module Main where

import Control.Lens
import Linear.V2
import Linear.V3
import Data.Matrix
--import Numeric.LinearAlgebra
import System.Random
import Foreign.Storable


data Square = X                 -- Attacked
              | Qu              -- Queen
              | O               -- Open/available
  deriving (Show, Eq)


--board = V3 <$> [0..8] <*> [0..8] <*> [0]
--board = [(r,c,X) | r <- [0..8], c <- [0..8] ]

lo8 = [0..8] -- list of 8
initBoard = matrix 8 8 $ \_ -> O

placeQueen (r,c) b = placeQueen' $ markAttacked b
  where
    placeQueen' b = setElem Qu (r,c) b
    markAttacked b = rowAttacked $ colAttacked $ diagAttacked b
    fX = (\_ x -> X)
    rowAttacked b = mapRow fX r b
    colAttacked b = mapCol fX c b
    diagAttacked b = let d = diag r c
                         attack ap ab  = setElem X ap ab
                         attackall [x] = attack x b
                         attackall (x:xs) = attack x (attackall xs)
                     in attackall d
--                     in last $ map (\p -> setElem X p b) d
--                     in last $ scanr (\p -> setElem X p) b

--solve b = placeQueen (nextAvail b) b

nextAvail b = head [(x,y) | x <- [1..8], y <- [1..8], b ! (x,y) == O]

solve b = solve $ placeQueen n b
  where n = nextAvail b
  

--diag r c = [(x,y) | x <- [1..8], y <- [1..8], (abs x-y) == 1 ]
diag r c = let rl = [1..r]
               rr = [r..8]
               cu = [1..c]
               cd = [c..8]
           in zip rl cu ++ zip rr cd ++
              zip (reverse rl) cd ++ zip (reverse rr) cu




-- diag (r,c) b =
--   where l = (r-1,c-1)
--         r = (r+1,c+1)
--         lowbound = 1
--         highbound = 8
        

--initBoard = (8><8) $ repeat O

--firstOpen b = take 1 [(r,c)| r <- [1..8], c <- [1..8], b ! (r,c) == O]

-- firstOpen b = let 
--                 elem x y = b ! (x, y)
--             in map 

-- nextOpen b = 

-- solve = let board = initBoard

--avail r c b =

--rowOccupied r b = any (== Q) $ getRow r b



-- diags p = let r = r p
--               l = l p
--           in p : inRange r
--   where inRange x = x >= 1 && x <= 8
--         inRange' (x,y) = inRange (x) && inRange (y)
--         r x = (fst x + 1, snd x + 1)
--         l x = (fst x - 1, snd x - 1)
--         nexts x = diags' x
--         diags' x = [(fst x - 1, snd x -1), (fst x + 1, snd x + 1)]
--         -- down x = (fst x - 1, snd x - 1)
--         -- down (r,c) = let d = (r-1,c-1) in if inRange d then d : down d else 
--         -- up (r,c) = let u = (r+1,c+1) in u : up u
        

--mapDiag r c = undefined

--placeAll = repeat 8 placeQueen

winnable = undefined

nextOpen board = undefined 

-- placeQueen r c =

--b = getE

--placeQueen r c b = b ^.

-- rand = do
--   g <- newStdGen
--   print $ take 8 $ (randomRs (0, 8) g)


-- try r c = let next b = placeQueen r c b
--           in next initBoard

-- try' p = let next b = p b
--           in next initBoard


--res = [ try x y | x <- lo8, y <- lo8 ]

main :: IO ()
main = do
  putStrLn "Hi"