gistfile1.hs

module Trial where

import System.IO
import System.Directory
import System.Time

fileExists :: FilePath -> IO Bool
fileExists name = do
    fileExists <- doesFileExist name
    if fileExists
      then return True
      else doesDirectoryExist name

readDay :: String -> Int
readDay = read . head . lines

readOrCreate :: FilePath -> String -> IO String
readOrCreate fp def = do
    exists <- fileExists fp
    if exists
      then readFile fp
      else writeFile fp def >> return def

class TrialMechanism a where
  daysRemaining :: Int -> a -> IO Int
  updateDaysRemaining :: a -> Int -> IO ()

instance TrialMechanism FilePath where
  daysRemaining def fp = fmap readDay (readOrCreate fp $ show def) 
  updateDaysRemaining fp newDays = writeFile fp $ show newDays