Snap.Internal.Core

Documentation

class (Monad m, MonadIO m, MonadBaseControl IO m, MonadPlus m, Functor m, Applicative m, Alternative m) => MonadSnap m where

MonadSnap is a type class, analogous to MonadIO for IO, that makes it easy to wrap Snap inside monad transformers.

Methods

liftSnap :: Snap a -> m a

Lift a computation from the Snap monad.

Instances

MonadSnap Snap

Defined in Snap.Internal.Core

Methods

liftSnap :: Snap a -> Snap a

MonadSnap m => MonadSnap (ListT m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> ListT m a

(MonadSnap m, Error e) => MonadSnap (ErrorT e m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> ErrorT e m a

(MonadSnap m, Monoid e) => MonadSnap (ExceptT e m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> ExceptT e m a

MonadSnap m => MonadSnap (ReaderT r m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> ReaderT r m a

MonadSnap m => MonadSnap (StateT s m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> StateT s m a

MonadSnap m => MonadSnap (StateT s m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> StateT s m a

(MonadSnap m, Monoid w) => MonadSnap (WriterT w m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> WriterT w m a

(MonadSnap m, Monoid w) => MonadSnap (WriterT w m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> WriterT w m a

(MonadSnap m, Monoid w) => MonadSnap (RWST r w s m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> RWST r w s m a

(MonadSnap m, Monoid w) => MonadSnap (RWST r w s m)

Defined in Snap.Internal.Instances

Methods

liftSnap :: Snap a -> RWST r w s m a

data SnapResult a

Constructors

SnapValue a

Zero Zero

type EscapeHttpHandler

Arguments

 = ((Int -> Int) -> IO ())

timeout modifier

-> InputStream ByteString

socket read end

-> OutputStream Builder

socket write end

-> IO ()

Type of external handler passed to escapeHttp.

data EscapeSnap

Used internally to implement escapeHttp.

Constructors

TerminateConnection SomeException

EscapeHttp EscapeHttpHandler

Instances

Exception EscapeSnap

Defined in Snap.Internal.Core

Methods

toException :: EscapeSnap -> SomeException

fromException :: SomeException -> Maybe EscapeSnap

displayException :: EscapeSnap -> String

Show EscapeSnap

Defined in Snap.Internal.Core

Methods

showsPrec :: Int -> EscapeSnap -> ShowS

show :: EscapeSnap -> String

showList :: [EscapeSnap] -> ShowS

data Zero

Constructors

PassOnProcessing

EarlyTermination Response

EscapeSnap EscapeSnap

newtype Snap a

Snap is the Monad that user web handlers run in. Snap gives you:

1. Stateful access to fetch or modify an HTTP Request.

   printRqContextPath :: Snap ()
   printRqContextPath = writeBS . rqContextPath =<< getRequest
   

2. Stateful access to fetch or modify an HTTP Response.

   printRspStatusReason :: Snap ()
   printRspStatusReason = writeBS . rspStatusReason =<< getResponse
   

3. Failure / Alternative / MonadPlus semantics: a Snap handler can choose not to handle a given request, using empty or its synonym pass, and you can try alternative handlers with the <|> operator:

   a :: Snap String
   a = pass
   
   b :: Snap String
   b = return "foo"
   
   c :: Snap String
   c = a <|> b             -- try running a, if it fails then try b
   

4. Convenience functions (writeBS, writeLBS, writeText, writeLazyText, addToOutput) for queueing output to be written to the Response, or for streaming to the response using io-streams:

   example :: (OutputStream Builder -> IO (OutputStream Builder)) -> Snap ()
   example streamProc = do
       writeBS   "I'm a strict bytestring"
       writeLBS  "I'm a lazy bytestring"
       writeText "I'm strict text"
       addToOutput streamProc
   

5. Early termination: if you call finishWith:

   a :: Snap ()
   a = do
       modifyResponse $ setResponseStatus 500 "Internal Server Error"
       writeBS "500 error"
       r <- getResponse
       finishWith r
   

   then any subsequent processing will be skipped and the supplied Response value will be returned from runSnap as-is.

6. Access to the IO monad through a MonadIO instance:

   a :: Snap ()
   a = liftIO fireTheMissiles
   

7. The ability to set or extend a timeout which will kill the handler thread after N seconds of inactivity (the default is 20 seconds):

   a :: Snap ()
   a = setTimeout 30
   

8. Throw and catch exceptions using a MonadBaseControl instance:

   import Control.Exception.Lifted (SomeException, throwIO, catch)
   
   foo :: Snap ()
   foo = bar `catch` (e::SomeException) -> baz
     where
       bar = throwIO FooException
   

9. Log a message to the error log:

   foo :: Snap ()
   foo = logError "grumble."
   

You may notice that most of the type signatures in this module contain a (MonadSnap m) => ... typeclass constraint. MonadSnap is a typeclass which, in essence, says "you can get back to the Snap monad from here". Using MonadSnap you can extend the Snap monad with additional functionality and still have access to most of the Snap functions without writing lift everywhere. Instances are already provided for most of the common monad transformers (ReaderT, WriterT, StateT, etc.).

Constructors

Snap

Fields

• unSnap :: forall r. (a -> SnapState -> IO r) -> (Zero -> SnapState -> IO r) -> SnapState -> IO r

Instances

MonadFail Snap

Defined in Snap.Internal.Core

Methods

fail :: String -> Snap a

MonadIO Snap

Defined in Snap.Internal.Core

Methods

liftIO :: IO a -> Snap a

Alternative Snap

Defined in Snap.Internal.Core

Methods

empty :: Snap a

(<|>) :: Snap a -> Snap a -> Snap a

some :: Snap a -> Snap [a]

many :: Snap a -> Snap [a]

Applicative Snap

Defined in Snap.Internal.Core

Methods

pure :: a -> Snap a

(<*>) :: Snap (a -> b) -> Snap a -> Snap b

liftA2 :: (a -> b -> c) -> Snap a -> Snap b -> Snap c

(*>) :: Snap a -> Snap b -> Snap b

(<*) :: Snap a -> Snap b -> Snap a

Functor Snap

Defined in Snap.Internal.Core

Methods

fmap :: (a -> b) -> Snap a -> Snap b

(<$) :: a -> Snap b -> Snap a

Monad Snap

Defined in Snap.Internal.Core

Methods

(>>=) :: Snap a -> (a -> Snap b) -> Snap b

(>>) :: Snap a -> Snap b -> Snap b

return :: a -> Snap a

MonadPlus Snap

Defined in Snap.Internal.Core

Methods

mzero :: Snap a

mplus :: Snap a -> Snap a -> Snap a

MonadSnap Snap

Defined in Snap.Internal.Core

Methods

liftSnap :: Snap a -> Snap a

MonadBaseControl IO Snap

Defined in Snap.Internal.Core

Associated Types

type StM Snap a

Methods

liftBaseWith :: (RunInBase Snap IO -> IO a) -> Snap a

restoreM :: StM Snap a -> Snap a

MonadBase IO Snap

Defined in Snap.Internal.Core

Methods

liftBase :: IO α -> Snap α

type StM Snap a

Defined in Snap.Internal.Core

type StM Snap a

data SnapState

Constructors

SnapState

Fields

• _snapRequest :: Request
• _snapResponse :: Response
• _snapLogError :: ByteString -> IO ()
• _snapModifyTimeout :: (Int -> Int) -> IO ()

runRequestBody :: MonadSnap m => (InputStream ByteString -> IO a) -> m a

Pass the request body stream to a consuming procedure, returning the result.

