basic prompting framework

src/Mtlstats/Prompt.hs

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+{- |
+
+mtlstats
+Copyright (C) 2019 Rhéal Lamothe
+<rheal.lamothe@gmail.com>
+
+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 <https://www.gnu.org/licenses/>.
+
+-}
+
+module Mtlstats.Prompt (
+  -- * Prompt Functions
+  drawPrompt,
+  promptHandler,
+) where
+
+import Control.Monad (when)
+import Control.Monad.Trans.State (gets, modify)
+import Data.Char (isDigit, toUpper)
+import Data.Foldable (forM_)
+import Lens.Micro ((^.), (.~), (?~))
+import Lens.Micro.Extras (view)
+import Text.Read (readMaybe)
+import qualified UI.NCurses as C
+
+import Mtlstats.Actions
+import Mtlstats.Types
+
+-- | Draws the prompt to the screen
+drawPrompt :: Prompt -> ProgState -> C.Update C.CursorMode
+drawPrompt p s = do
+  promptDrawer p s
+  return C.CursorVisible
+
+-- | Event handler for a prompt
+promptHandler :: Prompt -> C.Event -> Action ()
+promptHandler p (C.EventCharacter '\n') = do
+  val <- gets $ view inputBuffer
+  modify $ inputBuffer .~ ""
+  promptAction p val
+promptHandler p (C.EventCharacter c) = let
+  c' = toUpper c
+  in when (promptCharCheck p c') $
+   modify $ addChar c'
+promptHandler _ (C.EventSpecialKey C.KeyBackspace) =
+  modify removeChar
+promptHandler p (C.EventSpecialKey (C.KeyFunction k)) =
+  promptFunctionKey p k
+promptHandler _ _ = return ()
+
+-- | Builds a numeric prompt
+numPrompt
+  :: String
+  -- ^ The prompt string
+  -> (Int -> Action ())
+  -- ^ The callback function for the result
+  -> Prompt
+numPrompt pStr act = Prompt
+  { promptDrawer      = \s -> C.drawString $ pStr ++ s ^. inputBuffer
+  , promptCharCheck   = isDigit
+  , promptAction      = \inStr -> forM_ (readMaybe inStr) act
+  , promptFunctionKey = const $ return ()
+  }