module Mana where

data Color = Colorless
    | Black
    | White
    | Red
    | Blue
    | Green
    deriving (Show, Eq)

data Mana = Mana { amount :: Int
                 , color  :: Color
                 } deriving (Show, Eq)

data Cost = Cost [Mana]
    deriving (Eq)

instance Show Cost where
    show c = pretty c

class ManaCost a where
    converted :: a -> Int

instance ManaCost Cost where
    converted (Cost []) = 0
    converted (Cost cost) = (foldl (\t (Mana x _) -> t + x) 0) cost

pretty :: Cost -> String
pretty c = do
    let filtered c (Cost cost) = converted $ Cost $ filter (\x -> color x == c) cost
    let colored = concat [ replicate (filtered Black c) 'B'
                         , replicate (filtered White c) 'W'
                         , replicate (filtered Red   c) 'R'
                         , replicate (filtered Blue  c) 'U'
                         , replicate (filtered Green c) 'G'
                         ]
    let colorless = filtered Colorless c
    if length colored > 0 && colorless == 0 then
        colored
    else
        (show colorless) ++ colored