{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE TypeFamilies   #-}
module Language.Haskell.Stylish.Tests.Util
    ( dumpAst
    , dumpModule
    , testStep
    , testStep'
    , Snippet (..)
    , testSnippet
    , assertSnippet
    , withTestDirTree
    , (@=??)
    ) where


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import           Control.Exception              (bracket, try)
import           Control.Monad.Writer           (execWriter, tell)
import           Data.List                      (intercalate)
import           GHC.Exts                       (IsList (..))
import           GHC.Hs.Dump                    (showAstData, BlankSrcSpan(..))
import           Language.Haskell.Stylish.GHC   (baseDynFlags)
import           System.Directory               (createDirectory,
                                                 getCurrentDirectory,
                                                 getTemporaryDirectory,
                                                 removeDirectoryRecursive,
                                                 setCurrentDirectory)
import           System.FilePath                ((</>))
import           System.IO.Error                (isAlreadyExistsError)
import           System.Random                  (randomIO)
import           Test.HUnit                     (Assertion, assertFailure,
                                                 (@=?))
import           Outputable                     (showSDoc)
import           Data.Data                      (Data(..))

--------------------------------------------------------------------------------
import           Language.Haskell.Stylish.Parse
import           Language.Haskell.Stylish.Step
import           Language.Haskell.Stylish.Module (Module)

--------------------------------------------------------------------------------
-- | Takes a Haskell source as an argument and parse it into a Module.
-- Extract function selects element from that Module record and returns
-- its String representation.
--
-- This function should be used when trying to understand how particular
-- Haskell code will be represented by ghc-parser's AST
dumpAst :: Data a => (Module -> a) -> String -> String
dumpAst extract str =
  let Right(theModule) = parseModule [] Nothing str
      ast              = extract theModule
      sdoc             = showAstData BlankSrcSpan ast
  in  showSDoc baseDynFlags sdoc

dumpModule :: String -> String
dumpModule = dumpAst id

--------------------------------------------------------------------------------
testStep :: Step -> String -> String
testStep s str = case s of
  Step _ step ->
    case parseModule [] Nothing str of
      Left err      -> error err
      Right module' -> unlines $ step ls module'
  where
    ls = lines str


--------------------------------------------------------------------------------
testStep' :: Step -> Lines -> Lines
testStep' s ls = lines $ testStep s (unlines ls)


--------------------------------------------------------------------------------
-- | 'Lines' that show as a normal string.
newtype Snippet = Snippet {unSnippet :: Lines} deriving (Eq)

-- Prefix with one newline since so HUnit will use a newline after `got: ` or
-- `expected: `.
instance Show Snippet where show = unlines . ("" :) . unSnippet

instance IsList Snippet where
    type Item Snippet = String
    fromList = Snippet
    toList   = unSnippet


--------------------------------------------------------------------------------
testSnippet :: Step -> Snippet -> Snippet
testSnippet s = Snippet . lines . testStep s . unlines . unSnippet


--------------------------------------------------------------------------------
assertSnippet :: Step -> Snippet -> Snippet -> Assertion
assertSnippet step input expected = expected @=? testSnippet step input


--------------------------------------------------------------------------------
-- | Create a temporary directory with a randomised name built from the template
-- provided
createTempDirectory :: String -> IO FilePath
createTempDirectory template  = do
  tmpRootDir <- getTemporaryDirectory
  dirId <- randomIO :: IO Word
  findTempName tmpRootDir dirId
  where
    findTempName :: FilePath -> Word -> IO FilePath
    findTempName tmpRootDir x = do
      let dirpath = tmpRootDir </> template ++ show x
      r <- try $ createDirectory dirpath
      case r of
        Right _ -> return dirpath
        Left  e | isAlreadyExistsError e -> findTempName tmpRootDir (x+1)
                | otherwise              -> ioError e


--------------------------------------------------------------------------------
-- | Perform an action inside a temporary directory tree and purge the tree
-- afterwards
withTestDirTree :: IO a -> IO a
withTestDirTree action = bracket
    ((,) <$> getCurrentDirectory <*> createTempDirectory "stylish_haskell")
    (\(current, temp) ->
        setCurrentDirectory current *>
        removeDirectoryRecursive temp)
    (\(_, temp) -> setCurrentDirectory temp *> action)

(@=??) :: Lines -> Lines -> Assertion
expected @=?? actual =
  if expected == actual then pure ()
  else assertFailure $ intercalate "\n" $ execWriter do
    tell ["Expected:"]
    printLines expected
    tell ["Got:"]
    printLines actual
  where
    printLines =
      mapM_ \line -> tell ["  " <> line]