byline-1.0.0.0: examples/simple.hs

-- |
--
-- Copyright:
--   This file is part of the package byline. It is subject to the
--   license terms in the LICENSE file found in the top-level
--   directory of this distribution and at:
--
--     https://github.com/pjones/byline
--
--   No part of this package, including this file, may be copied,
--   modified, propagated, or distributed except according to the
--   terms contained in the LICENSE file.
--
-- License: BSD-2-Clause
module Main
  ( main,
  )
where

import Byline
import qualified Byline.Exit as Exit
import qualified Data.Text as Text

main :: IO ()
main = void $ runBylineT $ do
  -- Start with a simple message to standard output:
  sayLn ("I can use " <> ("color" <> fg blue) <> "!")

  -- Get user input with a stylized prompt:
  let question =
        "What's your favorite "
          <> ("language" <> bold <> fg green)
          <> "? "
  language <- askLn question Nothing

  if Text.null language
    then Exit.die ("Cat got your tongue?" <> fg magenta)
    else sayLn ("I see, you like " <> (text language <> fg red) <> ".")

  -- Keep prompting until a confirmation function indicates that the
  -- user's input is sufficient:
  let question =
        "What's your "
          <> ("name" <> fg green <> underline)
          <> "? "
  name <- askUntil question Nothing (pure . atLeastThreeChars)
  sayLn $ "Hey there " <> text name <> fg (rgb 108 113 196)

-- | Example confirmation function that requires the input to be three
-- or more characters long.
atLeastThreeChars :: Text -> Either (Stylized Text) Text
atLeastThreeChars input
  | Text.length input < 3 = Left ("You can do better." <> bg red)
  | otherwise = Right input