{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric      #-}
module Data.IP.Addr where

import Control.Monad
import Data.Bits
import Data.Char
import Data.Data (Data)
import Data.List (foldl', intersperse)
import Data.String
import Data.Typeable (Typeable)
import Data.Word
import Network.Socket
import Numeric (showHex, showInt)
import System.ByteOrder
import Text.Appar.String
import GHC.Enum (succError,predError)
import GHC.Generics

----------------------------------------------------------------

{-|
  A unified IP data for 'IPv4' and 'IPv6'.
  To create this, use the data constructors. Or use 'read' @\"192.0.2.1\"@ :: 'IP', for example. Also, @\"192.0.2.1\"@ can be used as literal with OverloadedStrings.

>>> (read "192.0.2.1" :: IP) == IPv4 (read "192.0.2.1" :: IPv4)
True
>>> (read "2001:db8:00:00:00:00:00:01" :: IP) == IPv6 (read "2001:db8:00:00:00:00:00:01" :: IPv6)
True
-}

data IP = IPv4 { ipv4 :: IPv4 }
        | IPv6 { ipv6 :: IPv6 }
        deriving (Data,Generic,Typeable)

{-|
  Equality over IP addresses. Correctly compare IPv4 and IPv4-embedded-in-IPv6 addresses.

>>> (read "2001:db8:00:00:00:00:00:01" :: IP) == (read "2001:db8:00:00:00:00:00:01" :: IP)
True
>>> (read "2001:db8:00:00:00:00:00:01" :: IP) == (read "2001:db8:00:00:00:00:00:05" :: IP)
False
>>> (read "127.0.0.1" :: IP) == (read "127.0.0.1" :: IP)
True
>>> (read "127.0.0.1" :: IP) == (read "10.0.0.1" :: IP)
False
>>> (read "::ffff:127.0.0.1" :: IP) == (read "127.0.0.1" :: IP)
True
>>> (read "::ffff:127.0.0.1" :: IP) == (read "127.0.0.9" :: IP)
False
>>> (read "::ffff:127.0.0.1" :: IP) >= (read "127.0.0.1" :: IP)
True
>>> (read "::ffff:127.0.0.1" :: IP) <= (read "127.0.0.1" :: IP)
True
-}
instance Eq IP where
  (IPv4 ip1) == (IPv4 ip2) = ip1 == ip2
  (IPv6 ip1) == (IPv6 ip2) = ip1 == ip2
  (IPv4 ip1) == (IPv6 ip2) = ipv4ToIPv6 ip1 == ip2
  (IPv6 ip1) == (IPv4 ip2) = ip1 == ipv4ToIPv6 ip2


instance Ord IP where
  (IPv4 ip1) `compare` (IPv4 ip2) = ip1 `compare` ip2
  (IPv6 ip1) `compare` (IPv6 ip2) = ip1 `compare` ip2
  (IPv4 ip1) `compare` (IPv6 ip2) = ipv4ToIPv6 ip1 `compare` ip2
  (IPv6 ip1) `compare` (IPv4 ip2) = ip1 `compare` ipv4ToIPv6 ip2

instance Show IP where
    show (IPv4 ip) = show ip
    show (IPv6 ip) = show ip

----------------------------------------------------------------

-- This is host byte order
type IPv4Addr = Word32
type IPv6Addr = (Word32,Word32,Word32,Word32)

{-|
  The abstract data type to express an IPv4 address.
  To create this, use 'toIPv4'. Or use 'read' @\"192.0.2.1\"@ :: 'IPv4', for example. Also, @\"192.0.2.1\"@ can be used as literal with OverloadedStrings.

>>> read "192.0.2.1" :: IPv4
192.0.2.1
-}
newtype IPv4 = IP4 IPv4Addr
  deriving (Eq, Ord, Bounded, Data, Generic, Typeable)

{-|
  The abstract data type to express an IPv6 address.
  To create this, use 'toIPv6'. Or use 'read' @\"2001:DB8::1\"@ :: 'IPv6', for example. Also, @\"2001:DB8::1\"@ can be used as literal with OverloadedStrings.

