{- This file is part of Vervis.
 -
 - Written in 2016 by fr33domlover <fr33domlover@riseup.net>.
 -
 - ♡ Copying is an act of love. Please copy, reuse and share.
 -
 - The author(s) have dedicated all copyright and related and neighboring
 - rights to this software to the public domain worldwide. This software is
 - distributed without any warranty.
 -
 - You should have received a copy of the CC0 Public Domain Dedication along
 - with this software. If not, see
 - <http://creativecommons.org/publicdomain/zero/1.0/>.
 -}

module Data.Attoparsec.ByteString.Local
    ( parseFileIncremental
    )
where

import Prelude

import Data.Attoparsec.ByteString
import System.IO

import qualified Data.ByteString as B (hGet)
import qualified Data.ByteString.Lazy.Internal as BLI (defaultChunkSize)

parseFileIncremental :: FilePath -> Parser a -> IO (Either String a)
parseFileIncremental file parser =
    withBinaryFile file ReadMode $ \ h -> do
        let getChunk = B.hGet h BLI.defaultChunkSize
            go (Fail _remainder _contexts msg) = return $ Left msg
            go (Partial cont)                  = getChunk >>= go . cont
            go (Done _remainder value)         = return $ Right value
        firstChunk <- getChunk
        let firstResult = parse parser firstChunk
        go firstResult