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{-# LANGUAGE DeriveDataTypeable #-}
import PGF
import FastCGIUtils
import Network.CGI hiding (Language)
import Text.JSON
import qualified Codec.Binary.UTF8.String as UTF8 (encodeString)
import Control.Exception
import Control.Monad
import Data.Dynamic
import Data.Maybe
grammarFile :: FilePath
grammarFile = "grammar.pgf"
newtype Record a = Record { unRecord :: [(String,a)] }
type Translation = Record [Record String]
instance JSON a => JSON (Record a) where
readJSON = fmap (Record . fromJSObject) . readJSON
showJSON = showJSON . toJSObject . unRecord
main :: IO ()
main = do initFastCGI
r <- newDataRef
loopFastCGI (handleErrors (handleCGIErrors (fcgiMain r)))
fcgiMain :: DataRef PGF -> CGI CGIResult
fcgiMain ref = getData readPGF ref grammarFile >>= cgiMain
cgiMain :: PGF -> CGI CGIResult
cgiMain pgf =
do path <- pathInfo
case path of
"/translate" -> do input <- liftM (fromMaybe "") $ getInput "input"
mcat <- getCat pgf "cat"
mfrom <- getLang pgf "from"
mto <- getLang pgf "to"
outputJSON $ translate pgf input mcat mfrom mto
"/categories" -> outputJSON $ categories pgf
"/languages" -> outputJSON $ languages pgf
_ -> outputNotFound path
getCat :: PGF -> String -> CGI (Maybe Category)
getCat pgf i =
do mcat <- getInput i
case mcat of
Just "" -> return Nothing
Just cat | cat `notElem` categories pgf ->
throwCGIError 400 "Unknown category" ["Unknown category: " ++ cat]
_ -> return mcat
getLang :: PGF -> String -> CGI (Maybe Language)
getLang pgf i =
do mlang <- getInput i
case mlang of
Just "" -> return Nothing
Just lang | lang `notElem` languages pgf ->
throwCGIError 400 "Unknown language" ["Unknown language: " ++ lang]
_ -> return mlang
outputJSON :: JSON a => a -> CGI CGIResult
outputJSON x = do setHeader "Content-Type" "text/json; charset=utf-8"
outputStrict $ UTF8.encodeString $ encode x
outputStrict :: String -> CGI CGIResult
outputStrict x | x == x = output x
| otherwise = fail "I am the pope."
translate :: PGF -> String -> Maybe Category -> Maybe Language -> Maybe Language -> Translation
translate pgf input mcat mfrom mto =
Record [(from, [Record [(to, linearize pgf to tree) | to <- toLangs] | tree <- trees])
| from <- fromLangs, let trees = parse pgf from cat input, not (null trees)]
where cat = fromMaybe (startCat pgf) mcat
fromLangs = maybe (languages pgf) (:[]) mfrom
toLangs = maybe (languages pgf) (:[]) mto
-- * General CGI Error exception mechanism
data CGIError = CGIError { cgiErrorCode :: Int, cgiErrorMessage :: String, cgiErrorText :: [String] }
deriving Typeable
throwCGIError :: Int -> String -> [String] -> CGI a
throwCGIError c m t = throwCGI $ DynException $ toDyn $ CGIError c m t
handleCGIErrors :: CGI CGIResult -> CGI CGIResult
handleCGIErrors x = x `catchCGI` \e -> case e of
DynException d -> case fromDynamic d of
Nothing -> throw e
Just (CGIError c m t) -> outputError c m t
_ -> throw e
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