Add System.Directory library, allow for testing file existence

package.yaml

@@ -45,6 +45,7 @@ dependencies:
 - foldl
 - linear
 - aeson
+- directory
 
 library:
   source-dirs: src

src/LoadConfig.hs

@@ -10,6 +10,8 @@ import qualified GHC.Int
 import qualified SDL
 import SDL.Internal.Numbered as SDL.Internal.Numbered
 
+import System.Directory
+
 data Configuration = Configuration
   { windowxsize :: Int,
     windowysize :: Int
@@ -133,33 +135,37 @@ instance FromJSON KeyConfig where
 
 loadKeyConfig :: IO KeyConfigSDL
 loadKeyConfig = do
-  mayConfig <- decodeFileStrict "keys.json"
-  print mayConfig
-  case mayConfig of
-    Just config ->
-      return
-        KeyConfigSDL
-          { moveUpKey = getSdlScancode $ moveUpBinding config,
-            moveDownKey = getSdlScancode $ moveDownBinding config,
-            moveLeftKey = getSdlScancode $ moveLeftBinding config,
-            moveRightKey = getSdlScancode $ moveRightBinding config,
-            pauseKey = getSdlScancode $ pauseBinding config,
-            escapeKey = getSdlScancode $ escapeBinding config,
-            dropItemKey = getSdlScancode $ dropItemBinding config,
-            toggleMapKey = getSdlScancode $ toggleMapBinding config,
-            reloadKey = getSdlScancode $ reloadBinding config,
-            testEventKey = getSdlScancode $ testEventBinding config,
-            spaceActionKey = getSdlScancode $ spaceActionBinding config,
-            rotateCameraPlusKey = getSdlScancode $ rotateCameraPlusBinding config,
-            rotateCameraMinusKey = getSdlScancode $ rotateCameraMinusBinding config,
-            zoomInKey = getSdlScancode $ zoomInBinding config,
-            zoomOutKey = getSdlScancode $ zoomOutBinding config,
-            newKey = getSdlScancode $ newBinding config
-          }
-    Nothing -> do
-      putStrLn "invalid keys.json, loading default config"
-      -- This is duplicated but not sure how to reduce
-      return defaultKeyConfigSDL
+    fExists <- doesFileExist "keys.json"
+    if fExists
+    then do
+        mayConfig <- decodeFileStrict "keys.json"
+        print mayConfig
+        case mayConfig of
+          Just config ->
+            return
+              KeyConfigSDL
+                { moveUpKey = getSdlScancode $ moveUpBinding config,
+                  moveDownKey = getSdlScancode $ moveDownBinding config,
+                  moveLeftKey = getSdlScancode $ moveLeftBinding config,
+                  moveRightKey = getSdlScancode $ moveRightBinding config,
+                  pauseKey = getSdlScancode $ pauseBinding config,
+                  escapeKey = getSdlScancode $ escapeBinding config,
+                  dropItemKey = getSdlScancode $ dropItemBinding config,
+                  toggleMapKey = getSdlScancode $ toggleMapBinding config,
+                  reloadKey = getSdlScancode $ reloadBinding config,
+                  testEventKey = getSdlScancode $ testEventBinding config,
+                  spaceActionKey = getSdlScancode $ spaceActionBinding config,
+                  rotateCameraPlusKey = getSdlScancode $ rotateCameraPlusBinding config,
+                  rotateCameraMinusKey = getSdlScancode $ rotateCameraMinusBinding config,
+                  zoomInKey = getSdlScancode $ zoomInBinding config,
+                  zoomOutKey = getSdlScancode $ zoomOutBinding config,
+                  newKey = getSdlScancode $ newBinding config
+                }
+          Nothing -> do
+            putStrLn "invalid keys.json, loading default config"
+            -- This is duplicated but not sure how to reduce
+            return defaultKeyConfigSDL
+    else return defaultKeyConfigSDL
 
 getSdlScancode :: Int -> SDL.Scancode
-getSdlScancode x = SDL.Internal.Numbered.fromNumber (fromIntegral x) :: SDL.Scancode
+getSdlScancode x = SDL.Internal.Numbered.fromNumber (fromIntegral x) :: SDL.Scancode