-- | Load a Mustache template file.
--
-- If the name is an absolute or relative path, the search path is
-- /not/ used, and the name is treated as a literal path.
--
-- If the @-fembed-data-files@ @Cabal@ flag is enabled, this also checks
-- the embedded @data-files@ from @criterion.cabal@.
--
-- This function throws a 'TemplateException' if the template could
-- not be found, or an 'IOException' if no template could be loaded.
loadTemplate :: [FilePath]      -- ^ Search path.
             -> FilePath        -- ^ Name of template file.
             -> IO TL.Text
loadTemplate paths name
    | any isPathSeparator name = readFileCheckEmbedded name
    | otherwise                = go Nothing paths
  where go me (p:ps) = do
          let cur = p </> name <.> "tpl"
          x <- doesFileExist' cur
          if x
            then readFileCheckEmbedded cur `E.catch` \e -> go (me `mplus` Just e) ps
            else go me ps
        go (Just e) _ = throwIO (e::IOException)
        go _        _ = throwIO . TemplateNotFound $ name

        doesFileExist' :: FilePath -> IO Bool
        doesFileExist' fp = do
          e <- doesFileExist fp
          pure $ e
#if defined(EMBED)
                 || (fp `elem` map fst dataFiles)
#endif

-- A version of 'readFile' that falls back on the embedded 'dataFiles'
-- from @criterion.cabal@.
loadTemplate :: [FilePath]      -- ^ Search path.
             -> FilePath        -- ^ Name of template file.
             -> IO TL.Text
loadTemplate paths name
    | any isPathSeparator name = readFileCheckEmbedded name
    | otherwise                = go Nothing paths
  where go me (p:ps) = do
          let cur = p </> name <.> "tpl"
          x <- doesFileExist' cur
          if x
            then readFileCheckEmbedded cur `E.catch` \e -> go (me `mplus` Just e) ps
            else go me ps
        go (Just e) _ = throwIO (e::IOException)
        go _        _ = throwIO . TemplateNotFound $ name

        doesFileExist' :: FilePath -> IO Bool
        doesFileExist' fp = do
          e <- doesFileExist fp
          pure $ e
#if defined(EMBED)
                 || (fp `elem` map fst dataFiles)
#endif

-- A version of 'readFile' that falls back on the embedded 'dataFiles'
-- from @criterion.cabal@.
loadTemplate paths name
    | any isPathSeparator name = readFileCheckEmbedded name
    | otherwise                = go Nothing paths
  where go me (p:ps) = do
          let cur = p </> name <.> "tpl"
          x <- doesFileExist' cur
          if x
            then readFileCheckEmbedded cur `E.catch` \e -> go (me `mplus` Just e) ps
            else go me ps
        go (Just e) _ = throwIO (e::IOException)
        go _        _ = throwIO . TemplateNotFound $ name

        doesFileExist' :: FilePath -> IO Bool
        doesFileExist' fp = do
          e <- doesFileExist fp
          pure $ e
#if defined(EMBED)
                 || (fp `elem` map fst dataFiles)
#endif

-- A version of 'readFile' that falls back on the embedded 'dataFiles'
-- from @criterion.cabal@.