X-Git-Url: http://git.cielonegro.org/gitweb.cgi?a=blobdiff_plain;f=Network%2FHTTP%2FLucu%2FResource.hs;h=01b61813971e9e1ce4ba80e18ed374e400a5ce5a;hb=ea2b7838f1b3d9d4923a220a601be2e04cc559d7;hp=d87e509b89d479ffcd39b97d58e0c01724bcb337;hpb=86ea98d8307ddc687696896a91bed9a05cbeb783;p=Lucu.git

diff --git a/Network/HTTP/Lucu/Resource.hs b/Network/HTTP/Lucu/Resource.hs
index d87e509..01b6181 100644
--- a/Network/HTTP/Lucu/Resource.hs
+++ b/Network/HTTP/Lucu/Resource.hs
@@ -1,6 +1,15 @@
+{-# LANGUAGE
+    GeneralizedNewtypeDeriving
+  , DoAndIfThenElse
+  , OverloadedStrings
+  , RecordWildCards
+  , UnicodeSyntax
+  #-}
+
 -- |This is the Resource Monad; monadic actions to define the behavior
--- of each resources. The 'Resource' Monad is a kind of IO Monad thus
--- it implements MonadIO class. It is also a state machine.
+-- of each resources. The 'Resource' Monad is a kind of 'Prelude.IO'
+-- Monad thus it implements 'Control.Monad.Trans.MonadIO' class. It is
+-- also a state machine.
 -- 
 -- Request Processing Flow:
 --
@@ -57,8 +66,10 @@
 
 module Network.HTTP.Lucu.Resource
     (
-    -- * Monad
-    Resource
+    -- * Types
+      Resource
+    , FormData(..)
+    , runRes
 
     -- * Actions
 
@@ -67,14 +78,23 @@ module Network.HTTP.Lucu.Resource
     -- |These actions can be computed regardless of the current state,
     -- and they don't change the state.
     , getConfig
+    , getRemoteAddr
+    , getRemoteAddr'
+    , getRemoteHost
+    , getRemoteCertificate
     , getRequest
     , getMethod
     , getRequestURI
+    , getRequestVersion
     , getResourcePath
     , getPathInfo
+    , getQueryForm
     , getHeader
     , getAccept
+    , getAcceptEncoding
+    , isEncodingAcceptable
     , getContentType
+    , getAuthorization
 
     -- ** Finding an entity
 
@@ -92,8 +112,6 @@ module Network.HTTP.Lucu.Resource
     -- Body/.
     , input
     , inputChunk
-    , inputBS
-    , inputChunkBS
     , inputForm
     , defaultLimit
 
@@ -105,6 +123,9 @@ module Network.HTTP.Lucu.Resource
     , setHeader
     , redirect
     , setContentType
+    , setLocation
+    , setContentEncoding
+    , setWWWAuthenticate
 
     -- ** Writing a response body
 
@@ -112,63 +133,121 @@ module Network.HTTP.Lucu.Resource
     -- Body/.
     , output
     , outputChunk
-    , outputBS
-    , outputChunkBS
 
-    , driftTo
+    , driftTo -- private
     )
     where
-
-import           Control.Concurrent.STM
-import           Control.Monad.Reader
-import qualified Data.ByteString.Lazy.Char8 as B
-import           Data.ByteString.Lazy.Char8 (ByteString)
-import           Data.List
-import           Data.Maybe
-import           GHC.Conc (unsafeIOToSTM)
-import           Network.HTTP.Lucu.Abortion
-import           Network.HTTP.Lucu.Config
-import           Network.HTTP.Lucu.DefaultPage
-import           Network.HTTP.Lucu.ETag
+import Blaze.ByteString.Builder (Builder)
+import qualified Blaze.ByteString.Builder.ByteString as BB
+import Control.Applicative
+import Control.Concurrent.STM
+import Control.Monad.Reader
+import Control.Monad.Unicode
+import Data.Ascii (Ascii, CIAscii)
+import qualified Data.Ascii as A
+import qualified Data.Attoparsec.Char8 as P
+import qualified Data.Attoparsec.Lazy  as LP
+import Data.ByteString (ByteString)
+import qualified Data.ByteString as Strict
+import qualified Data.ByteString.Lazy as Lazy
+import Data.Foldable (toList)
+import Data.List
+import qualified Data.Map as M
+import Data.Maybe
+import Data.Monoid
+import Data.Monoid.Unicode
+import Data.Sequence (Seq)
+import Data.Text (Text)
+import qualified Data.Text as T
+import qualified Data.Text.Encoding as T
+import Data.Time
+import qualified Data.Time.HTTP as HTTP
+import Network.HTTP.Lucu.Abortion
+import Network.HTTP.Lucu.Authorization
+import Network.HTTP.Lucu.Config
+import Network.HTTP.Lucu.ContentCoding
+import Network.HTTP.Lucu.DefaultPage
+import Network.HTTP.Lucu.ETag
 import qualified Network.HTTP.Lucu.Headers as H
-import           Network.HTTP.Lucu.HttpVersion
-import           Network.HTTP.Lucu.Interaction
-import           Network.HTTP.Lucu.Parser
-import           Network.HTTP.Lucu.Postprocess
-import           Network.HTTP.Lucu.RFC1123DateTime
-import           Network.HTTP.Lucu.Request
-import           Network.HTTP.Lucu.Response
-import           Network.HTTP.Lucu.MIMEType
-import           Network.HTTP.Lucu.Utils
-import           Network.URI
-import           System.Time
-
--- |The 'Resource' monad. /Interaction/ is an internal state thus it
--- is not exposed to users. This monad implements 'MonadIO' so it can
--- do any IO actions.
-type Resource a = ReaderT Interaction IO a
-
--- |Get the 'Network.HTTP.Lucu.Config.Config' value which is used for
--- the httpd.
-getConfig :: Resource Config
-getConfig = do itr <- ask
-               return $ itrConfig itr
-
--- |Get the 'Network.HTTP.Lucu.Request.Request' value which represents
--- the request header. In general you don't have to use this action.
-getRequest :: Resource Request
-getRequest = do itr <- ask
-                return $ fromJust $ itrRequest itr
-
--- |Get the 'Network.HTTP.Lucu.Request.Method' value of the request.
-getMethod :: Resource Method
-getMethod = do req <- getRequest
-               return $ reqMethod req
+import Network.HTTP.Lucu.HttpVersion
+import Network.HTTP.Lucu.Interaction
+import Network.HTTP.Lucu.MultipartForm
+import Network.HTTP.Lucu.Postprocess
+import Network.HTTP.Lucu.Request
+import Network.HTTP.Lucu.Response
+import Network.HTTP.Lucu.MIMEType
+import Network.HTTP.Lucu.Utils
+import Network.Socket hiding (accept)
+import Network.URI hiding (path)
+import OpenSSL.X509
+import Prelude.Unicode
+
+-- |The 'Resource' monad. This monad implements 'MonadIO' so it can do
+-- any 'IO' actions.
+newtype Resource a
+    = Resource {
+        unRes ∷ ReaderT Interaction IO a
+      }
+    deriving (Applicative, Functor, Monad, MonadIO)
+
+runRes ∷ Resource a → Interaction → IO a
+runRes r itr
+    = runReaderT (unRes r) itr
+
+getInteraction ∷ Resource Interaction
+getInteraction = Resource ask
+
+-- |Get the 'Config' value which is used for the httpd.
+getConfig ∷ Resource Config
+getConfig = itrConfig <$> getInteraction
+
+-- |Get the 'SockAddr' of the remote host. If you want a string
+-- representation instead of 'SockAddr', use 'getRemoteAddr''.
+getRemoteAddr ∷ Resource SockAddr
+getRemoteAddr = itrRemoteAddr <$> getInteraction
+
+-- |Get the string representation of the address of remote host. If
+-- you want a 'SockAddr' instead of 'String', use 'getRemoteAddr'.
+getRemoteAddr' ∷ Resource HostName
+getRemoteAddr'
+    = do sa          ← getRemoteAddr
+         (Just a, _) ← liftIO $ getNameInfo [NI_NUMERICHOST] False False sa
+         return a
+
+-- |Resolve an address to the remote host.
+getRemoteHost ∷ Resource (Maybe HostName)
+getRemoteHost
+    = do sa ← getRemoteAddr
+         fst <$> (liftIO $ getNameInfo [] True False sa)
+
+-- | Return the X.509 certificate of the client, or 'Nothing' if:
+--
+--   * This request didn't came through an SSL stream.
+--
+--   * The client didn't send us its certificate.
+--
+--   * The 'OpenSSL.Session.VerificationMode' of
+--   'OpenSSL.Session.SSLContext' in 'SSLConfig' has not been set to
+--   'OpenSSL.Session.VerifyPeer'.
+getRemoteCertificate ∷ Resource (Maybe X509)
+getRemoteCertificate = itrRemoteCert <$> getInteraction
+
+-- |Get the 'Request' value which represents the request header. In
+-- general you don't have to use this action.
+getRequest ∷ Resource Request
+getRequest = (fromJust ∘ itrRequest) <$> getInteraction
+
+-- |Get the 'Method' value of the request.
+getMethod ∷ Resource Method
+getMethod = reqMethod <$> getRequest
 
