{-# LANGUAGE BangPatterns #-}

module Main (main) where

import Data.Bits
import Data.ByteString.Lazy qualified as BSL
import Data.CBF (decodePixels, readCBF)
import Data.Int
import Data.Word

unconsW8 :: BSL.ByteString -> Maybe (Word8, BSL.ByteString)
unconsW8 = BSL.uncons

unconsW16 :: BSL.ByteString -> Maybe (Word16, BSL.ByteString)
unconsW16 bs = do
  (x, bs') <- unconsW8 bs
  (y, bs'') <- unconsW8 bs'
  pure (fromIntegral x .|. (fromIntegral y `shiftL` 8), bs'')

unconsW32 :: BSL.ByteString -> Maybe (Word32, BSL.ByteString)
unconsW32 bs = do
  (x, bs') <- unconsW16 bs
  (y, bs'') <- unconsW16 bs'
  pure (fromIntegral x .|. (fromIntegral y `shiftL` 16), bs'')

unconsI32 :: BSL.ByteString -> Maybe (Int32, BSL.ByteString)
unconsI32 bs = do
  (x, bs') <- unconsW32 bs
  pure (fromIntegral x, bs')

ref :: BSL.ByteString -> [Int64]
ref bs = case unconsI32 bs of
  Nothing -> []
  Just (x, bs')
    | otherwise -> fromIntegral x : ref bs'

diff :: Int -> [Int64] -> [Int64] -> [(Int, Int64, Int64)]
diff !n (x : xs) (y : ys)
  | x /= y = (n, x, y) : diff (n + 1) xs ys
  | otherwise = diff (n + 1) xs ys
diff _ [] [] = []
diff _ [] _ = error "diff: too short"
diff _ _ [] = error "diff: too long"

main :: IO ()
main = do
  contents <- readCBF "test-data/test_lysozyme_001_00200.cbf"
  case contents of
    Left _ -> error "couldn't read file"
    Right image -> do
      referenceOutput <- BSL.readFile "test-data/expected_output.bin"
      case decodePixels image of
        Left e -> error $ "error decompressing: " <> e
        Right decompressedVector -> do
          let referenceOutputInt32 = ref referenceOutput
          print (take 10 (diff 0 decompressedVector referenceOutputInt32))