeAbsolute)
@@ -30,7 +29,7 @@ import System.FSNotify (
     WatchConfig (..),
     WatchMode (..),
     defaultConfig,
-    watchTreeChan,
+    watchDir,
     withManagerConf,
  )
 import System.FilePath (makeRelative, (</>))
@@ -69,34 +68,19 @@ app recipeDir = do
     isRight (Left _) = False
 
 {- | Watch a directory for .cook file changes and update the shared state.
-Implements debouncing: events for the same path within 200ms are skipped.
+Uses watchDir callback for simplicity.
 -}
 watchRecipes :: FilePath -> IORef (Map FilePath Idx.RecipeInfo) -> IO ()
 watchRecipes dir state = do
     putStrLn $ "[roux] watching " <> dir <> " for changes"
     let cfg = defaultConfig{confWatchMode = WatchModeOS}
     withManagerConf cfg $ \mgr -> do
-        chan <- newChan
-        _stopListening <- watchTreeChan mgr dir ((".cook" `isSuffixOf`) . eventPath) chan
-        debounceLoop chan state dir Map.empty
-  where
-    debounceLoop :: Chan Event -> IORef (Map FilePath Idx.RecipeInfo) -> FilePath -> Map FilePath UTCTime -> IO ()
-    debounceLoop chan st dr lastSeen = do
-        ev <- readChan chan
-        if eventIsDirectory ev == IsDirectory
-            then debounceLoop chan st dr lastSeen
-            else do
-                let path = makeRelative dr (eventPath ev)
-                let key = map toLower (stripCookExt path)
-                now <- getCurrentTime
-                let lastTime = Map.lookup key lastSeen
-                case lastTime of
-                    Just t
-                        | diffUTCTime now t < 0.2 ->
-                            debounceLoop chan st dr lastSeen
-                    _ -> do
-                        reReadRecipe dr path st
-                        debounceLoop chan st dr (Map.insert key now lastSeen)
+        _stopListening <- watchDir mgr dir (const True) $ \ev ->
+            when (eventIsDirectory ev == IsFile && ".cook" `isSuffixOf` eventPath ev) $ do
+                let path = makeRelative dir (eventPath ev)
+                reReadRecipe dir path state
+        -- Keep the thread alive (watchDir runs the callback on the manager thread)
+        forever $ threadDelay 1000000
 
 {- | Re-read a single recipe file and update the shared state.
 On read/parse errors, logs the error and keeps the previous version.