 -- |Get the URI of the request.
-getRequestURI :: Resource URI
-getRequestURI = do req <- getRequest
-                   return $ reqURI req
+getRequestURI ∷ Resource URI
+getRequestURI = reqURI <$> getRequest
+
+-- |Get the HTTP version of the request.
+getRequestVersion ∷ Resource HttpVersion
+getRequestVersion = reqVersion <$> getRequest
 
 -- |Get the path of this 'Resource' (to be exact,
 -- 'Network.HTTP.Lucu.Resource.Tree.ResourceDef') in the
@@ -183,28 +262,27 @@ getRequestURI = do req <- getRequest
 -- >
 -- > resFoo = ResourceDef {
 -- >     resIsGreedy = True
--- >   , resGet = Just $ do requestURI   <- getRequestURI
--- >                        resourcePath <- getResourcePath
--- >                        pathInfo     <- getPathInfo
+-- >   , resGet = Just $ do requestURI   ← getRequestURI
+-- >                        resourcePath ← getResourcePath
+-- >                        pathInfo     ← getPathInfo
 -- >                        -- uriPath requestURI == "/foo/bar/baz"
 -- >                        -- resourcePath       == ["foo"]
 -- >                        -- pathInfo           == ["bar", "baz"]
 -- >                        ...
 -- >   , ...
 -- >   }
-getResourcePath :: Resource [String]
-getResourcePath = do itr <- ask
-                     return $ fromJust $ itrResourcePath itr
-
-
--- |This is an analogy of CGI PATH_INFO. Its result is always @[]@ if
--- the 'Network.HTTP.Lucu.Resource.Tree.ResourceDef' is not
--- greedy. See 'getResourcePath'.
-getPathInfo :: Resource [String]
-getPathInfo = do rsrcPath <- getResourcePath
-                 reqURI   <- getRequestURI
-                 let reqPathStr = uriPath reqURI
-                     reqPath    = [x | x <- splitBy (== '/') reqPathStr, x /= ""]
+getResourcePath ∷ Resource [Text]
+getResourcePath = (fromJust ∘ itrResourcePath) <$> getInteraction
+
+-- |This is an analogy of CGI PATH_INFO. The result is
+-- URI-unescaped. It is always @[]@ if the
+-- 'Network.HTTP.Lucu.Resource.Tree.ResourceDef' is not greedy. See
+-- 'getResourcePath'.
+--
+-- Note that the returned path is URI-decoded and then UTF-8 decoded.
+getPathInfo ∷ Resource [Text]
+getPathInfo = do rsrcPath ← getResourcePath
+                 reqPath  ← splitPathInfo <$> getRequestURI
                  -- rsrcPath と reqPath の共通する先頭部分を reqPath か
                  -- ら全部取り除くと、それは PATH_INFO のやうなものにな
                  -- る。rsrcPath は全部一致してゐるに決まってゐる（でな
@@ -212,36 +290,127 @@ getPathInfo = do rsrcPath <- getResourcePath
                  -- rsrcPath の長さの分だけ削除すれば良い。
                  return $ drop (length rsrcPath) reqPath
 