If the consuming procedure you pass in here throws an exception, Snap will attempt to clear the rest of the unread request body (using skipToEof) before rethrowing the exception. If you used terminateConnection, however, Snap will give up and immediately close the socket.

To prevent slowloris attacks, the connection will be also terminated if the input socket produces data too slowly (500 bytes per second is the default limit).

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.ByteString.Char8 as B8
ghci> import qualified Data.ByteString.Lazy as L
ghci> import Data.Char (toUpper)
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified System.IO.Streams as Streams
ghci> let r = T.put "/foo" "text/plain" "some text"
ghci> :{
ghci| let f s = do u <- Streams.map (B8.map toUpper) s
ghci|              l <- Streams.toList u
ghci|              return $ L.fromChunks l
ghci| :}
ghci> T.runHandler r (runRequestBody f >>= writeLBS)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 20:48:40 GMT

SOME TEXT

readRequestBody

Arguments

:: MonadSnap m

=> Word64

size of the largest request body we're willing to accept. If a request body longer than this is received, a TooManyBytesReadException is thrown. See takeNoMoreThan.

-> m ByteString

Returns the request body as a lazy bytestring. /Note that the request is not actually provided lazily!/

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.put "/foo" "text/plain" "some text"
ghci> T.runHandler r (readRequestBody 2048 >>= writeLBS)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 20:08:44 GMT

some text

Since: 0.6

transformRequestBody

Arguments

:: (InputStream ByteString -> IO (InputStream ByteString))

the InputStream from the Request is passed to this function, and then the resulting InputStream is fed to the output.

-> Snap ()

Normally Snap is careful to ensure that the request body is fully consumed after your web handler runs, but before the Response body is streamed out the socket. If you want to transform the request body into some output in O(1) space, you should use this function.

Take care: in order for this to work, the HTTP client must be written with input-to-output streaming in mind.

Note that upon calling this function, response processing finishes early as if you called finishWith. Make sure you set any content types, headers, cookies, etc. before you call this function.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.ByteString.Char8 as B8
ghci> import Data.Char (toUpper)
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified System.IO.Streams as Streams
ghci> let r = T.put "/foo" "text/plain" "some text"
ghci> let f = Streams.map (B8.map toUpper)
ghci> T.runHandler r (transformRequestBody f >> readRequestBody 2048 >>= writeLBS)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 20:30:15 GMT

SOME TEXT

finishWith :: MonadSnap m => Response -> m a

Short-circuits a Snap monad action early, storing the given Response value in its state.

IMPORTANT: Be vary careful when using this with things like a DB library's withTransaction function or any other kind of setup/teardown block, as it can prevent the cleanup from being called and result in resource leaks.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import Control.Applicative
ghci> let r = T.get "/" M.empty
ghci> T.runHandler r ((ifTop $ writeBS "TOP") <|> finishWith emptyResponse)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 16:58:57 GMT

TOP
ghci> let r' = T.get "/foo/bar" M.empty
ghci> T.runHandler r' ((ifTop $ writeBS "TOP") <|> finishWith emptyResponse)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 17:50:50 GMT

catchFinishWith :: Snap a -> Snap (Either Response a)

Capture the flow of control in case a handler calls finishWith.

WARNING: in the event of a call to transformRequestBody it is possible to violate HTTP protocol safety when using this function. If you call catchFinishWith it is suggested that you do not modify the body of the Response which was passed to the finishWith call.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.ByteString.Char8 as B8
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import Control.Applicative
ghci> let r = T.get "/foo/bar" M.empty
ghci> let h = (ifTop $ writeBS "TOP") <|> finishWith emptyResponse
ghci> T.runHandler r (catchFinishWith h >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 18:35:42 GMT

Left HTTP/1.1 200 OK

pass :: MonadSnap m => m a

Fails out of a Snap monad action. This is used to indicate that you choose not to handle the given request within the given handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r pass
HTTP/1.1 404 Not Found
server: Snap/test
date: Thu, 07 Aug 2014 13:35:42 GMT

<!DOCTYPE html>
<html>
<head>
<title>Not found</title>
</head>
<body>
<code>No handler accepted "/foo/bar"/code
</body></html>

method :: MonadSnap m => Method -> m a -> m a

Runs a Snap monad action only if the request's HTTP method matches the given method.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (method GET $ writeBS "OK")
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 13:38:48 GMT

OK
ghci> T.runHandler r (method POST $ writeBS "OK")
HTTP/1.1 404 Not Found
...

methods :: MonadSnap m => [Method] -> m a -> m a

Runs a Snap monad action only if the request's HTTP method matches one of the given methods.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (methods [GET, POST] $ writeBS "OK")
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 13:38:48 GMT

OK
ghci> T.runHandler r (methods [POST] $ writeBS "OK")
HTTP/1.1 404 Not Found
...

updateContextPath :: Int -> Request -> Request

pathWith :: MonadSnap m => (ByteString -> ByteString -> Bool) -> ByteString -> m a -> m a

dir

Arguments

:: MonadSnap m

=> ByteString

path component to match

-> m a

handler to run

-> m a

Runs a Snap monad action only when the rqPathInfo of the request starts with the given path. For example,

dir "foo" handler

Will fail if rqPathInfo is not "/foo" or "/foo/...", and will add "foo/" to the handler's local rqContextPath.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (dir "foo" $ writeBS "OK")
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 14:52:24 GMT

OK
ghci> T.runHandler r (dir "baz" $ writeBS "OK")
HTTP/1.1 404 Not Found
...

path

Arguments

:: MonadSnap m

=> ByteString

path to match against

-> m a

handler to run

-> m a

Runs a Snap monad action only for requests where rqPathInfo is exactly equal to the given string. If the path matches, locally sets rqContextPath to the old value of rqPathInfo, sets rqPathInfo="", and runs the given handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> T.runHandler (T.get "/foo" M.empty) (path "foo" $ writeBS "bar")
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 14:15:42 GMT

bar
ghci> T.runHandler (T.get "/foo" M.empty) (path "bar" $ writeBS "baz")
HTTP/1.1 404 Not Found
...

pathArg :: (Readable a, MonadSnap m) => (a -> m b) -> m b

Runs a Snap monad action only when the first path component is successfully parsed as the argument to the supplied handler function.

