Merge pull request #7 from ArktinenSieni/mem-backend

Upload files to memory

Author: phadej

exe/Upload.hs

@@ -14,10 +14,12 @@ import Network.Wai.Handler.Warp
 import Servant
 import Servant.Multipart
 
+import qualified Data.ByteString.Lazy as LBS
+
 -- Our API, which consists in a single POST endpoint at /
 -- that takes a multipart/form-data request body and
 -- pretty-prints the data it got to stdout before returning 0.
-type API = MultipartForm MultipartData :> Post '[JSON] Integer
+type API = MultipartForm Mem (MultipartData Mem) :> Post '[JSON] Integer
 
 api :: Proxy API
 api = Proxy
@@ -38,10 +40,9 @@ upload multipartData = do
             ++ " -> " ++ show (iValue input)
 
     forM_ (files multipartData) $ \file -> do
-      content <- readFile (fdFilePath file)
+      let content = fdPayload file
       putStrLn $ "Content of " ++ show (fdFileName file)
-              ++ " at " ++ fdFilePath file
-      putStrLn content
+      LBS.putStr content
   return 0
 
 startServer :: IO ()

servant-multipart.cabal

@@ -42,6 +42,7 @@ executable upload
   build-depends:
                 base,
                 http-client,
+                bytestring,
                 network,
                 servant,
                 servant-multipart,

src/Servant/Multipart.hs

@@ -8,6 +8,8 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeSynonymInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE UndecidableInstances #-}
 -- | @multipart/form-data@ support for servant.
 --
 --   This is mostly useful for adding file upload support to
@@ -20,7 +22,8 @@ module Servant.Multipart
   , lookupFile
   , MultipartOptions(..)
   , defaultMultipartOptions
-  , TmpBackendOptions(..)
+  , Tmp
+  , Mem
   , defaultTmpBackendOptions
   , Input(..)
   , FileData(..)
@@ -58,6 +61,10 @@ import qualified Data.ByteString.Lazy as LBS
 --   stand now. This also means that 'MultipartForm' can't be used in
 --   conjunction with 'ReqBody' in an endpoint.
 --
+--   The 'tag' type parameter instructs the function to handle data
+--   either as data to be saved to temporary storage ('Tmp') or saved to
+--   memory ('Mem').
+--
 --   The 'a' type parameter represents the Haskell type to which
 --   you are going to decode the multipart data to, where the
 --   multipart data consists in all the usual form inputs along
@@ -70,12 +77,12 @@ import qualified Data.ByteString.Lazy as LBS
 --   Example:
 --
 --   @
---   type API = MultipartForm MultipartData :> Post '[PlainText] String
+--   type API = MultipartForm Tmp (MultipartData Tmp) :> Post '[PlainText] String
 --
 --   api :: Proxy API
 --   api = Proxy
 --
---   server :: MultipartData -> Handler String
+--   server :: MultipartData Tmp -> Handler String
 --   server multipartData = return str
 --
 --     where str = "The form was submitted with "
@@ -97,12 +104,12 @@ import qualified Data.ByteString.Lazy as LBS
 --   @
 --   data User = User { username :: Text, pic :: FilePath }
 --
---   instance FromMultipart User where
+--   instance FromMultipart Tmp User where
 --     fromMultipart multipartData =
 --       User \<$\> lookupInput "username" multipartData
 --            \<*\> fmap fileContent (lookupFile "pic" multipartData)
 --
---   type API = MultipartForm User :> Post '[PlainText] String
+--   type API = MultipartForm Tmp User :> Post '[PlainText] String
 --
 --   server :: User -> Handler String
 --   server usr = return str
@@ -125,10 +132,14 @@ import qualified Data.ByteString.Lazy as LBS
 --   after your handler has run, if they are still there. It is
 --   therefore recommended to move or copy them somewhere in your
 --   handler code if you need to keep the content around.
-data MultipartForm a
+data MultipartForm tag a
 
 -- | What servant gets out of a @multipart/form-data@ form submission.
 --
+--   The type parameter 'tag' tells if 'MultipartData' is stored as a
+--   temporary file or stored in memory. 'tag' is type of either 'Mem'
+--   or 'Tmp'.
+--
 --   The 'inputs' field contains a list of textual 'Input's, where
 --   each input for which a value is provided gets to be in this list,
 --   represented by the input name and the input value. See haddocks for
@@ -139,20 +150,19 @@ data MultipartForm a
 --   'FileData' which among other things contains the path to the temporary file
 --   (to be removed when your handler is done running) with a given uploaded
 --   file's content. See haddocks for 'FileData'.
-data MultipartData = MultipartData
+data MultipartData tag = MultipartData
   { inputs :: [Input]
-  , files  :: [FileData]
+  , files  :: [FileData tag]
   }
 
--- TODO: this is specific to Tmp. we need a version that
--- can handle Mem as well.
-fromRaw :: ([Network.Wai.Parse.Param], [File FilePath]) -> MultipartData
+fromRaw :: forall tag. ([Network.Wai.Parse.Param], [File (MultipartResult tag)])
+        -> MultipartData tag
 fromRaw (inputs, files) = MultipartData is fs
 
   where is = map (\(name, val) -> Input (dec name) (dec val)) inputs
         fs = map toFile files
 
