From f06db720ea2df4336b78a7041ce03213f9b5562f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Frederik=20Hangh=C3=B8j=20Iversen?=
 <fhanghojiversen@zendesk.com>
Date: Sat, 14 Nov 2020 13:37:37 +0100
Subject: [PATCH] Cache data

---
 Main.hs | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/Main.hs b/Main.hs
index 5b97373..8abbf91 100644
--- a/Main.hs
+++ b/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
-   b <- build
-   ByteString.writeFile cache $ Binary.encode b
-   pure b
+  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"