module DND.Dice
( rolls
, d20
, rollCheck
, rollAttackDamage
, RollMod(..)
) where

import           Prelude       hiding (mod)
import           System.Random

data RollMod = Advantage | Disadvantage | Neutral

rolls :: RandomGen a => a -> Int -> Int -> [Int]
rolls rnd x y = take x . randomRs (1, y) $ rnd

d20 :: RandomGen a => a -> Int
d20 rnd = minimum $ rolls rnd 1 20

rollCheck :: Int -> RollMod -> IO (Int, [Int])
rollCheck scoreMod rollMod = do
    rnd <- getStdGen
    let dice = rolls rnd 2 20
        mod = (+) scoreMod $ case rollMod of
              Advantage    -> maximum dice
              Disadvantage -> minimum dice
              Neutral      -> head dice
    return (mod,dice)

rollAttackDamage :: Int -> Int -> Int -> IO Int
-- dmgMod is proficiency in normal DND rules
rollAttackDamage sides count dmgMod = do
    rnd <- getStdGen
    return $ (+) dmgMod . sum $ rolls rnd sides count