{-# LANGUAGE CPP #-}
module System.Global6 where

import Control.Monad
import Control.Applicative
#if MIN_VERSION_iproute(1,7,4)
import Data.IP hiding (fromSockAddr)
#else
import Data.IP
#endif
import Data.List
import Data.Maybe
import Network.Socket
import System.Process
import Text.Read
import System.IO

parseIpAddr :: String -> Maybe IPv6
parseIpAddr s = do
    let ws        = words s
        (addr,bs) = splitAt 1 $ drop 1 $ dropWhile (/= "inet6") ws
    guard ("global" `elem` bs)
    addr <- listToMaybe addr
    guard (not $ isPrefixOf "fd" addr)
    guard (not $ isPrefixOf "fc" addr)
    let (addr',slash) = break (=='/') addr
    ip6 <- readMaybe addr'
    return $ (ip6 :: IPv6)


global6 :: IO (Maybe IPv6)
global6 = do
    addrs <- lines <$> readProcess "ip" ["-o","-6","addr"] ""
    return $ foldr1 mplus $ map parseIpAddr addrs

everyOther (x:_:xs) = x : everyOther xs
everyOther xs       = xs


-- | Obtain all available IP broadcast addresses (in dotted quad or IPv6 colon
-- format) as Strings.
broadcastAddrs :: IO [String]
broadcastAddrs = parseBroadcastAddrs <$> readProcess "ip" ["-o","addr"] ""

parseBroadcastAddrs :: String -> [String]
parseBroadcastAddrs ipoutput = brds
 where
    brds = mapMaybe getbrd as
    assoclist ws = zip (everyOther ws) (everyOther $ drop 1 ws)
    as = map (assoclist . drop 2 . words) $ lines ipoutput
    getbrd alist = do
        ip <- lookup "inet" alist <|> lookup "inet6" alist
        lookup "brd" alist