X-Git-Url: http://git.cielonegro.org/gitweb.cgi?a=blobdiff_plain;f=Network%2FHTTP%2FLucu%2FResource.hs;h=fcf23593e9ee89ca83d8c3e768242740c79ed717;hb=636a3b3334f1ede61dc1e6faa2c4a021ea9bbd5c;hp=2e4d46e858f447fcec98601b1fc016e6f0272fd9;hpb=3c7a58ab749a55a30466a033b170536bcdf18b98;p=Lucu.git

diff --git a/Network/HTTP/Lucu/Resource.hs b/Network/HTTP/Lucu/Resource.hs
index 2e4d46e..fcf2359 100644
--- a/Network/HTTP/Lucu/Resource.hs
+++ b/Network/HTTP/Lucu/Resource.hs
@@ -1,109 +1,900 @@
+-- #prune
+
+-- |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.
+-- 
+-- Request Processing Flow:
+--
+--   1. A client issues an HTTP request.
+--
+--   2. If the URI of it matches to any resource, the corresponding
+--      'Resource' Monad starts running on a newly spawned thread.
+--
+--   3. The 'Resource' Monad looks at the request header, find (or not
+--      find) an entity, receive the request body (if any), decide the
+--      response header, and decide the response body. This process
+--      will be discussed later.
+--
+--   4. The 'Resource' Monad and its thread stops running. The client
+--      may or may not be sending us the next request at this point.
+--
+-- 'Resource' Monad takes the following states. The initial state is
+-- /Examining Request/ and the final state is /Done/.
+--
+--   [/Examining Request/] In this state, a 'Resource' looks at the
+--   request header and thinks about an entity for it. If there is a
+--   suitable entity, the 'Resource' tells the system an entity tag
+--   and its last modification time ('foundEntity'). If it found no
+--   entity, it tells the system so ('foundNoEntity'). In case it is
+--   impossible to decide the existence of entity, which is a typical
+--   case for POST requests, 'Resource' does nothing in this state.
+--
+--   [/Getting Body/] A 'Resource' asks the system to receive a
+--   request body from client. Before actually reading from the
+--   socket, the system sends \"100 Continue\" to the client if need
+--   be. When a 'Resource' transits to the next state without
+--   receiving all or part of request body, the system still reads it
+--   and just throws it away.
+--
+--   [/Deciding Header/] A 'Resource' makes a decision of status code
+--   and response header. When it transits to the next state, the
+--   system checks the validness of response header and then write
+--   them to the socket.
+--
+--   [/Deciding Body/] In this state, a 'Resource' asks the system to
+--   write some response body to the socket. When it transits to the
+--   next state without writing any response body, the system
+--   completes it depending on the status code.
+--
+--   [/Done/] Everything is over. A 'Resource' can do nothing for the
+--   HTTP interaction anymore.
+--
+-- Note that the state transition is one-way: for instance, it is an
+-- error to try to read a request body after writing some
+-- response. This limitation is for efficiency. We don't want to read
+-- the entire request before starting 'Resource', nor we don't want to
+-- postpone writing the entire response till the end of 'Resource'
+-- computation.
+
 module Network.HTTP.Lucu.Resource
-    ( ResourceDef(..)
-    , Resource
-    , ResTree
-    , mkResTree    -- [ ([String], ResourceDef) ] -> ResTree
-    , findResource -- ResTree -> URI -> Maybe ResourceDef
-    , runResource  -- ResourceDef -> Interaction -> IO ThreadId
+    (
+    -- * Monad
+    Resource
+
+    -- * Actions
+
+    -- ** Getting request header
+
+    -- |These actions can be computed regardless of the current state,
+    -- and they don't change the state.
+    , getConfig
+    , getRemoteAddr
+    , getRemoteAddr'
+    , getRequest
+    , getMethod
+    , getRequestURI
+    , getRequestVersion
+    , getResourcePath
+    , getPathInfo
+    , getQueryForm
+    , getHeader
+    , getAccept
+    , getAcceptEncoding
+    , getContentType
+
+    -- ** Finding an entity
+
+    -- |These actions can be computed only in the /Examining Request/
+    -- state. After the computation, the 'Resource' transits to
+    -- /Getting Body/ state.
