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|
{-# LANGUAGE DeriveDataTypeable #-}
import PGF (PGF)
import qualified PGF
import FastCGIUtils
import Network.CGI
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"
main :: IO ()
main = do initFastCGI
r <- newDataRef
loopFastCGI (handleErrors (handleCGIErrors (fcgiMain r)))
fcgiMain :: DataRef PGF -> CGI CGIResult
fcgiMain ref = getData PGF.readPGF ref grammarFile >>= cgiMain
cgiMain :: PGF -> CGI CGIResult
cgiMain pgf =
do path <- pathInfo
json <- case path of
"/parse" -> return (doParse pgf) `ap` getText `ap` getCat `ap` getFrom
"/linearize" -> return (doLinearize pgf) `ap` getTree `ap` getTo
"/translate" -> return (doTranslate pgf) `ap` getText `ap` getCat `ap` getFrom `ap` getTo
"/categories" -> return $ doCategories pgf
"/languages" -> return $ doLanguages pgf
_ -> throwCGIError 404 "Not Found" ["Resource not found: " ++ path]
outputJSON json
where
getText :: CGI String
getText = liftM (fromMaybe "") $ getInput "input"
getTree :: CGI PGF.Tree
getTree = do mt <- getInput "tree"
t <- maybe (throwCGIError 400 "No tree given" ["No tree given"]) return mt
maybe (throwCGIError 400 "Bad tree" ["Bad tree: " ++ t]) return (PGF.readTree t)
getCat :: CGI (Maybe PGF.Category)
getCat =
do mcat <- getInput "cat"
case mcat of
Just "" -> return Nothing
Just cat | cat `notElem` PGF.categories pgf ->
throwCGIError 400 "Unknown category" ["Unknown category: " ++ cat]
_ -> return mcat
getFrom :: CGI (Maybe PGF.Language)
getFrom = getLang "from"
getTo :: CGI (Maybe PGF.Language)
getTo = getLang "to"
getLang :: String -> CGI (Maybe PGF.Language)
getLang i =
do mlang <- getInput i
case mlang of
Just "" -> return Nothing
Just lang | lang `notElem` PGF.languages pgf ->
throwCGIError 400 "Unknown language" ["Unknown language: " ++ lang]
_ -> return mlang
doTranslate :: PGF -> String -> Maybe PGF.Category -> Maybe PGF.Language -> Maybe PGF.Language -> JSValue
doTranslate pgf input mcat mfrom mto = showJSON $ toJSObject $
[(from, [toJSObject (linearize' pgf mto tree) | tree <- trees])
| (from,trees) <- parse' pgf input mcat mfrom]
doParse :: PGF -> String -> Maybe PGF.Category -> Maybe PGF.Language -> JSValue
doParse pgf input mcat mfrom = showJSON $ toJSObject $
[(from, map PGF.showTree trees) | (from,trees) <- parse' pgf input mcat mfrom]
doLinearize :: PGF -> PGF.Tree -> Maybe PGF.Language -> JSValue
doLinearize pgf tree mto = showJSON $ toJSObject $ linearize' pgf mto tree
doLanguages :: PGF -> JSValue
doLanguages pgf = showJSON $ toJSObject [(l,toJSObject (info l)) | l <- PGF.languages pgf]
where info l = [("languageCode", showJSON (fromMaybe "" (PGF.languageCode pgf l))),
("canParse", showJSON (PGF.canParse pgf l))]
doCategories :: PGF -> JSValue
doCategories pgf = showJSON (PGF.categories pgf)
-- * PGF utilities
parse' :: PGF -> String -> Maybe PGF.Category -> Maybe PGF.Language -> [(PGF.Language,[PGF.Tree])]
parse' pgf input mcat mfrom =
case mfrom of
Nothing -> PGF.parseAllLang pgf cat input
Just from -> [(from, PGF.parse pgf from cat input)]
where cat = fromMaybe (PGF.startCat pgf) mcat
linearize' :: PGF -> Maybe PGF.Language -> PGF.Tree -> [(PGF.Language,String)]
linearize' pgf mto tree =
case mto of
Nothing -> PGF.linearizeAllLang pgf tree
Just to -> [(to,PGF.linearize pgf to tree)]
-- * 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
-- * General CGI and JSON stuff
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."
|
