{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NoImplicitPrelude #-}

-- | A general purpose build tool.
--
-- - with a nix build, results are linked in _bild/nix/<target>
-- - for a dev build, results are stored in _bild/dev/<target>
module Biz.Bild where

import Alpha
import qualified System.Directory as Dir
import qualified System.Environment as Env
import qualified System.Exit as Exit
import System.FilePath ((</>))
import qualified System.Process as Process

main :: IO ()
main = Env.getArgs /> head >>= \case
  Nothing -> do
    basename <- Env.getProgName
    Exit.die <| "usage: " <> basename <> " <target>"
  Just target -> nixBuild target

{-
TODO:
- parse target syntax
- write dev builder for ghc/ghcjs
-}

type Target = String

nixBuild :: Target -> IO ()
nixBuild target = do
  root <- Env.getEnv "BIZ_ROOT"
  cwd <- Dir.getCurrentDirectory
  let qualifiedTarget = reps root "" cwd <> target
  Process.callProcess
    "nix-build"
    [ "-o",
      root </> "_bild/nix" </> qualifiedTarget,
      root </> "default.nix",
      "--attr",
      qualifiedTarget
    ]

-- | Replace 'a' in 's' with 'b'.
reps :: String -> String -> String -> String
reps a b s@(x : xs) =
  if isPrefixOf a s
    then-- then, write 'b' and replace jumping 'a' substring
      b ++ reps a b (drop (length a) s)
    else-- then, write 'x' char and try to replace tail string
      x : reps a b xs
reps _ _ [] = []