import Distribution.Simple
import Distribution.Simple.PreProcess
import Distribution.PackageDescription
import Distribution.Simple.LocalBuildInfo
import Distribution.Simple.Program

-- This Setup script installs a handler for .hsx files that need to be preprocessed
-- with `trhsx'. In order to use it, specify Build-Type: Custom in the .cabal file.

newpp = hookedPreProcessors simpleUserHooks ++ [("hsx", ppTrhsx)]

-- Define the custom hook which contains the handler for the .hsx suffix.

main = defaultMainWithHooks (simpleUserHooks {hookedPreProcessors = newpp})

-- Preprocessor definition for trhsx. Based upon examples in Cabal sources.
-- Trhsx needs to be called with two parameters: input filepath and output filepath.

ppTrhsx :: BuildInfo -> LocalBuildInfo -> PreProcessor

ppTrhsx _bi lbi = 
  PreProcessor {
    platformIndependent = False,
    runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity ->
      rawSystemProgram verbosity progTrhsx [inFile, outFile] }

-- Here we assume that trhsx is on the PATH so we just specify its name.

progTrhsx = ConfiguredProgram {
  programId = "trhsx"
 ,programVersion = Nothing
 ,programArgs = []
 ,programLocation = FoundOnSystem "trhsx"
}