    {-# LANGUAGE TypeSynonymInstances, FlexibleInstances,
        OverloadedStrings, GeneralizedNewtypeDeriving #-}
    {-
    Copyright (C) 2009-2016 John MacFarlane <jgm@berkeley.edu>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    -}

    {- |
       Module      : Text.Pandoc.Templates
       Copyright   : Copyright (C) 2009-2016 John MacFarlane
       License     : GNU GPL, version 2 or above

       Maintainer  : John MacFarlane <jgm@berkeley.edu>
       Stability   : alpha
       Portability : portable

    A simple templating system with variable substitution and conditionals.

    -}

    module Text.Pandoc.Templates ( renderTemplate
                                 , renderTemplate'
                                 , TemplateTarget
                                 , varListToJSON
                                 , compileTemplate
                                 , Template
                                 , getDefaultTemplate ) where

    import Text.DocTemplates (Template, TemplateTarget, compileTemplate,
                              renderTemplate, applyTemplate,
                              varListToJSON)
    import Data.Aeson (ToJSON(..))
    import qualified Data.Text as T
    import System.FilePath ((</>), (<.>))
    import qualified Control.Exception.Extensible as E (try, IOException)
    import Text.Pandoc.Shared (readDataFileUTF8)

    -- | Get default template for the specified writer.
    getDefaultTemplate :: (Maybe FilePath) -- ^ User data directory to search first
                       -> String           -- ^ Name of writer
                       -> IO (Either E.IOException String)
    getDefaultTemplate user writer = do
      let format = takeWhile (`notElem` ("+-" :: String)) writer  -- strip off extensions
      case format of
           "native" -> return $ Right ""
           "json"   -> return $ Right ""
           "docx"   -> return $ Right ""
           "fb2"    -> return $ Right ""
           "odt"    -> getDefaultTemplate user "opendocument"
           "markdown_strict"   -> getDefaultTemplate user "markdown"
           "multimarkdown"     -> getDefaultTemplate user "markdown"
           "markdown_github"   -> getDefaultTemplate user "markdown"
           "markdown_mmd"      -> getDefaultTemplate user "markdown"
           "markdown_phpextra" -> getDefaultTemplate user "markdown"
           _        -> let fname = "templates" </> "default" <.> format
                       in  E.try $ readDataFileUTF8 user fname

    -- | Like 'applyTemplate', but raising an error if compilation fails.
    renderTemplate' :: (ToJSON a, TemplateTarget b) => String -> a -> b
    renderTemplate' template = either error id . applyTemplate (T.pack template)