implemented readMax

I disagree with the use of `<$>` in place of `.`, but not enough to fight hlint on it.

gemcap.cabal

@@ -40,6 +40,7 @@ library
     , tcp-streams >=1.0.1.1 && <1.1
     , text >=1.2.4.1 && <1.3
     , tls
+    , transformers
     , x509
   default-language: Haskell2010
   autogen-modules: Paths_gemcap
@@ -65,6 +66,7 @@ test-suite gemcap-test
     , tcp-streams >=1.0.1.1 && <1.1
     , text >=1.2.4.1 && <1.3
     , tls
+    , transformers
     , x509
   default-language: Haskell2010
   autogen-modules: Paths_gemcap

package.yaml

@@ -31,6 +31,7 @@ dependencies:
 - io-streams
 - network
 - tls
+- transformers
 - x509
 
 library:

src/Network/Gemini/Capsule/Internal.hs

@@ -34,10 +34,21 @@ time.
 
 module Network.Gemini.Capsule.Internal (
   readURL,
-  sendResponse
+  sendResponse,
+  strFromConn,
+  readMax,
+  stripCRLF
 ) where
 
-import Data.Connection (Connection)
+import Control.Monad.Trans.Class (lift)
+import Control.Monad.Trans.Maybe (MaybeT (..))
+import qualified Data.ByteString as BS
+import Data.ByteString.Builder (Builder, byteString, toLazyByteString)
+import qualified Data.ByteString.Lazy as BSL
+import Data.Connection (Connection, source)
+import qualified Data.Text as T
+import Data.Text.Encoding (decodeUtf8')
+import System.IO.Streams as S
 
 import Network.Gemini.Capsule.Encoding
 import Network.Gemini.Capsule.Types
@@ -54,7 +65,7 @@ readURL
   -- ^ the connection
   -> IO (Maybe GemURL)
 readURL conn =
-  strFromConn inBufSize conn >>= return . \case
+  strFromConn inBufSize conn >>= return <$> \case
     Nothing  -> Nothing
     Just str -> decodeGemURL str
 
@@ -76,6 +87,41 @@ strFromConn
   -> Connection a
   -- ^ The connection to read from
   -> IO (Maybe String)
-strFromConn = undefined
+strFromConn maxLen conn = do
+  mbs <- readMax maxLen conn
+  return $ do
+    bs  <- mbs
+    txt <- case decodeUtf8' bs of
+      Left _  -> Nothing
+      Right s -> Just s
+    stripCRLF $ T.unpack txt
+
+-- | Reads from a connection up to a maximum number of bytes,
+-- returning 'Nothing' if the limit is exceeded
+readMax
+  :: Int
+  -- ^ the maximum number of bytes
+  -> Connection a
+  -- ^ the 'Connection' to read from
+  -> IO (Maybe BS.ByteString)
+readMax maxLen conn = do
+  let src = source conn
+  runMaybeT $
+    BS.pack . BSL.unpack . toLazyByteString
+    <$> readLoop maxLen src
+
+-- | Strips the CR/LF characters from the end of a string, retuning
+-- Nothing if they are not present
+stripCRLF :: String -> Maybe String
+stripCRLF = undefined
+
+readLoop :: Int -> S.InputStream BS.ByteString -> MaybeT IO Builder
+readLoop maxLen src =
+  lift (S.read src) >>= \case
+    Nothing -> return mempty
+    Just bs -> let len = BS.length bs in
+      if len > maxLen
+        then MaybeT $ return Nothing
+        else (byteString bs <>) <$> readLoop (maxLen - len) src
 
 --jl

test/Network/Gemini/Capsule/InternalSpec.hs

@@ -20,7 +20,7 @@ License along with this program.  If not, see
 
 -}
 
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE OverloadedStrings, RecordWildCards #-}
 
 module Network.Gemini.Capsule.InternalSpec (spec) where
 
@@ -28,7 +28,7 @@ import qualified Data.ByteString as BS
 import Data.Char (ord)
 import Data.Connection (Connection (..))
 import System.IO.Streams (nullInput, unRead)
-import Test.Hspec (Spec, context, describe, shouldReturn, xit)
+import Test.Hspec (Spec, context, describe, it, shouldReturn, xit)
 