-        toFile :: File FilePath -> FileData
+        toFile :: File (MultipartResult tag) -> FileData tag
         toFile (iname, fileinfo) =
           FileData (dec iname)
                    (dec $ fileName fileinfo)
@@ -164,20 +174,24 @@ fromRaw (inputs, files) = MultipartData is fs
 -- | Representation for an uploaded file, usually resulting from
 --   picking a local file for an HTML input that looks like
 --   @\<input type="file" name="somefile" /\>@.
-data FileData = FileData
+data FileData tag = FileData
   { fdInputName :: Text     -- ^ @name@ attribute of the corresponding
                             --   HTML @\<input\>@
   , fdFileName  :: Text     -- ^ name of the file on the client's disk
   , fdFileCType :: Text     -- ^ MIME type for the file
-  , fdFilePath  :: FilePath -- ^ path to the temporary file that has the
+  , fdPayload   :: MultipartResult tag
+                            -- ^ path to the temporary file that has the
                             --   content of the user's original file. Only
                             --   valid during the execution of your handler as
                             --   it gets removed right after, which means you
                             --   really want to move or copy it in your handler.
-  } deriving (Eq, Show)
+  }
+
+deriving instance Eq (MultipartResult tag) => Eq (FileData tag)
+deriving instance Show (MultipartResult tag) => Show (FileData tag)
 
 -- | Lookup a file input with the given @name@ attribute.
-lookupFile :: Text -> MultipartData -> Maybe FileData
+lookupFile :: Text -> MultipartData tag -> Maybe (FileData tag)
 lookupFile iname = find ((==iname) . fdInputName) . files
 
 -- | Representation for a textual input (any @\<input\>@ type but @file@).
@@ -189,7 +203,7 @@ data Input = Input
   } deriving (Eq, Show)
 
 -- | Lookup a textual input with the given @name@ attribute.
-lookupInput :: Text -> MultipartData -> Maybe Text
+lookupInput :: Text -> MultipartData tag -> Maybe Text
 lookupInput iname = fmap iValue . find ((==iname) . iName) . inputs
 
 -- | 'MultipartData' is the type representing
@@ -209,62 +223,71 @@ lookupInput iname = fmap iValue . find ((==iname) . iName) . inputs
 --       User \<$\> lookupInput "username" (inputs form)
 --            \<*\> fmap fdFilePath (lookupFile "pic" $ files form)
 --   @
-class FromMultipart a where
+class FromMultipart tag a where
   -- | Given a value of type 'MultipartData', which consists
   --   in a list of textual inputs and another list for
   --   files, try to extract a value of type @a@. When
   --   extraction fails, servant errors out with status code 400.
-  fromMultipart :: MultipartData -> Maybe a
+  fromMultipart :: MultipartData tag -> Maybe a
 
-instance FromMultipart MultipartData where
+instance FromMultipart tag (MultipartData tag) where
   fromMultipart = Just
 
 -- | Upon seeing @MultipartForm a :> ...@ in an API type,
 ---  servant-server will hand a value of type @a@ to your handler
 --   assuming the request body's content type is
 --   @multipart/form-data@ and the call to 'fromMultipart' succeeds.
-instance ( FromMultipart a
-         , LookupContext config MultipartOptions
+instance ( FromMultipart tag a
+         , MultipartBackend tag
+         , LookupContext config (MultipartOptions tag)
          , HasServer sublayout config )
-      => HasServer (MultipartForm a :> sublayout) config where
+      => HasServer (MultipartForm tag a :> sublayout) config where
 
-  type ServerT (MultipartForm a :> sublayout) m =
+  type ServerT (MultipartForm tag a :> sublayout) m =
     a -> ServerT sublayout m
 
   route Proxy config subserver =
     route psub config subserver'
     where
       psub  = Proxy :: Proxy sublayout
       pbak  = Proxy :: Proxy b
-      popts = Proxy :: Proxy MultipartOptions
-      multipartOpts = fromMaybe defaultMultipartOptions
+      popts = Proxy :: Proxy (MultipartOptions tag)
+      multipartOpts = fromMaybe (defaultMultipartOptions pbak)
                     $ lookupContext popts config
-      subserver' = addMultipartHandling multipartOpts subserver
+      subserver' = addMultipartHandling pbak multipartOpts subserver
 
 -- Try and extract the request body as multipart/form-data,
 -- returning the data as well as the resourcet InternalState
 -- that allows us to properly clean up the temporary files
 -- later on.
-check :: MultipartOptions -> DelayedIO MultipartData
-check opts = withRequest $ \request -> do
+check :: MultipartBackend tag
+      => Proxy tag
+      -> MultipartOptions tag
+      -> DelayedIO (MultipartData tag)
+check pTag tag = withRequest $ \request -> do
   st <- liftResourceT getInternalState
-  rawData <- liftIO $ parseRequestBodyEx parseOpts (tmpBackend opts st) request
+  rawData <- liftIO
+      $ parseRequestBodyEx
+          parseOpts
+          (backend pTag (backendOptions tag) st)
+          request
   return (fromRaw rawData)
-  where parseOpts = generalOptions opts
+  where parseOpts = generalOptions tag
 
