wordpuzzle.hs

-- |
module Game where

import Data.List (isInfixOf, sort, nub, any)

newtype Available = Available String deriving (Show, Eq)
type Word = [Char]
data WordError = NothingAvailable | CharNotAvailable Char deriving (Show)

deleteFirst _ [] = []
deleteFirst a (b:bc)
  | a == b    = bc
  | otherwise = b : deleteFirst a bc

useWord :: Game.Word -> Available -> Either WordError Available
useWord []     (Available "") = Right $ Available ""
useWord (_)    (Available "") = Left NothingAvailable
useWord []     (Available a)  = Right $ Available a
useWord (x:xs) (Available y)
  | elem x y = useWord xs $ Available $ deleteFirst x y
  | otherwise = Left $ CharNotAvailable x

guardWord :: Available -> Game.Word -> Either WordError Bool
guardWord available word =
  fmap null $ useWord word available