{-# LANGUAGE TypeApplications #-}

{-# OPTIONS_HADDOCK hide #-}

-- |
-- Copyright: 2020 Input Output (Hong Kong) Ltd., 2021-2022 Input Output Global Inc. (IOG), 2023-2025 Intersect
-- License: Apache-2.0

module System.Git.TH
    ( gitRevParseHEAD
    ) where

import Prelude

import Control.Exception
    ( SomeException, try )
import Language.Haskell.TH
    ( Exp (..), Lit (..), Q, runIO )
import System.Environment
    ( lookupEnv )
import System.Exit
    ( ExitCode (..) )
import System.Process
    ( readProcessWithExitCode )

gitRevParseHEAD :: Q Exp
gitRevParseHEAD =
    LitE . StringL <$> runIO findGitRev
  where
    findGitRev :: IO String
    findGitRev = do
        envRev <- lookupEnv "GITREV"
        maybe runGitRevParse pure envRev

    runGitRevParse :: IO String
    runGitRevParse = do
        result <- try @SomeException $
            readProcessWithExitCode "git" ["rev-parse", "--verify", "HEAD"] ""
        case result of
            Right (ExitSuccess, revision, _) -> pure revision
            _ -> pure "unknown revision"