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