1 files changed, 46 insertions, 0 deletions
diff --git a/apps/Prompt.hs b/apps/Prompt.hs
new file mode 100644
index 0000000..97c23fa
--- /dev/null
+++ b/apps/Prompt.hs
@@ -0,0 +1,46 @@
+{-
+ - 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 Prompt
+    ( withPrompt
+    , withoutPrompt
+    ) where
+
+import Control.Monad (liftM, void, when)
+import Data.Char     (toLower)
+import System.IO     (hFlush, stdout)
+
+prompt :: String -> IO String
+prompt banner = do
+    putStr banner
+    hFlush stdout
+    getLine
+
+promptYesNo :: String -> IO Bool
+promptYesNo banner = do
+    response <- liftM (map toLower) $ prompt banner
+    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 -> IO a -> IO Bool
+withPrompt banner m = do
+    putStr banner
+    hFlush stdout
+    agreed <- promptToContinue
+    when agreed $ void m
+    return agreed
+
+withoutPrompt :: IO a -> IO Bool
+withoutPrompt m = m >> return True