Cache data

Main.hs

@@ -1,5 +1,6 @@
 {-# language TypeApplications #-}
 {-# language DataKinds #-}
+{-# language LambdaCase #-}
 {-# options_ghc -Wall -Werror #-}
 module Main (main) where
 
@@ -13,6 +14,7 @@ import qualified Data.ByteString.Lazy as ByteString
 import System.Directory
 import System.FilePath
 import System.Environment
+import Control.Monad (guard)
 
 main :: IO ()
 main = do
@@ -25,24 +27,29 @@ main = do
 cachedLoad :: IO (Bloom Size String)
 cachedLoad = do
   cache <- getCachePath
-  cacheExists <- doesFileExist cache
-  if cacheExists
-  then load cache
-  else do
+  load cache >>= \case
+    Nothing -> do
       b <- build
       ByteString.writeFile cache $ Binary.encode b
       pure b
+    Just a -> pure a
 
 getCachePath :: IO FilePath
 getCachePath = (</> "bloom-spell/words.bin") <$> getEnv "XDG_DATA_HOME"
 
-load :: FilePath -> IO (Bloom Size String)
-load p = Binary.decode @(Bloom Size _) <$> ByteString.readFile p
+load :: FilePath -> IO (Maybe (Bloom Size String))
+load p = do
+  cacheExists <- doesFileExist p
+  guard cacheExists
+  s <- ByteString.readFile p
+  case Binary.decodeOrFail @(Bloom Size _) s of
+    Left{} -> pure Nothing
+    Right (_, _, a) -> pure $ pure a
 
 build :: IO (Bloom Size String)
 build = fromList @(Bloom Size _) . lines <$> readFile dict
 
-type Size = 0xfffff
+type Size = 0xffff0
 
 dict :: FilePath
 dict = "/usr/share/dict/words"