{-# LANGUAGE NamedFieldPuns #-}
module Main (main) where

import Data.Char qualified as Char
import Data.List qualified as List
import Distribution.Package (PackageIdentifier(..), unPackageName)
import Distribution.PackageDescription (PackageDescription(package))
import Distribution.Pretty (prettyShow)
import Distribution.Simple (defaultMainWithHooks, simpleUserHooks, buildHook)
import Distribution.Simple.BuildPaths (autogenPackageModulesDir)
import Distribution.Simple.LocalBuildInfo (LocalBuildInfo, localPkgDescr)
import Distribution.Simple.Setup (BuildFlags(buildVerbosity), fromFlag)
import Distribution.Simple.Utils (notice, rewriteFileEx)
import System.Directory (createDirectoryIfMissing)
import System.FilePath ((</>), (<.>))
import System.IO.Error (catchIOError)
import System.Process (readProcess)


main :: IO ()
main = defaultMainWithHooks simpleUserHooks
  { buildHook = \pd lbi uh bf -> do generateMeta lbi bf; buildHook simpleUserHooks pd lbi uh bf
  }

generateMeta :: LocalBuildInfo -> BuildFlags -> IO ()
generateMeta lbi bf = let
    verbosity = fromFlag (buildVerbosity bf)
    PackageIdentifier {pkgName, pkgVersion} = package (localPkgDescr lbi)
    metaName = "Meta_" ++ replace '-' '_' (unPackageName pkgName)
    metaPath = autogen </> metaName <.> "hs"
  in do
    hash <- gitHash
    createDirectoryIfMissing True autogen
    notice verbosity ("Generating " ++ metaPath ++ " ...")
    rewriteFileEx verbosity metaPath (unlines
      [ "module " ++ metaName
      , "  ( name"
      , "  , version"
      , "  ) where"
      , ""
      , "import Data.String (IsString(fromString))"
      , ""
      , "name :: IsString str => str"
      , "name = fromString " ++ show (unPackageName pkgName)
      , ""
      , "version :: IsString str => str"
      , "version = fromString " ++ show (prettyShow pkgVersion ++ "-" ++ hash)
      ])
 where
  autogen = autogenPackageModulesDir lbi
  replace x y =
    map (\c -> if c == x then y else c)

gitHash :: IO String
gitHash =
  catchIOError (fmap sanitize (readProcess "git" ["describe", "--always", "--dirty=-dirty"] ""))
               (\_ -> return "unknown")
 where
  sanitize = List.dropWhileEnd Char.isSpace