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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE OverloadedStrings #-}
module PandocCGI
( app
, Params(..)
) where
import Data.Aeson
import Data.Aeson.TH
import Network.Wai
import Servant
import Text.Pandoc
import Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL
import qualified Data.Text.Lazy.Encoding as TLE
import Data.Maybe (fromMaybe)
import Data.Char (isAlphaNum)
-- This is the data to be supplied by the JSON payload
-- of requests. Maybe values may be omitted and will be
-- given default values.
data Params = Params
{ text :: Text
, from :: Maybe Text
, to :: Maybe Text
, wrapText :: Maybe WrapOption
, columns :: Maybe Int
, standalone :: Maybe Bool
, template :: Maybe Text
} deriving (Show)
-- Automatically derive code to convert to/from JSON.
$(deriveJSON defaultOptions ''Params)
-- This is the API. The "/convert" endpoint takes a request body
-- consisting of a JSON-encoded Params structure and responds to
-- Get requests with either plain text or JSON, depending on the
-- Accept header.
type API =
"convert" :> ReqBody '[JSON] Params :> Post '[PlainText, JSON] Text
:<|>
"convert-batch" :> ReqBody '[JSON] [Params] :> Post '[JSON] [Text]
app :: Application
app = serve api server
api :: Proxy API
api = Proxy
server :: Server API
server = convert
:<|> mapM convert
where
-- We use runPure for the pandoc conversions, which ensures that
-- they will do no IO. This makes the server safe to use. However,
-- it will mean that features requiring IO, like RST includes, will not work.
-- Changing this to
-- handleErr =<< liftIO (runIO (convert' params))
-- will allow the IO operations.
convert params = handleErr $ runPure (convert' params)
convert' :: PandocMonad m => Params -> m Text
convert' params = do
let readerFormat = fromMaybe "markdown" $ from params
let writerFormat = fromMaybe "html" $ to params
(readerSpec, readerExts) <- getReader readerFormat
(writerSpec, writerExts) <- getWriter writerFormat
let isStandalone = fromMaybe False (standalone params)
let toformat = T.toLower $ T.takeWhile isAlphaNum $ writerFormat
mbTemplate <- if isStandalone
then case template params of
Nothing -> Just <$>
compileDefaultTemplate toformat
Just t -> Just <$>
compileCustomTemplate toformat t
else return Nothing
-- We don't yet handle binary formats:
reader <- case readerSpec of
TextReader r -> return r
_ -> throwError $ PandocAppError $
readerFormat <> " is not a text reader"
writer <- case writerSpec of
TextWriter w -> return w
_ -> throwError $ PandocAppError $
readerFormat <> " is not a text reader"
reader def{ readerExtensions = readerExts
, readerStandalone = isStandalone }
(text params) >>=
writer def{ writerExtensions = writerExts
, writerWrapText = fromMaybe WrapAuto (wrapText params)
, writerColumns = fromMaybe 72 (columns params)
, writerTemplate = mbTemplate }
handleErr (Right t) = return t
handleErr (Left err) = throwError $
err500 { errBody = TLE.encodeUtf8 $ TL.fromStrict $ renderError err }
compileCustomTemplate toformat t = do
res <- runWithPartials $ compileTemplate ("custom." <> T.unpack toformat) t
case res of
Left e -> throwError $ PandocTemplateError (T.pack e)
Right tpl -> return tpl
|