+    , foundEntity
+    , foundETag
+    , foundTimeStamp
+    , foundNoEntity
+
+    -- ** Getting a request body
+
+    -- |Computation of these actions changes the state to /Getting
+    -- Body/.
+    , input
+    , inputChunk
+    , inputBS
+    , inputChunkBS
+    , inputForm
+    , defaultLimit
+
+    -- ** Setting response headers
+    
+    -- |Computation of these actions changes the state to /Deciding
+    -- Header/.
+    , setStatus
+    , setHeader
+    , redirect
+    , setContentType
+    , setLocation
+    , setContentEncoding
+
+    -- ** Writing a response body
+
+    -- |Computation of these actions changes the state to /Deciding
+    -- Body/.
+    , output
+    , outputChunk
+    , outputBS
+    , outputChunkBS
+
+    , driftTo
     )
     where
 
-import           Control.Concurrent
+import           Control.Concurrent.STM
 import           Control.Monad.Reader
+import           Data.Bits
 import qualified Data.ByteString.Lazy.Char8 as B
 import           Data.ByteString.Lazy.Char8 (ByteString)
+import           Data.Char
 import           Data.List
-import qualified Data.Map as M
-import           Data.Map (Map)
+import           Data.Maybe
+import           Network.HTTP.Lucu.Abortion
+import           Network.HTTP.Lucu.Config
+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.Parser.Http
+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.Socket
 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
 
-{- /aaa/bbb/ccc にアクセスされた時、もし /aaa/bbb に貪欲なリソースがあ
-   れば、假に /aaa/bbb/ccc に何らかのリソースがあったとしても必ず
-   /aaa/bbb が撰ばれる。/aaa/bbb のリソースが貪欲でなければ、それは無視
-   される。 -}
-data ResourceDef = ResourceDef {
-      resUsesNativeThread :: Bool
-    , resIsGreedy         :: Bool
-    , resResource         :: Resource ()
-    }
-type ResTree    = ResNode -- root だから Map ではない
-type ResSubtree = Map String ResNode
-data ResNode    = ResNode (Maybe ResourceDef) ResSubtree
 
+-- |Get the SockAddr of the remote host. If you want a string
+-- representation instead of SockAddr, use 'getRemoteAddr''.
+getRemoteAddr :: Resource SockAddr
+getRemoteAddr = do itr <- ask
+                   return $! itrRemoteAddr itr
 
-mkResTree :: [ ([String], ResourceDef) ] -> ResTree
-mkResTree list = processRoot list
-    where
-      processRoot :: [ ([String], ResourceDef) ] -> ResTree
-      processRoot list
-          = let (roots, nonRoots) = partition (\ (path, _) -> path == []) list
-                children = processNonRoot nonRoots
-            in
-              if null roots then
-                  -- / にリソースが定義されない。/foo とかにはあるかも。
-                  ResNode Nothing children
-              else
-                  -- / がある。
-                  let (_, def) = last roots
-                  in 
-                    ResNode (Just def) children
-
-      processNonRoot :: [ ([String], ResourceDef) ] -> ResSubtree
-      processNonRoot list
-          = let subtree    = M.fromList [(name, node name)
-                                             | name <- childNames]
-                childNames = [name | (name:_, _) <- list]
-                node name  = let defs = [def | (path, def) <- list, path == [name]]
+
+-- |Get the string representation of the address of remote host. If
+-- you want a SockAddr instead of String, use 'getRemoteAddr'.
