{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Hanafuda.ID (
      ID(..)
    , IDType(..)
    , Prefix(..)
  ) where

import Data.Char (isDigit)
import System.Random (Random(..))
import Text.ParserCombinators.ReadP (char, munch, string)
import Text.ParserCombinators.ReadPrec (lift)
import Text.Read (readPrec)

newtype ID a = ID {
    getID :: Int
  } deriving (Eq, Ord)

newtype Prefix a = Prefix String

class IDType a where
  prefix :: Prefix a

instance IDType a => Show (ID a) where
  show (ID someID) = p ++ ('#' : show someID)
    where Prefix p = (prefix :: Prefix a)

instance IDType a => Read (ID a) where
  readPrec = fmap (ID . read) . lift $
    string p >> char '#' >> munch (isDigit)
    where Prefix p = (prefix :: Prefix a)

rIntToRID :: (Int, g) -> (ID a, g)
rIntToRID (someID, g) = (ID someID, g)

instance Random (ID a) where
  random = rIntToRID . randomR (0, maxBound)
  randomR (ID idA, ID idB) = rIntToRID . randomR (idA, idB)