Only open the cover image if needed

Author: jecaro

data/htagcli.toml

@@ -86,7 +86,8 @@ enable = true
 enable = true
 filenames = ["cover.jpg", "cover.png", "cover.gif"]
 # optional size constraints in pixels, not taken into account if left
-# unspecified
+# unspecified.
+# Warning: this makes the check significantly slower
 min_size = { width = 300, height = 300 }
 max_size = { width = 1000, height = 1000 }
 

lib/Check/Album.hs

@@ -73,15 +73,18 @@ check (HaveCover cover@Cover {..}) album
         maybeToExceptT (MissingCover dir) $
           MaybeT $
             Monad.findM Path.doesFileExist (toList absFiles)
-      picture <-
-        Except.withExceptT (UnableToReadCover coverFile . toText) $
-          ExceptT $
-            readImage coverFile
+      -- Reading the image is very slow, so only do it if we have size
+      -- constraints
+      when (Cover.haveRange cover) $ do
+        picture <-
+          Except.withExceptT (UnableToReadCover coverFile . toText) $
+            ExceptT $
+              readImage coverFile
 
-      let size = Cover.pictureSize picture
-      unless (Cover.withinRange cover size) $
-        Except.throwE $
-          BadCoverSize coverFile size
+        let size = Cover.pictureSize picture
+        unless (Cover.withinRange cover size) $
+          Except.throwE $
+            BadCoverSize coverFile size
   | otherwise = pure $ Left NotInSameDir
   where
     readImage = liftIO . Picture.readImage . Path.toFilePath

lib/Model/Cover.hs

@@ -3,6 +3,7 @@ module Model.Cover
     Size (..),
     sizeToText,
     pictureSize,
+    haveRange,
     withinRange,
   )
 where
@@ -38,6 +39,9 @@ pictureSize picture =
       siHeight = Picture.dynamicMap Picture.imageHeight picture
     }
 
+haveRange :: Cover -> Bool
+haveRange Cover {..} = isJust coMinSize || isJust coMaxSize
+
 withinRange :: Cover -> Size -> Bool
 withinRange Cover {..} size =
   maybe True (size `greaterThan`) coMinSize