From 6c5f0b513c980544fd6784a1fb5a2af42f97c57a Mon Sep 17 00:00:00 2001
From: Alexander Kobjolke <me@failco.de>
Date: Tue, 31 Oct 2023 13:28:08 +0100
Subject: [PATCH] lib: Make generic FilePack of any encodable type

---
 src/FilePack/Encode.hs   |  6 +++
 src/FilePack/FileData.hs | 81 +++++++++++++++++++++++++---------------
 2 files changed, 56 insertions(+), 31 deletions(-)

diff --git a/src/FilePack/Encode.hs b/src/FilePack/Encode.hs
index e71e4f7..c2e54e4 100644
--- a/src/FilePack/Encode.hs
+++ b/src/FilePack/Encode.hs
@@ -73,3 +73,9 @@ instance Encode Word32 where
 
 instance Encode FileMode where
   encode (CMode mode) = encode mode
+
+instance (Encode a, Encode b) => Encode (a, b) where
+  encode (a, b) = encodeWithSize a <> encodeWithSize b
+
+instance {-# OVERLAPPABLE #-} Encode a => Encode [a] where
+  encode = foldMap encodeWithSize
diff --git a/src/FilePack/FileData.hs b/src/FilePack/FileData.hs
index 2cbae28..b5ad5bc 100644
--- a/src/FilePack/FileData.hs
+++ b/src/FilePack/FileData.hs
@@ -1,42 +1,61 @@
+{-# LANGUAGE ImpredicativeTypes #-}
+{-# LANGUAGE RecordWildCards #-}
+
 module FilePack.FileData where
 
-import Data.ByteString (ByteString)
+import Data.Text
 
-import Data.Text (Text)
+import System.Posix.Types (FileMode)
 
-import Data.ByteString.Base64 qualified as B64
-import Data.ByteString.Char8 qualified as BC
-import GHC.Natural (Natural)
-import System.Posix.Types (CMode (..), FileMode)
-import Text.Read (readEither)
+import Data.Word (Word32)
+import FilePack.Encode (Encode (encode, encodeWithSize))
 
-import FilePack.Encode ()
+data FileData a = FileData
+  { fileName :: Text
+  , fileSize :: Word32
+  , filePermissions :: FileMode
+  , fileData :: a
+  }
+  deriving (Eq, Read, Show)
 
-data FileData = FileData
-    { fileName :: Text
-    , fileSize :: Natural
-    , filePermissions :: FileMode
-    , fileData :: ByteString
-    }
-    deriving (Eq, Read, Show)
+instance Encode a => Encode (FileData a) where
+  encode FileData{..} =
+    mconcat
+      [ encodeWithSize fileName
+      , encodeWithSize fileSize
+      , encodeWithSize filePermissions
+      , encodeWithSize fileData
+      ]
 
-newtype FilePack = FilePack {getPackedFiles :: [FileData]}
-    deriving (Eq, Read, Show)
+data Packable = forall a. Encode a => Packable {getPackable :: a}
 
-{- | @packFiles@ takes a FilePack and encodes it into a serialized form.
+instance Encode Packable where
+  encode (Packable a) = encode a
 
- >>> import Data.Text qualified as T
- >>> import Data.ByteString qualified as BS
- >>> import System.Posix.Files (stdFileMode)
- >>> let sampleFileData = FileData{fileName=T.pack "foo.txt", fileSize = 1024, filePermissions = stdFileMode, fileData = BS.empty}
- >>> let sampleFilePack = FilePack [sampleFileData]
- >>> (Right sampleFilePack) == (unpackFiles . packFiles $ sampleFilePack)
- True
--}
-packFiles :: FilePack -> ByteString
-packFiles = B64.encode . BC.pack . show
+newtype FilePack = FilePack [Packable]
+
+instance Encode FilePack where
+  encode (FilePack ps) = encode ps
+
+infixr 6 .:
+(.:) :: Encode a => FileData a -> FilePack -> FilePack
+(.:) = addFileDataToPack
+
+-- | @addFileDataToPack@ takes an encodeable FileData and adds it to a FilePack.
+--
+-- >>> import Data.ByteString qualified as BS
+-- >>> d = FileData{fileName = pack "a", fileSize = 4, filePermissions = 0644, fileData = "foo"}
+-- >>> BS.length $ encode d
+-- 28
+addFileDataToPack :: Encode a => FileData a -> FilePack -> FilePack
+addFileDataToPack a (FilePack as) = FilePack (Packable a : as)
+
+-- | @packFiles@ takes a FilePack and encodes it into a serialized form.
+--
+-- packFiles :: FilePack -> ByteString
+-- packFiles = B64.encode . encode
 
 -- | @unpackFiles@ tries to recover a FilePack from its serialized form.
-unpackFiles :: ByteString -> Either String FilePack
-unpackFiles serializedData =
-    B64.decode serializedData >>= readEither . BC.unpack
+-- unpackFiles :: ByteString -> Either String FilePack
+-- unpackFiles serializedData =
+--     B64.decode serializedData >>= readEither . BC.unpack