+getRemoteAddr' :: Resource String
+getRemoteAddr' = do addr <- getRemoteAddr
+                    case addr of
+                      -- Network.Socket は IPv6 を考慮してゐないやうだ…
+                      (SockAddrInet _ v4addr)
+                          -> let b1 = (v4addr `shiftR` 24) .&. 0xFF
+                                 b2 = (v4addr `shiftR` 16) .&. 0xFF
+                                 b3 = (v4addr `shiftR`  8) .&. 0xFF
+                                 b4 =  v4addr              .&. 0xFF
                              in
-                               if null defs then
-                                   -- この位置にリソースが定義されない。
-                                   -- もっと下にはあるかも。
-                                   ResNode Nothing children
-                               else
-                                   -- この位置にリソースがある。
-                                   ResNode (Just $ last defs) children
-                children   = processNonRoot [(path, def)
-                                                 | (_:path, def) <- list, not (null path)]
-            in
-              subtree
-
-
-findResource :: ResTree -> URI -> Maybe ResourceDef
-findResource (ResNode rootDefM subtree) uri
-    = let pathStr = uriPath uri
-          path    = [x | x <- splitBy (== '/') pathStr, x /= ""]
-      in
-        if null path then
-            rootDefM
-        else
-            walkTree subtree path
+                               return $ concat $ intersperse "." $ map show [b1, b2, b3, b4]
+                      (SockAddrUnix path)
+                          -> return path
+
+
+-- |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
+                req <- liftIO $! atomically $! readItr itr itrRequest fromJust
+                return req
+
+-- |Get the 'Network.HTTP.Lucu.Request.Method' value of the request.
+getMethod :: Resource Method
+getMethod = do req <- getRequest
+               return $! reqMethod req
+
+-- |Get the URI of the request.
+getRequestURI :: Resource URI
+getRequestURI = do req <- getRequest
+                   return $! reqURI req
+
+-- |Get the HTTP version of the request.
+getRequestVersion :: Resource HttpVersion
+getRequestVersion = do req <- getRequest
+                       return $! reqVersion req
+
+-- |Get the path of this 'Resource' (to be exact,
+-- 'Network.HTTP.Lucu.Resource.Tree.ResourceDef') in the
+-- 'Network.HTTP.Lucu.Resource.Tree.ResTree'. The result of this
+-- action is the exact path in the tree even if the
+-- 'Network.HTTP.Lucu.Resource.Tree.ResourceDef' is greedy.
+--
+-- Example:
+--
+-- > main = let tree = mkResTree [ (["foo"], resFoo) ]
+-- >        in runHttpd defaultConfig tree
+-- >
+-- > resFoo = ResourceDef {
+-- >     resIsGreedy = True
+-- >   , 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 /= ""]
+                 -- 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
+                 -- ければこの Resource が撰ばれた筈が無い）ので、
+                 -- 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. This action
+-- doesn't parse the request body. See 'inputForm'.
+getQueryForm :: Resource [(String, String)]
+getQueryForm = do reqURI <- getRequestURI
+                  return $! parseWWWFormURLEncoded $ uriQuery reqURI
+
+-- |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 actions like 'getContentType' for
+-- every common headers.
+getHeader :: String -> Resource (Maybe String)
+getHeader name = name `seq`
+                 do req <- getRequest
+                    return $! H.getHeader name req
+
+-- |Get a list of 'Network.HTTP.Lucu.MIMEType.MIMEType' enumerated on
+-- header \"Accept\".
+getAccept :: Resource [MIMEType]
+getAccept = do acceptM <- getHeader "Accept"
+               case acceptM of
+                 Nothing 
+                     -> return []
+                 Just accept
+                     -> case parseStr mimeTypeListP accept of
+                          (Success xs, _) -> return xs
+                          _               -> abort BadRequest []
+                                             (Just $ "Unparsable Accept: " ++ accept)
+
+-- |Get a list of @(contentCoding, qvalue)@ enumerated on header
+-- \"Accept-Encoding\".
+getAcceptEncoding :: Resource [(String, 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)]
+           Just ""
+               -- identity のみが許される。
+               -> return [("identity", Nothing)]
+           Just accEnc
+               -> case parseStr accEncListP accEnc of
+                    (Success x, _) -> return x
+                    _              -> abort BadRequest []
+                                      (Just $ "Unparsable Accept-Encoding: " ++ accEnc)
     where
-      walkTree :: ResSubtree -> [String] -> Maybe ResourceDef
+      accEncListP :: Parser [(String, Maybe Double)]
+      accEncListP = allowEOF $! listOf accEncP
+      
+      accEncP :: Parser (String, Maybe Double)
+      accEncP = do coding <- token
+                   qVal   <- option Nothing
+                             $ do string ";q="
+                                  q <- qvalue
+                                  return $ Just q
+                   return (normalizeCoding coding, qVal)
+
+      normalizeCoding :: String -> String
+      normalizeCoding coding
+          = case map toLower coding of
+              "x-gzip"     -> "gzip"
+              "x-compress" -> "compress"
+              other        -> other
+
+-- |Get the header \"Content-Type\" as
+-- 'Network.HTTP.Lucu.MIMEType.MIMEType'.