Note that the path segment is url-decoded prior to being passed to fromBS; this is new as of snap-core 0.10.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/11/foo/bar" M.empty
ghci> let f = (\i -> if i == 11 then writeBS "11" else writeBS "???")
ghci> T.runHandler r (pathArg f)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 14:27:10 GMT

11
ghci> let r' = T.get "/foo/11/bar" M.empty
ghci> T.runHandler r' (pathArg f)
HTTP/1.1 404 Not Found
...

ifTop :: MonadSnap m => m a -> m a

Runs a Snap monad action only when rqPathInfo is empty.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/" M.empty
ghci> T.runHandler r (ifTop $ writeBS OK)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 14:56:39 GMT

OK
ghci> let r' = T.get "/foo" M.empty
ghci> T.runHandler r' (ifTop $ writeBS "OK")
HTTP/1.1 404 Not Found
...

sget :: Snap SnapState

Local Snap version of get.

smodify :: (SnapState -> SnapState) -> Snap ()

Local Snap monad version of modify.

getRequest :: MonadSnap m => m Request

Grabs the Request object out of the Snap monad.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBS . rqURI =<< getRequest)
HTTP/1.1 200 OK
server: Snap/test
date: Sat, 02 Aug 2014 07:51:54 GMT

/foo/bar

getResponse :: MonadSnap m => m Response

Grabs the Response object out of the Snap monad.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBS . rspStatusReason =<< getResponse)
HTTP/1.1 200 OK
server: Snap/test
date: Sat, 02 Aug 2014 15:06:00 GMT

OK

getsRequest :: MonadSnap m => (Request -> a) -> m a

Grabs something out of the Request object, using the given projection function. See gets.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBS =<< getsRequest rqURI)
HTTP/1.1 200 OK
server: Snap/test
date: Sat, 02 Aug 2014 07:51:54 GMT

/foo/bar

getsResponse :: MonadSnap m => (Response -> a) -> m a

Grabs something out of the Response object, using the given projection function. See gets.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBS =<< getsResponse rspStatusReason)
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 13:35:45 GMT

OK

putRequest :: MonadSnap m => Request -> m ()

Puts a new Request object into the Snap monad. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> :{
ghci| let hndlr = do rq <- T.buildRequest (T.get "/bar/foo" M.empty)
ghci|                putRequest rq
ghci|                uri' <- getsRequest rqURI
ghci|                writeBS uri'
ghci| :}
ghci> T.runHandler (T.get "/foo/bar" M.empty) hndlr
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 15:13:46 GMT

/bar/foo

putResponse :: MonadSnap m => Response -> m ()

Puts a new Response object into the Snap monad.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let rsp = setResponseCode 404 emptyResponse
ghci> let req = T.get "/foo/bar" M.empty
ghci> T.runHandler req (putResponse rsp)
HTTP/1.1 404 Not Found
server: Snap/test
date: Wed, 06 Aug 2014 13:59:58 GMT

modifyRequest :: MonadSnap m => (Request -> Request) -> m ()

Modifies the Request object stored in a Snap monad. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> r' <- T.buildRequest $ T.get "/bar/foo" M.empty
ghci> T.runHandler r (modifyRequest (const r') >> getsRequest rqURI >>= writeBS)
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 15:24:25 GMT

/bar/foo

modifyResponse :: MonadSnap m => (Response -> Response) -> m ()

Modifes the Response object stored in a Snap monad. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (modifyResponse $ setResponseCode 404)
HTTP/1.1 404 Not Found
server: Snap/test
date: Wed, 06 Aug 2014 15:27:11 GMT

redirect :: MonadSnap m => ByteString -> m a

Performs a redirect by setting the Location header to the given target URL/path and the status code to 302 in the Response object stored in a Snap monad. Note that the target URL is not validated in any way. Consider using redirect' instead, which allows you to choose the correct status code.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (redirect "http://snapframework.com")
HTTP/1.1 302 Found
content-length: 0
location: http://snapframework.com
server: Snap/test
date: Thu, 07 Aug 2014 08:52:11 GMT
Content-Length: 0

redirect' :: MonadSnap m => ByteString -> Int -> m a

Performs a redirect by setting the Location header to the given target URL/path and the status code (should be one of 301, 302, 303 or 307) in the Response object stored in a Snap monad. Note that the target URL is not validated in any way.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (redirect' "http://snapframework.com" 301)
HTTP/1.1 307 Temporary Redirect
content-length: 0
location: http://snapframework.com
server: Snap/test
date: Thu, 07 Aug 2014 08:55:51 GMT
Content-Length: 0

logError :: MonadSnap m => ByteString -> m ()

Log an error message in the Snap monad.

Example:

ghci> import qualified Data.ByteString.Char8 as B8
ghci> runSnap (logError "fatal error!") (error . B8.unpack) undefined undefined
*** Exception: fatal error!

addToOutput

Arguments

:: MonadSnap m

=> (OutputStream Builder -> IO (OutputStream Builder))

output to add

-> m ()

Run the given stream procedure, adding its output to the Response stored in the Snap monad state.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Builder as B
ghci> import qualified System.IO.Streams as Streams
ghci> let r = T.get "/foo/bar" M.empty
ghci> :{
ghci| let f str = do {
ghci|   Streams.write (Just $ B.byteString "Hello, streams world") str;
ghci|   return str }
ghci| :}
ghci> T.runHandler r (addToOutput f)
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:55:47 GMT

Hello, streams world

writeBuilder :: MonadSnap m => Builder -> m ()

Adds the given Builder to the body of the Response stored in the | Snap monad state.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Builder as B
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBuilder $ B.byteString "Hello, world")
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:33:33 GMT

Hello, world

writeBS :: MonadSnap m => ByteString -> m ()

Adds the given strict ByteString to the body of the Response stored in the Snap monad state.

Warning: This function is intentionally non-strict. If any pure exceptions are raised by the expression creating the ByteString, the exception won't actually be raised within the Snap handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeBS "Hello, bytestring world")
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:34:27 GMT

Hello, bytestring world

writeLBS :: MonadSnap m => ByteString -> m ()

Adds the given lazy ByteString to the body of the Response stored in the Snap monad state.

Warning: This function is intentionally non-strict. If any pure exceptions are raised by the expression creating the ByteString, the exception won't actually be raised within the Snap handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeLBS "Hello, lazy bytestring world")
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:35:15 GMT

Hello, lazy bytestring world

writeText :: MonadSnap m => Text -> m ()

Adds the given strict Text to the body of the Response stored in the Snap monad state.

