-- cabal-helper: Simple interface to Cabal's configuration state
-- Copyright (C) 2018  Daniel Gröber <cabal-helper@dxld.at>
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.

{-|
Module      : CabalHelper.Compiletime.Process
Description : System process utilities
License     : GPL-3
-}

module CabalHelper.Compiletime.Process
    ( module CabalHelper.Compiletime.Process
    , module System.Process
    ) where

import Control.Arrow (second)
import Data.Char
import Data.List
import qualified Data.Map.Strict as Map
import GHC.IO.Exception (IOErrorType(OtherError))
import System.IO
import System.IO.Error
import System.Environment
import System.Exit
import System.Process

import CabalHelper.Compiletime.Types
import CabalHelper.Compiletime.Log

readProcess' :: Verbose => FilePath -> [String] -> String -> IO String
readProcess' exe args inp = do
  vLog $ intercalate " " $ map formatProcessArg (exe:args)
  outp <- readProcess exe args inp
  vLog $ unlines $ map ("=> "++) $ lines outp
  return outp


-- | Essentially 'System.Process.callProcess' but returns exit code, has
-- additional options and logging to stderr when verbosity is enabled.
callProcessStderr'
    :: Verbose => Maybe FilePath -> [(String, EnvOverride)]
    -> FilePath -> [String] -> IO ExitCode
callProcessStderr' mwd env exe args = do
  let cd = case mwd of
             Nothing -> []; Just wd -> [ "cd", formatProcessArg wd++";" ]
  vLog $ intercalate " " $
    cd ++ map formatProcessArg (map (\(k,v) -> k ++ "=" ++ show v) env ++ exe:args)

  env' <- execEnvOverrides env
  (_, _, _, h) <- createProcess (proc exe args)
    { std_out = UseHandle stderr
    , env = if env == [] then Nothing else Just env'
    , cwd = mwd
    }
  waitForProcess h

execEnvOverride :: EnvOverride -> String -> String
execEnvOverride (EnvPrepend x) y = x ++ y
execEnvOverride (EnvAppend  y) x = x ++ y
execEnvOverride (EnvReplace x) _ = x

execEnvOverrides :: [(String, EnvOverride)] -> IO [(String, String)]
execEnvOverrides overrides = do
  envs <- getEnvironment
  return $ do
    (k,v) <- envs
    case Map.lookup k overrides_map of
      Just os -> return (k, foldr execEnvOverride v os)
      Nothing -> return (k, v)
  where
    overrides_map = Map.fromListWith (++) $ map (second (:[])) overrides

-- | Essentially 'System.Process.callProcess' but with additional options
-- and logging to stderr when verbosity is enabled.
callProcessStderr :: Verbose => Maybe FilePath -> [(String, EnvOverride)]
                  -> FilePath -> [String] -> IO ()
callProcessStderr mwd env exe args = do
  rv <- callProcessStderr' mwd env exe args
  case rv of
    ExitSuccess -> return ()
    ExitFailure v -> processFailedException "callProcessStderr" exe args v

processFailedException :: String -> String -> [String] -> Int -> IO a
processFailedException fn exe args rv =
    ioError $ mkIOError OtherError msg Nothing Nothing
  where
    msg = concat [ fn, ": ", exe, " "
                 , intercalate " " (map formatProcessArg args)
                 , " (exit " ++ show rv ++ ")"
                 ]

formatProcessArg :: String -> String
formatProcessArg xs
    | any isSpace xs = "'"++ xs ++"'"
    | otherwise      = xs