+-- |Assume the query part of request URI as
+-- application\/x-www-form-urlencoded, and parse it to pairs of
+-- @(name, formData)@. This action doesn't parse the request body. See
+-- 'inputForm'. Field names are decoded in UTF-8.
+getQueryForm ∷ Resource [(Text, FormData)]
+getQueryForm = parse' <$> getRequestURI
+    where
+      parse' = map toPairWithFormData ∘
+               parseWWWFormURLEncoded ∘
+               fromJust ∘
+               A.fromChars ∘
+               drop 1 ∘
+               uriQuery
+
+toPairWithFormData ∷ (ByteString, ByteString) → (Text, FormData)
+toPairWithFormData (name, value)
+    = let fd = FormData {
+                 fdFileName = Nothing
+               , fdContent  = Lazy.fromChunks [value]
+               }
+      in (T.decodeUtf8 name, fd)
+
 -- |Get a value of given request header. Comparison of header name is
 -- case-insensitive. Note that this action is not intended to be used
--- so frequently: there should be an action like 'getContentType' for
+-- so frequently: there should be actions like 'getContentType' for
 -- every common headers.
-getHeader :: String -> Resource (Maybe String)
-getHeader name = do itr <- ask
-                    return $ H.getHeader name $ fromJust $ itrRequest itr
-
--- |Get a list of 'Network.HTTP.Lucu.MIMEType.MIMEType' enumerated on
--- header \"Accept\".
-getAccept :: Resource [MIMEType]
-getAccept = do accept <- getHeader "Accept"
-               if accept == Nothing then
-                   return []
-                 else
-                   case parseStr mimeTypeListP $ fromJust accept of
-                     (Success xs, _) -> return xs
-                     _               -> return []
-
--- |Get the header \"Content-Type\" as
--- 'Network.HTTP.Lucu.MIMEType.MIMEType'.
-getContentType :: Resource (Maybe MIMEType)
-getContentType = do cType <- getHeader "Content-Type"
-                    if cType == Nothing then
-                        return Nothing
-                      else
-                        case parseStr mimeTypeP $ fromJust cType of
-                          (Success t, _) -> return $ Just t
-                          _              -> return Nothing
+getHeader ∷ CIAscii → Resource (Maybe Ascii)
+getHeader name
+    = H.getHeader name <$> getRequest
+
+-- |Get a list of 'MIMEType' enumerated on header \"Accept\".
+getAccept ∷ Resource [MIMEType]
+getAccept
+    = do acceptM ← getHeader "Accept"
+         case acceptM of
+           Nothing
+               → return []
+           Just accept
+               → case P.parseOnly p (A.toByteString accept) of
+                    Right xs → return xs
+                    Left  _  → abort BadRequest []
+                               (Just $ "Unparsable Accept: " ⊕ A.toText accept)
+    where
+      p = do xs ← mimeTypeListP
+             P.endOfInput
+             return xs
+
+-- |Get a list of @(contentCoding, qvalue)@ enumerated on header
+-- \"Accept-Encoding\". The list is sorted in descending order by
+-- qvalue.
+getAcceptEncoding ∷ Resource [(CIAscii, Maybe Double)]
+getAcceptEncoding
+    = do accEncM ← getHeader "Accept-Encoding"
+         case accEncM of
+           Nothing
+               -- HTTP/1.0 には Accept-Encoding が無い場合の規定が無い
+               -- ので安全の爲 identity が指定された事にする。HTTP/1.1
+               -- の場合は何でも受け入れて良い事になってゐるので "*" が
+               -- 指定された事にする。
+               → do ver ← getRequestVersion
+                    case ver of
+                      HttpVersion 1 0 → return [("identity", Nothing)]
+                      HttpVersion 1 1 → return [("*"       , Nothing)]
+                      _               → abort InternalServerError []
+                                        (Just "getAcceptEncoding: unknown HTTP version")
+           Just ae
+               → if ae ≡ "" then
+                      -- identity のみが許される。
+                      return [("identity", Nothing)]
+                  else
+                      case P.parseOnly p (A.toByteString ae) of
+                        Right xs → return $ map toTuple $ reverse $ sort xs
+                        Left  _  → abort BadRequest []
+                                   (Just $ "Unparsable Accept-Encoding: " ⊕ A.toText ae)
+    where
+      p = do xs ← acceptEncodingListP
+             P.endOfInput
+             return xs
+
+      toTuple (AcceptEncoding {..})
+          = (aeEncoding, aeQValue)
 
+-- |Check whether a given content-coding is acceptable.
+isEncodingAcceptable ∷ CIAscii → Resource Bool
+isEncodingAcceptable encoding = any f <$> getAcceptEncoding
+    where
+      f (e, q)
+          = (e ≡ "*" ∨ e ≡ encoding) ∧ q ≢ Just 0
+
+-- |Get the header \"Content-Type\" as 'MIMEType'.
+getContentType ∷ Resource (Maybe MIMEType)
+getContentType
+    = do cTypeM ← getHeader "Content-Type"
+         case cTypeM of
+           Nothing
+               → return Nothing
+           Just cType
+               → case P.parseOnly p (A.toByteString cType) of
+                    Right t → return $ Just t
+                    Left  _ → abort BadRequest []
+                              (Just $ "Unparsable Content-Type: " ⊕ A.toText cType)
+    where
+      p = do t ← mimeTypeP
+             P.endOfInput
+             return t
+
+-- |Get the header \"Authorization\" as 'AuthCredential'.
+getAuthorization ∷ Resource (Maybe AuthCredential)
+getAuthorization
+    = do authM ← getHeader "Authorization"
+         case authM of
+           Nothing
+               → return Nothing
+           Just auth
+               → case P.parseOnly p (A.toByteString auth) of
+                    Right ac → return $ Just ac
+                    Left  _  → return Nothing
+    where
+      p = do ac ← authCredentialP
+             P.endOfInput
+             return ac
 
 
 {- ExaminingRequest 時に使用するアクション群 -}
@@ -249,7 +418,7 @@ getContentType = do cType <- getHeader "Content-Type"
 -- |Tell the system that the 'Resource' found an entity for the
 -- request URI. If this is a GET or HEAD request, a found entity means
 -- a datum to be replied. If this is a PUT or DELETE request, it means
--- a datum which was stored for the URI up to now. It is an error to
+-- a datum which was stored for the URI until now. It is an error to
 -- compute 'foundEntity' if this is a POST request.
 --
 -- Computation of 'foundEntity' performs \"If-Match\" test or
@@ -260,16 +429,16 @@ getContentType = do cType <- getHeader "Content-Type"
 --
 -- If this is a GET or HEAD request, 'foundEntity' automatically puts
 -- \"ETag\" and \"Last-Modified\" headers into the response.
-foundEntity :: ETag -> ClockTime -> Resource ()
+foundEntity ∷ ETag → UTCTime → Resource ()
 foundEntity tag timeStamp
     = do driftTo ExaminingRequest
 
-         method <- getMethod
-         when (method == GET || method == HEAD)
-                  $ setHeader' "Last-Modified" $ formatHTTPDateTime timeStamp
-         when (method == POST)
-                  $ abort InternalServerError []
-                        (Just "Illegal computation of foundEntity for POST request.")
+         method ← getMethod
+         when (method ≡ GET ∨ method ≡ HEAD)
+             $ setHeader' "Last-Modified" (HTTP.toAscii timeStamp)
+         when (method ≡ POST)
+             $ abort InternalServerError []
+               (Just "Illegal computation of foundEntity for a POST request.")
          foundETag tag
 
          driftTo GettingBody
@@ -279,50 +448,63 @@ foundEntity tag timeStamp
 -- 'foundETag' doesn't (and can't) put \"Last-Modified\" header into
 -- the response.
 --
--- This action is not preferred. You should use 'foundEntity' when
+-- This action is not preferred. You should use 'foundEntity' whenever
 -- possible.
-foundETag :: ETag -> Resource ()
+foundETag ∷ ETag → Resource ()
 foundETag tag
     = do driftTo ExaminingRequest
       
-         method <- getMethod
-         when (method == GET || method == HEAD)
-                  $ setHeader' "ETag" $ show tag
-         when (method == POST)
-                  $ abort InternalServerError []
-                        (Just "Illegal computation of foundETag for POST request.")
+         method ← getMethod
+         when (method ≡ GET ∨ method ≡ HEAD)
+              $ setHeader' "ETag" (printETag tag)
+         when (method ≡ POST)
+              $ abort InternalServerError []
+                (Just "Illegal computation of foundETag for POST request.")
 