>>> read "2001:db8:00:00:00:00:00:01" :: IPv6
2001:db8::1
>>> read "2001:db8:11e:c00::101" :: IPv6
2001:db8:11e:c00::101
>>> read "2001:db8:11e:c00:aa:bb:192.0.2.1" :: IPv6
2001:db8:11e:c00:aa:bb:c000:201
>>> read "2001:db8::192.0.2.1" :: IPv6
2001:db8::c000:201
>>> read "0::ffff:192.0.2.1" :: IPv6
::ffff:192.0.2.1
>>> read "0::0:c000:201" :: IPv6
::192.0.2.1
>>> read "::0.0.0.1" :: IPv6
::1
-}
newtype IPv6 = IP6 IPv6Addr
  deriving (Eq, Ord, Bounded, Data, Generic, Typeable)


----------------------------------------------------------------
--
-- Enum
--

instance Enum IPv4 where
    fromEnum (IP4 a) = fromEnum a
    toEnum = IP4 . toEnum

instance Enum IPv6 where
    -- fromEnum and toEnum are not really useful, but I defined them anyway
    fromEnum (IP6 (a,b,c,d)) = let a' = fromEnum a `shift` 96
                                   b' = fromEnum b `shift` 64
                                   c' = fromEnum c `shift` 32
                                   d' = fromEnum d
                               in a' .|. b' .|. c' .|. d'
    toEnum i = let a = toEnum (i `shiftR` 96 .&. 0xffffffff)
                   b = toEnum (i `shiftR` 64 .&. 0xffffffff)
                   c = toEnum (i `shiftR` 32 .&. 0xffffffff)
                   d = toEnum (i             .&. 0xffffffff)
               in IP6 (a,b,c,d)

    succ (IP6 (0xffffffff,0xffffffff,0xffffffff,0xffffffff)) = succError "IPv6"
    succ (IP6 (a,         0xffffffff,0xffffffff,0xffffffff)) = IP6 (succ a,0,0,0)
    succ (IP6 (a,                  b,0xffffffff,0xffffffff)) = IP6 (a,succ b,0,0)
    succ (IP6 (a,                  b,         c,0xffffffff)) = IP6 (a,b,succ c,0)
    succ (IP6 (a,                  b,         c,         d)) = IP6 (a,b,c,succ d)

    pred (IP6 (0,0,0,0)) = predError "IPv6"
    pred (IP6 (a,0,0,0)) = IP6 (pred a, 0xffffffff, 0xffffffff, 0xffffffff)
    pred (IP6 (a,b,0,0)) = IP6 (     a,     pred b, 0xffffffff, 0xffffffff)
    pred (IP6 (a,b,c,0)) = IP6 (     a,          b,     pred c, 0xffffffff)
    pred (IP6 (a,b,c,d)) = IP6 (     a,          b,          c,     pred d)

    enumFrom ip = ip:gen ip
        where gen i = let i' = succ i in i':gen i'

    enumFromTo ip ip' = ip:gen ip
        where gen i
                | i == ip' = []
                | otherwise = let i' = succ i in i':gen i'

    -- These two are implemented via the integer enum instance.
    -- A more correct implementation would essentially require
    -- implementing instance Num IPv6, which isn't something
    -- I wanna do. Another approach is to use Word128 to store
    -- an IPv6 address.
    enumFromThen ip ip' = fmap integerToIP6 [ip6ToInteger ip, ip6ToInteger ip' ..]
    enumFromThenTo ip inc fin = fmap integerToIP6 [ip6ToInteger ip, ip6ToInteger inc .. ip6ToInteger fin]

instance Enum IP where
    fromEnum (IPv4 ip) = fromEnum ip
    fromEnum (IPv6 ip) = fromEnum ip

    -- Because Int cannot hold an IPv6 anyway
    toEnum = IPv4 . toEnum

    succ (IPv4 ip) = IPv4 $ succ ip
    succ (IPv6 ip) = IPv6 $ succ ip

    pred (IPv4 ip) = IPv4 $ pred ip
    pred (IPv6 ip) = IPv6 $ pred ip

    enumFrom (IPv4 ip) = fmap IPv4 $ enumFrom ip
    enumFrom (IPv6 ip) = fmap IPv6 $ enumFrom ip

    enumFromTo (IPv4 ip) (IPv4 ip') = fmap IPv4 $ enumFromTo ip ip'
    enumFromTo (IPv6 ip) (IPv6 ip') = fmap IPv6 $ enumFromTo ip ip'
    enumFromTo _ _ = error "enumFromTo: Incompatible IP families"

    enumFromThen (IPv4 ip) (IPv4 ip') = fmap IPv4 $ enumFromThen ip ip'
    enumFromThen (IPv6 ip) (IPv6 ip') = fmap IPv6 $ enumFromThen ip ip'
    enumFromThen _ _ = error "enumFromThen: Incompatible IP families"

