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{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE OverloadedStrings #-}
module Hosts
( Hosts
, assignName
, assignNewName
, inet_pton
, inet_ntop
, empty
, hasName
, hasAddr
, encode
, decode
, diff
) where
import Data.Maybe
import Data.Monoid ( (<>) )
import Data.List (foldl')
import Data.Ord
import Data.Char (isSpace)
import qualified Data.Map as Map
import Data.Map (Map)
import qualified Data.ByteString.Lazy.Char8 as L
import System.IO.Unsafe (unsafePerformIO)
import Control.Exception as Exception (IOException(..),catch)
import Control.Applicative ( (<$>), (<*>) )
import Control.Monad (mplus)
import Network.Socket
handleIO_ h a = Exception.catch a (\(_ :: IOException) -> h)
inet_pton :: String -> Maybe SockAddr
inet_pton p = n
where
n = unsafePerformIO $ do
handleIO_ (return Nothing) $ do
info <- getAddrInfo safe_hints (Just p) Nothing
return $ fmap addrAddress $ listToMaybe info
safe_hints = Just $ defaultHints { addrFlags=[AI_NUMERICHOST] }
inet_ntop :: SockAddr -> String
inet_ntop n = p
where
p = case show n of
'[':xs -> fst $ break (==']') xs
xs -> fst $ break (==':') xs
data Hosts = Hosts
{ lineCount :: Int
, numline :: Map Int L.ByteString
, namenum :: Map L.ByteString [Int]
, addrnum :: Map SockAddr Int
}
instance Show Hosts where
show = L.unpack . encode
encode = L.unlines . map snd . Map.assocs . numline
parseLine s = (addr,names)
where
(addr0,names) = splitAt 1 $ L.words (uncom s)
addr = do
a <- fmap L.unpack $ listToMaybe addr0
n <- inet_pton a
return $ n -- inet_ntop n
uncom s = fst $ L.break (=='#') s
empty = Hosts { lineCount = 0
, numline = Map.empty
, addrnum = Map.empty
, namenum = Map.empty
}
parseHosts fname = do
input <- L.readFile fname
decode input
decode input = do
let ls = L.lines input
ans = map (\l->(parseLine l,l)) ls
hosts = foldl' upd empty ans
upd hosts ((addr,names),line) = hosts
{ lineCount = count
, numline = Map.insert count line (numline hosts)
, addrnum = maybeInsert (addrnum hosts) addr
, namenum = foldl' (\m x->Map.alter (cons count) x m)
(namenum hosts)
names
}
where count = lineCount hosts + 1
cons v xs = Just $ maybe [v] (v:) xs
maybeInsert m x = maybe m
(\x->Map.insert x count m)
x
return hosts
hasName :: L.ByteString -> Hosts -> Bool
hasName name hosts = Map.member name $ namenum hosts
hasAddr :: SockAddr -> Hosts -> Bool
hasAddr addr hosts = Map.member addr $ addrnum hosts
scrubName f line = line'
where
(x,ign) = L.break (=='#') line
ws = L.groupBy ( (==EQ) `oo` comparing isSpace) x
where oo = (.) . (.)
(a,ws') = splitAt 2 ws
ws'' = f ws'
line' = if null ws'' then "# " <> line
else L.concat (a ++ ws'') <> ign
assignName addr name hosts = assignName0 False addr name hosts
assignName0 iscannon addr name hosts = hosts'
where
ns = Map.lookup name (namenum hosts)
a = Map.lookup addr (addrnum hosts)
hosts' = do
if (== Just True) $ elem <$> a <*> ns
then hosts -- address already has name, nothing to do
else
let hosts0 = -- remove name if it's present
maybe hosts (removeName hosts) ns
hosts1 = -- insert name, or add new line
maybe (newLine hosts0) (appendName hosts0) a
in hosts1
removeName hosts nums = hosts
{ namenum = Map.delete name (namenum hosts)
, numline = foldl' scrub (numline hosts) nums
}
where scrub m num = Map.adjust (scrubName $ filter (/=name)) num m
appendName hosts num = hosts
{ numline = Map.adjust (scrubName f) num (numline hosts)
, namenum = Map.alter (cons num) name (namenum hosts)
}
where f ws = if iscannon
then [name, " "] ++ ws
else let rs = reverse ws
(sp,rs') = span (L.any isSpace) rs
in reverse $ sp ++ [name," "] ++ rs'
cons v xs = Just $ maybe [v] (v:) xs
newLine hosts = hosts
{ lineCount = cnt
, numline = Map.insert cnt line $ numline hosts
, addrnum = Map.insert addr cnt $ addrnum hosts
, namenum = Map.alter (cons cnt) name $ namenum hosts
}
where cnt = lineCount hosts + 1
line = L.pack (inet_ntop addr) <> " " <> name
cons v xs = Just $ maybe [v] (v:) xs
assignNewName addr name hosts =
if hasName name hosts then hosts
else assignName0 True addr name hosts
-- Returns a list of bytestrings intended to show the
-- differences between the two host databases. It is
-- assumed that no lines are deleted, only altered or
-- appended.
diff :: Hosts -> Hosts -> [L.ByteString]
diff as bs = cs
where
[as',bs'] = map (L.lines . Hosts.encode) [as,bs]
ext xs = map Just xs ++ repeat Nothing
ds = takeWhile (isJust . uncurry mplus) $ zip (ext as') (ext bs')
es = filter (uncurry (/=)) ds
cs = do
(a,b) <- es
[a,b] <- return $ map maybeToList [a,b]
fmap ("- " <>) a ++ fmap ("+ " <>) b
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