become a proper stack project

1 files changed, 65 insertions, 0 deletions

diff --git a/apps/UnsetEnv.hs b/apps/UnsetEnv.hs
new file mode 100644
index 0000000..cd43696
--- /dev/null
+++ b/apps/UnsetEnv.hs
@@ -0,0 +1,65 @@
+{-
+ - Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
+ - This file is licensed under the terms of the MIT License.
+ - See LICENSE.txt for details.
+-}
+
+module Main ( main ) where
+
+import System.Console.GetOpt
+import System.Environment ( getArgs, getProgName )
+import System.Exit ( exitFailure, exitSuccess )
+import System.IO ( hPutStr, stderr )
+
+import qualified EnvUtils
+
+main :: IO ()
+main = do
+  rawArgs <- getArgs
+  case getOpt Permute optionDescription rawArgs of
+    (actions, args, []) -> do
+      options <- foldl (>>=) (return defaultOptions) actions
+      case args of
+        [name] -> unsetEnv name options
+        _ -> invalidNumberOfArguments
+    (_, _, errorMessages) -> exitWithUsageErrors errorMessages
+
+unsetEnv :: String -> Options -> IO ()
+unsetEnv name options = EnvUtils.wipeFromRegistryWithPrompt (env options) name
+
+data Options = Options { env :: EnvUtils.RegistryBasedEnvironment } deriving (Eq, Show)
+
+defaultOptions :: Options
+defaultOptions = Options { env = EnvUtils.CurrentUserEnvironment }
+
+buildHelpMessage :: IO String
+buildHelpMessage = do
+  header <- buildHeader
+  return $ usageInfo header optionDescription
+    where
+      buildHeader :: IO String
+      buildHeader = do
+        progName <- getProgName
+        return $ "Usage: " ++ progName ++ " [OPTIONS...] NAME\nOptions:"
+
+exitWithHelpMessage :: a -> IO b
+exitWithHelpMessage _ = do
+  helpMessage <- buildHelpMessage
+  putStr helpMessage
+  exitSuccess
+
+exitWithUsageErrors :: [String] -> IO a
+exitWithUsageErrors errorMessages = do
+  hPutStr stderr $ concatMap ("Usage error: " ++) errorMessages
+  helpMessage <- buildHelpMessage
+  hPutStr stderr helpMessage
+  exitFailure
+
+invalidNumberOfArguments :: IO a
+invalidNumberOfArguments = exitWithUsageErrors ["invalid number of arguments\n"]
+
+optionDescription :: [OptDescr (Options -> IO Options)]
+optionDescription = [
+    Option "g" ["global"] (NoArg $ \opts -> return opts { env = EnvUtils.AllUsersEnvironment }) "delete from the registry key for all users",
+    Option "h" ["help"] (NoArg exitWithHelpMessage) "show this message and exit"
+  ]