    enumFromThenTo (IPv4 ip) (IPv4 inc) (IPv4 fin) = fmap IPv4 $ enumFromThenTo ip inc fin
    enumFromThenTo (IPv6 ip) (IPv6 inc) (IPv6 fin) = fmap IPv6 $ enumFromThenTo ip inc fin
    enumFromThenTo _ _ _ = error "enumFromThenTo: Incompatible IP families"

ip6ToInteger :: IPv6 -> Integer
ip6ToInteger (IP6 (a,b,c,d)) = let a' = word32ToInteger a `shift` 96
                                   b' = word32ToInteger b `shift` 64
                                   c' = word32ToInteger c `shift` 32
                                   d' = word32ToInteger d
                               in a' .|. b' .|. c' .|. d'
    where
        word32ToInteger :: Word32 -> Integer
        word32ToInteger = toEnum . fromEnum

integerToIP6 :: Integer -> IPv6
integerToIP6 i = let a = integerToWord32 (i `shiftR` 96 .&. 0xffffffff)
                     b = integerToWord32 (i `shiftR` 64 .&. 0xffffffff)
                     c = integerToWord32 (i `shiftR` 32 .&. 0xffffffff)
                     d = integerToWord32 (i             .&. 0xffffffff)
                 in IP6 (a,b,c,d)
    where
        integerToWord32 :: Integer -> Word32
        integerToWord32 = toEnum . fromEnum

----------------------------------------------------------------
--
-- Show
--

instance Show IPv4 where
    show ip = showIPv4 ip ""

instance Show IPv6 where
    show ip = showIPv6 ip ""

-- | Show an IPv4 address in the dot-decimal notation.
showIPv4 :: IPv4 -> ShowS
showIPv4 = foldr1 (.) . intersperse (showChar '.') . map showInt . fromIPv4

-- | Show an IPv6 address in the most appropriate notation, based on recommended
-- representation proposed by <http://tools.ietf.org/html/rfc5952 RFC 5952>.
--
-- /The implementation is completely compatible with the current implementation
-- of the `inet_ntop` function in glibc./
showIPv6 :: IPv6 -> ShowS
showIPv6 ip@(IP6 (a1,a2,a3,a4))
  -- IPv4-Mapped IPv6 Address
  | a1 == 0 && a2 == 0 && a3 == 0xffff =
      showString "::ffff:" . showIPv4 (IP4 a4)
  -- IPv4-Compatible IPv6 Address (exclude IPRange ::/112)
  | a1 == 0 && a2 == 0 && a3 == 0 && a4 >= 0x10000 =
      showString "::" . showIPv4 (IP4 a4)
  -- length of longest run > 1, replace it with "::"
  | end - begin > 1 =
      showFields prefix . showString "::" . showFields suffix
  -- length of longest run <= 1, don't use "::"
  | otherwise =
      showFields fields
  where
    fields = fromIPv6 ip
    showFields = foldr (.) id . intersperse (showChar ':') . map showHex
    prefix = take begin fields  -- fields before "::"
    suffix = drop end fields    -- fields after "::"
    begin = end + diff          -- the longest run of zeros
    (diff, end) = minimum $
        scanl (\c i -> if i == 0 then c - 1 else 0) 0 fields `zip` [0..]

----------------------------------------------------------------
--
-- IntToIP
--

{-|
  The 'toIPv4' function takes a list of 'Int' and returns 'IPv4'.

>>> toIPv4 [192,0,2,1]
192.0.2.1
-}
toIPv4 :: [Int] -> IPv4
toIPv4 = IP4 . toWord32
  where
    toWord32 [a1,a2,a3,a4] = fromIntegral $ shift a1 24 + shift a2 16 + shift a3 8 + a4
    toWord32 _             = error "toWord32"

{-|
  The 'toIPv6' function takes a list of 'Int' and returns 'IPv6'.

>>> toIPv6 [0x2001,0xDB8,0,0,0,0,0,1]
2001:db8::1
-}
toIPv6 :: [Int] -> IPv6
toIPv6 ad = IP6 (x1,x2,x3,x4)
  where
    [x1,x2,x3,x4] = map toWord32 $ split2 ad
    split2 [] = []
    split2 x  = take 2 x : split2 (drop 2 x)
    toWord32 [a1,a2] = fromIntegral $ shift a1 16 + a2
    toWord32 _       = error "toWord32"

{-|
  The 'toIPv6b' function takes a list of 'Int'
  where each member repserents a single byte and returns 'IPv6'.

