{-# OPTIONS_GHC -fno-warn-orphans #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveFunctor #-}

module Parse
  ( parsePackageDescription
  , readPackageDescription
  , displayError
  , printWarnings
  , Result(..)
  , result
  ) where

import Control.DeepSeq
import Control.Monad.Compat
import Data.Data
import Data.Maybe
import Distribution.PackageDescription
import Distribution.PackageDescription.Parsec
  ( parseGenericPackageDescription
  , runParseResult
  )
import Distribution.Parsec.Common
import Distribution.Simple.Utils
import Distribution.Verbosity
import Distribution.Version
import GHC.Generics
import Prelude.Compat
import System.Exit
#if MIN_VERSION_base(4,9,0)
import Data.Functor.Classes
#endif
-- | Like Cabal's @ParseResult@, but treats warnings as a separate failure
-- case.
data Result a
  = Error [PError] -- ^ Parse errors.
  | Warn [PWarning] -- ^ Warnings emitted during parse.
  | Success a -- ^ The input is a compliant package description.
  deriving (Show, Eq, Functor, Generic, Typeable, Data)
#if MIN_VERSION_base(4,6,0)
deriving instance Generic1 Result
#endif

#if !MIN_VERSION_base(4,8,0)
deriving instance Typeable PError

deriving instance Typeable Position

deriving instance Typeable PWarnType
#endif

#if MIN_VERSION_base(4,9,0)
instance Show1 Result where
  liftShowsPrec sp _ p (Success n) = showsUnaryWith sp "Success" p n
  liftShowsPrec _ _ p (Warn pws) = showsUnaryWith showsPrec "Warn" p pws
  liftShowsPrec _ _ p (Error s) = showsUnaryWith showsPrec "Error" p s

instance Eq1 Result where
  liftEq eq (Success a) (Success b) = eq a b
  liftEq _ (Error s) (Error s2) = s == s2
  liftEq _ (Warn pws) (Warn pws2) = pws == pws2
  liftEq _ _ _ = False
#endif
-- | Case analysis for 'Result'.
result :: ([PError] -> b) -> ([PWarning] -> b) -> (a -> b) -> Result a -> b
result e w s p =
  case p of
    Error l -> e l
    Warn ws -> w ws
    Success r -> s r

deriving instance Data PError

deriving instance Eq PError

deriving instance Eq PWarning

instance NFData a => NFData (Result a)

deriving instance Data PWarning

deriving instance Data Position

deriving instance Data PWarnType

deriving instance Typeable PWarning

-- | This function is similar to Cabal's own file parser, except that it
-- treats warnings as a separate failure case. There are a wide range of
-- different behaviors accepted by different Cabal parser versions. Parse
-- warnings generally indicate a version-related inconsistency, so we play
-- it safe here.
parsePackageDescription input =
  let (warnings, r) = runParseResult $ parseGenericPackageDescription input
   in case r of
        Left (_, errors) -> Error errors
        Right x
          | null warnings -> parseResult x
          | otherwise -> Warn warnings
  where
    parseResult gpd =
      if specVersionRaw (packageDescription gpd) == Right anyVersion
        then Warn [PWarning PWTOther zeroPos versWarning]
        else Success gpd
    versWarning =
      "File does not specify a cabal-version. stylish-cabal requires at least 1.2"

-- | Shorthand to combine 'parsePackageDescription' and one of 'printWarnings' or
-- 'displayError'. The given 'FilePath' is used only for error messages and
-- is not read from.
readPackageDescription fpath =
  result (displayError fpath) (printWarnings fpath) return . parsePackageDescription

-- | Print some warnings to 'stderr' and exit.
printWarnings :: Maybe FilePath -> [PWarning] -> IO a
printWarnings fpath ps =
  mapM_ (warn normal . showPWarning (fromMaybe "<input>" fpath)) ps >> exitFailure

-- | Print a parse error to 'stderr', annotated with filepath if available,
-- then exit.
displayError :: Maybe FilePath -> [PError] -> IO a
displayError fpath warns =
  mapM_ (warn normal . showPError (fromMaybe "<input>" fpath)) warns >> exitFailure