{-# LANGUAGE OverloadedStrings #-}
-- | Various utilities used in the scaffolded site.
module Yesod.Default.Util
    ( addStaticContentExternal
    ) where

import Control.Monad.IO.Class (liftIO)
import qualified Data.ByteString.Lazy as L
import Data.Text (Text, pack, unpack)
import Yesod.Core -- purposely using complete import so that Haddock will see addStaticContent
import Control.Monad (unless)
import System.Directory (doesFileExist, createDirectoryIfMissing)

-- | An implementation of 'addStaticContent' which stores the contents in an
-- external file. Files are created in the given static folder with names based
-- on a hash of their content. This allows expiration dates to be set far in
-- the future without worry of users receiving stale content.
addStaticContentExternal
    :: (L.ByteString -> Either a L.ByteString) -- ^ javascript minifier
    -> (L.ByteString -> String) -- ^ hash function to determine file name
    -> FilePath -- ^ location of static directory. files will be placed within a "tmp" subfolder
    -> ([Text] -> Route master) -- ^ route constructor, taking a list of pieces
    -> Text -- ^ filename extension
    -> Text -- ^ mime type
    -> L.ByteString -- ^ file contents
    -> GHandler sub master (Maybe (Either Text (Route master, [(Text, Text)])))
addStaticContentExternal minify hash staticDir toRoute ext' _ content = do
    liftIO $ createDirectoryIfMissing True statictmp
    exists <- liftIO $ doesFileExist fn'
    unless exists $ liftIO $ L.writeFile fn' content'
    return $ Just $ Right (toRoute ["tmp", pack fn], [])
  where
    fn, statictmp, fn' :: FilePath
    -- by basing the hash off of the un-minified content, we avoid a costly
    -- minification if the file already exists
    fn = hash content ++ '.' : unpack ext'
    statictmp = staticDir ++ "/tmp/"
    fn' = statictmp ++ fn

    content' :: L.ByteString
    content'
        | ext' == "js" = either (const content) id $ minify content
        | otherwise = content