>>> toIPv6b [0x20,0x01,0xD,0xB8,0,0,0,0,0,0,0,0,0,0,0,1]
2001:db8::1
-}
toIPv6b :: [Int] -> IPv6
toIPv6b ad = IP6 (x1,x2,x3,x4)
  where
    [x1,x2,x3,x4] = map toWord32 $ split4 ad
    split4 [] = []
    split4 x  = take 4 x : split4 (drop 4 x)
    toWord32 [a1,a2,a3,a4] = fromIntegral $ shift a1 24 + shift a2 16 + shift a3 8 + a4
    toWord32 _       = error "toWord32"

----------------------------------------------------------------
--
-- IPToInt
--

{-|
  The 'fromIPv4' function converts 'IPv4' to a list of 'Int'.

>>> fromIPv4 (toIPv4 [192,0,2,1])
[192,0,2,1]
-}
fromIPv4 :: IPv4 -> [Int]
fromIPv4 (IP4 w) = map (\n -> fromEnum $ (w `shiftR` n) .&. 0xff) [0o30, 0o20, 0o10, 0o00]

{-|
  The 'toIPv6' function converts 'IPv6' to a list of 'Int'.

>>> fromIPv6 (toIPv6 [0x2001,0xDB8,0,0,0,0,0,1])
[8193,3512,0,0,0,0,0,1]
-}
fromIPv6 :: IPv6 -> [Int]
fromIPv6 (IP6 (w1, w2, w3, w4)) = map fromEnum (concatMap split [w1,w2,w3,w4])
  where
    split :: Word32 -> [Word32]
    split n = [n `shiftR` 0x10 .&. 0xffff, n .&. 0xffff]

{-|
  The 'fromIPv6b' function converts 'IPv6' to a list of 'Int'
  where each member represents a single byte.

>>> fromIPv6b (toIPv6b [0x20,0x01,0xD,0xB8,0,0,0,0,0,0,0,0,0,0,0,1])
[32,1,13,184,0,0,0,0,0,0,0,0,0,0,0,1]
-}
fromIPv6b :: IPv6 -> [Int]
fromIPv6b (IP6 (w1, w2, w3, w4)) = map fromEnum (concatMap split [w1,w2,w3,w4])
  where
    split n = fmap (\s -> n `shiftR` s .&. 0xff) [24,16,8,0]

----------------------------------------------------------------
--
-- Read
--

instance Read IP where
    readsPrec _ = parseIP

instance Read IPv4 where
    readsPrec _ = parseIPv4

instance Read IPv6 where
    readsPrec _ = parseIPv6

parseIP :: String -> [(IP,String)]
parseIP cs = case runParser ip4 cs of
    (Just ip,rest) -> [(IPv4 ip,rest)]
    (Nothing,_) -> case runParser ip6 cs of
        (Just ip,rest) -> [(IPv6 ip,rest)]
        (Nothing,_) -> []

parseIPv4 :: String -> [(IPv4,String)]
parseIPv4 cs = case runParser ip4 cs of
    (Nothing,_)    -> []
    (Just a4,rest) -> [(a4,rest)]

parseIPv6 :: String -> [(IPv6,String)]
parseIPv6 cs = case runParser ip6 cs of
    (Nothing,_)    -> []
    (Just a6,rest) -> [(a6,rest)]

----------------------------------------------------------------
--
-- IsString
--

instance IsString IP where
    fromString = read

instance IsString IPv4 where
    fromString = read

instance IsString IPv6 where
    fromString = read

----------------------------------------------------------------
--
-- IPv4 Parser
--

dig :: Parser Int
dig = 0 <$ char '0'
  <|> toInt <$> oneOf ['1'..'9'] <*> many digit
  where
    toInt n ns = foldl' (\x y -> x * 10 + y) 0 . map digitToInt $ n : ns

ip4 :: Parser IPv4
ip4 = skipSpaces >> toIPv4 <$> ip4'

ip4' :: Parser [Int]
ip4' = do
    as <- dig `sepBy1` char '.'
    check as
    return as
  where
    test errmsg adr = when (adr < 0 || 255 < adr) (fail errmsg)
    check as = do
        let errmsg = "IPv4 adddress"
        when (length as /= 4) (fail errmsg)
        mapM_ (test errmsg) as

skipSpaces :: Parser ()
skipSpaces = void $ many (char ' ')