+getContentType :: Resource (Maybe MIMEType)
+getContentType
+    = do cTypeM <- getHeader "Content-Type"
+         case cTypeM of
+           Nothing
+               -> return Nothing
+           Just cType
+               -> case parseStr mimeTypeP cType of
+                    (Success t, _) -> return $ Just t
+                    _              -> abort BadRequest []
+                                      (Just $ "Unparsable Content-Type: " ++ cType)
+
+
+{- ExaminingRequest 時に使用するアクション群 -}
+
+-- |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
+-- compute 'foundEntity' if this is a POST request.
+--
+-- Computation of 'foundEntity' performs \"If-Match\" test or
+-- \"If-None-Match\" test if possible. When those tests fail, the
+-- computation of 'Resource' immediately aborts with status \"412
+-- Precondition Failed\" or \"304 Not Modified\" depending on the
+-- situation.
+--
+-- If this is a GET or HEAD request, 'foundEntity' automatically puts
+-- \"ETag\" and \"Last-Modified\" headers into the response.
+foundEntity :: ETag -> ClockTime -> Resource ()
+foundEntity tag timeStamp
+    = tag `seq` timeStamp `seq`
+      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.")
+         foundETag tag
+
+         driftTo GettingBody
+
+-- |Tell the system that the 'Resource' found an entity for the
+-- request URI. The only difference from 'foundEntity' is that
+-- 'foundETag' doesn't (and can't) put \"Last-Modified\" header into
+-- the response.
+--
+-- This action is not preferred. You should use 'foundEntity' when
+-- possible.
+foundETag :: ETag -> Resource ()
+foundETag tag
+    = tag `seq`
+      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.")
+
+         -- If-Match があればそれを見る。
+         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
+
+         -- If-None-Match があればそれを見る。
+         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)
+
+         driftTo GettingBody
+
+-- |Tell the system that the 'Resource' found an entity for the
+-- request URI. The only difference from 'foundEntity' is that
+-- 'foundTimeStamp' performs \"If-Modified-Since\" test or
+-- \"If-Unmodified-Since\" test instead of \"If-Match\" test or
+-- \"If-None-Match\" test. Be aware that any tests based on last
+-- 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
+-- possible.
+foundTimeStamp :: ClockTime -> Resource ()
+foundTimeStamp timeStamp
+    = timeStamp `seq`
+      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.")
+
+         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"
+         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 ()
+
+         -- If-Unmodified-Since があればそれを見る。
+         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 ()
+
+         driftTo GettingBody
+
+-- | 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, POST or DELETE request,
+-- 'foundNoEntity' always aborts with status \"404 Not Found\".
+foundNoEntity :: Maybe String -> Resource ()
+foundNoEntity msgM
+    = msgM `seq`
+      do driftTo ExaminingRequest
+
+         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
+
+         driftTo GettingBody
 
-      walkTree subtree (name:[])
-          = case M.lookup name subtree of
-              Nothing               -> Nothing
-              Just (ResNode defM _) -> defM
 
-      walkTree subtree (x:xs)
-          = case M.lookup x subtree of
-              Nothing                      -> Nothing
-              Just (ResNode defM children) -> case defM of
-                                                Just (ResourceDef { resIsGreedy = True })
-                                                    -> defM
-                                                _   -> walkTree children xs
+{- GettingBody 時に使用するアクション群 -}
 
+-- | 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
+-- ('Network.HTTP.Lucu.Config.cnfMaxEntityLength') is used. See
+-- 'defaultLimit'.
+--
+-- Note that 'inputBS' is more efficient than 'input' so you should
+-- use it whenever possible.
+input :: Int -> Resource String
+input limit = limit `seq`
+              inputBS limit >>= return . B.unpack
 
-runResource :: ResourceDef -> Interaction -> IO ThreadId
-runResource def itr = fork $ runReaderT rsrc itr -- FIXME: 例外をcatch
+
+-- | This is mostly the same as 'input' but is more
+-- efficient. 'inputBS' returns a lazy ByteString but it's not really
+-- lazy: reading from the socket just happens at the computation of
+-- 'inputBS', not at the lazy evaluation of the ByteString. The same
+-- goes for 'inputChunkBS'.
