{-# LANGUAGE OverloadedStrings #-}

module Samples where

import           Test.Tasty (TestTree, testGroup)
import           Test.Tasty.Golden (goldenVsFile)
import           System.FilePath ((</>))
import           Data.Maybe (mapMaybe)

import qualified Data.List
import qualified Data.Text
import qualified Data.Text.IO
import qualified System.Environment
import qualified System.FilePath
import qualified System.Directory
import qualified System.IO
import qualified System.IO.Temp
import qualified System.Process

import           Data.Text.IO                   ( hPutStrLn )
import qualified Update.Nix.FetchGit
import           Update.Nix.FetchGit.Types      ( Dryness(..)
                                                , Env(Env)
                                                )

-- | Provided output file @f@ pointing to e.g. @tests/test_rec_sets.out.nix@
-- * turn this into @tests/test_rec_sets.in.nix@
-- * copy to temporary directory
-- * create fake git repositories using @tests/fakeRepo.sh@
-- * adjust @url@ to point to the faked git repositories in the temporary directory
-- * perform update
-- * adjust @url@ to point to the expected one
-- * copy file back to @tests/test_rec_sets.out.nix@ so it be compared to @expected.nix@
runTest :: String -> IO ()
runTest f =
  System.IO.Temp.withSystemTempDirectory "test-update-nix-fetchgit" $ \dir ->
    System.IO.Temp.withSystemTempDirectory "test-update-nix-fetchgit-store" $ \storeDir -> do
  let
      inFile = Data.Text.unpack
        $ Data.Text.replace ".out.nix" ".in.nix"
        $ Data.Text.pack f
      inBase = System.FilePath.takeBaseName inFile

  System.Directory.copyFile inFile (dir </> inBase)

  System.Directory.copyFile "tests/fakeRepo.sh" (dir </> "fakeRepo.sh")

  _ <- System.Process.readCreateProcess
        ((System.Process.shell (dir </> "fakeRepo.sh")) { System.Process.cwd = Just dir })
        mempty

  replaceFile (dir </> inBase) "/tmp/nix-update-fetchgit-test" (Data.Text.pack dir)

  System.Environment.setEnv "NIX_STATE_DIR" $ storeDir </> "state"
  System.Environment.setEnv "NIX_STORE_DIR" $ storeDir

  -- work around race condition https://github.com/NixOS/nix/issues/2706
  System.Directory.createDirectoryIfMissing True $ storeDir </> "state/gcroots"

  -- and another - error: SQLite database storeDir </> 'state/db/db.sqlite' is busy
  _ <- System.Process.readCreateProcess
        (System.Process.shell ("nix-store --init"))
        mempty

  let env = Env (const (Data.Text.IO.hPutStrLn System.IO.stderr)) [] [] Wet False
  Update.Nix.FetchGit.processFile env (dir </> inBase)

  replaceFile (dir </> inBase) (Data.Text.pack dir) "/tmp/nix-update-fetchgit-test"

  System.Directory.copyFile (dir </> inBase) f
  where
    replaceFile f' what with =
      Data.Text.IO.readFile f' >>= Data.Text.IO.writeFile f' . Data.Text.replace what with

test_derivation :: IO TestTree
test_derivation = do
  localSamples     <- findSamples "tests"
  networkedSamples <- findSamples "tests/networked"
  samples          <- inNixBuild >>= \case
    False -> pure $ localSamples <> networkedSamples
    True  -> do
      hPutStrLn System.IO.stderr "Skipping networked tests inside Nix build"
      pure localSamples
  pure $ testGroup "golden" $ map mk samples
 where
  mk n =
    let tEx  = (n ++ ".expected.nix")
        tOut = (n ++ ".out.nix")
    in  goldenVsFile ("update of " ++ tOut) tEx tOut (runTest tOut)

findSamples :: FilePath -> IO [String]
findSamples dir =
  fmap (dir </>)
    .   mapMaybe (dropSuffix ".in.nix")
    <$> System.Directory.listDirectory dir

dropSuffix :: String -> String -> Maybe String
dropSuffix s t = if s `Data.List.isSuffixOf` t
  then Just $ take (length t - length s) t
  else Nothing

-- From https://github.com/input-output-hk/ouroboros-network
-- | Infer from environment variables whether we are running within a Nix build
-- (and not just a nix-shell).
inNixBuild :: IO Bool
inNixBuild = do
  let testEnv = fmap (maybe False (not . null)) . System.Environment.lookupEnv
  haveNixBuildDir <- testEnv "NIX_BUILD_TOP"
  inNixShell      <- testEnv "IN_NIX_SHELL"
  pure (haveNixBuildDir && not inNixShell)