Warning: This function is intentionally non-strict. If any pure exceptions are raised by the expression creating the ByteString, the exception won't actually be raised within the Snap handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeText "Hello, text world")
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:36:38 GMT

Hello, text world

writeLazyText :: MonadSnap m => Text -> m ()

Adds the given lazy Text to the body of the Response stored in the Snap monad state.

Warning: This function is intentionally non-strict. If any pure exceptions are raised by the expression creating the ByteString, the exception won't actually be raised within the Snap handler.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (writeLazyText "Hello, lazy text world")
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 17:37:41 GMT

Hello, lazy text world

sendFile :: MonadSnap m => FilePath -> m ()

Sets the output to be the contents of the specified file.

Calling sendFile will overwrite any output queued to be sent in the Response. If the response body is not modified after the call to sendFile, Snap will use the efficient sendfile() system call on platforms that support it.

If the response body is modified (using modifyResponseBody), the file will be read using mmap().

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> writeFile "/tmp/snap-file" "Hello, sendFile world"
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (sendFile "/tmp/snap-file")
HTTP/1.1 200 OK
content-length: 21
server: Snap/test
date: Wed, 06 Aug 2014 17:45:10 GMT
Content-Length: 21

Hello, sendFile world

sendFilePartial :: MonadSnap m => FilePath -> (Word64, Word64) -> m ()

Sets the output to be the contents of the specified file, within the given (start,end) range.

Calling sendFilePartial will overwrite any output queued to be sent in the Response. If the response body is not modified after the call to sendFilePartial, Snap will use the efficient sendfile() system call on platforms that support it.

If the response body is modified (using modifyResponseBody), the file will be read using mmap().

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> writeFile "/tmp/snap-file" "Hello, sendFilePartial world"
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (sendFilePartial "/tmp/snap-file" (7, 28))
HTTP/1.1 200 OK
content-length: 21
server: Snap/test
date: Wed, 06 Aug 2014 17:47:20 GMT
Content-Length: 21

sendFilePartial world

localRequest :: MonadSnap m => (Request -> Request) -> m a -> m a

Runs a Snap action with a locally-modified Request state object. The Request object in the Snap monad state after the call to localRequest will be unchanged. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> r' <- T.buildRequest $ T.get "/bar/foo" M.empty
ghci> let printRqURI = getsRequest rqURI >>= writeBS >> writeBS "\n"
ghci> T.runHandler r (printRqURI >> localRequest (const r') printRqURI)
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 15:34:12 GMT

/foo/bar
/bar/foo

withRequest :: MonadSnap m => (Request -> m a) -> m a

Fetches the Request from state and hands it to the given action. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import Control.Monad.IO.Class
ghci> let r = T.get "/foo/bar" M.empty
ghci> let h = withRequest (\rq -> liftIO (T.requestToString rq) >>= writeBS)
ghci> T.runHandler r h
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 15:44:24 GMT

GET /foo/bar HTTP/1.1
host: localhost

withResponse :: MonadSnap m => (Response -> m a) -> m a

Fetches the Response from state and hands it to the given action. Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (withResponse $ writeBS . rspStatusReason)
HTTP/1.1 200 OK
server: Snap/test
date: Wed, 06 Aug 2014 15:48:45 GMT

OK

ipHeaderFilter :: MonadSnap m => m ()

Modifies the Request in the state to set the rqRemoteAddr field to the value in the X-Forwarded-For header. If the header is not present, this action has no effect.

This action should be used only when working behind a reverse http proxy that sets the X-Forwarded-For header. This is the only way to ensure the value in the X-Forwarded-For header can be trusted.

This is provided as a filter so actions that require the remote address can get it in a uniform manner. It has specifically limited functionality to ensure that its transformation can be trusted, when used correctly.

ipHeaderFilter' :: MonadSnap m => CI ByteString -> m ()

Modifies the Request in the state to set the rqRemoteAddr field to the value from the header specified. If the header specified is not present, this action has no effect.

This action should be used only when working behind a reverse http proxy that sets the header being looked at. This is the only way to ensure the value in the header can be trusted.

This is provided as a filter so actions that require the remote address can get it in a uniform manner. It has specifically limited functionality to ensure that its transformation can be trusted, when used correctly.

bracketSnap :: IO a -> (a -> IO b) -> (a -> Snap c) -> Snap c

This function brackets a Snap action in resource acquisition and release. This is provided because MonadCatchIO's bracket function doesn't work properly in the case of a short-circuit return from the action being bracketed.

In order to prevent confusion regarding the effects of the aquisition and release actions on the Snap state, this function doesn't accept Snap actions for the acquire or release actions.

This function will run the release action in all cases where the acquire action succeeded. This includes the following behaviors from the bracketed Snap action.

1. Normal completion
2. Short-circuit completion, either from calling fail or finishWith
3. An exception being thrown.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let br = bracketSnap (putStrLn "before") (const $ putStrLn "after")
ghci> T.runHandler (T.get "/" M.empty) (br $ const $ writeBS "OK")
before
after
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 18:41:50 GMT

OK

data NoHandlerException

This exception is thrown if the handler you supply to runSnap fails.

Constructors

NoHandlerException String

Instances

Exception NoHandlerException

Defined in Snap.Internal.Core

Methods

toException :: NoHandlerException -> SomeException

fromException :: SomeException -> Maybe NoHandlerException

displayException :: NoHandlerException -> String

Show NoHandlerException

Defined in Snap.Internal.Core

Methods

showsPrec :: Int -> NoHandlerException -> ShowS

show :: NoHandlerException -> String

showList :: [NoHandlerException] -> ShowS

Eq NoHandlerException

Defined in Snap.Internal.Core

Methods

(==) :: NoHandlerException -> NoHandlerException -> Bool

(/=) :: NoHandlerException -> NoHandlerException -> Bool

terminateConnection :: (Exception e, MonadSnap m) => e -> m a

Terminate the HTTP session with the given exception.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Control.Exception as E
ghci> let r = T.get "/foo/bar" M.empty
ghci> T.runHandler r (terminateConnection $ E.AssertionFailed "Assertion failed!")
*** Exception: <terminated: Assertion failed!>

escapeHttp :: MonadSnap m => EscapeHttpHandler -> m ()

Terminate the HTTP session and hand control to some external handler, escaping all further HTTP traffic.

The external handler takes three arguments: a function to modify the thread's timeout, and a read and a write ends to the socket.

runSnap

Arguments

:: Snap a

Action to run.

-> (ByteString -> IO ())

Error logging action.

-> ((Int -> Int) -> IO ())

Timeout action.

-> Request

HTTP request.

-> IO (Request, Response)

Runs a Snap monad action.