+inputBS :: Int -> Resource ByteString
+inputBS limit
+    = limit `seq`
+      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
+         return chunk
+    where
+      askForInput :: Interaction -> Resource ByteString
+      askForInput itr
+          = itr `seq`
+            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)
+               -- 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
+               driftTo DecidingHeader
+               return chunk
+
+      tooLarge :: Int -> STM ()
+      tooLarge lim = lim `seq`
+                     abortSTM RequestEntityTooLarge []
+                     $! Just ("Request body must be smaller than "
+                              ++ show lim ++ " bytes.")
+         
+-- | 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
+-- ('Network.HTTP.Lucu.Config.cnfMaxEntityLength') is used. See
+-- 'defaultLimit'.
+--
+-- Note that 'inputChunkBS' is more efficient than 'inputChunk' so you
+-- should use it whenever possible.
+inputChunk :: Int -> Resource String
+inputChunk limit = limit `seq`
+                   inputChunkBS limit >>= return . B.unpack
+
+
+-- | This is mostly the same as 'inputChunk' but is more
+-- efficient. See 'inputBS'.
+inputChunkBS :: Int -> Resource ByteString
+inputChunkBS limit
+    = limit `seq`
+      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
+         return chunk
+    where
+      askForInput :: Interaction -> Resource ByteString
+      askForInput itr
+          = itr `seq`
+            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)
+               -- Reader にリクエスト
+               liftIO $! atomically
+                          $! do writeItr itr itrReqBodyWanted $! Just actualLimit
+                                writeItr itr itrWillReceiveBody True
+               -- 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
+               return chunk
+
+-- | Computation of @'inputForm' limit@ attempts to read the request
+-- body with 'input' and parse it as
+-- application\/x-www-form-urlencoded. If the request header
+-- \"Content-Type\" is not application\/x-www-form-urlencoded,
+-- 'inputForm' makes 'Resource' abort with status \"415 Unsupported
+-- Media Type\". If the request has no \"Content-Type\", it aborts
+-- with \"400 Bad Request\".
+--
+-- This action should also support multipart\/form-data somehow, but
+-- it is not (yet) done.
+inputForm :: Int -> Resource [(String, String)]
+inputForm limit
+    = limit `seq` 
+      do cTypeM <- getContentType
+         case cTypeM of
+           Nothing
+               -> abort BadRequest [] (Just "Missing Content-Type")
+           Just (MIMEType "application" "x-www-form-urlencoded" _)
+               -> readWWWFormURLEncoded
+           Just (MIMEType "multipart" "form-data" _)
+               -> readMultipartFormData
+           Just cType
+               -> abort UnsupportedMediaType [] (Just $! "Unsupported media type: "
+                                                          ++ show cType)
     where
-      fork = if (resUsesNativeThread def)
-             then forkOS
-             else forkIO
-      rsrc = resResource def
\ No newline at end of file
+      readWWWFormURLEncoded
+          = do src <- input limit
+               return $ parseWWWFormURLEncoded src
+
+      readMultipartFormData -- FIXME: 未對應
+          = abort UnsupportedMediaType []
+            (Just $! "Sorry, inputForm does not currently support multipart/form-data.")
+
+-- | 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 -}
+
+-- | 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 code
+    = code `seq`
+      do driftTo DecidingHeader
+         itr <- ask
+         liftIO $! atomically $! updateItr itr itrResponse
+                    $! \ res -> res {
+                                  resStatus = code
+                                }
+
+-- | 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 actions like 'setContentType'
+-- for every common headers.
+--
+-- Some important headers (especially \"Content-Length\" and
+-- \"Transfer-Encoding\") may be silently dropped or overwritten by
+-- the system not to corrupt the interaction with client at the
+-- 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 :: String -> String -> Resource ()
+setHeader name value
+    = name `seq` value `seq`
+      driftTo DecidingHeader >> setHeader' name value
+         
+
+setHeader' :: String -> String -> Resource ()
+setHeader' name value
+    = name `seq` value `seq`
+      do itr <- ask
+         liftIO $ atomically
+                    $ updateItr itr itrResponse
+                          $ H.setHeader name value
+
+-- | Computation of @'redirect' code uri@ sets the response status to
+-- @code@ and \"Location\" header to @uri@. @code@ must satisfy
+-- 'Network.HTTP.Lucu.Response.isRedirection' or it causes an error.
