module Exercise_4 where

import Control.Arrow
import Data.Bool
import Data.List
import Data.Maybe

{-H4.1.10-}
editDistance :: Eq a => [a] -> [a] -> Int
editDistance a b = d !! length a !! length b
  where
    d =
      map
        (\i ->
           map
             (\j ->
                if (min i j == 0)
                  then max i j
                  else minimum $
                       (d !! (i - 1) !! j + 1) :
                       (d !! i !! (j - 1) + 1) :
                       (bool
                          (d !! (i - 1) !! (j - 1) + 1)
                          (d !! (i - 1) !! (j - 1)) $
                        a !! (i - 1) == b !! (j - 1)) :
                       (bool [] [d !! (i - 2) !! (j - 2) + 1] $
                        i > 1 &&
                        j > 1 &&
                        a !! (i - 1) == b !! (j - 2) &&
                        a !! (i - 2) == b !! (j - 1)))
             [0 ..])
        [0 ..]

{-H4.1.11-}
{-WETT-}
spellCorrect :: [String] -> [String] -> [[String]]
spellCorrect ws = map minEdit
  where
    minEdit x = map fst $ filter ((== minDist) . snd) mapped
      where
        mapped = map (id &&& editDistance x) ws
        minDist = minimum $ map snd mapped
{-TTEW-}