 import Network.Gemini.Capsule.Types
 import Network.Gemini.Capsule.Internal
@@ -38,6 +38,8 @@ spec = describe "Internal" $ do
   readURLSpec
   sendResponseSpec
   strFromConnSpec
+  readMaxSpec
+  stripCRLFSpec
 
 readURLSpec :: Spec
 readURLSpec = describe "readURL" $ mapM_
@@ -56,10 +58,10 @@ readURLSpec = describe "readURL" $ mapM_
   ]
 
   where
-    validConn   = mkConn "gemini://example.com/\r\n"
+    validConn   = mkInConn ["gemini://example.com/\r\n"]
-    longConn    = mkConn longBS
+    longConn    = mkInConn [longBS]
-    tooLongConn = mkConn tooLongBS
+    tooLongConn = mkInConn [tooLongBS]
-    gibConn     = mkConn "aosidjfwoeinboijwefr"
+    gibConn     = mkInConn ["aosidjfwoeinboijwefr"]
     longBS      = BS.pack (take 1024 bytes) <> "\r\n"
     tooLongBS   = BS.pack (take 1025 bytes) <> "\r\n"
     bytes       = BS.unpack prefix ++ repeat (fromIntegral $ ord 'A')
@@ -67,23 +69,62 @@ readURLSpec = describe "readURL" $ mapM_
     longExp     = validExp { gemPath = [longDir] }
     longDir     = replicate (1024 - BS.length prefix) 'A'
     prefix      = "gemini://example.com/"
-    mkConn bs   = do
-      s <- nullInput
-      unRead bs s
-      return sampleConnection { source = s }
 
 sendResponseSpec :: Spec
 sendResponseSpec = describe "sendResponse" $ return ()
 
-sampleConnection :: Connection a
-sampleConnection = Connection
-  { source        = undefined
-  , send          = const $ return ()
-  , close         = return ()
-  , connExtraInfo = undefined
-  }
-
 strFromConnSpec :: Spec
-strFromConnSpec = describe "strFromConn" $ return ()
+strFromConnSpec = describe "strFromConn" $ mapM_
+  ( \(desc, maxLen, ioConn, expect) -> context desc $
+    xit ("should return " ++ show expect) $ do
+      conn <- ioConn
+      strFromConn maxLen conn `shouldReturn` expect
+  )
+
+  --  description,    max size, connection,                expected
+  [ ( "valid string", 100,      mkInConn ["foo\r\n"],      Just "foo"  )
+  , ( "long string",  5,        mkInConn ["too long\r\n"], Nothing     )
+  , ( "no CR/LF",     100,      mkInConn ["foo"],          Nothing     )
+  , ( "bad UTF-8",    100,      mkInConn ["foo\xff\r\n"],  Nothing     )
+  , ( "non-ASCII",    100,      mkInConn ["\xc3\xa9\r\n"], Just "\xe9" )
+  ]
+
+readMaxSpec :: Spec
+readMaxSpec = describe "readMax" $ mapM_
+  ( \(desc, maxLen, ioConn, expect) -> context desc $
+    it ("should return " ++ show expect) $ do
+      conn <- ioConn
+      readMax maxLen conn `shouldReturn` expect
+  )
+
+  --  description,    max length,   connection, expected
+  [ ( "single input", 1024,         singleConn,  Just singleBS )
+  , ( "multi input",  1024,         multiConn,   Just multiBS  )
+  , ( "long input",   longLen,      longConn,    Just longBS   )
+  , ( "too long",     pred longLen, longConn,    Nothing       )
+  , ( "empty input",  1024,         mkInConn [], Just ""       )
+  ]
+
+  where
+    singleConn = mkInConn ["foo"]
+    multiConn  = mkInConn ["foo", "bar", "baz"]
+    longConn   = mkInConn [longBS]
+    longLen    = BS.length longBS
+    singleBS   = "foo"
+    multiBS    = "foobarbaz"
+    longBS     = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+stripCRLFSpec :: Spec
+stripCRLFSpec = describe "stripCRLF" $ return ()
+
+mkInConn :: [BS.ByteString] -> IO (Connection ())
+mkInConn bss = do
+  source <- nullInput
+  mapM_ (`unRead` source) (reverse bss)
+  let
+    send          = const $ return ()
+    close         = return ()
+    connExtraInfo = ()
+  return Connection {..}
 
 --jl