+redirect :: StatusCode -> URI -> Resource ()
+redirect code uri
+    = code `seq` uri `seq`
+      do when (code == NotModified || not (isRedirection code))
+                  $ abort InternalServerError []
+                        $! Just ("Attempted to redirect with status " ++ show code)
+         setStatus code
+         setLocation uri
+{-# INLINE redirect #-}
+
+
+-- | Computation of @'setContentType' mType@ sets the response header
+-- \"Content-Type\" to @mType@.
+setContentType :: MIMEType -> Resource ()
+setContentType mType
+    = setHeader "Content-Type" $! show mType
+
+-- | Computation of @'setLocation' uri@ sets the response header
+-- \"Location\" to @uri@.
+setLocation :: URI -> Resource ()
+setLocation uri
+    = setHeader "Location" $ uriToString id uri $ ""
+
+-- |Computation of @'setContentEncoding' codings@ sets the response
+-- header \"Content-Encoding\" to @codings@.
+setContentEncoding :: [String] -> Resource ()
+setContentEncoding codings
+    = setHeader "Content-Encoding" $ joinWith ", " codings
+
+
+{- DecidingBody 時に使用するアクション群 -}
+
+-- | Computation of @'output' str@ writes @str@ as a response body,
+-- and then make the 'Resource' transit to /Done/ state. It is safe to
+-- apply 'output' to an infinite string, such as a lazy stream of
+-- \/dev\/random.
+--
+-- Note that 'outputBS' is more efficient than 'output' so you should
+-- use it whenever possible.
+output :: String -> Resource ()
+output str = outputBS $! B.pack str
+{-# INLINE output #-}
+
+-- | This is mostly the same as 'output' but is more efficient.
+outputBS :: ByteString -> Resource ()
+outputBS str = do outputChunkBS str
+                  driftTo Done
+{-# INLINE outputBS #-}
+
+-- | Computation of @'outputChunk' str@ writes @str@ as a part of
+-- response body. You can compute this action multiple times to write
+-- a body little at a time. It is safe to apply 'outputChunk' to an
+-- infinite string.
+--
+-- Note that 'outputChunkBS' is more efficient than 'outputChunk' so
+-- you should use it whenever possible.
+outputChunk :: String -> Resource ()
+outputChunk str = outputChunkBS $! B.pack str
+{-# INLINE outputChunk #-}
+
+-- | This is mostly the same as 'outputChunk' but is more efficient.
+outputChunkBS :: ByteString -> Resource ()
+outputChunkBS str
+    = str `seq`
+      do driftTo DecidingBody
+         itr <- ask
+         
+         let limit = cnfMaxOutputChunkLength $ itrConfig itr
+         when (limit <= 0)
+                  $ fail ("cnfMaxOutputChunkLength must be positive: "
+                          ++ show limit)
+
+         discardBody <- liftIO $ atomically $
+                        readItr itr itrWillDiscardBody id
+
+         unless (discardBody)
+                    $ sendChunks str limit
+
+         unless (B.null str)
+                    $ liftIO $ atomically $
+                      writeItr itr itrBodyIsNull False
+    where
+      {- 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。 -}
+      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
+
+{-
+
+  [GettingBody からそれ以降の状態に遷移する時]
+  
+  body を讀み終へてゐなければ、殘りの body を讀み捨てる。
+
+
+  [DecidingHeader からそれ以降の状態に遷移する時]
+
+  postprocess する。
+
+
+  [Done に遷移する時]
+
+  bodyIsNull が False ならば何もしない。True だった場合は出力補完す
+  る。
+
+-}
+
+driftTo :: InteractionState -> Resource ()
+driftTo newState
+    = newState `seq`
+      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
+    where
+      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
+
+      drift itr DecidingHeader _
+          = postprocess itr
+
+      drift itr _ Done
+          = do bodyIsNull <- readItr itr itrBodyIsNull id
+               when bodyIsNull
+                        $ writeDefaultPage itr
+
+      drift _ _ _
+          = return ()