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{-# LANGUAGE DeriveDataTypeable, FlexibleContexts, GeneralizedNewtypeDeriving
, MultiParamTypeClasses, OverloadedStrings, ScopedTypeVariables, TemplateHaskell
, TypeFamilies, FlexibleInstances #-}
module Main where
import Control.Applicative (Applicative, Alternative, (<$>))
import Control.Exception.Lifted (bracket)
import Control.Monad.Trans.Control (MonadBaseControl)
import Control.Monad (MonadPlus, mplus)
import Control.Monad.Reader (MonadReader, ReaderT(..), ask)
import Control.Monad.Trans (MonadIO(..))
import Data.Acid ( AcidState(..), EventState(..), EventResult(..)
, Query(..), QueryEvent(..), Update(..), UpdateEvent(..)
, IsAcidic(..), makeAcidic, openLocalState
)
import Data.Acid.Local ( createCheckpointAndClose
, openLocalStateFrom
)
import Data.Acid.Advanced (query', update')
import Data.Maybe (fromMaybe)
import Data.SafeCopy (SafeCopy, base, deriveSafeCopy)
import Data.Data (Data, Typeable)
import Data.Lens ((%=), (!=))
import Data.Lens.Template (makeLens)
import Data.Text.Lazy (Text)
import Happstack.Server ( Happstack, HasRqData, Method(GET, POST), Request(rqMethod)
, Response
, ServerPartT(..), WebMonad, FilterMonad, ServerMonad
, askRq, decodeBody, dir, defaultBodyPolicy, lookText
, mapServerPartT, nullConf, nullDir, ok, simpleHTTP
, toResponse
)
import Prelude hiding (head, id)
import System.FilePath ((</>))
import Text.Blaze ((!))
import Text.Blaze.Html4.Strict (body, head, html, input, form, label, p, title, toHtml)
import Text.Blaze.Html4.Strict.Attributes (action, enctype, for, id, method, name, type_, value)
class HasAcidState m st where
getAcidState :: m (AcidState st)
query :: forall event m.
( Functor m
, MonadIO m
, QueryEvent event
, HasAcidState m (EventState event)
) =>
event
-> m (EventResult event)
query event =
do as <- getAcidState
query' (as :: AcidState (EventState event)) event
update :: forall event m.
( Functor m
, MonadIO m
, UpdateEvent event
, HasAcidState m (EventState event)
) =>
event
-> m (EventResult event)
update event =
do as <- getAcidState
update' (as :: AcidState (EventState event)) event
-- | bracket the opening and close of the `AcidState` handle.
-- automatically creates a checkpoint on close
withLocalState :: (MonadBaseControl IO m, MonadIO m, IsAcidic st, Typeable st) =>
Maybe FilePath -- ^ path to state directory
-> st -- ^ initial state value
-> (AcidState st -> m a) -- ^ function which uses the `AcidState` handle
-> m a
withLocalState mPath initialState =
bracket (liftIO $ (maybe openLocalState openLocalStateFrom mPath) initialState)
(liftIO . createCheckpointAndClose)
-- State that stores a hit count
data CountState = CountState { _count :: Integer }
deriving (Eq, Ord, Data, Typeable, Show)
$(deriveSafeCopy 0 'base ''CountState)
$(makeLens ''CountState)
initialCountState :: CountState
initialCountState = CountState { _count = 0 }
incCount :: Update CountState Integer
incCount = count %= succ
$(makeAcidic ''CountState ['incCount])
-- State that stores a greeting
data GreetingState = GreetingState { _greeting :: Text }
deriving (Eq, Ord, Data, Typeable, Show)
$(deriveSafeCopy 0 'base ''GreetingState)
$(makeLens ''GreetingState)
initialGreetingState :: GreetingState
initialGreetingState = GreetingState { _greeting = "Hello" }
getGreeting :: Query GreetingState Text
getGreeting = _greeting <$> ask
setGreeting :: Text -> Update GreetingState Text
setGreeting txt = greeting != txt
$(makeAcidic ''GreetingState ['getGreeting, 'setGreeting])
data Acid = Acid { acidCountState :: AcidState CountState