 -- Add multipart extraction support to a Delayed.
-addMultipartHandling :: FromMultipart multipart
-                     => MultipartOptions
+addMultipartHandling :: forall tag multipart env a. (FromMultipart tag multipart, MultipartBackend tag)
+                     => Proxy tag
+                     -> MultipartOptions tag
                      -> Delayed env (multipart -> a)
                      -> Delayed env a
-addMultipartHandling opts subserver =
+addMultipartHandling pTag opts subserver =
   addBodyCheck subserver contentCheck bodyCheck
   where
     contentCheck = withRequest $ \request ->
       fuzzyMultipartCTCheck (contentTypeH request)
 
     bodyCheck () = do
-      mpd <- check opts :: DelayedIO MultipartData
+      mpd <- check pTag opts :: DelayedIO (MultipartData tag)
       case fromMultipart mpd of
         Nothing -> liftRouteResult $ FailFatal
           err400 { errBody = "fromMultipart returned Nothing" }
@@ -289,31 +312,60 @@ fuzzyMultipartCTCheck ct
           "multipart/form-data" | Just _bound <- lookup "boundary" attrs -> True
           _ -> False
 
-tmpBackend :: MultipartOptions
-           -> InternalState
-           -> ignored1
-           -> ignored2
-           -> IO SBS.ByteString
-           -> IO FilePath
-tmpBackend opts =
-    tempFileBackEndOpts (getTmpDir tmpOpts) (filenamePat tmpOpts)
-  where
-    tmpOpts = tmpOptions opts
-
 -- | Global options for configuring how the
 --   server should handle multipart data.
 --
 --   'generalOptions' lets you specify mostly multipart parsing
 --   related options, such as the maximum file size, while
---   'tmpOptions' lets you configure aspects specific to
---   the temporary file backend. See haddocks for
---   'ParseRequestBodyOptions' and 'TmpBackendOptions' respectively
---   for more information on what you can tweak.
-data MultipartOptions = MultipartOptions
-  { generalOptions :: ParseRequestBodyOptions
-  , tmpOptions     :: TmpBackendOptions
+--   'backendOptions' lets you configure aspects specific to the chosen
+--   backend. Note: there isn't anything to tweak in a memory
+--   backend ('Mem'). Maximum file size etc. options are in
+--   'ParseRequestBodyOptions'.
+--
+--   See haddocks for 'ParseRequestBodyOptions' and
+--   'TmpBackendOptions' respectively for more information on
+--   what you can tweak.
+data MultipartOptions tag = MultipartOptions
+  { generalOptions        :: ParseRequestBodyOptions
+  , backendOptions        :: MultipartBackendOptions tag
   }
 
+class MultipartBackend tag where
+    type MultipartResult tag :: *
+    type MultipartBackendOptions tag :: *
+
+    backend :: Proxy tag
+            -> MultipartBackendOptions tag
+            -> InternalState
+            -> ignored1
+            -> ignored2
+            -> IO SBS.ByteString
+            -> IO (MultipartResult tag)
+
+    defaultBackendOptions :: Proxy tag -> MultipartBackendOptions tag
+
+-- | Tag for data stored as a temporary file
+data Tmp
+
+-- | Tag for data stored in memory
+data Mem
+
+instance MultipartBackend Tmp where
+    type MultipartResult Tmp = FilePath
+    type MultipartBackendOptions Tmp = TmpBackendOptions
+
+    defaultBackendOptions _ = defaultTmpBackendOptions
+    backend _ opts = tmpBackend
+      where
+        tmpBackend = tempFileBackEndOpts (getTmpDir opts) (filenamePat opts)
+
+instance MultipartBackend Mem where
+    type MultipartResult Mem = LBS.ByteString
+    type MultipartBackendOptions Mem = ()
+
+    defaultBackendOptions _ = ()
+    backend _ opts _ = lbsBackEnd
+
 -- | Configuration for the temporary file based backend.
 --
 --   You can configure the way servant-multipart gets its hands
@@ -337,11 +389,11 @@ defaultTmpBackendOptions = TmpBackendOptions
 -- | Default configuration for multipart handling.
 --
 --   Uses 'defaultParseRequestBodyOptions' and
---   'defaultTmpBackendOptions' respectively.
-defaultMultipartOptions :: MultipartOptions
-defaultMultipartOptions = MultipartOptions
+--   'defaultBackendOptions' respectively.
+defaultMultipartOptions :: MultipartBackend tag => Proxy tag -> MultipartOptions tag
+defaultMultipartOptions pTag = MultipartOptions
   { generalOptions = defaultParseRequestBodyOptions
-  , tmpOptions = defaultTmpBackendOptions
+  , backendOptions = defaultBackendOptions pTag
   }
 
 -- Utility class that's like HasContextEntry