{-# LANGUAGE NoImplicitPrelude, TypeSynonymInstances, FlexibleInstances #-}

module IHaskell.Display.Diagrams.Animation (animation) where

import           ClassyPrelude hiding (filename)

import           Diagrams.Prelude
import           Diagrams.Backend.Cairo
import           Diagrams.Backend.Cairo.CmdLine (GifOpts(..))
import           Diagrams.Backend.CmdLine (DiagramOpts(..), mainRender)

import           IHaskell.Display

instance IHaskellDisplay (QAnimation Cairo V2 Double Any) where
  display renderable = do
    gif <- animationData renderable
    return $ Display [html $ "<img src=\"data:image/gif;base64,"
                             ++ gif ++ "\" />"]

animationData :: Animation Cairo V2 Double -> IO String
animationData renderable = do
  switchToTmpDir

  -- Generate the frames
  let fps = 30
      animAdjusted = animEnvelope' fps renderable
      frames = simulate fps animAdjusted
      timediff = 100 `div` ceiling fps :: Int
      frameSet = map (\x -> (x # bg white, timediff)) frames

  -- Compute width and height.
  let shape = activeStart animAdjusted
      w = width shape
      h = height shape
      aspect = w / h
      imgHeight = 300
      imgWidth = aspect * imgHeight

  -- Write the image.
  let filename = ".ihaskell-diagram.gif"
      diagOpts = DiagramOpts
        { _width = Just . ceiling $ imgWidth
        , _height = Just . ceiling $ imgHeight
        , _output = filename
        }
      gifOpts = GifOpts { _dither = True, _noLooping = False, _loopRepeat = Nothing }
  mainRender (diagOpts, gifOpts) frameSet

  -- Convert to ascii represented base64 encoding
  imgData <- readFile filename
  return . unpack . base64 $ imgData

-- Rendering hint.
animation :: Animation Cairo V2 Double -> Animation Cairo V2 Double
animation = id