{-# LANGUAGE DataKinds, GeneralizedNewtypeDeriving, OverloadedStrings #-}
module IntegrationSpec where

import Data.Functor.Both
import Data.List (union, concat, transpose)
import qualified Data.Text as T
import qualified Data.ByteString as B
import Data.Text.Encoding (decodeUtf8)
import GHC.Show (Show(..))
import Prologue hiding (fst, snd, readFile)
import System.FilePath
import System.FilePath.Glob
import SpecHelpers
import Test.Hspec (Spec, describe, it, SpecWith, runIO, parallel)
import Test.Hspec.Expectations.Pretty

spec :: Spec
spec = parallel $ do
  it "lists example fixtures" $ do
    examples "test/fixtures/go/" `shouldNotReturn` []
    examples "test/fixtures/javascript/" `shouldNotReturn` []
    examples "test/fixtures/ruby/" `shouldNotReturn` []
    examples "test/fixtures/typescript/" `shouldNotReturn` []

  describe "go" $ runTestsIn "test/fixtures/go/"
  describe "javascript" $ runTestsIn "test/fixtures/javascript/"
  describe "ruby" $ runTestsIn "test/fixtures/ruby/"
  describe "typescript" $ runTestsIn "test/fixtures/typescript/"

  where
    runTestsIn :: FilePath -> SpecWith ()
    runTestsIn directory = do
      examples <- runIO $ examples directory
      traverse_ runTest examples
    runTest ParseExample{..} = it ("parses " <> file) $ testParse file parseOutput
    runTest DiffExample{..} = it ("diffs " <> diffOutput) $ testDiff (both fileA fileB) diffOutput

data Example = DiffExample { fileA :: FilePath, fileB :: FilePath, diffOutput :: FilePath }
             | ParseExample { file :: FilePath, parseOutput :: FilePath }
             deriving (Eq, Show)

-- | Return all the examples from the given directory. Examples are expected to
-- | have the form:
-- |
-- | example-name.A.rb - The left hand side of the diff.
-- | example-name.B.rb - The right hand side of the diff.
-- |
-- | example-name.diffA-B.txt - The expected sexpression diff output for A -> B.
-- | example-name.diffB-A.txt - The expected sexpression diff output for B -> A.
-- |
-- | example-name.parseA.txt - The expected sexpression parse tree for example-name.A.rb
-- | example-name.parseB.txt - The expected sexpression parse tree for example-name.B.rb
examples :: FilePath -> IO [Example]
examples directory = do
  as <- globFor "*.A.*"
  bs <- globFor "*.B.*"
  sExpAs <- globFor "*.parseA.txt"
  sExpBs <- globFor "*.parseB.txt"
  sExpDiffsAddA <- globFor "*.diff+A.txt"
  sExpDiffsRemoveA <- globFor "*.diff-A.txt"
  sExpDiffsAddB <- globFor "*.diff+B.txt"
  sExpDiffsRemoveB <- globFor "*.diff-B.txt"
  sExpDiffsAB <- globFor "*.diffA-B.txt"
  sExpDiffsBA <- globFor "*.diffB-A.txt"

  let exampleDiff lefts rights out name = DiffExample (lookupNormalized name lefts) (lookupNormalized name rights) out
  let exampleAddDiff files out name = DiffExample "" (lookupNormalized name files) out
  let exampleRemoveDiff files out name = DiffExample (lookupNormalized name files) "" out
  let exampleParse files out name = ParseExample (lookupNormalized name files) out

  let keys = (normalizeName <$> as) `union` (normalizeName <$> bs)
  pure $ merge [ getExamples (exampleParse as) sExpAs keys
               , getExamples (exampleParse bs) sExpBs keys
               , getExamples (exampleAddDiff as) sExpDiffsAddA keys
               , getExamples (exampleRemoveDiff as) sExpDiffsRemoveA keys
               , getExamples (exampleAddDiff bs) sExpDiffsAddB keys
               , getExamples (exampleRemoveDiff bs) sExpDiffsRemoveB keys
               , getExamples (exampleDiff as bs) sExpDiffsAB keys
               , getExamples (exampleDiff bs as) sExpDiffsBA keys ]
  where
    merge = concat . transpose
    -- Only returns examples if they exist
    getExamples f list = foldr (go f list) []
      where go f list name acc = case lookupNormalized' name list of
              Just out -> f out name : acc
              Nothing -> acc

    lookupNormalized :: FilePath -> [FilePath] -> FilePath
    lookupNormalized name xs = fromMaybe
      (panic ("cannot find " <> T.pack name <> " make sure .A, .B and exist." :: Text))
      (lookupNormalized' name xs)

    lookupNormalized' :: FilePath -> [FilePath] -> Maybe FilePath
    lookupNormalized' name = find ((== name) . normalizeName)

    globFor :: FilePath -> IO [FilePath]
    globFor p = globDir1 (compile p) directory

-- | Given a test name like "foo.A.js", return "foo".
normalizeName :: FilePath -> FilePath
normalizeName path = dropExtension $ dropExtension path

testParse :: FilePath -> FilePath -> Expectation
testParse path expectedOutput = do
  actual <- verbatim <$> parseFilePath path
  expected <- verbatim <$> B.readFile expectedOutput
  actual `shouldBe` expected

testDiff :: Both FilePath -> FilePath -> Expectation
testDiff paths expectedOutput = do
  actual <- verbatim <$> diffFilePaths paths
  expected <- verbatim <$> B.readFile expectedOutput
  actual `shouldBe` expected

stripWhitespace :: ByteString -> ByteString
stripWhitespace = B.foldl' go B.empty
  where go acc x | x `B.elem` " \t\n" = acc
                 | otherwise = B.snoc acc x

-- | A wrapper around `ByteString` with a more readable `Show` instance.
newtype Verbatim = Verbatim ByteString
  deriving (Eq, NFData)

instance Show Verbatim where
  showsPrec _ (Verbatim byteString) = ('\n':) . (T.unpack (decodeUtf8 byteString) ++)

verbatim :: ByteString -> Verbatim
verbatim = Verbatim . stripWhitespace