Documentation

[Lucu.git] / Network / HTTP / Lucu / Abortion.hs

diff --git a/Network/HTTP/Lucu/Abortion.hs b/Network/HTTP/Lucu/Abortion.hs
index b9e4b116250cedee3692aedb9a082ece6d812420..0a42d71353b552bdbff1fc7231f0f0d39f87756b 100644 (file)
--- a/Network/HTTP/Lucu/Abortion.hs
+++ b/Network/HTTP/Lucu/Abortion.hs
@@ -1,3 +1,7 @@
+-- #prune
+
+-- | Aborting the computation of 'Network.HTTP.Lucu.Resource.Resource'
+-- in any IO monads or arrows.
 module Network.HTTP.Lucu.Abortion
     ( Abortion(..)
     , abort
@@ -33,7 +37,29 @@ data Abortion = Abortion {
     , aboMessage :: Maybe String
     } deriving (Show, Typeable)
 
-
+-- | Computation of @'abort' status headers msg@ aborts the
+-- 'Network.HTTP.Lucu.Resource.Resource' monad with given status,
+-- additional response headers, and optional message string.
+--
+-- What this really does is to just throw a special DynException. The
+-- exception will be caught by the system.
+--
+-- 1. If the 'Network.HTTP.Lucu.Resource.Resource' is in the /Deciding
+--    Header/ or any precedent states, it is possible to use the
+--    @status@ and such like as a HTTP response to be sent to the
+--    client.
+--
+-- 2. Otherwise the HTTP response can't be modified anymore so the
+--    only possible thing the system can do is to dump it to the
+--    stderr. See
+--    'Network.HTTP.Lucu.Config.cnfDumpTooLateAbortionToStderr'.
+--
+-- Note that the status code doesn't have to be an error code so you
+-- can use this action for redirection as well as error reporting e.g.
+--
+-- > abort MovedPermanently
+-- >       [("Location", "http://example.net/")]
+-- >       (Just "It has been moved to example.net")
 abort :: MonadIO m => StatusCode -> [ (String, String) ] -> Maybe String -> m a
 abort status headers msg
     = let abo = Abortion status headers msg
@@ -41,12 +67,14 @@ abort status headers msg
       in
         liftIO $ throwIO exc
 
-
+-- | Computation of @'abortSTM' status headers msg@ just computes
+-- 'abort' in a STM monad.
 abortSTM :: StatusCode -> [ (String, String) ] -> Maybe String -> STM a
 abortSTM status headers msg
     = unsafeIOToSTM $ abort status headers msg
 
-
+-- | Computation of @'abortA' -< (status, (headers, msg))@ just
+-- computes 'abort' in an ArrowIO.
 abortA :: ArrowIO a => a (StatusCode, ([ (String, String) ], Maybe String)) c
 abortA 
     = arrIO3 abort