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

module Main (main) where

import Codec.Picture
import Control.Monad
import Data.ByteString (ByteString)
import Data.ByteString qualified as B
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)

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 ::
  -- | Identicon generator
  (Int -> Int -> ByteString -> Maybe (Image PixelRGB8)) ->
  -- | Input to use for identicon generation
  [Word8] ->
  -- | Where to get image to compare with
  FilePath ->
  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 ::
  -- | Identicon generator
  (Int -> Int -> ByteString -> Maybe (Image PixelRGB8)) ->
  -- | Input to use for identicon generation
  ByteString ->
  -- | Where to get image to compare with
  FilePath ->
  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