{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE FlexibleContexts #-}

import Control.Monad.Reader (ReaderT, runReaderT)
import Data.ByteString.Lazy.Char8 (ByteString)
import qualified Data.ByteString.Char8 as BS (readFile)
import qualified Data.ByteString.Lazy.Char8 as Lazy (putStrLn)
import Data.Id (Id(..))
import PDF (Document(..), parseDocument)
import PDF.Box (Box(..))
import PDF.Layer (Layer(..), unify)
import PDF.Object (Object(..))
import PDF.Object.Navigation (
    Nav(..), PPath(..), StreamContent(..), (//), objectById, catalog
  )
import PDF.Output (Output)
import qualified PDF.Output as Output (render)
import Prelude hiding (fail)
import System.Environment (getArgs, getProgName)
import System.Exit (die)
import Text.Printf (printf)
import Text.Read (readMaybe)

decodedStream :: Object -> Object
decodedStream object =
  either (const object) id $ r Clear object >>= flip (w Raw) object

display :: Functor m => Output a => ReaderT Layer m a -> Document -> m ByteString
display getter (Document {eolStyle, layers}) =
  Output.render eolStyle <$> runReaderT getter (unify layers)

parse :: [String] -> IO (FilePath, Document -> Either String ByteString)
parse [inputFile] = return (inputFile, display $ value <$> catalog)
parse [inputFile, key] =
  return (inputFile, clear . maybe (byPath key) byId $ readMaybe key)
  where
    byId = objectById . Id
    byPath path = (catalog // PPath (explode path))
    explode "" = []
    explode path =
      case break (== '.') path of
        (name, "") -> [name]
        (name, rest) -> name : explode (drop 1 rest)
    clear = display . fmap (decodedStream . value)
parse _ =
  die . printf "Syntax: %s inputFile [OBJECT_ID | PATH_TO_OBJ]\n" =<< getProgName

main :: IO ()
main = do
  (inputFile, getData) <- parse =<< getArgs
  input <- BS.readFile inputFile
  either die Lazy.putStrLn $ (parseDocument input >>= getData)