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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE OverloadedStrings #-}
module Main where
------------------------------------------------------------------------------
-- explicit imports
------------------------------------------------------------------------------
import Control.Monad.Reader (asks)
import Data.ByteString (ByteString)
import Control.Lens (makeLenses, view, over)
import Data.SafeCopy (base, deriveSafeCopy)
import qualified Data.Text as T
import Data.Typeable (Typeable)
import Snap.Util.FileServe (serveDirectory)
import Snap (SnapletInit, Snaplet, Handler,
addRoutes, nestSnaplet, serveSnaplet,
defaultConfig, makeSnaplet,
snapletValue, writeText, modify)
import Snap.Snaplet.AcidState (Update, Query, Acid,
HasAcid (getAcidStore), makeAcidic, update, query, acidInit)
------------------------------------------------------------------------------
-- acid-state code
------------------------------------------------------------------------------
data PersistentState = PersistentState
{ _psCounter :: Int
} deriving (Show,Ord,Eq,Typeable)
makeLenses ''PersistentState
deriveSafeCopy 0 'base ''PersistentState
incCounter :: Update PersistentState ()
incCounter = modify (over psCounter (+1))
myQuery :: Query PersistentState Int
myQuery = asks _psCounter
makeAcidic ''PersistentState ['incCounter, 'myQuery]
------------------------------------------------------------------------------
-- snap code
------------------------------------------------------------------------------
data App = App
{ _acid :: Snaplet (Acid PersistentState)
}
type AppHandler = Handler App App
makeLenses ''App
------------------------------------------------------------------------------
-- | This instance is optional. It just allows you to avoid putting the call
-- "with acid" in front of your calls to query and update.
instance HasAcid App PersistentState where
getAcidStore = view (acid.snapletValue)
------------------------------------------------------------------------------
-- | The application's routes.
routes :: [(ByteString, Handler App App ())]
routes = [ ("", serveDirectory "resources/static")
, ("/inc", update IncCounter)
, ("/count", writeText . T.pack . show =<< query MyQuery)
]
------------------------------------------------------------------------------
-- | The application initializer.
app :: SnapletInit App App
app = makeSnaplet "app" "An snaplet example application." Nothing $ do
a <- nestSnaplet "acid" acid $ acidInit (PersistentState 0)
addRoutes routes
return $ App a
main = serveSnaplet defaultConfig app
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