{-# LANGUAGE OverloadedStrings #-}

module Main where

import Control.Monad (when)
import qualified Data.Text as T
import qualified Data.Text.IO as T
import Nock
import System.Exit (exitSuccess)

main :: IO ()
main = do
  input <- T.getContents

  when (T.length input == 0) $ do
    T.putStrLn "USAGE: echo EXPR | ./hnock"
    exitSuccess

  case parse input of
    Left parseErr -> T.putStrLn (T.pack (show parseErr))
    Right e -> case eval e of
      Left err   -> T.putStrLn (T.pack (show err))
      Right noun -> T.putStrLn (T.pack (show noun))