module Network.DNS.Internal where

import Data.Maybe
import Data.IP

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

data TYPE = A | AAAA | NS | TXT | MX | UNKNOWN deriving (Eq, Show, Read)

rrDB :: [(TYPE, Int)]
rrDB = [
    (A,     1)
  , (NS,    2)
  , (MX,   15)
  , (TXT,  16)
  , (AAAA, 28)
  ]

rookup                  :: (Eq b) => b -> [(a,b)] -> Maybe a
rookup _    []          =  Nothing
rookup  key ((x,y):xys)
  | key == y          =  Just x
  | otherwise         =  rookup key xys

intToType :: Int -> TYPE
intToType n = maybe UNKNOWN id $ rookup n rrDB
typeToInt :: TYPE -> Int
typeToInt t = maybe 0 id $ lookup t rrDB

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

data QorR = QR_Query | QR_Response deriving (Eq, Show)

data OPCODE = OP_STD | OP_INV | OP_SSR deriving (Eq, Show, Enum)

data RCODE = NoErr | FormatErr | ServFail | NameErr | NotImpl | Refused deriving (Eq, Show, Enum)

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

type Domain = String

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

data Question = Question {
    qname  :: Domain
  , qtype  :: TYPE
  } deriving (Eq, Show)

makeQuestion :: Domain -> TYPE -> Question
makeQuestion dom typ = Question dom typ

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

data ResourceRecord = ResourceRecord {
    rrname :: Domain
  , rrtype :: TYPE
  , rrttl  :: Int
  , rdlen  :: Int
  , rdata  :: RDATA
  } deriving (Eq, Show)

data RDATA = RD_NS Domain | RD_A IPv4 | RD_AAAA IPv6 | RD_OTH [Int] deriving (Eq, Show)

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

data DNSFlags = DNSFlags {
    qOrR         :: QorR
  , opcode       :: OPCODE
  , authAnswer   :: Bool
  , trunCation   :: Bool
  , recDesired   :: Bool
  , recAvailable :: Bool
  , rcode        :: RCODE
  } deriving (Eq, Show)

data DNSHeader = DNSHeader {
    identifier :: Int
  , flags      :: DNSFlags
  , qdCount    :: Int
  , anCount    :: Int
  , nsCount    :: Int
  , arCount    :: Int
  } deriving (Eq, Show)

data DNSFormat = DNSFormat {
    header     :: DNSHeader
  , question   :: [Question]
  , answer     :: [ResourceRecord]
  , authority  :: [ResourceRecord]
  , additional :: [ResourceRecord]
  } deriving (Eq, Show)

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

defaultQuery :: DNSFormat
defaultQuery = DNSFormat {
    header = DNSHeader {
       identifier = 0
     , flags = undefined
     , qdCount = 0
     , anCount = 0
     , nsCount = 0
     , arCount = 0
     }
  , question   = []
  , answer     = []
  , authority  = []
  , additional = []
  }