-- should probably have used Data.Map for dictionary instead of list of pairs
-- also, 100% of functions are IO actions!

import System.IO
import System.Random

type Dict = [(String, String)]

-- calls main loop with empty dictionary
main :: IO ()
main = mainloop []


mainloop :: Dict -> IO ()
mainloop dict =
  do printGreeting
     selection <- getLine
     performActivity dict selection

-- this probably doesn't need to be its own function
printGreeting :: IO ()
printGreeting = putStrLn "e to enter words into dictionary\ns to start testing"

-- procedure called by the main loop to start up either
-- word entry or the test itself
performActivity :: Dict -> String -> IO ()
performActivity dict selection
  | selection == "e" = dictEntry dict >>= mainloop
  | selection == "s" = doGame dict >> mainloop dict
  | otherwise = putStrLn "Invalid entry" >> mainloop dict

-- user prompt to enter things into dictionary
-- to do: allow removal from dictionary
--        allow read/write dictionary to/from file
dictEntry :: Dict -> IO Dict
dictEntry dict =
  do a <- getLine
     if (a == "EXIT") then return dict else
       do b <- getLine
          if (b == "EXIT") then return dict else
	    let newdict = (:) (a, b) dict in (dictEntry newdict)

-- the actual test component
doGame :: Dict -> IO ()
doGame dict
  | dict == [] = putStrLn "No entries in dictionary." >> mainloop dict
  | otherwise =
     do choice <- randomIndex
        let pair = dict !! choice
        response <- doQuestion pair
        if response == "EXIT"
           then return ()
           else if response == snd pair
                   then doGame dict
                   else putStrLn (snd pair) >> doGame dict
     where randomIndex = randomRIO (0, (length dict) - 1)

-- prints word to translate and accepts user input
doQuestion :: (String, String) -> IO String
doQuestion pair =
  do putStrLn $ fst pair
     getLine