          -- If-Match があればそれを見る。
-         ifMatch <- getHeader "If-Match"
+         ifMatch ← getHeader "If-Match"
          case ifMatch of
-           Nothing   -> return ()
-           Just "*"  -> return ()
-           Just list -> case parseStr eTagListP list of
-                          (Success tags, _)
-                              -- tags の中に一致するものが無ければ
-                              -- PreconditionFailed で終了。
-                              -> when (not $ any (== tag) tags)
-                                 $ abort PreconditionFailed []
-                                       $ Just ("The entity tag doesn't match: " ++ list)
-                          _   -> abort BadRequest [] $ Just ("Unparsable If-Match: " ++ fromJust ifMatch)
-
-         let statusForNoneMatch = if method == GET || method == HEAD then
-                                      NotModified
-                                  else
-                                      PreconditionFailed
+           Nothing    → return ()
+           Just value → if value ≡ "*" then
+                            return ()
+                        else
+                            case P.parseOnly p (A.toByteString value) of
+                              Right tags
+                                 -- tags の中に一致するものが無ければ
+                                 -- PreconditionFailed で終了。
+                                 → when ((¬) (any (≡ tag) tags))
+                                       $ abort PreconditionFailed []
+                                         (Just $ "The entity tag doesn't match: " ⊕ A.toText value)
+                              Left _
+                                   → abort BadRequest [] (Just $ "Unparsable If-Match: " ⊕ A.toText value)
+
+         let statusForNoneMatch
+                 = if method ≡ GET ∨ method ≡ HEAD then
+                       NotModified
+                   else
+                       PreconditionFailed
 
          -- If-None-Match があればそれを見る。
-         ifNoneMatch <- getHeader "If-None-Match"
+         ifNoneMatch ← getHeader "If-None-Match"
          case ifNoneMatch of
-           Nothing   -> return ()
-           Just "*"  -> abort statusForNoneMatch [] $ Just ("The entity tag matches: *")
-           Just list -> case parseStr eTagListP list of
-                          (Success tags, _)
-                              -> when (any (== tag) tags)
-                                 $ abort statusForNoneMatch [] $ Just ("The entity tag matches: " ++ list)
-                          _   -> abort BadRequest [] $ Just ("Unparsable If-None-Match: " ++ list)
+           Nothing    → return ()
+           Just value → if value ≡ "*" then
+                             abort statusForNoneMatch [] (Just "The entity tag matches: *")
+                         else
+                             case P.parseOnly p (A.toByteString value) of
+                               Right tags
+                                   → when (any (≡ tag) tags)
+                                         $ abort statusForNoneMatch []
+                                           (Just $ "The entity tag matches: " ⊕ A.toText value)
+                               Left _
+                                   → abort BadRequest []
+                                     (Just $ "Unparsable If-None-Match: " ⊕ A.toText value)
 
          driftTo GettingBody
+    where
+      p = do xs ← eTagListP
+             P.endOfInput
+             return xs
 
 -- |Tell the system that the 'Resource' found an entity for the
 -- request URI. The only difference from 'foundEntity' is that
@@ -332,334 +514,400 @@ foundETag tag
 -- modification time are unsafe because it is possible to mess up such
 -- tests by modifying the entity twice in a second.
 --
--- This action is not preferred. You should use 'foundEntity' when
+-- This action is not preferred. You should use 'foundEntity' whenever
 -- possible.
-foundTimeStamp :: ClockTime -> Resource ()
+foundTimeStamp ∷ UTCTime → Resource ()
 foundTimeStamp timeStamp
     = do driftTo ExaminingRequest
 
-         method <- getMethod
-         when (method == GET || method == HEAD)
-                  $ setHeader' "Last-Modified" $ formatHTTPDateTime timeStamp
-         when (method == POST)
-                  $ abort InternalServerError []
-                        (Just "Illegal computation of foundTimeStamp for POST request.")
+         method ← getMethod
+         when (method ≡ GET ∨ method ≡ HEAD)
+             $ setHeader' "Last-Modified" (HTTP.toAscii timeStamp)
+         when (method ≡ POST)
+             $ abort InternalServerError []
+               (Just "Illegal computation of foundTimeStamp for POST request.")
 
-         let statusForIfModSince = if method == GET || method == HEAD then
-                                       NotModified
-                                   else
-                                       PreconditionFailed
+         let statusForIfModSince
+                 = if method ≡ GET ∨ method ≡ HEAD then
+                       NotModified
+                   else
+                       PreconditionFailed
 
          -- If-Modified-Since があればそれを見る。
-         ifModSince <- getHeader "If-Modified-Since"
+         ifModSince ← getHeader "If-Modified-Since"
          case ifModSince of
-           Just str -> case parseHTTPDateTime str of
-                         Just lastTime
-                             -> when (timeStamp <= lastTime)
-                                $ abort statusForIfModSince []
-                                      $ Just ("The entity has not been modified since " ++ str)
-                         Nothing
-                             -> return () -- 不正な時刻は無視
-           Nothing  -> return ()
+           Just str → case HTTP.fromAscii str of
+                         Right lastTime
+                             → when (timeStamp ≤ lastTime)
+                               $ abort statusForIfModSince []
+                                 (Just $ "The entity has not been modified since " ⊕ A.toText str)
+                         Left _
+                             → return () -- 不正な時刻は無視
+           Nothing  → return ()
 
