import Prelude
import Control.Monad
import Data.List

data Spider = Darkback | RaftSpider | WhipSpider | WolfSpider deriving (Eq,Show)
data Winner = Anthony | Georgia | Olga | Rafael deriving (Eq,Show)
type Price = Integer

-- triple pairing
data Tripling = Tripling { spider :: Spider, winner :: Winner, price :: Price } deriving (Show)

spiders = [Darkback, RaftSpider, WhipSpider, WolfSpider]
winners = [Anthony, Georgia, Olga, Rafael]
prices = [45, 60, 75, 90]

-- each solution is 4 triples
type Solution = [Tripling]

answers :: [Solution]
answers = do
  -- spiders arent permutated so they will be in that order always, dont need to find them
  solution@[darkback, raft, whip, _] <- [zipWith3 Tripling spiders wns prs
	       				| wns <- permutations winners
	       				, prs <- permutations prices]

  -- clue 1
  Just georgia <- [find (\x -> winner x == Georgia) solution]
  guard (price raft == ((price georgia) - 15))
 
  -- clue 2
  Just anthony <- [find (\x -> winner x == Anthony) solution]
  guard (price darkback < price anthony)
   
  -- clue 3
  guard (spider anthony == RaftSpider)

  -- clue 4
  Just olga <- [find (\x -> winner x == Olga) solution]
  guard (spider olga == WhipSpider || price olga == 90) 

  -- clue 5
  guard ((price whip + 15) == price darkback)

  return solution