This function is mostly intended for library writers; instead of invoking runSnap directly, use httpServe or runHandler (for testing).

fixupResponse :: Request -> Response -> IO Response

Post-process a finalized HTTP response:

• fixup content-length header
• properly handle 204/304 responses
• if request was HEAD, remove response body

Note that we do NOT deal with transfer-encoding: chunked or "connection: close" here.

evalSnap

Arguments

:: Snap a

Action to run.

-> (ByteString -> IO ())

Error logging action.

-> ((Int -> Int) -> IO ())

Timeout action.

-> Request

HTTP request.

-> IO a

Evaluates a Snap monad action.

Unlike runSnap, evalSnap evaluates to the value, not the Response. Like runSnap, evalSnap is intended for library writers. Note that there is no meaningful way of evaluating a Snap monad action that contains pass without alternative (i.e. failure), finishWith (i.e. early termination), or escapeHttp (i.e. escaping Snap). In all of those three cases evalSnap throws an IO exception.

getParamFrom :: MonadSnap m => (ByteString -> Request -> Maybe [ByteString]) -> ByteString -> m (Maybe ByteString)

getParam

Arguments

:: MonadSnap m

=> ByteString

parameter name to look up

-> m (Maybe ByteString)

See rqParam. Looks up a value for the given named parameter in the Request. If more than one value was entered for the given parameter name, getParam gloms the values together with intercalate " ".

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.get "/foo/bar" $ M.fromList [("foo", ["bar"])]
ghci> T.runHandler r (getParam "foo" >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 12:57:20 GMT

Just "bar"

getPostParam

Arguments

:: MonadSnap m

=> ByteString

parameter name to look up

-> m (Maybe ByteString)

See rqPostParam. Looks up a value for the given named parameter in the POST form parameters mapping in Request. If more than one value was entered for the given parameter name, getPostParam gloms the values together with: intercalate " ".

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.postUrlEncoded "/foo/bar" $ M.fromList [("foo", ["bar"])]
ghci> T.runHandler r (getPostParam "foo" >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 13:01:04 GMT

Just "bar"

getQueryParam

Arguments

:: MonadSnap m

=> ByteString

parameter name to look up

-> m (Maybe ByteString)

See rqQueryParam. Looks up a value for the given named parameter in the query string parameters mapping in Request. If more than one value was entered for the given parameter name, getQueryParam gloms the values together with intercalate " ".

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.postUrlEncoded "/foo/bar" M.empty >> T.setQueryStringRaw "foo=bar&foo=baz"
ghci> T.runHandler r (getQueryParam "foo" >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 13:06:50 GMT

Just "bar baz"

getParams :: MonadSnap m => m Params

See rqParams. Convenience function to return Params from the Request inside of a MonadSnap instance.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.get "/foo/bar" $ M.fromList [("foo", ["bar"])]
ghci> T.runHandler r (getParams >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 13:02:54 GMT

fromList [("foo",["bar"])]

getPostParams :: MonadSnap m => m Params

See rqParams. Convenience function to return Params from the Request inside of a MonadSnap instance.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.postUrlEncoded "/foo/bar" $ M.fromList [("foo", ["bar"])]
ghci> T.runHandler r (getPostParams >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 13:04:34 GMT

fromList [("foo",["bar"])]

getQueryParams :: MonadSnap m => m Params

See rqParams. Convenience function to return Params from the Request inside of a MonadSnap instance.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let r = T.postUrlEncoded "/foo/bar" M.empty >> T.setQueryStringRaw "foo=bar&foo=baz"
ghci> T.runHandler r (getQueryParams >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Mon, 11 Aug 2014 13:10:17 GMT

fromList [("foo",["bar","baz"])]

getCookie :: MonadSnap m => ByteString -> m (Maybe Cookie)

Gets the HTTP Cookie with the specified name.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> import qualified Data.ByteString.Char8 as B8
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> let r = T.get "/foo/bar" M.empty >> T.addCookies [cookie]
ghci> T.runHandler r (getCookie "name" >>= writeBS . B8.pack . show)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 12:16:58 GMT

Just (Cookie {cookieName = "name", cookieValue = "value", ...})

readCookie :: (MonadSnap m, Readable a) => ByteString -> m a

Gets the HTTP Cookie with the specified name and decodes it. If the decoding fails, the handler calls pass.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> let r = T.get "/foo/bar" M.empty >> T.addCookies [cookie]
ghci> T.runHandler r (readCookie "name" >>= writeBS)
HTTP/1.1 200 OK
server: Snap/test
date: Thu, 07 Aug 2014 12:20:09 GMT

value

expireCookie :: MonadSnap m => Cookie -> m ()

Expire given Cookie in client's browser.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/foo/bar" M.empty
ghci> let cookie = Cookie "name" "" Nothing (Just "/subsite") Nothing True False
ghci> T.runHandler r (expireCookie cookie)
HTTP/1.1 200 OK
set-cookie: name=; path=/subsite; expires=Sat, 24 Dec 1994 06:28:16 GMT; Secure
server: Snap/test

date: Thu, 07 Aug 2014 12:21:27 GMT
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> let r2 = T.get "/foo/bar" M.empty >> T.addCookies [cookie]
ghci> T.runHandler r (getCookie "name" >>= maybe (return ()) expireCookie)
HTTP/1.1 200 OK
set-cookie: name=; expires=Sat, 24 Dec 1994 06:28:16 GMT
server: Snap/test

setTimeout :: MonadSnap m => Int -> m ()

Causes the handler thread to be killed n seconds from now.

extendTimeout :: MonadSnap m => Int -> m ()

Causes the handler thread to be killed at least n seconds from now.

modifyTimeout :: MonadSnap m => (Int -> Int) -> m ()

Modifies the amount of time remaining before the request times out.

getTimeoutModifier :: MonadSnap m => m ((Int -> Int) -> IO ())

Returns an IO action which you can use to modify the timeout value.

data Response

Represents an HTTP response.

Constructors

Response

Fields

• rspHeaders :: Headers
• rspCookies :: Map ByteString Cookie
• rspContentLength :: !(Maybe Word64)

  We will need to inspect the content length no matter what, and looking up "content-length" in the headers and parsing the number out of the text will be too expensive.

• rspBody :: ResponseBody
• rspStatus :: !Int

  Returns the HTTP status code.

  Example:

  ghci> rspStatus emptyResponse
  200
  

• rspStatusReason :: !ByteString

  Returns the HTTP status explanation string.

