{-# LANGUAGE CPP #-}

module Codec.Picture.Jpg.Metadata ( extractMetadatas, encodeMetadatas ) where

#if !MIN_VERSION_base(4,8,0)

import Control.Applicative( pure )

import Data.Monoid( mempty )

import Data.Word( Word )

#endif

import Data.Word( Word16 )

import Data.Maybe( fromMaybe )

import qualified Codec.Picture.Metadata as Met

import Codec.Picture.Metadata( Metadatas )

import Codec.Picture.Jpg.Types

scalerOfUnit :: JFifUnit -> Met.Keys Word -> Word16 -> Metadatas -> Metadatas

scalerOfUnit unit k v = case unit of

  JFifUnitUnknown -> id

  JFifPixelsPerInch -> Met.insert k (fromIntegral v)

  JFifPixelsPerCentimeter ->

    Met.insert k (Met.dotsPerCentiMeterToDotPerInch $ fromIntegral v)

extractMetadatas :: JpgJFIFApp0 -> Metadatas

extractMetadatas jfif = 

    inserter Met.DpiX (_jfifDpiX jfif)

        $ inserter Met.DpiY (_jfifDpiY jfif) mempty

  where

    inserter = scalerOfUnit $ _jfifUnit jfif

encodeMetadatas :: Metadatas -> [JpgFrame]

encodeMetadatas metas = fromMaybe [] $ do

  dpiX <- Met.lookup Met.DpiX metas

  dpiY <- Met.lookup Met.DpiY metas

  pure . pure . JpgJFIF $ JpgJFIFApp0

    { _jfifUnit      = JFifPixelsPerInch

    , _jfifDpiX      = fromIntegral dpiX

    , _jfifDpiY      = fromIntegral dpiY

    , _jfifThumbnail = Nothing

    }