{-# LANGUAGE CPP               #-}
{-# LANGUAGE DataKinds         #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeOperators     #-}

module Main (main) where

import Codec.Picture
import Control.Monad
import Data.ByteString (ByteString)
import Data.Function (on)
import Data.Proxy
import Data.Word (Word8)
import Graphics.Identicon
import Graphics.Identicon.Primitive
import Test.Hspec
import Test.QuickCheck hiding (oneof)
import qualified Data.ByteString as B

#if !MIN_VERSION_base(4,8,0)
import Data.Monoid
#endif

main :: IO ()
main = hspec spec

spec :: Spec
spec = do
  describe "renderIdenticon" renderIdenticonSpec
  ω gen0 [0x00,0x00,0x00,0x00] "data-examples/identicon-00.png"
  ω gen0 [0x8f,0x55,0x6e,0x93] "data-examples/identicon-01.png"
  ω gen0 [0x31,0xa8,0x29,0x5b] "data-examples/identicon-02.png"
  ω gen1 [0x3e,0xf1,0xde,0x08,0x85,0x0b,0x9c,0x81,0x25,0xf0,0x53,0x0b]
    "data-examples/identicon-10.png"
  ω gen1 [0xa9,0xf7,0x66,0xf0,0xd7,0xf9,0xb0,0x8e,0x57,0x21,0xc5,0x06]
    "data-examples/identicon-11.png"
  ω gen1 [0x23,0x29,0x2d,0x29,0x2f,0x05,0x28,0x11,0x1e,0x0e,0x0d,0x06]
    "data-examples/identicon-12.png"
  ω gen2 [0xcf,0xe7,0xb9,0x49,0x93,0xb1,0x01]
    "data-examples/identicon-20.png"
  ω gen2 [0xc8,0xa4,0xda,0xa1,0xe9,0x93,0x86]
    "data-examples/identicon-21.png"
  ω gen2 [0xf9,0x9b,0xb7,0x11,0x5b,0xca,0x00]
    "data-examples/identicon-22.png"
  describe "Semigroup and Monoid instances of Layer" $ do
    it "mempty always returns black pixel" $
      property $ \w h x y ->
        let (Layer f) = mempty
        in f w h x y `shouldBe` PixelRGB8 0 0 0
    it "mappend combines layers" $
      property $ \w'' h'' x'' y'' ->
        let w = w'' `mod` 10
            h = h'' `mod` 10
            x = x'' `mod` 10
            y = y'' `mod` 10
            (Layer f) = Layer a `mappend` Layer b
            a w' h' x' y' = PixelRGB8 (g $ w' + h') (g $ h' + x') (g $ x' + y')
            b w' h' x' y' = PixelRGB8 (g $ w' + y') (g $ h' + w') (g $ x' + w')
            g = fromIntegral
        in f w h x y
           `shouldBe` PixelRGB8
           (g $ w + h + w + y)
           (g $ h + x + h + w)
           (g $ x + y + x + w)

renderIdenticonSpec :: Spec
renderIdenticonSpec = do
  context "when we pass too short byte string" $
    it "returns Nothing" $
      shouldBeNothing (gen0 100 100 "aaa")
  context "when we pass nonsential width value" $
    it "returns Nothing" $
      shouldBeNothing (gen0 0 100 "aaaa")
  context "when we pass nonsential height value" $
    it "returns Nothing" $
      shouldBeNothing (gen0 100 0 "aaaa")

----------------------------------------------------------------------------
-- Identicon generators

type Gen0 = Identicon 4 :+ Consumer 4

gen0 :: Int -> Int -> ByteString -> Maybe (Image PixelRGB8)
gen0 = renderIdenticon (Proxy :: Proxy Gen0) i
  where
    i = Identicon :+ a
    a r g b n = rsym $ onGrid 4 4 n $
      circle $ gradientLR (edge . mid) black (PixelRGB8 r g b)

type Gen1 = Identicon 12 :+ Consumer 4 :+ Consumer 4 :+ Consumer 4

gen1 :: Int -> Int -> ByteString -> Maybe (Image PixelRGB8)
gen1 = renderIdenticon (Proxy :: Proxy Gen1) i
  where
    i = Identicon :+ a0 :+ a1 :+ a2
    a0 r g b n = hsym $ onGrid 3 3 n $
      gradientTLBR id black (PixelRGB8 r g b)
    a1 r g b n = vsym $ onGrid 4 4 n $
      gradientXY id black (PixelRGB8 r g b)
    a2 r g b n = hvsym $ onGrid 5 5 n $
      circle $ gradientTRBL mid (PixelRGB8 r g b) black

type Gen2 = Identicon 7 :+ Consumer 3 :+ Consumer 4

gen2 :: Int -> Int -> ByteString -> Maybe (Image PixelRGB8)
gen2 = renderIdenticon (Proxy :: Proxy Gen2) i
  where
    i = Identicon :+ a0 :+ a1
    a0 r g b = gradientTB edge (PixelRGB8 r g b) black
    a1 r g b n = oneof [gradientXY id black, color] n (PixelRGB8 r g b)

----------------------------------------------------------------------------
-- Helpers

-- | A helper to check that 'Nothing' is returned without requiring that
-- argument is an instance of 'Show' or 'Eq' type class.

shouldBeNothing :: Maybe a -> Expectation
shouldBeNothing m =
  case m of
    Nothing -> return ()
    Just _  ->
      expectationFailure "it returned not Nothing"

-- | A shorthand for test cases.

ω
  :: (Int -> Int -> ByteString -> Maybe (Image PixelRGB8))
     -- ^ Identicon generator
  -> [Word8]           -- ^ Input to use for identicon generation
  -> FilePath          -- ^ Where to get image to compare with
  -> Spec
ω f bs path = describe path $ it ("reproduces " ++ path) $
  compareWithFile f (B.pack bs) path

-- | Take function that produces identicon, binary input for it, path to
-- already rendered identicon and compare them. Fail with informative
-- message if they differ.

compareWithFile
  :: (Int -> Int -> ByteString -> Maybe (Image PixelRGB8))
     -- ^ Identicon generator
  -> ByteString        -- ^ Input to use for identicon generation
  -> FilePath          -- ^ Where to get image to compare with
  -> Expectation
compareWithFile f bs path = do
  (Right (ImageRGB8 img)) <- readImage path
  let mimg = f (imageWidth img) (imageHeight img) bs
  case mimg of
    Nothing -> expectationFailure "failed to generate an image"
    Just img' ->
      unless (imageEq img img') $
        expectationFailure ("generated image is different from " ++ path)

-- | Since 'Image' for some reason is not an instance of 'Eq', we use this
-- to compare 'Image's.

imageEq :: Image PixelRGB8 -> Image PixelRGB8 -> Bool
imageEq a b =
  ((==) `on` imageWidth)  a b &&
  ((==) `on` imageHeight) a b &&
  ((==) `on` imageData)   a b