{-# LANGUAGE CPP #-}

module Development.Shake.Cabal ( getCabalDeps
                               , getCabalDepsV
                               ) where

import           Control.Arrow
import           Control.Monad
import           Data.Foldable                         (toList)
import           Data.Maybe                            (catMaybes)
#if __GLASGOW_HASKELL__ < 804
import           Data.Semigroup
#endif
import           Distribution.ModuleName
import           Distribution.PackageDescription
import           Distribution.PackageDescription.Parse
import           Distribution.Types.CondTree
import           Distribution.Verbosity

libraryToFiles :: Library -> [FilePath]
libraryToFiles lib = cs <> is <> ((<> ".hs") . toFilePath <$> explicitLibModules lib)
    where (cs, is) = (cSources &&& includes) $ libBuildInfo lib

extract :: CondTree a b Library -> [Library]
extract (CondNode d _ []) = [d]
extract (CondNode d _ bs) = d : (g =<< bs)
    where g (CondBranch _ tb fb) = join $ catMaybes [Just $ extract tb, extract <$> fb]

-- | Get library dependencies from a @.cabal@ file. This will only work for
-- @.hs@ files; module signatures are not supported.
getCabalDeps :: FilePath -> IO [FilePath]
getCabalDeps = getCabalDepsV normal

-- | Same as above, but we set the 'Verbosity' to be used during parsing.
getCabalDepsV :: Verbosity -> FilePath -> IO [FilePath]
getCabalDepsV v p = do
    pkg <- readGenericPackageDescription v p
    let extraSrc = extraSrcFiles $ packageDescription pkg
        libs = toList (condLibrary pkg)
        normalSrc = (libraryToFiles <=< extract) =<< libs
    pure (extraSrc <> normalSrc)