{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE ViewPatterns #-}

module Ormolu.Utils.IO
  ( findClosestFileSatisfying,
    Cache,
    newCache,
    withCache,
  )
where

import Control.Exception (catch, throwIO)
import Control.Monad (void)
import Control.Monad.IO.Class
import Data.IORef
import Data.Map.Lazy (Map)
import Data.Map.Lazy qualified as M
import System.Directory
import System.FilePath
import System.IO.Error (isDoesNotExistError)

-- | Find the path to the closest file higher in the file hierarchy that
-- satisfies a given predicate.
findClosestFileSatisfying ::
  (MonadIO m) =>
  -- | The predicate that determines what we are looking for
  (FilePath -> Bool) ->
  -- | Path to the starting point for the search
  FilePath ->
  -- | Absolute path to the found file if available
  m (Maybe FilePath)
findClosestFileSatisfying :: forall (m :: * -> *).
MonadIO m =>
(FilePath -> Bool) -> FilePath -> m (Maybe FilePath)
findClosestFileSatisfying FilePath -> Bool
isRightFile FilePath
rootOfSearch = IO (Maybe FilePath) -> m (Maybe FilePath)
forall a. IO a -> m a
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO (Maybe FilePath) -> m (Maybe FilePath))
-> IO (Maybe FilePath) -> m (Maybe FilePath)
forall a b. (a -> b) -> a -> b
$ do
  parentDir <- FilePath -> FilePath
takeDirectory (FilePath -> FilePath) -> IO FilePath -> IO FilePath
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> FilePath -> IO FilePath
makeAbsolute FilePath
rootOfSearch
  dirEntries <-
    listDirectory parentDir `catch` \case
      (IOError -> Bool
isDoesNotExistError -> Bool
True) -> [FilePath] -> IO [FilePath]
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure []
      IOError
e -> IOError -> IO [FilePath]
forall e a. (HasCallStack, Exception e) => e -> IO a
throwIO IOError
e
  let searchAtParentDirLevel = \case
        [] -> Maybe FilePath -> IO (Maybe FilePath)
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure Maybe FilePath
forall a. Maybe a
Nothing
        FilePath
x : [FilePath]
xs ->
          if FilePath -> Bool
isRightFile FilePath
x
            then
              FilePath -> IO Bool
doesFileExist (FilePath
parentDir FilePath -> FilePath -> FilePath
</> FilePath
x) IO Bool -> (Bool -> IO (Maybe FilePath)) -> IO (Maybe FilePath)
forall a b. IO a -> (a -> IO b) -> IO b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
                Bool
True -> Maybe FilePath -> IO (Maybe FilePath)
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (FilePath -> Maybe FilePath
forall a. a -> Maybe a
Just FilePath
x)
                Bool
False -> [FilePath] -> IO (Maybe FilePath)
searchAtParentDirLevel [FilePath]
xs
            else [FilePath] -> IO (Maybe FilePath)
searchAtParentDirLevel [FilePath]
xs
  searchAtParentDirLevel dirEntries >>= \case
    Just FilePath
foundFile -> Maybe FilePath -> IO (Maybe FilePath)
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Maybe FilePath -> IO (Maybe FilePath))
-> (FilePath -> Maybe FilePath) -> FilePath -> IO (Maybe FilePath)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. FilePath -> Maybe FilePath
forall a. a -> Maybe a
Just (FilePath -> IO (Maybe FilePath))
-> FilePath -> IO (Maybe FilePath)
forall a b. (a -> b) -> a -> b
$ FilePath
parentDir FilePath -> FilePath -> FilePath
</> FilePath
foundFile
    Maybe FilePath
Nothing ->
      if FilePath -> Bool
isDrive FilePath
parentDir
        then Maybe FilePath -> IO (Maybe FilePath)
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure Maybe FilePath
forall a. Maybe a
Nothing
        else (FilePath -> Bool) -> FilePath -> IO (Maybe FilePath)
forall (m :: * -> *).
MonadIO m =>
(FilePath -> Bool) -> FilePath -> m (Maybe FilePath)
findClosestFileSatisfying FilePath -> Bool
isRightFile FilePath
parentDir

newtype Cache k v = Cache (IORef (Map k v))

newCache :: (Ord k) => IO (Cache k v)
newCache :: forall k v. Ord k => IO (Cache k v)
newCache = do
  var <- Map k v -> IO (IORef (Map k v))
forall a. a -> IO (IORef a)
newIORef Map k v
forall a. Monoid a => a
mempty
  pure (Cache var)

-- | Execute an 'IO' action but only if the given key is not found in the
-- cache.
withCache :: (Ord k) => Cache k v -> k -> IO v -> IO v
withCache :: forall k v. Ord k => Cache k v -> k -> IO v -> IO v
withCache (Cache IORef (Map k v)
cacheVar) k
k IO v
action = do
  cache <- IORef (Map k v) -> IO (Map k v)
forall a. IORef a -> IO a
readIORef IORef (Map k v)
cacheVar
  case M.lookup k cache of
    Just v
v -> v -> IO v
forall a. a -> IO a
forall (f :: * -> *) a. Applicative f => a -> f a
pure v
v
    Maybe v
Nothing -> do
      v <- IO v
action
      void $ atomicModifyIORef cacheVar (pure . M.insert k v)
      pure v