DyreExample.hs

module DyreExample
  ( Config(..)
  , defaultConfig
  , dyreExample
  ) where

import qualified Config.Dyre as Dyre (wrapMain, defaultParams, Params(..))
import Config.Dyre.Relaunch (restoreTextState, relaunchMaster, saveTextState)

import System.IO (hFlush, stdout)

dyreExample = Dyre.wrapMain $ Dyre.defaultParams
    { Dyre.projectName = "dyreExample"
    , Dyre.realMain    = realMain
    , Dyre.showError   = showError
    }

data Config = Config { message :: String, errorMsg :: Maybe String }
defaultConfig :: Config
defaultConfig = Config "Dyre Example v0.1" Nothing

data State  = State { bufferLines :: [String] } deriving (Read, Show)

realMain config@Config{message = message, errorMsg = errorMsg } = do
    (State buffer) <- restoreTextState $ State []
    case errorMsg of
         Nothing -> main' buffer
         Just em -> putStrLn ("Error: " ++ em) >> main' buffer
  where
    main' buffer = do
        putStrLn message
        mapM putStrLn . reverse $ buffer

        putStr "> " >> hFlush stdout
        input <- getLine
        case input of
             "exit" -> return ()
             "recompile" -> relaunchMaster Nothing
             other  -> saveTextState (State $ other:buffer) >> realMain config

showError :: Config -> String -> Config
showError cfg msg = cfg { errorMsg = Just msg }

dyreExample.hs

import DyreExample

main = dyreExample $ defaultConfig { message = "modified" }

Main.hs

import DyreExample

main = dyreExample $ defaultConfig { message = "sample" }