  Example:

  ghci> rspStatusReason emptyResponse
  OK
  

• rspTransformingRqBody :: !Bool

  If true, we are transforming the request body with transformRequestBody

Instances

Show Response

Defined in Snap.Internal.Http.Types

Methods

showsPrec :: Int -> Response -> ShowS

show :: Response -> String

showList :: [Response] -> ShowS

HasHeaders Response

Defined in Snap.Internal.Http.Types

Methods

updateHeaders :: (Headers -> Headers) -> Response -> Response

headers :: Response -> Headers

data ResponseBody

Constructors

Stream StreamProc

output body is a function that writes to a Builder stream

SendFile FilePath (Maybe (Word64, Word64))

output body is sendfile(), optional second argument is a byte range to send

type StreamProc = OutputStream Builder -> IO (OutputStream Builder)

data Request

Contains all of the information about an incoming HTTP request.

Constructors

Request

Fields

• rqHostName :: ByteString

  The server name of the request, as it came in from the request's Host: header.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> :{
  ghci| rq <- T.buildRequest $ do
  ghci|         T.get "/foo/bar" M.empty
  ghci|         T.setHeader "host" "example.com"
  ghci| :}
  ghci> rqHostName rq
  "example.com"
  

• rqClientAddr :: ByteString

  The remote IP address.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqClientAddr `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "127.0.0.1"
  

• rqClientPort :: !Int

  The remote TCP port number.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqClientPort `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "60000"
  

• rqServerAddr :: ByteString

  The local IP address for this request.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqServerAddr `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "127.0.0.1"
  

• rqServerPort :: !Int

  Returns the port number the HTTP server is listening on. This may be useless from the perspective of external requests, e.g. if the server is running behind a proxy.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqServerPort `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  8080
  

• rqLocalHostname :: ByteString

  Returns the HTTP server's idea of its local hostname, including port. This is as configured with the Config object at startup.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqLocalHostname `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "localhost"
  

• rqIsSecure :: !Bool

  Returns True if this is an HTTPS session.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqIsSecure `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  False
  

• rqHeaders :: Headers

  Contains all HTTP Headers associated with this request.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqHeaders `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  H {unH = [("host","localhost")]}
  

• rqBody :: InputStream ByteString

  Actual body of the request.

• rqContentLength :: !(Maybe Word64)

  Returns the Content-Length of the HTTP request body.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqContentLength `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  Nothing
  

• rqMethod :: !Method

  Returns the HTTP request method.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqMethod `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  GET
  

• rqVersion :: !HttpVersion

  Returns the HTTP version used by the client.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqVersion `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  (1,1)
  

• rqCookies :: [Cookie]

  Returns a list of the cookies that came in from the HTTP request headers.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqCookies `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  []
  

• rqPathInfo :: ByteString

  Handlers can be hung on a URI "entry point"; this is called the "context path". If a handler is hung on the context path "/foo/", and you request "/foo/bar", the value of rqPathInfo will be "bar".

  The following identity holds:

  rqURI r == S.concat [ rqContextPath r
                      , rqPathInfo r
                      , let q = rqQueryString r
                        in if S.null q
                             then ""
                             else S.append "?" q
                      ]

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqPathInfo `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "foo/bar"
  

• rqContextPath :: ByteString

  The "context path" of the request; catenating rqContextPath, and rqPathInfo should get you back to the original rqURI (ignoring query strings). The rqContextPath always begins and ends with a slash ("/") character, and represents the path (relative to your component/snaplet) you took to get to your handler.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqContextPath `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "/"
  

• rqURI :: ByteString

  Returns the URI requested by the client.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rqURI `fmap` T.buildRequest (T.get "/foo/bar" M.empty)
  "foo/bar"
  

• rqQueryString :: ByteString

  Returns the HTTP query string for this Request.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> rq <- T.buildRequest (T.get "/foo/bar" (M.fromList [("name", ["value"])]))
  ghci> rqQueryString rq
  "name=value"
  

• rqParams :: Params

  Returns the parameters mapping for this Request. "Parameters" are automatically decoded from the URI's query string and POST body and entered into this mapping. The rqParams value is thus a union of rqQueryParams and rqPostParams.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> :{
  ghci| rq <- T.buildRequest $ do
  ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
  ghci|         T.setQueryStringRaw "baz=quux"
  ghci| :}
  ghci> rqParams rq
  fromList [("baz",["qux","quux"])]
  

• rqQueryParams :: Params

  The parameter mapping decoded from the URI's query string.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> :{
  ghci| rq <- T.buildRequest $ do
  ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
  ghci|         T.setQueryStringRaw "baz=quux"
  ghci| :}
  ghci> rqQueryParams rq
  fromList [("baz",["quux"])]
  

• rqPostParams :: Params

  The parameter mapping decoded from the POST body. Note that Snap only auto-decodes POST request bodies when the request's Content-Type is application/x-www-form-urlencoded. For multipart/form-data use handleFileUploads to decode the POST request and fill this mapping.

  Example:

  ghci> :set -XOverloadedStrings
  ghci> import qualified Snap.Test as T
  ghci> import qualified Data.Map as M
  ghci> :{
  ghci| rq <- T.buildRequest $ do
  ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
  ghci|         T.setQueryStringRaw "baz=quux"
  ghci| :}
  ghci> rqPostParams rq
  fromList [("baz",["qux"])]
  

Instances

Show Request

Defined in Snap.Internal.Http.Types

Methods

showsPrec :: Int -> Request -> ShowS

show :: Request -> String

showList :: [Request] -> ShowS

HasHeaders Request

Defined in Snap.Internal.Http.Types

Methods

updateHeaders :: (Headers -> Headers) -> Request -> Request

headers :: Request -> Headers

Monad m => MonadState Request (RequestBuilder m)

Defined in Snap.Internal.Test.RequestBuilder

Methods

get :: RequestBuilder m Request

put :: Request -> RequestBuilder m ()

state :: (Request -> (a, Request)) -> RequestBuilder m a

type Params = Map ByteString [ByteString]

A type alias for the HTTP parameters mapping. Each parameter key maps to a list of ByteString values; if a parameter is specified multiple times (e.g.: "GET /foo?param=bar1&param=bar2"), looking up "param" in the mapping will give you ["bar1", "bar2"].

data Cookie

A datatype representing an HTTP cookie.

Constructors

Cookie

Fields

• cookieName :: !ByteString

  The name of the cookie.

• cookieValue :: !ByteString

  The cookie's string value.

• cookieExpires :: !(Maybe UTCTime)

  The cookie's expiration value, if it has one.

• cookieDomain :: !(Maybe ByteString)

  The cookie's "domain" value, if it has one.

• cookiePath :: !(Maybe ByteString)

  The cookie path.

• cookieSecure :: !Bool

  Tag as secure cookie?

• cookieHttpOnly :: !Bool

  HTTP only?

Instances

Show Cookie

Defined in Snap.Internal.Http.Types

Methods

showsPrec :: Int -> Cookie -> ShowS

show :: Cookie -> String

showList :: [Cookie] -> ShowS

Eq Cookie

Defined in Snap.Internal.Http.Types

Methods

(==) :: Cookie -> Cookie -> Bool

(/=) :: Cookie -> Cookie -> Bool

type HttpVersion = (Int, Int)

Represents a (major, minor) version of the HTTP protocol.

data Method

Enumerates the HTTP method values (see http://tools.ietf.org/html/rfc2068.html#section-5.1.1).

