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+-- |
+-- Copyright : (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
+-- License : MIT
+-- Maintainer : Egor.Tensin@gmail.com
+-- Stability : experimental
+-- Portability : portable
+
+module Prompt
+ ( withPrompt
+ , withoutPrompt
+ ) where
+
+import Control.Monad (void, when)
+import Control.Monad.Trans.Class (lift)
+import Control.Monad.Trans.Except (ExceptT)
+import Data.Char (toLower)
+import System.IO (hFlush, stdout)
+
+prompt :: String -> IO String
+prompt msg = do
+ putStr msg
+ hFlush stdout
+ getLine
+
+promptYesNo :: String -> IO Bool
+promptYesNo msg = do
+ response <- map toLower <$> prompt msg
+ if response `elem` yeses
+ then return True
+ else if response `elem` noes
+ then return False
+ else promptToContinue
+ where
+ yeses = ["y", "yes"]
+ noes = ["n", "no"]
+
+promptToContinue :: IO Bool
+promptToContinue = promptYesNo "Continue? (y/n) "
+
+withPrompt :: String -> ExceptT IOError IO a -> ExceptT IOError IO Bool
+withPrompt msg m = do
+ lift $ do
+ putStr msg
+ hFlush stdout
+ agreed <- lift promptToContinue
+ when agreed $ void m
+ return agreed
+
+withoutPrompt :: ExceptT IOError IO a -> ExceptT IOError IO Bool
+withoutPrompt m = m >> return True