          -- If-Unmodified-Since があればそれを見る。
-         ifUnmodSince <- getHeader "If-Unmodified-Since"
+         ifUnmodSince ← getHeader "If-Unmodified-Since"
          case ifUnmodSince of
-           Just str -> case parseHTTPDateTime str of
-                         Just lastTime
-                             -> when (timeStamp > lastTime)
-                                $ abort PreconditionFailed []
-                                      $ Just  ("The entity has not been modified since " ++ str)
-                         Nothing
-                             -> return () -- 不正な時刻は無視
-           Nothing  -> return ()
+           Just str → case HTTP.fromAscii str of
+                         Right lastTime
+                             → when (timeStamp > lastTime)
+                               $ abort PreconditionFailed []
+                                 (Just $ "The entity has not been modified since " ⊕ A.toText str)
+                         Left _
+                             → return () -- 不正な時刻は無視
+           Nothing  → return ()
 
          driftTo GettingBody
 
--- |Computation of @'foundNoEntity' mStr@ tell the system that the
+-- | Computation of @'foundNoEntity' mStr@ tells the system that the
 -- 'Resource' found no entity for the request URI. @mStr@ is an
 -- optional error message to be replied to the client.
 --
 -- If this is a PUT request, 'foundNoEntity' performs \"If-Match\"
 -- test and aborts with status \"412 Precondition Failed\" when it
--- failed. If this is a GET, HEAD or DELETE request, 'foundNoEntity'
--- always aborts with status \"404 Not Found\". It is an error to
--- compute 'foundNoEntity' if this is a POST request.
-foundNoEntity :: Maybe String -> Resource ()
+-- failed. If this is a GET, HEAD, POST or DELETE request,
+-- 'foundNoEntity' always aborts with status \"404 Not Found\".
+foundNoEntity ∷ Maybe Text → Resource ()
 foundNoEntity msgM
     = do driftTo ExaminingRequest
 
-         method <- getMethod
-         when (method == POST)
-                  $ abort InternalServerError []
-                        (Just "Illegal computation of foundNoEntity for POST request.")
-         when (method /= PUT)
-                  $ abort NotFound [] msgM
+         method ← getMethod
+         when (method ≢ PUT)
+             $ abort NotFound [] msgM
 
          -- エンティティが存在しないと云ふ事は、"*" も含めたどのやうな
          -- If-Match: 條件も滿たさない。
-         ifMatch <- getHeader "If-Match"
-         when (ifMatch /= Nothing)
-                  $ abort PreconditionFailed [] msgM
+         ifMatch ← getHeader "If-Match"
+         when (ifMatch ≢ Nothing)
+             $ abort PreconditionFailed [] msgM
 
          driftTo GettingBody
 
 
 {- GettingBody 時に使用するアクション群 -}
 
-input :: Int -> Resource String
-input limit = inputBS limit >>= return . B.unpack
-
-
--- 多くとも limit バイトまでのリクエストボディ全體を受信する。limit が
--- 零以下なら Config で設定されたデフォルトのボディ長により制限される。
-inputBS :: Int -> Resource ByteString
-inputBS limit
+-- | Computation of @'input' limit@ attempts to read the request body
+-- up to @limit@ bytes, and then make the 'Resource' transit to
+-- /Deciding Header/ state. When the actual size of body is larger
+-- than @limit@ bytes, computation of 'Resource' immediately aborts
+-- with status \"413 Request Entity Too Large\". When the request has
+-- no body, 'input' returns an empty string.
+--
+-- @limit@ may be less than or equal to zero. In this case, the
+-- default limitation value ('cnfMaxEntityLength') is used. See
+-- 'defaultLimit'.
+--
+-- 'input' returns a 'Lazy.ByteString' but it's not really lazy:
+-- reading from the socket just happens at the computation of 'input',
+-- not at the evaluation of the 'Lazy.ByteString'. The same goes for
+-- 'inputChunk'.
+input ∷ Int → Resource Lazy.ByteString
+input limit
     = do driftTo GettingBody
-         itr     <- ask
-         hasBody <- liftIO $ atomically $ readItr itr itrRequestHasBody id
-         chunk   <- if hasBody then
-                        askForInput itr
-                    else
-                        do driftTo DecidingHeader
-                           return B.empty
+         itr     ← getInteraction
+         chunk   ← if reqHasBody $ fromJust $ itrRequest itr then
+                       askForInput itr
+                   else
+                       do driftTo DecidingHeader
+                          return (∅)
          return chunk
     where
-      askForInput :: Interaction -> Resource ByteString
-      askForInput itr
-          = do let defaultLimit = cnfMaxEntityLength $ itrConfig itr
-                   actualLimit  = if limit <= 0 then
-                                      defaultLimit
-                                  else
-                                      limit
-               when (actualLimit <= 0)
-                        $ fail ("inputBS: limit must be positive: " ++ show actualLimit)
+      askForInput ∷ Interaction → Resource Lazy.ByteString
+      askForInput (Interaction {..})
+          = do let confLimit   = cnfMaxEntityLength itrConfig
+                   actualLimit = if limit ≤ 0 then
+                                     confLimit
+                                 else
+                                     limit
+               when (actualLimit ≤ 0)
+                        $ fail ("inputLBS: limit must be positive: " ⧺ show actualLimit)
                -- Reader にリクエスト
                liftIO $ atomically
-                          $ do chunkLen <- readItr itr itrReqChunkLength id
-                               writeItr itr itrWillReceiveBody True
-                               if fmap (> actualLimit) chunkLen == Just True then
-                                   -- 受信前から多過ぎる事が分かってゐる
-                                   tooLarge actualLimit
-                                 else
-                                   writeItr itr itrReqBodyWanted $ Just actualLimit
-               -- 應答を待つ。トランザクションを分けなければ當然デッドロック。
-               chunk <- liftIO $ atomically
-                        $ do chunk       <- readItr itr itrReceivedBody id
-                             chunkIsOver <- readItr itr itrReqChunkIsOver id
-                             if B.length chunk < fromIntegral actualLimit then
-                                 -- 要求された量に滿たなくて、まだ殘り
-                                 -- があるなら再試行。
-                                 unless chunkIsOver
-                                            $ retry
-                               else
-                                 -- 制限値一杯まで讀むやうに指示したの
-                                 -- にまだ殘ってゐるなら、それは多過ぎ
-                                 -- る。
-                                 unless chunkIsOver
-                                            $ tooLarge actualLimit
-                             -- 成功。itr 内にチャンクを置いたままにす
-                             -- るとメモリの無駄になるので除去。
-                             writeItr itr itrReceivedBody B.empty
-                             return chunk
+                      $ writeTVar itrReqBodyWanted actualLimit
+               -- 應答を待つ。トランザクションを分けなければ當然デッドロックする。
+               chunk ← liftIO $ atomically
+                       $ do chunkLen    ← readTVar itrReceivedBodyLen
+                            chunkIsOver ← readTVar itrReqChunkIsOver
+                            if chunkLen < actualLimit then
+                                -- 要求された量に滿たなくて、まだ殘りが
+                                -- あるなら再試行。
+                                unless chunkIsOver
+                                    $ retry
+                            else
+                                -- 制限値一杯まで讀むやうに指示したのに
+                                -- まだ殘ってゐるなら、それは多過ぎる。
+                                unless chunkIsOver
+                                    $ tooLarge actualLimit
+                            -- 成功。itr 内にチャンクを置いたままにする
+                            -- とメモリの無駄になるので除去。
+                            chunk ← seqToLBS <$> readTVar itrReceivedBody
+                            writeTVar itrReceivedBody    (∅)
+                            writeTVar itrReceivedBodyLen 0
+                            return chunk
+
                driftTo DecidingHeader
                return chunk
 
-      tooLarge :: Int -> STM ()
+      tooLarge ∷ Int → STM ()
       tooLarge lim = abortSTM RequestEntityTooLarge []
-                     $ Just ("Request body must be smaller than "
-                             ++ show lim ++ " bytes.")
-         
-
-inputChunk :: Int -> Resource String
-inputChunk limit = inputChunkBS limit >>= return . B.unpack
-
+                     (Just $ "Request body must be smaller than "
+                             ⊕ T.pack (show lim) ⊕ " bytes.")
 
