module Snakey.TwoSnakes where
import Graphics.Gloss.Interface.Pure.Game
import Scratchy.Syntax

-- Helper functions
moveSnake :: SpritePtr -> [SpritePtr] -> Dir -> SProg ()
moveSnake h t d =
  OnTargetReached h (\pos ->
    let newPos = nextCell d pos in
    InspectCell newPos (\case
      HasSprite ->
        SetBackgroundColor black $
        After 1 (SetBackgroundColor white $ Pure ()) $
        Pure ()
      HasBarrier ->
        SetBackgroundColor red $
        After 1 (SetBackgroundColor white $ Pure ()) $
        Pure ()
      IsFree ->
        SetTarget h newPos $
        moveTail pos t $
        Pure ()
    )
  ) $
  Pure ()

moveTail :: Cell -> [SpritePtr] -> SProg () -> SProg ()
moveTail _ [] cont = cont
moveTail prevPos (t:ts) cont =
  GetTarget t (\curPos ->
    SetTarget t prevPos $
    moveTail curPos ts cont
  )

twoSnakes :: SProg ()
twoSnakes = 
  let headRadius = cellSize * 0.6
      tailSize   = cellSize * 0.9
  in

  -- Green snake
  NewSprite (5, 5) (Color green $ circleSolid headRadius) $ \gHead ->
  NewSprite (4, 5) (Color green $ rectangleSolid tailSize tailSize) $ \gt1 ->
  NewSprite (3, 5) (Color green $ rectangleSolid tailSize tailSize) $ \gt2 ->
  NewSprite (2, 5) (Color green $ rectangleSolid tailSize tailSize) $ \gt3 ->
  NewSprite (1, 5) (Color green $ rectangleSolid tailSize tailSize) $ \gt4 ->
  NewSprite (0, 5) (Color green $ rectangleSolid tailSize tailSize) $ \gt5 ->
  NewSprite (0, 4) (Color green $ rectangleSolid tailSize tailSize) $ \gt6 ->
  NewSprite (0, 3) (Color green $ rectangleSolid tailSize tailSize) $ \gt7 ->

  -- Blue snake
  NewSprite (15, 15) (Color blue $ circleSolid headRadius) $ \bHead ->
  NewSprite (16, 15) (Color blue $ rectangleSolid tailSize tailSize) $ \bt1 ->
  NewSprite (17, 15) (Color blue $ rectangleSolid tailSize tailSize) $ \bt2 ->
  NewSprite (18, 15) (Color blue $ rectangleSolid tailSize tailSize) $ \bt3 ->
  NewSprite (19, 15) (Color blue $ rectangleSolid tailSize tailSize) $ \bt4 ->
  NewSprite (19, 16) (Color blue $ rectangleSolid tailSize tailSize) $ \bt5 ->
  NewSprite (19, 17) (Color blue $ rectangleSolid tailSize tailSize) $ \bt6 ->
  NewSprite (19, 18) (Color blue $ rectangleSolid tailSize tailSize) $ \bt7 ->

  -- List of tail sprites
  let bTail = [bt1, bt2, bt3, bt4, bt5, bt6, bt7]
      gTail = [gt1, gt2, gt3, gt4, gt5, gt6, gt7]
  in

  -- Green snake movement
  OnKeyEvent (Char 'w') (moveSnake gHead gTail U) $
  OnKeyEvent (Char 's') (moveSnake gHead gTail D) $
  OnKeyEvent (Char 'a') (moveSnake gHead gTail L) $
  OnKeyEvent (Char 'd') (moveSnake gHead gTail R) $

  -- Blue snake movement
  OnKeyEvent (Char 'i') (moveSnake bHead bTail U) $
  OnKeyEvent (Char 'k') (moveSnake bHead bTail D) $
  OnKeyEvent (Char 'j') (moveSnake bHead bTail L) $
  OnKeyEvent (Char 'l') (moveSnake bHead bTail R) $

  Pure ()