module Exercise_7 where

import           Data.List
import           Data.Function
import           Data.Maybe

{-WETT-}
trancl :: Eq a => [(Integer, (a, a))] -> [(Integer, (a, a))]
trancl xs = snd $ head $ dropWhile (uncurry (/=)) $ zip p $ tail p
 where
  f b = nubBy ((==) `on` snd) $ sortOn fst $ b ++ comp xs b
  p = iterate f xs

comp
  :: Eq b => [(Integer, (a, b))] -> [(Integer, (b, c))] -> [(Integer, (a, c))]
comp _abs bcs = concat
  [ [ (i + j, (fst e, snd e')) | (j, e') <- bcs, snd e == fst e' ]
  | (i, e) <- _abs
  ]
{-MCCOMMENT
Takes too long, but works in theory for the tests, felt that it was too cheeky of a solution, but hey, if you accept it, fine by me!
trancl :: Eq a => [(Integer, (a, a))] -> [(Integer, (a, a))]
trancl [] = []
trancl xs = last $ take 50 $ iterate f xs
  where f b = nubBy ((==) `on` snd) $ sortOn fst $ b ++ comp xs b

comp
  :: Eq b => [(Integer, (a, b))] -> [(Integer, (b, c))] -> [(Integer, (a, c))]
comp _abs bcs = concat
  [ [ (i + j, (fst e, snd e')) | (j, e') <- bcs, snd e == fst e' ]
  | (i, e) <- _abs
  ]

-}
{-TTEW-}