, acidGreetingState :: AcidState GreetingState
}
withAcid :: Maybe FilePath -> (Acid -> IO a) -> IO a
withAcid mBasePath action =
let basePath = fromMaybe "_state" mBasePath
in withLocalState (Just $ basePath </> "count") initialCountState $ \c ->
withLocalState (Just $ basePath </> "greeting") initialGreetingState $ \g ->
action (Acid c g)
newtype App a = App { unApp :: ServerPartT (ReaderT Acid IO) a }
deriving ( Functor, Alternative, Applicative, Monad, MonadPlus, MonadIO
, HasRqData, ServerMonad ,WebMonad Response, FilterMonad Response
, Happstack, MonadReader Acid)
runApp :: Acid -> App a -> ServerPartT IO a
runApp acid (App sp) = mapServerPartT (flip runReaderT acid) sp
instance HasAcidState App CountState where
getAcidState = acidCountState <$> ask
instance HasAcidState App GreetingState where
getAcidState = acidGreetingState <$> ask
page :: App Response
page =
do nullDir
g <- greet
c <- update IncCount -- ^ a CountState event
ok $ toResponse $
html $ do
head $ do
title "acid-state demo"
body $ do
form ! action "/" ! method "POST" ! enctype "multipart/form-data" $ do
label "new message: " ! for "msg"
input ! type_ "text" ! id "msg" ! name "greeting"
input ! type_ "submit" ! value "update message"
p $ toHtml g
p $ do "This page has been loaded "
toHtml c
" time(s)."
where
greet =
do m <- rqMethod <$> askRq
case m of
POST ->
do decodeBody (defaultBodyPolicy "/tmp/" 0 1000 1000)
newGreeting <- lookText "greeting"
update (SetGreeting newGreeting) -- ^ a GreetingState event
return newGreeting
GET ->
do query GetGreeting -- ^ a GreetingState event
main :: IO ()
main =
withAcid Nothing $ \acid ->
simpleHTTP nullConf $ runApp acid page
newtype FooState = FooState { foo :: Text }
deriving (Eq, Ord, Data, Typeable, SafeCopy)
initialFooState :: FooState
initialFooState = FooState { foo = "foo" }
askFoo :: Query FooState Text
askFoo = foo <$> ask
$(makeAcidic ''FooState ['askFoo])
fooPlugin :: (Happstack m, HasAcidState m FooState) => m Response
fooPlugin =
dir "foo" $ do
txt <- query AskFoo
ok $ toResponse txt
data Acid' = Acid' { acidCountState' :: AcidState CountState
, acidGreetingState' :: AcidState GreetingState
, acidFooState' :: AcidState FooState
}
withAcid' :: Maybe FilePath -> (Acid' -> IO a) -> IO a
withAcid' mBasePath action =
let basePath = fromMaybe "_state" mBasePath
in withLocalState (Just $ basePath </> "count") initialCountState $ \c ->
withLocalState (Just $ basePath </> "greeting") initialGreetingState $ \g ->
withLocalState (Just $ basePath </> "foo") initialFooState $ \f ->
action (Acid' c g f)
newtype App' a = App' { unApp' :: ServerPartT (ReaderT Acid' IO) a }
deriving ( Functor, Alternative, Applicative, Monad, MonadPlus, MonadIO
, HasRqData, ServerMonad ,WebMonad Response, FilterMonad Response
, Happstack, MonadReader Acid')
instance HasAcidState App' FooState where
getAcidState = acidFooState' <$> ask
fooAppPlugin :: App' Response
fooAppPlugin = fooPlugin
fooReaderPlugin :: ReaderT (AcidState FooState) (ServerPartT IO) Response
fooReaderPlugin = fooPlugin
instance HasAcidState (ReaderT (AcidState FooState) (ServerPartT IO)) FooState where
getAcidState = ask
withFooPlugin :: (MonadIO m, MonadBaseControl IO m) =>
FilePath -- ^ path to state directory
-> (ServerPartT IO Response -> m a) -- ^ function that uses fooPlugin
-> m a
withFooPlugin basePath f =
do withLocalState (Just $ basePath </> "foo") initialFooState $ \fooState ->
f $ runReaderT fooReaderPlugin fooState
main' :: IO ()
main' =
withFooPlugin "_state" $ \fooPlugin' ->
withAcid Nothing $ \acid ->
simpleHTTP nullConf $ fooPlugin' `mplus` runApp acid page
|
