module Main
where

import qualified Data.ByteString.Char8 as BS (pack)
import Data.List ((\\))
import Data.String.Utils (join, splitWs)

import Network.DNS (
  Domain,
  FileOrNumericHost(RCHostName),
  ResolvConf(resolvInfo),
  defaultResolvConf,
  lookupNS,
  makeResolvSeed,
  withResolver
  )

import System.IO (hGetContents, stdin)

import CommandLine (Args(..), Delegates(..), get_args)

report :: (Domain, Maybe [Domain]) -> IO ()
report (d, Nothing) =
  putStrLn $ "Domain " ++ (show d) ++ " not delegated."
report (d, Just leftovers) =
  if null leftovers
  then return ()
  else putStrLn $ "Domain " ++
                  (show d) ++
                  " delegates somewhere else: " ++
                  (join " " (map show leftovers))

clean :: Delegates -> (Domain, Maybe [Domain]) -> (Domain, Maybe [Domain])
clean _ p@(_, Nothing) = p
clean (Delegates ds') (d, Just targets) =
  (d, Just $ targets \\ ds)
  where
    ds = map BS.pack ds'

main :: IO ()
main = do
  cfg <- get_args
  print cfg
  input <- hGetContents stdin

  -- Split the input on any whitespace characters.
  let domains' = splitWs input

  -- Convert those Strings to ByteStrings
  let domains  = map BS.pack domains'

  let rc = case (server cfg) of
             Nothing -> defaultResolvConf
             Just s -> defaultResolvConf { resolvInfo = RCHostName s }

  rs <- makeResolvSeed rc
  withResolver rs $ \resolver -> do
    -- This function keeps the domain matches with its NS records.
    let lookupNS' = \d -> (lookupNS resolver d) >>= (return . ((,) d))
    domains_ns <- mapM lookupNS' domains
    let cdns = map (clean (delegates cfg)) domains_ns

    case cfg of
      (NS _ _) ->
        -- We're only checking NS records, so report what we found.
        mapM_ report cdns
      (MX _ _) ->
        print "Hello, world."