--- 多くとも limit バイトまでのリクエストボディの一部を受信する。limit
--- が 0 以下なら Config で設定されたデフォルトのボディ長により制限され
--- る。これ以上ボディが殘ってゐなければ空文字列を返す。
-inputChunkBS :: Int -> Resource ByteString
-inputChunkBS limit
+seqToLBS ∷ Seq ByteString → Lazy.ByteString
+{-# INLINE seqToLBS #-}
+seqToLBS = Lazy.fromChunks ∘ toList
+         
+-- | Computation of @'inputChunk' limit@ attempts to read a part of
+-- request body up to @limit@ bytes. You can read any large request by
+-- repeating computation of this action. When you've read all the
+-- request body, 'inputChunk' returns an empty string and then make
+-- the 'Resource' transit to /Deciding Header/ state.
+--
+-- @limit@ may be less than or equal to zero. In this case, the
+-- default limitation value ('cnfMaxEntityLength') is used. See
+-- 'defaultLimit'.
+--
+-- Note that 'inputChunkLBS' is more efficient than 'inputChunk' so you
+-- should use it whenever possible.
+inputChunk ∷ Int → Resource Lazy.ByteString
+inputChunk limit
     = do driftTo GettingBody
-         itr <- ask
-         hasBody <- liftIO $ atomically $ readItr itr itrRequestHasBody id
-         chunk   <- if hasBody then
-                        askForInput itr
-                    else
-                        do driftTo DecidingHeader
-                           return B.empty
+         itr     ← getInteraction
+         chunk   ← if reqHasBody $ fromJust $ itrRequest itr then
+                       askForInput itr
+                   else
+                       do driftTo DecidingHeader
+                          return (∅)
          return chunk
     where
-      askForInput :: Interaction -> Resource ByteString
-      askForInput itr
-          = do let defaultLimit = cnfMaxEntityLength $ itrConfig itr
-                   actualLimit  = if limit < 0 then
-                                      defaultLimit
-                                  else
-                                      limit
-               when (actualLimit <= 0)
-                        $ fail ("inputChunkBS: limit must be positive: " ++ show actualLimit)
+      askForInput ∷ Interaction → Resource Lazy.ByteString
+      askForInput (Interaction {..})
+          = do let confLimit   = cnfMaxEntityLength itrConfig
+                   actualLimit = if limit < 0 then
+                                     confLimit
+                                 else
+                                     limit
+               when (actualLimit ≤ 0)
+                        $ fail ("inputChunkLBS: limit must be positive: " ++ show actualLimit)
                -- Reader にリクエスト
                liftIO $ atomically
-                          $ do writeItr itr itrReqBodyWanted $ Just actualLimit
-                               writeItr itr itrWillReceiveBody True
+                      $ writeTVar itrReqBodyWanted actualLimit
                -- 應答を待つ。トランザクションを分けなければ當然デッドロック。
-               chunk <- liftIO $ atomically
-                        $ do chunk <- readItr itr itrReceivedBody id
-                             -- 要求された量に滿たなくて、まだ殘りがあ
-                             -- るなら再試行。
-                             when (B.length chunk < fromIntegral actualLimit)
-                                      $ do chunkIsOver <- readItr itr itrReqChunkIsOver id
-                                           unless chunkIsOver
-                                                      $ retry
-                             -- 成功
-                             writeItr itr itrReceivedBody B.empty
-                             return chunk
-               when (B.null chunk)
-                        $ driftTo DecidingHeader
+               chunk ← liftIO $ atomically
+                       $ do chunkLen ← readTVar itrReceivedBodyLen
+                            -- 要求された量に滿たなくて、まだ殘りがある
+                            -- なら再試行。
+                            when (chunkLen < actualLimit)
+                                $ do chunkIsOver ← readTVar itrReqChunkIsOver
+                                     unless chunkIsOver
+                                         $ retry
+                            -- 成功
+                            chunk ← seqToLBS <$> readTVar itrReceivedBody
+                            writeTVar itrReceivedBody    (∅)
+                            writeTVar itrReceivedBodyLen 0
+                            return chunk
+               when (Lazy.null chunk)
+                   $ driftTo DecidingHeader
                return chunk
 
