-- The code is mostly ripped from
-- https://github.com/ekmett/lens/blob/697582fb9a980f273dbf8496253c5bbefedd0a8b/Setup.lhs
import Data.List (nub)
import Data.Version (showVersion)
import Distribution.Package (PackageName(PackageName), Package, PackageId, InstalledPackageId, packageVersion, packageName)
import Distribution.PackageDescription (PackageDescription(), TestSuite(..))
import Distribution.Simple (defaultMainWithHooks, UserHooks(..), simpleUserHooks)
import Distribution.Simple.Utils (rewriteFile, createDirectoryIfMissingVerbose, copyFiles)
import Distribution.Simple.BuildPaths (autogenModulesDir)
import Distribution.Simple.Setup (BuildFlags(buildVerbosity), Flag(..), fromFlag, HaddockFlags(haddockDistPref))
import Distribution.Simple.LocalBuildInfo (withLibLBI, withTestLBI, LocalBuildInfo(), ComponentLocalBuildInfo(componentPackageDeps))
import Distribution.Text (display)
import Distribution.Verbosity (Verbosity, normal)
import System.FilePath ((</>))

main :: IO ()
main = defaultMainWithHooks simpleUserHooks
  { buildHook = \pkg lbi hooks flags -> do
     generateBuildModule (fromFlag (buildVerbosity flags)) pkg lbi
     buildHook simpleUserHooks pkg lbi hooks flags
  }

generateBuildModule :: Verbosity -> PackageDescription -> LocalBuildInfo -> IO ()
generateBuildModule verbosity pkg lbi = do
  let dir = autogenModulesDir lbi
  createDirectoryIfMissingVerbose verbosity True dir
  withLibLBI pkg lbi $ \_ libcfg -> do
    withTestLBI pkg lbi $ \suite suitecfg -> do
      rewriteFile (dir </> "Build_" ++ testName suite ++ ".hs") $ unlines
        [ "module Build_" ++ testName suite ++ " where"
        , "import Prelude"
        , "deps :: [String]"
        , "deps = " ++ (show $ formatdeps (testDeps libcfg suitecfg))
        ]
  where
    formatdeps = map (formatone . snd)
    formatone p = case packageName p of
      PackageName n -> n ++ "-" ++ showVersion (packageVersion p)

testDeps :: ComponentLocalBuildInfo -> ComponentLocalBuildInfo -> [(InstalledPackageId, PackageId)]
testDeps xs ys = nub $ componentPackageDeps xs ++ componentPackageDeps ys