{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}

module IHaskell.Display.Diagrams (diagram, animation) where

import           System.Directory
import qualified Data.ByteString.Char8 as Char
import           System.IO.Unsafe

import           Diagrams.Prelude
import           Diagrams.Backend.Cairo

import           IHaskell.Display
import           IHaskell.Display.Diagrams.Animation

instance IHaskellDisplay (QDiagram Cairo V2 Double Any) where
  display renderable = do
    png <- diagramData renderable PNG
    svg <- diagramData renderable SVG
    return $ Display [png, svg]

diagramData :: Diagram Cairo -> OutputType -> IO DisplayData
diagramData renderable format = do
  switchToTmpDir

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

  -- Write the image.
  let filename = ".ihaskell-diagram." ++ extension format
  renderCairo filename (mkSizeSpec2D (Just imgWidth) (Just imgHeight)) renderable

  -- Convert to base64.
  imgData <- readFile filename
  let value =
        case format of
          PNG -> png (floor imgWidth) (floor imgHeight) $ base64 (Char.pack imgData)
          SVG -> svg imgData

  return value

  where
    extension SVG = "svg"
    extension PNG = "png"

-- Rendering hint.
diagram :: Diagram Cairo -> Diagram Cairo
diagram = id