-- cabal-helper: Simple interface to Cabal's configuration state
-- Copyright (C) 2015-2017  Daniel Gröber <cabal-helper@dxld.at>
--
-- 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 3 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, see <http://www.gnu.org/licenses/>.

{-# LANGUAGE TemplateHaskell, ScopedTypeVariables #-}
{-# OPTIONS_GHC -fforce-recomp #-}

{-|
Module      : CabalHelper.Compiletime.Data
Description : Embeds source code for runtime component using TH
License     : GPL-3
-}

module CabalHelper.Compiletime.Data where

import Control.Monad
import Control.Monad.IO.Class
import Data.Digest.Pure.SHA
import Data.Functor
import Data.List
import qualified Data.ByteString as BS
import qualified Data.ByteString.UTF8 as UTF8
import qualified Data.ByteString.Lazy as LBS
import qualified Data.ByteString.Lazy.UTF8 as LUTF8
import Language.Haskell.TH
import System.Directory
import System.FilePath
import System.IO.Temp
import System.PosixCompat.Files
import System.PosixCompat.Time
import System.PosixCompat.Types
import Prelude

import CabalHelper.Compiletime.Compat.Environment

withSystemTempDirectoryEnv :: String -> (FilePath -> IO b) -> IO b
withSystemTempDirectoryEnv tpl f = do
  m <- liftIO $ lookupEnv "CABAL_HELPER_KEEP_SOURCEDIR"
  case m of
    Nothing -> withSystemTempDirectory tpl f
    Just _  -> do
           tmpdir <- getCanonicalTemporaryDirectory
           f =<< createTempDirectory tmpdir tpl

createHelperSources :: FilePath -> IO ()
createHelperSources dir = do
    let chdir = dir </> "CabalHelper"
    liftIO $ do
      createDirectoryIfMissing True $ chdir </> "Runtime"
      createDirectoryIfMissing True $ chdir </> "Shared"

    let modtime :: EpochTime
        modtime = fromIntegral $ (read :: String -> Integer)
          -- See https://reproducible-builds.org/specs/source-date-epoch/
          $(runIO $ do
             msde :: Maybe Integer
                  <- fmap read <$> lookupEnv "SOURCE_DATE_EPOCH"
             (current_time :: Integer) <- round . toRational <$> epochTime
             return $ LitE . StringL $ show $ maybe current_time id msde)

    liftIO $ forM_ sourceFiles $ \(fn, src) -> do
        let path = chdir </> fn
        BS.writeFile path $ UTF8.fromString src
        setFileTimes path modtime modtime

sourceHash :: String
sourceHash  = fst runtimeSources

sourceFiles :: [(FilePath, String)]
sourceFiles = snd runtimeSources

runtimeSources :: (String, [(FilePath, FilePath)])
runtimeSources = $(
  let files = map (\f -> (f, ("src/CabalHelper" </> f))) $ sort $
        [ ("Runtime/Main.hs")
        , ("Runtime/HelperMain.hs")
        , ("Runtime/Compat.hs")
        , ("Shared/Common.hs")
        , ("Shared/InterfaceTypes.hs")
        ]
  in do
    contents <- mapM (\lf -> runIO (LBS.readFile lf)) $ map snd files
    let hashes = map (bytestringDigest . sha256) contents
    let top_hash = showDigest $ sha256 $ LBS.concat hashes

    thfiles <- forM (map fst files `zip` contents) $ \(f, xs) -> do
      return $ TupE [LitE (StringL f), LitE (StringL (LUTF8.toString xs))]


    return $ TupE [LitE (StringL top_hash), ListE thfiles]

  )

-- - $(LitE . StringL <$> runIO (UTF8.toString <$> BS.readFile