import qualified Data.ByteString.Char8 as BS (readFile)
import qualified Data.Map as Map (toList)
import qualified Data.Text.IO as Text (putStrLn)
import PDF (Document(..), parseDocument)
import PDF.Object (Content)
import PDF.Pages (Page(..), get, getAll)
import PDF.Update (unify)
import System.Environment (getArgs)
import System.Exit (die)
import System.IO (BufferMode(..), hSetBuffering, stdout)

onDoc :: FilePath -> (Content -> Either String a) -> IO a
onDoc inputFile f = do
  content <- fmap (unify . updates) . parseDocument <$> BS.readFile inputFile
  case content >>= f of
    Left someError -> die someError
    Right value -> return value

displayPage :: Page -> IO ()
displayPage = mapM_ Text.putStrLn . contents

wholeDoc :: FilePath -> IO ()
wholeDoc inputFile = do
  pages <- onDoc inputFile getAll
  mapM_ (displayPage . snd) $ Map.toList pages

singlePage :: FilePath -> Int -> IO ()
singlePage inputFile pageNumber =
  onDoc inputFile (`get` pageNumber) >>= displayPage

main :: IO ()
main = do
  hSetBuffering stdout LineBuffering
  args <- getArgs
  case args of
    [inputFile] -> wholeDoc inputFile
    [inputFile, pageNumber] -> singlePage inputFile (read pageNumber)
    _ -> die "Syntax: getText INPUT_FILE [PAGE_NUMBER]"