-
--- application/x-www-form-urlencoded または multipart/form-data をパー
--- スする。もし Content-Type が無かったら BadRequest で終了し、未對應の
--- タイプであったら UnsupportedMediaType で終了する。
-inputForm :: Int -> Resource [(String, String)]
+-- | Computation of @'inputForm' limit@ attempts to read the request
+-- body with 'input' and parse it as
+-- @application\/x-www-form-urlencoded@ or @multipart\/form-data@. If
+-- the request header \"Content-Type\" is neither of them, 'inputForm'
+-- makes 'Resource' abort with status \"415 Unsupported Media
+-- Type\". If the request has no \"Content-Type\", it aborts with
+-- \"400 Bad Request\".
+--
+-- Field names in @multipart\/form-data@ will be precisely decoded in
+-- accordance with RFC 2231. On the other hand,
+-- @application\/x-www-form-urlencoded@ says nothing about the
+-- encoding of field names, so they'll always be decoded in UTF-8.
+inputForm ∷ Int → Resource [(Text, FormData)]
 inputForm limit
-    = do cTypeM <- getContentType
+    = do cTypeM ← getContentType
          case cTypeM of
            Nothing
-               -> abort BadRequest [] (Just "Missing Content-Type")
+               → abort BadRequest [] (Just "Missing Content-Type")
            Just (MIMEType "application" "x-www-form-urlencoded" _)
-               -> readWWWFormURLEncoded
-           Just (MIMEType "multipart" "form-data" _)
-               -> readMultipartFormData
+               → readWWWFormURLEncoded
+           Just (MIMEType "multipart" "form-data" params)
+               → readMultipartFormData params
            Just cType
-               -> abort UnsupportedMediaType [] (Just $ "Unsupported media type: "
-                                                          ++ show cType)
+               → abort UnsupportedMediaType []
+                 $ Just
+                 $ A.toText
+                 $ A.fromAsciiBuilder
+                 $ A.toAsciiBuilder "Unsupported media type: "
+                 ⊕ printMIMEType cType
     where
       readWWWFormURLEncoded
-          = do src <- input limit
-               return $ do pairStr <- splitBy (\ c -> c == ';' || c == '&') src
-                           let pair = break (== '=') pairStr
-                           return ( unEscapeString $ fst pair
-                                  , unEscapeString $ snd pair
-                                  )
-      readMultipartFormData -- FIXME: 未對應
-          = abort UnsupportedMediaType []
-            (Just $ "Sorry, inputForm does not currently support multipart/form-data.")
-
-
-defaultLimit :: Int
+          = (map toPairWithFormData ∘ parseWWWFormURLEncoded)
+            <$>
+            (bsToAscii =≪ input limit)
+
+      bsToAscii bs
+          = case A.fromByteString (Strict.concat (Lazy.toChunks bs)) of
+              Just a  → return a
+              Nothing → abort BadRequest [] (Just "Malformed x-www-form-urlencoded")
+
+      readMultipartFormData params
+          = do case M.lookup "boundary" params of
+                 Nothing
+                     → abort BadRequest [] (Just "Missing boundary of multipart/form-data")
+                 Just boundary
+                     → do src ← input limit
+                          b   ← case A.fromText boundary of
+                                   Just b  → return b
+                                   Nothing → abort BadRequest []
+                                             (Just $ "Malformed boundary: " ⊕ boundary)
+                          case LP.parse (p b) src of
+                            LP.Done _ formList
+                                → return formList
+                            _   → abort BadRequest [] (Just "Unparsable multipart/form-data")
+          where
+            p b = do xs ← multipartFormP b
+                     P.endOfInput
+                     return xs
+
+-- | This is just a constant @-1@. It's better to say @'input'
+-- 'defaultLimit'@ than to say @'input' (-1)@ but these are exactly
+-- the same.
+defaultLimit ∷ Int
 defaultLimit = (-1)
 
 
-
 {- DecidingHeader 時に使用するアクション群 -}
 
-setStatus :: StatusCode -> Resource ()
-setStatus code
+-- | Set the response status code. If you omit to compute this action,
+-- the status code will be defaulted to \"200 OK\".
+setStatus ∷ StatusCode → Resource ()
+setStatus sc
     = do driftTo DecidingHeader
-         itr <- ask
-         liftIO $ atomically $ updateItr itr itrResponse
-                    $ \ res -> res {
-                                 resStatus = code
-                               }
+         itr ← getInteraction
+         liftIO
+             $ atomically
+             $ setResponseStatus itr sc
 
 -- | Set a value of given resource header. Comparison of header name
 -- is case-insensitive. Note that this action is not intended to be
--- used so frequently: there should be an action like 'setContentType'
+-- used so frequently: there should be actions like 'setContentType'
 -- for every common headers.
 --
 -- Some important headers (especially \"Content-Length\" and
--- \"Transfer-Encoding\") may be silently deleted or overwritten by
+-- \"Transfer-Encoding\") may be silently dropped or overwritten by
 -- the system not to corrupt the interaction with client at the
--- viewpoint of HTTP protocol. For instance, if we are keeping
--- connection alive, for an obvious reason it causes a catastrophe to
--- send header \"Content-Length: 10\" and actually sending body of 20
--- bytes long.
-setHeader :: String -> String -> Resource ()
+-- viewpoint of HTTP protocol layer. For instance, if we are keeping
+-- the connection alive, without this process it causes a catastrophe
+-- to send a header \"Content-Length: 10\" and actually send a body of
+-- 20 bytes long. In this case the client shall only accept the first
+-- 10 bytes of response body and thinks that the residual 10 bytes is
+-- a part of header of the next response.
+setHeader ∷ CIAscii → Ascii → Resource ()
 setHeader name value
-    = driftTo DecidingHeader >> setHeader' name value
-         
+    = driftTo DecidingHeader ≫ setHeader' name value
 
-setHeader' :: String -> String -> Resource()
+setHeader' ∷ CIAscii → Ascii → Resource ()
 setHeader' name value
-    = do itr <- ask
+    = do itr ← getInteraction
          liftIO $ atomically
-                    $ updateItr itr itrResponse
-                          $ H.setHeader name value
-
-
-redirect :: StatusCode -> URI -> Resource ()
+                $ do res ← readTVar $ itrResponse itr
+                     let res' = H.setHeader name value res
+                     writeTVar (itrResponse itr) res'
+
+-- | Computation of @'redirect' code uri@ sets the response status to
+-- @code@ and \"Location\" header to @uri@. The @code@ must satisfy
+-- 'isRedirection' or it causes an error.
+redirect ∷ StatusCode → URI → Resource ()
 redirect code uri
-    = do when (code == NotModified || not (isRedirection code))
-                  $ abort InternalServerError []
-                        $ Just ("Attempted to redirect with status " ++ show code)
+    = do when (code ≡ NotModified ∨ not (isRedirection code))
+             $ abort InternalServerError []
+             $ Just
+             $ A.toText
+             $ A.fromAsciiBuilder
+             $ A.toAsciiBuilder "Attempted to redirect with status "
+             ⊕ printStatusCode code
          setStatus code
-         setHeader "Location" (uriToString id uri $ "")
-
+         setLocation uri
+
+-- | Computation of @'setContentType' mType@ sets the response header
+-- \"Content-Type\" to @mType@.
+setContentType ∷ MIMEType → Resource ()
+setContentType
+    = setHeader "Content-Type" ∘ A.fromAsciiBuilder ∘ printMIMEType
+
+-- | Computation of @'setLocation' uri@ sets the response header
+-- \"Location\" to @uri@.
+setLocation ∷ URI → Resource ()
+setLocation uri
+    = case A.fromChars uriStr of
+        Just a  → setHeader "Location" a
+        Nothing → abort InternalServerError []
+                  (Just $ "Malformed URI: " ⊕ T.pack uriStr)
+    where
+      uriStr = uriToString id uri ""
+
+-- |Computation of @'setContentEncoding' codings@ sets the response
+-- header \"Content-Encoding\" to @codings@.
+setContentEncoding ∷ [CIAscii] → Resource ()
+setContentEncoding codings
+    = do ver ← getRequestVersion
+         tr  ← case ver of
+                  HttpVersion 1 0 → return (toAB ∘ unnormalizeCoding)
+                  HttpVersion 1 1 → return toAB
+                  _               → abort InternalServerError []
+                                    (Just "setContentEncoding: Unknown HTTP version")
+         setHeader "Content-Encoding"
+                   (A.fromAsciiBuilder $ joinWith ", " $ map tr codings)
+    where
+      toAB = A.toAsciiBuilder ∘ A.fromCIAscii
 