----------------------------------------------------------------
--
-- IPv6 Parser (RFC 4291)
--

hex :: Parser Int
hex = do
    ns <- some hexDigit
    check ns
    let ms = map digitToInt ns
        val = foldl' (\x y -> x * 16 + y) 0 ms
    return val
  where
    check ns = when (length ns > 4) (fail "IPv6 address -- more than 4 hex")

colon2 :: Parser ()
colon2 = void $ string "::"

format :: [Int] -> [Int] -> Parser [Int]
format bs1 bs2 = do
    let len1 = length bs1
        len2 = length bs2
    when (len1 > 7) (fail "IPv6 address1")
    when (len2 > 7) (fail "IPv6 address2")
    let len = 8 - len1 - len2
    when (len <= 0) (fail "IPv6 address3")
    let spring = replicate len 0
    return $ bs1 ++ spring ++ bs2

ip6 :: Parser IPv6
ip6 = skipSpaces >> toIPv6 <$> ip6'

ip6' :: Parser [Int]
ip6' = ip4Embedded
   <|> do colon2
          bs <- option [] hexcolon
          format [] bs
   <|> try (do rs <- hexcolon
               check rs
               return rs)
   <|> do bs1 <- hexcolon2
          bs2 <- option [] hexcolon
          format bs1 bs2
  where
    hexcolon = hex `sepBy1` char ':'
    hexcolon2 = manyTill (hex <* char ':') (char ':')
    check bs = when (length bs /= 8) (fail "IPv6 address4")

ip4Embedded :: Parser [Int]
ip4Embedded = try (do colon2
                      bs <- beforeEmbedded
                      embedded <- ip4'
                      format [] (bs ++ ip4ToIp6 embedded))
              -- matches 2001:db8::192.0.2.1
          <|> try (do bs1 <- manyTill (try $ hex <* char ':') (char ':')
                      bs2 <- option [] beforeEmbedded
                      embedded <- ip4'
                      format bs1 (bs2 ++ ip4ToIp6 embedded))
              -- matches 2001:db8:11e:c00:aa:bb:192.0.2.1
          <|> try (do bs <- beforeEmbedded
                      embedded <- ip4'
                      let rs = bs ++ ip4ToIp6 embedded
                      check rs
                      return rs)
  where
    beforeEmbedded = many $ try $ hex <* char ':'
    ip4ToIp6 [a,b,c,d] = [ a `shiftL` 8 .|. b
                         , c `shiftL` 8 .|. d ]
    ip4ToIp6 _ = error "ip4ToIp6"
    check bs = when (length bs /= 8) (fail "IPv6 address4")

----------------------------------------------------------------
--
-- HostAddress and HostAddress6
--

-- | The 'fromHostAddress' function converts 'HostAddress' to 'IPv4'.
fromHostAddress :: HostAddress -> IPv4
fromHostAddress addr4
  | byteOrder == LittleEndian = IP4 $ fixByteOrder addr4
  | otherwise                 = IP4 addr4

-- | The 'toHostAddress' function converts 'IPv4' to 'HostAddress'.
toHostAddress :: IPv4 -> HostAddress
toHostAddress (IP4 addr4)
  | byteOrder == LittleEndian = fixByteOrder addr4
  | otherwise                 = addr4

-- | The 'fromHostAddress6' function converts 'HostAddress6' to 'IPv6'.
fromHostAddress6 :: HostAddress6 -> IPv6
fromHostAddress6 = IP6

-- | The 'toHostAddress6' function converts 'IPv6' to 'HostAddress6'.
toHostAddress6 :: IPv6 -> HostAddress6
toHostAddress6 (IP6 addr6) = addr6

fixByteOrder :: Word32 -> Word32
fixByteOrder s = d1 .|. d2 .|. d3 .|. d4
  where
    d1 = shiftL s 24
    d2 = shiftL s  8 .&. 0x00ff0000
    d3 = shiftR s  8 .&. 0x0000ff00
    d4 = shiftR s 24 .&. 0x000000ff

-- | Convert IPv4 address to IPv4-embedded-in-IPv6
ipv4ToIPv6 :: IPv4 -> IPv6
ipv4ToIPv6 ip = toIPv6b [0,0,0,0,0,0,0,0,0,0,0xff,0xff,i1,i2,i3,i4]
  where
    [i1,i2,i3,i4] = fromIPv4 ip