Constructors

GET

HEAD

POST

PUT

DELETE

TRACE

OPTIONS

CONNECT

PATCH

Method ByteString

Instances

Read Method

Defined in Snap.Internal.Http.Types

Methods

readsPrec :: Int -> ReadS Method

readList :: ReadS [Method]

readPrec :: ReadPrec Method

readListPrec :: ReadPrec [Method]

Show Method

Defined in Snap.Internal.Http.Types

Methods

showsPrec :: Int -> Method -> ShowS

show :: Method -> String

showList :: [Method] -> ShowS

Eq Method

Defined in Snap.Internal.Http.Types

Methods

(==) :: Method -> Method -> Bool

(/=) :: Method -> Method -> Bool

Ord Method

Defined in Snap.Internal.Http.Types

Methods

compare :: Method -> Method -> Ordering

(<) :: Method -> Method -> Bool

(<=) :: Method -> Method -> Bool

(>) :: Method -> Method -> Bool

(>=) :: Method -> Method -> Bool

max :: Method -> Method -> Method

min :: Method -> Method -> Method

class HasHeaders a where

A typeclass for datatypes which contain HTTP headers.

Methods

updateHeaders :: (Headers -> Headers) -> a -> a

Modify the datatype's headers.

headers :: a -> Headers

Retrieve the headers from a datatype that has headers.

Instances

HasHeaders Request

Defined in Snap.Internal.Http.Types

Methods

updateHeaders :: (Headers -> Headers) -> Request -> Request

headers :: Request -> Headers

HasHeaders Response

Defined in Snap.Internal.Http.Types

Methods

updateHeaders :: (Headers -> Headers) -> Response -> Response

headers :: Response -> Headers

HasHeaders Headers

Defined in Snap.Internal.Http.Types

Methods

updateHeaders :: (Headers -> Headers) -> Headers -> Headers

headers :: Headers -> Headers

addHeader :: HasHeaders a => CI ByteString -> ByteString -> a -> a

Adds a header key-value-pair to the HasHeaders datatype. If a header with the same name already exists, the new value is appended to the headers list.

Example:

ghci> import qualified Snap.Types.Headers as H
ghci> addHeader "Host" "localhost" H.empty
H {unH = [("host","localhost")]}
ghci> addHeader "Host" "127.0.0.1" it
H {unH = [("host","localhost,127.0.0.1")]}

setHeader :: HasHeaders a => CI ByteString -> ByteString -> a -> a

Sets a header key-value-pair in a HasHeaders datatype. If a header with the same name already exists, it is overwritten with the new value.

Example:

ghci> import qualified Snap.Types.Headers as H
ghci> setHeader "Host" "localhost" H.empty
H {unH = [("host","localhost")]}
ghci> setHeader "Host" "127.0.0.1" it
H {unH = [("host","127.0.0.1")]}

getHeader :: HasHeaders a => CI ByteString -> a -> Maybe ByteString

Gets a header value out of a HasHeaders datatype.

Example:

ghci> import qualified Snap.Types.Headers as H
ghci> getHeader "Host" $ setHeader "Host" "localhost" H.empty
Just "localhost"

listHeaders :: HasHeaders a => a -> [(CI ByteString, ByteString)]

Lists all the headers out of a HasHeaders datatype. If many headers came in with the same name, they will be catenated together.

Example:

ghci> import qualified Snap.Types.Headers as H
ghci> listHeaders $ setHeader "Host" "localhost" H.empty
[("host","localhost")]

deleteHeader :: HasHeaders a => CI ByteString -> a -> a

Clears a header value from a HasHeaders datatype.

Example:

ghci> import qualified Snap.Types.Headers as H
ghci> deleteHeader "Host" $ setHeader "Host" "localhost" H.empty
H {unH = []}

normalizeMethod :: Method -> Method

Equate the special case constructors with their corresponding Method name variant.

rspBodyMap :: (StreamProc -> StreamProc) -> ResponseBody -> ResponseBody

rspBodyToEnum :: ResponseBody -> StreamProc

rqParam

Arguments

:: ByteString

parameter name to look up

-> Request

HTTP request

-> Maybe [ByteString]

Looks up the value(s) for the given named parameter. Parameters initially come from the request's query string and any decoded POST body (if the request's Content-Type is application/x-www-form-urlencoded). Parameter values can be modified within handlers using "rqModifyParams".

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Snap.Test as T
ghci> import qualified Data.Map as M
ghci> :{
ghci| rq <- T.buildRequest $ do
ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
ghci|         T.setQueryStringRaw "baz=quux"
ghci| :}
ghci> rqParam "baz" rq
Just ["qux","quux"]

rqPostParam

Arguments

:: ByteString

parameter name to look up

-> Request

HTTP request

-> Maybe [ByteString]

Looks up the value(s) for the given named parameter in the POST parameters mapping.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Snap.Test as T
ghci> import qualified Data.Map as M
ghci> :{
ghci| rq <- T.buildRequest $ do
ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
ghci|         T.setQueryStringRaw "baz=quux"
ghci| :}
ghci> rqPostParam "baz" rq
Just ["qux"]

rqQueryParam

Arguments

:: ByteString

parameter name to look up

-> Request

HTTP request

-> Maybe [ByteString]

Looks up the value(s) for the given named parameter in the query parameters mapping.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Snap.Test as T
ghci> import qualified Data.Map as M
ghci> :{
ghci| rq <- T.buildRequest $ do
ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
ghci|         T.setQueryStringRaw "baz=quux"
ghci| :}
ghci> rqQueryParam "baz" rq
Just ["quux"]

rqModifyParams :: (Params -> Params) -> Request -> Request

Modifies the parameters mapping (which is a Map ByteString ByteString) in a Request using the given function.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Snap.Test as T
ghci> import qualified Data.Map as M
ghci> :{
ghci| rq <- T.buildRequest $ do
ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
ghci|         T.setQueryStringRaw "baz=quux"
ghci| :}
ghci> rqParams rq
fromList [("baz",["qux","quux"])]
ghci> rqParams $ rqModifyParams (M.delete "baz") rq
fromList []

rqSetParam

Arguments

:: ByteString

parameter name

-> [ByteString]

parameter values

-> Request

request

-> Request

Writes a key-value pair to the parameters mapping within the given request.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Snap.Test as T
ghci> import qualified Data.Map as M
ghci> :{
ghci| rq <- T.buildRequest $ do
ghci|         T.postUrlEncoded "/foo/bar" $ M.fromList [("baz", ["qux"])]
ghci|         T.setQueryStringRaw "baz=quux"
ghci| :}
ghci> rqParams rq
fromList [("baz",["qux","quux"])]
ghci> rqParams $ rqSetParam "baz" ["corge"] rq
fromList [("baz", ["corge"])]

emptyResponse :: Response

An empty Response.

