refactor history

1 files changed, 26 insertions, 0 deletions

diff --git a/app/History/Cache.hs b/app/History/Cache.hs
new file mode 100644
index 0000000..af40a84
--- /dev/null
+++ b/app/History/Cache.hs
@@ -0,0 +1,26 @@
+module History.Cache (cached) where
+
+import Data.Binary (Binary, decodeFileOrFail, encodeFile)
+import Data.Text qualified as T
+import System.Directory (createDirectoryIfMissing, doesFileExist, getCurrentDirectory)
+
+cached :: Binary a => T.Text -> (T.Text -> IO a) -> IO a
+cached hash func = do
+  -- FIXME Cache inside Git root
+  --
+  -- The cache location should not be dependant on the current directory, but
+  -- should be placed alongside the `.git` directory.
+  cwd <- getCurrentDirectory
+  createDirectoryIfMissing True (cwd ++ "/.anissue")
+  let file = (cwd ++ "/.anissue/" ++ T.unpack hash)
+  doesFileExist file >>= \case
+    True ->
+      decodeFileOrFail file >>= \case
+        Left _ -> generate file
+        Right blob -> pure blob
+    False -> generate file
+  where
+    generate file = do
+      blob <- func hash
+      encodeFile file blob
+      pure blob