From 0a20f0a5ff565e4621b780af1d02b1c25defb090 Mon Sep 17 00:00:00 2001
From: Sam Tay <sam.chong.tay@gmail.com>
Date: Thu, 15 Jun 2017 20:50:31 -0400
Subject: [PATCH] Implement safe rotations

---
 src/Tetris.hs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/Tetris.hs b/src/Tetris.hs
index 608378b..429cff8 100644
--- a/src/Tetris.hs
+++ b/src/Tetris.hs
@@ -13,6 +13,8 @@ import Lens.Micro.TH
 import System.Random (getStdRandom, randomR)
 
 import Prelude hiding (Left, Right)
+import Data.Maybe (fromMaybe)
+import Data.Monoid (First(..))
 
 -- Types and instances
 
@@ -152,9 +154,16 @@ clearFullRows g = g & board %~ clearBoard
            in (x, y - offset)
 
 -- | Handle counterclockwise block rotation (if possible)
--- TODO wallkicks http://tetris.wikia.com/wiki/TGM_rotation
+-- Allows wallkicks: http://tetris.wikia.com/wiki/TGM_rotation
 rotate :: Game -> Game
-rotate = undefined
+rotate g = g & currBlock .~ nextB
+  where nextB     = fromMaybe blk $ getFirst . mconcat $ bs
+        bs        = map ($ blk) safeFuncs
+        safeFuncs = map (mkSafe .) funcs
+        mkSafe b  = if isValidBlockPosition b brd then First (Just b) else First Nothing
+        funcs     = [rotate', rotate' . translate Left, rotate' . translate Right]
+        blk       = g ^. currBlock
+        brd       = g ^. board
 
 -- | Check if a block on a board is stopped from further gravitation
 isStopped :: Board -> Block -> Bool