Example:

ghci> emptyResponse
HTTP/1.1 200 OK

setResponseBody

Arguments

:: (OutputStream Builder -> IO (OutputStream Builder))

new response body

-> Response

response to modify

-> Response

Sets an HTTP response body to the given stream procedure.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified System.IO.Streams as Streams
ghci> import qualified Data.ByteString.Builder as Builder
ghci> :{
ghci| let r = setResponseBody
ghci|         (out -> do
ghci|             Streams.write (Just $ Builder.byteString "Hello, world!") out
ghci|             return out)
ghci|         emptyResponse
ghci| :}
ghci> r
HTTP/1.1 200 OK

Hello, world!

setResponseStatus

Arguments

:: Int

HTTP response integer code

-> ByteString

HTTP response explanation

-> Response

Response to be modified

-> Response

Sets the HTTP response status. Note: normally you would use setResponseCode unless you needed a custom response explanation.

Example:

ghci> :set -XOverloadedStrings
ghci> setResponseStatus 500 "Internal Server Error" emptyResponse
HTTP/1.1 500 Internal Server Error

setResponseCode

Arguments

:: Int

HTTP response integer code

-> Response

Response to be modified

-> Response

Sets the HTTP response code.

Example:

ghci> setResponseCode 404 emptyResponse
HTTP/1.1 404 Not Found

modifyResponseBody :: ((OutputStream Builder -> IO (OutputStream Builder)) -> OutputStream Builder -> IO (OutputStream Builder)) -> Response -> Response

Modifies a response body.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified System.IO.Streams as Streams
ghci> import qualified Data.ByteString.Builder as Builder
ghci> :{
ghci| let r = setResponseBody
ghci|         (out -> do
ghci|             Streams.write (Just $ Builder.byteString "Hello, world!") out
ghci|             return out)
ghci|         emptyResponse
ghci| :}
ghci> r
HTTP/1.1 200 OK

Hello, world!
ghci> :{
ghci| let r' = modifyResponseBody
ghci|          (f out -> do
ghci|              out' <- f out
ghci|              Streams.write (Just $ Builder.byteString "\nBye, world!") out'
ghci|              return out') r
ghci| :}
ghci> r'
HTTP/1.1 200 OK

Hello, world!
Bye, world!

setContentType :: ByteString -> Response -> Response

Sets the Content-Type in the Response headers.

Example:

ghci> :set -XOverloadedStrings
ghci> setContentType "text/html" emptyResponse
HTTP/1.1 200 OK
content-type: text/html

addResponseCookie

Arguments

:: Cookie

cookie value

-> Response

response to modify

-> Response

Adds an HTTP Cookie to Response headers.

Example:

ghci> :set -XOverloadedStrings
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> getResponseCookie "name" $ addResponseCookie cookie emptyResponse
Just (Cookie {cookieName = "name", cookieValue = "value", ...})

getResponseCookie

Arguments

:: ByteString

cookie name

-> Response

response to query

-> Maybe Cookie

Gets an HTTP Cookie with the given name from Response headers.

Example:

ghci> :set -XOverloadedStrings
ghci> getResponseCookie "cookie-name" emptyResponse
Nothing

getResponseCookies

Arguments

:: Response

response to query

-> [Cookie]

Returns a list of Cookies present in Response

Example:

ghci> getResponseCookies emptyResponse
[]

deleteResponseCookie

Arguments

:: ByteString

cookie name

-> Response

response to modify

-> Response

Deletes an HTTP Cookie from the Response headers. Please note this does not necessarily erase the cookie from the client browser.

Example:

ghci> :set -XOverloadedStrings
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> let rsp    = addResponseCookie cookie emptyResponse
ghci> getResponseCookie "name" rsp
Just (Cookie {cookieName = "name", cookieValue = "value", ...})
ghci> getResponseCookie "name" $ deleteResponseCookie "name" rsp
Nothing

modifyResponseCookie

Arguments

:: ByteString

cookie name

-> (Cookie -> Cookie)

modifier function

-> Response

response to modify

-> Response

Modifies an HTTP Cookie with given name in Response headers. Nothing will happen if a matching Cookie can not be found in Response.

Example:

ghci> :set -XOverloadedStrings
ghci> import Data.Monoid
ghci> let cookie = Cookie "name" "value" Nothing Nothing Nothing False False
ghci> let rsp    = addResponseCookie cookie emptyResponse
ghci> getResponseCookie "name" rsp
Just (Cookie {cookieName = "name", cookieValue = "value", ...})
ghci> let f ck@(Cookie { cookieName = name }) = ck { cookieName = name <> "'"}
ghci> let rsp' = modifyResponseCookie "name" f rsp
ghci> getResponseCookie "name'" rsp'
Just (Cookie {cookieName = "name'", ...})
ghci> getResponseCookie "name" rsp'
Just (Cookie {cookieName = "name", ...})

setContentLength :: Word64 -> Response -> Response

A note here: if you want to set the Content-Length for the response, Snap forces you to do it with this function rather than by setting it in the headers; the Content-Length in the headers will be ignored.

The reason for this is that Snap needs to look up the value of Content-Length for each request, and looking the string value up in the headers and parsing the number out of the text will be too expensive.

If you don't set a content length in your response, HTTP keep-alive will be disabled for HTTP/1.0 clients, forcing a Connection: close. For HTTP/1.1 clients, Snap will switch to the chunked transfer encoding if Content-Length is not specified.

Example:

ghci> setContentLength 400 emptyResponse
HTTP/1.1 200 OK
Content-Length: 400

clearContentLength :: Response -> Response

Removes any Content-Length set in the Response.

Example:

ghci> clearContentLength $ setContentLength 400 emptyResponse
HTTP/1.1 200 OK

formatLogTime :: CTime -> IO ByteString

Convert a CTime into common log entry format.

formatHttpTime :: CTime -> IO ByteString

Convert a CTime into an HTTP timestamp.

Example:

ghci> formatHttpTime . fromIntegral $ 10
"Thu, 01 Jan 1970 00:00:10 GMT"

parseHttpTime :: ByteString -> IO CTime

Converts an HTTP timestamp into a CTime.

If the given time string is unparseable, this function will return 0.

Example:

ghci> :set -XOverloadedStrings
ghci> parseHttpTime "Thu, 01 Jan 1970 00:00:10 GMT"
10

statusReasonMap :: IntMap ByteString

Adapted from:

https://www.iana.org/assignments/http-status-codes/http-status-codes.txt