yesod/demo/appcache/AppCache.hs
2013-04-11 17:07:22 +03:00

61 lines
2.0 KiB
Haskell

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
module AppCache where
import Control.Monad (when)
import Control.Monad.Trans.Writer
import Data.Hashable (hashWithSalt)
import Data.List (intercalate)
import qualified Data.Set as Set
import Data.Text (Text)
import Data.Text (pack)
import Language.Haskell.TH.Syntax
import Yesod.Core
import Yesod.Routes.TH
newtype AppCache = AppCache { unAppCache :: Text }
appCache :: [ResourceTree String] -> Q Exp
appCache trees = do
piecesSet <- execWriterT $ mapM_ (goTree id) trees
let body = unlines $ map toPath $ Set.toList piecesSet
hash = hashWithSalt 0 body
total = concat
[ "CACHE MANIFEST\n# Version: "
, show hash
, "\n\nCACHE:\n"
, body
]
[|return (AppCache (pack total))|]
where
toPath [] = "/"
toPath x = concatMap ('/':) x
goTree :: Monad m
=> ([String] -> [String])
-> ResourceTree String
-> WriterT (Set.Set [String]) m ()
goTree front (ResourceLeaf res) = do
pieces' <- goPieces (resourceName res) $ resourcePieces res
when ("CACHE" `elem` resourceAttrs res) $
tell $ Set.singleton $ front pieces'
goTree front (ResourceParent name pieces trees) = do
pieces' <- goPieces name pieces
mapM_ (goTree $ front . (pieces' ++)) trees
goPieces :: Monad m => String -> [(CheckOverlap, Piece String)] -> m [String]
goPieces name =
mapM (goPiece . snd)
where
goPiece (Static s) = return s
goPiece (Dynamic _) = fail $ concat
[ "AppCache only applies to fully-static paths, but "
, name
, " has dynamic pieces."
]
instance ToContent AppCache where
toContent = toContent . unAppCache
instance ToTypedContent AppCache where
toTypedContent = TypedContent "text/cache-manifest" . toContent