From 0fba7a2d5082bffeda214b40b4ab6939c797ecdc Mon Sep 17 00:00:00 2001
From: smparsons <samuel.m.parsons@gmail.com>
Date: Mon, 3 Sep 2018 11:35:01 -0400
Subject: [PATCH] Creating function to retrieve graphics as bytestring for
 rendering

---
 lazy-chip8.cabal  |  6 ++++--
 src/Chip8.hs      | 16 ++++++++++++++--
 test/Chip8Spec.hs | 21 +++++++++++++++++++++
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/lazy-chip8.cabal b/lazy-chip8.cabal
index 47def9e..11fdae5 100644
--- a/lazy-chip8.cabal
+++ b/lazy-chip8.cabal
@@ -34,7 +34,8 @@ library
     vector,
     random,
     lens,
-    mtl
+    mtl,
+    bytestring
   default-language: Haskell2010
 
 executable lazy-chip8
@@ -57,7 +58,8 @@ test-suite hspec
       vector,
       random,
       lens,
-      mtl
+      mtl,
+      bytestring
     default-language: Haskell2010
     hs-source-dirs: test
     main-is: Spec.hs
diff --git a/src/Chip8.hs b/src/Chip8.hs
index f41d5b8..f5b1de5 100644
--- a/src/Chip8.hs
+++ b/src/Chip8.hs
@@ -2,7 +2,8 @@ module Chip8
 ( emulateCpuCycle,
   initializeChip8,
   loadFontsetIntoMemory,
-  loadGameIntoMemory
+  loadGameIntoMemory,
+  getGraphicsAsByteString
 ) where
 
 import System.Random
@@ -10,6 +11,7 @@ import Data.Word
 import qualified Data.Vector as V
 import Control.Monad.State
 import Control.Lens
+import qualified Data.ByteString as BS
 
 import Constants
 import Cpu
@@ -38,4 +40,14 @@ emulateCpuCycle :: Chip8 ()
 emulateCpuCycle = do
   executeOpcode
   decrementDelayTimer
-  decrementSoundTimer
\ No newline at end of file
+  decrementSoundTimer
+
+getGraphicsAsByteString :: Chip8 BS.ByteString
+getGraphicsAsByteString = do
+  chip8Graphics <- gets (\givenState -> V.toList $ givenState^.graphics)
+  let black = [0, 0, 0, 0] :: [Word8]
+      white = [255, 255, 255, 255] :: [Word8]
+      flatten xs = (\z n -> foldr (\x y -> foldr z y x) n xs) (:) []
+      rgbaFormatGraphics = flatten $ map (\pixelState -> if pixelState == 1 then white else black) chip8Graphics
+      graphicsByteString = BS.pack rgbaFormatGraphics
+  return graphicsByteString
diff --git a/test/Chip8Spec.hs b/test/Chip8Spec.hs
index 069693c..9a44701 100644
--- a/test/Chip8Spec.hs
+++ b/test/Chip8Spec.hs
@@ -10,6 +10,7 @@ import Constants
 import qualified Data.Vector as V
 import Control.Monad.State
 import Control.Lens
+import qualified Data.ByteString as BS
 
 spec :: Spec
 spec = do
@@ -37,3 +38,23 @@ spec = do
       let numberOfBytesToSlice = 0x22
       let loadedGame = V.toList $ V.slice 0x200 numberOfBytesToSlice resultingMemory
       loadedGame `shouldMatchList` mazeGame 
+
+  describe "getGraphicsAsByteString" $ do
+    it "packs the pixel array into a bytestring" $ do
+      let chip8State = chip8InitialState {
+        _graphics = V.update (chip8InitialState^.graphics) $ V.fromList 
+          [ (0x1, 1)
+          , (0x3, 1)
+          , (0x7FC, 1)
+          , (0x7FE, 1) ]}
+          bsResult = evalState getGraphicsAsByteString chip8State
+          byteList = BS.unpack bsResult
+          slice start end = take (end - start + 1) . drop start
+          beginningByteSlice = slice 0 0xF byteList
+          endingByteSlice = slice 0x1FF0 0x2000 byteList
+
+      beginningByteSlice `shouldMatchList` 
+        [0x0, 0x0, 0x0, 0x0, 0xFF, 0xFF, 0xFF, 0xFF, 0x0, 0x0, 0x0, 0x0, 0xFF, 0xFF, 0xFF, 0xFF]
+
+      endingByteSlice `shouldMatchList`
+        [0xFF, 0xFF, 0xFF, 0xFF, 0x0, 0x0, 0x0, 0x0, 0xFF, 0xFF, 0xFF, 0xFF, 0x0, 0x0, 0x0, 0x0]
\ No newline at end of file