-- cabal-helper: Simple interface to Cabal's configuration state
-- Copyright (C) 2018  Daniel Gröber <cabal-helper@dxld.at>
--
-- SPDX-License-Identifier: Apache-2.0
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0

{-|
Module      : CabalHelper.Compiletime.Process
Description : System process utilities
License     : Apache-2.0
-}

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

import Data.Char
import Data.List
import Data.Maybe
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 =
  readProcessStderr Nothing [] exe args inp

readProcessStderr :: Verbose => Maybe FilePath -> [(String, EnvOverride)]
                  -> FilePath -> [String] -> String -> IO String
readProcessStderr mcwd env exe args inp = do
  logProcessCall mcwd env exe args
  env' <- execEnvOverrides env <$> getEnvironment
  outp <- readCreateProcess (proc exe args)
    { cwd = mcwd
    , env = if env == [] then Nothing else Just env'
    } 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' mcwd env exe args = do
  logProcessCall mcwd env exe args
  env' <- execEnvOverrides env <$> getEnvironment
  (_, _, _, h) <- createProcess (proc exe args)
    { std_out = UseHandle stderr
    , env = if env == [] then Nothing else Just env'
    , cwd = mcwd
    }
  waitForProcess h

logProcessCall :: Verbose => Maybe FilePath -> [(String, EnvOverride)]
               -> FilePath -> [String] -> IO ()
logProcessCall mcwd env exe args = do
  vLog $ intercalate " " $ cd ++ env_args ++ map formatProcessArg (exe:args)
  where
    env_args = map (\(k,v) -> k ++ "=" ++ show v) env
    cd = case mcwd of
      Nothing -> []; Just cwd -> [ "cd", formatProcessArg cwd++";" ]

execEnvOverride :: EnvOverride -> String -> Maybe String
execEnvOverride (EnvPrepend x) y = Just (x ++ y)
execEnvOverride (EnvAppend  y) x = Just (x ++ y)
execEnvOverride (EnvSet x)     _ = Just x
execEnvOverride  EnvUnset      _ = Nothing

execEnvOverrides
    :: [(String, EnvOverride)] -> [(String, String)] -> [(String, String)]
execEnvOverrides overrides env =
    Map.toList $ foldl f (Map.fromList env) overrides
  where
    f em (k, o) = Map.alter (execEnvOverride o . fromMaybe "") k em

-- | 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