-setContentType :: MIMEType -> Resource ()
-setContentType mType
-    = setHeader "Content-Type" $ show mType
+-- |Computation of @'setWWWAuthenticate' challenge@ sets the response
+-- header \"WWW-Authenticate\" to @challenge@.
+setWWWAuthenticate ∷ AuthChallenge → Resource ()
+setWWWAuthenticate challenge
+    = setHeader "WWW-Authenticate" (printAuthChallenge challenge)
 
 
 {- DecidingBody 時に使用するアクション群 -}
 
-output :: String -> Resource ()
-output = outputBS . B.pack
-
-
-outputBS :: ByteString -> Resource ()
-outputBS str = do outputChunkBS str
-                  driftTo Done
-
-
-outputChunk :: String -> Resource ()
-outputChunk = outputChunkBS . B.pack
-
-
-{- チャンクの大きさは Config で制限されてゐる。もし例へば /dev/zero を
-   B.readFile して作った ByteString をそのまま ResponseWriter に渡した
-   りすると大變な事が起こる。何故なら ResponseWriter は
-   Transfer-Encoding: chunked の時、ヘッダを書く爲にチャンクの大きさを
-   測るから、その時に起こるであらう事は言ふまでも無い。 -}
-
-outputChunkBS :: ByteString -> Resource ()
-outputChunkBS str
+-- | Write a 'Lazy.ByteString' to the response body, and then transit
+-- to the /Done/ state. It is safe to apply 'output' to an infinite
+-- string, such as the lazy stream of \/dev\/random.
+output ∷ Lazy.ByteString → Resource ()
+{-# INLINE output #-}
+output str = outputChunk str *> driftTo Done
+
+-- | Write a 'Lazy.ByteString' to the response body. This action can
+-- be repeated as many times as you want. It is safe to apply
+-- 'outputChunk' to an infinite string.
+outputChunk ∷ Lazy.ByteString → Resource ()
+outputChunk wholeChunk
     = do driftTo DecidingBody
-         itr <- ask
+         itr ← getInteraction
          
          let limit = cnfMaxOutputChunkLength $ itrConfig itr
-         when (limit <= 0)
-                  $ fail ("cnfMaxOutputChunkLength must be positive: "
-                          ++ show limit)
-
-         discardBody <- liftIO $ atomically $
-                        readItr itr itrWillDiscardBody id
+         when (limit ≤ 0)
+             $ abort InternalServerError []
+               (Just $ "cnfMaxOutputChunkLength must be positive: " ⊕ T.pack (show limit))
 
+         discardBody ← liftIO $ atomically $ readTVar $ itrWillDiscardBody itr
          unless (discardBody)
-                    $ sendChunks str limit
+             $ sendChunks itr wholeChunk limit
 
-         unless (B.null str)
-                    $ liftIO $ atomically $
-                      writeItr itr itrBodyIsNull False
+         unless (Lazy.null wholeChunk)
+             $ liftIO $ atomically $
+               writeTVar (itrSentNoBodySoFar itr) False
     where
-      sendChunks :: ByteString -> Int -> Resource ()
-      sendChunks str limit
-          | B.null str = return ()
-          | otherwise  = do let (chunk, remaining) = B.splitAt (fromIntegral limit) str
-                            itr <- ask
-                            liftIO $ atomically $ 
-                                   do buf <- readItr itr itrBodyToSend id
-                                      if B.null buf then
-                                          -- バッファが消化された
-                                          writeItr itr itrBodyToSend chunk
-                                        else
-                                          -- 消化されるのを待つ
-                                          retry
-                            -- 殘りのチャンクについて繰り返す
-                            sendChunks remaining limit
+      sendChunks ∷ Interaction → Lazy.ByteString → Int → Resource ()
+      sendChunks itr@(Interaction {..}) str limit
+          | Lazy.null str = return ()
+          | otherwise     = do let (chunk, remaining) = Lazy.splitAt (fromIntegral limit) str
+                               liftIO $ atomically
+                                      $ putTMVar itrBodyToSend (chunkToBuilder chunk)
+                               sendChunks itr remaining limit
+
+      chunkToBuilder ∷ Lazy.ByteString → Builder
+      chunkToBuilder = mconcat ∘ map BB.fromByteString ∘ Lazy.toChunks
 
 {-
 
@@ -680,40 +928,34 @@ outputChunkBS str
 
 -}
 
-driftTo :: InteractionState -> Resource ()
+driftTo ∷ InteractionState → Resource ()
 driftTo newState
-    = do itr <- ask
-         liftIO $ atomically $ do oldState <- readItr itr itrState id
-                                  if newState < oldState then
-                                      throwStateError oldState newState
-                                    else
-                                      do let a = [oldState .. newState]
-                                             b = tail a
-                                             c = zip a b
-                                         mapM_ (uncurry $ drift itr) c
-                                         writeItr itr itrState newState
+    = do itr ← getInteraction
+         liftIO $ atomically
+                $ do oldState ← readTVar $ itrState itr
+                     if newState < oldState then
+                         throwStateError oldState newState
+                     else
+                         do let a = [oldState .. newState]
+                                b = tail a
+                                c = zip a b
+                            mapM_ (uncurry $ drift itr) c
+                            writeTVar (itrState itr) newState
     where
-      throwStateError :: Monad m => InteractionState -> InteractionState -> m a
-
+      throwStateError ∷ Monad m ⇒ InteractionState → InteractionState → m a
       throwStateError Done DecidingBody
           = fail "It makes no sense to output something after finishing to output."
-
       throwStateError old new
-          = fail ("state error: " ++ show old ++ " ==> " ++ show new)
-
-
-      drift :: Interaction -> InteractionState -> InteractionState -> STM ()
-
-      drift itr GettingBody _
-          = writeItr itr itrReqBodyWasteAll True
+          = fail ("state error: " ⧺ show old ⧺ " ==> " ⧺ show new)
 
+      drift ∷ Interaction → InteractionState → InteractionState → STM ()
+      drift (Interaction {..}) GettingBody _
+          = writeTVar itrReqBodyWasteAll True
       drift itr DecidingHeader _
           = postprocess itr
-
-      drift itr _ Done
-          = do bodyIsNull <- readItr itr itrBodyIsNull id
+      drift itr@(Interaction {..}) _ Done
+          = do bodyIsNull ← readTVar itrSentNoBodySoFar
                when bodyIsNull
-                        $ writeDefaultPage itr
-
+                   $ writeDefaultPage itr
       drift _ _ _
           = return ()