NmcTransform.hs

module NmcTransform ( seedNmcDom
                    , descendNmcDom
                    ) where

import Prelude hiding (lookup, null)
import Data.ByteString.Lazy (ByteString)
import Data.Map.Lazy (Map, empty, lookup, delete, null, singleton
                     , foldrWithKey, insert, insertWith)
import Control.Monad (foldM)
import Data.Maybe (fromMaybe)
import Data.Aeson (decode)
import Data.Default.Class (def)

import NmcDom

-- | Perform query and return error string or parsed domain object
queryNmcDom ::
  (String -> IO (Either String ByteString)) -- ^ query operation action
  -> String                                 -- ^ key
  -> IO (Either String NmcDom)              -- ^ error string or domain
queryNmcDom queryOp key = do
  l <- queryOp key
  case l of
    Left estr -> return $ Left estr
    Right str -> case decode str :: Maybe NmcDom of
      Nothing  -> return $ Left $ "Unparseable value: " ++ (show str)
      Just dom -> return $ Right dom

-- | Try to fetch "delegate" or "import" object and merge them into the
--   base domain. Original "import" element is removed, but newly
--   merged data may contain new "import" or "delegate", so the objects
--   that are about to be merged are processed recursively until there
--   are no more "import" and "deletage" attributes (or the depth gauge
--   reaches zero).
mergeIncl ::
  (String -> IO (Either String ByteString)) -- ^ query operation action
  -> Int                                    -- ^ recursion counter
  -> NmcDom                                 -- ^ base domain
  -> IO (Either String NmcDom)              -- ^ result with merged import
mergeIncl queryOp depth base = do
  let
    mbase = mergeSelf base
    base' = mbase {domDelegate = Nothing, domImport = Nothing}
  -- print base
  if depth <= 0 then return $ Left "Nesting of imports is too deep"
    else case ((domDelegate mbase), (domImport mbase)) of
      (Nothing,  Nothing  ) -> return $ Right base'
      (Nothing,  Just keys) -> foldM mergeIncl1 (Right base') keys
      (Just key, _        ) -> mergeIncl1 (Right def) key
  where
    mergeIncl1 (Left  err) _   = return $ Left err -- can never happen
    mergeIncl1 (Right acc) key = do
      sub <- queryNmcDom queryOp key
      case sub of
        Left  err  -> return $ Left err
        Right sub' -> mergeIncl queryOp (depth - 1) $ sub' `merge` acc

-- | If there is an element in the map with key "", merge the contents
--   and remove this element. Do this recursively.
mergeSelf :: NmcDom -> NmcDom
mergeSelf base =
  let
    map   = domSubmap base
    base' = base {domSubmap = removeSelf map}
    removeSelf Nothing    = Nothing
    removeSelf (Just map) = if null map' then Nothing else Just map'
      where map' = delete "" map
  in
    case map of
      Nothing   -> base'
      Just map' ->
        case lookup "" map' of
          Nothing  -> base'
          Just sub -> (mergeSelf sub) `merge` base'
        -- recursion depth limited by the size of the record

-- | transfer some elements of `base` into `sub`, notably TLSA
propagate :: NmcDom -> NmcDom -> NmcDom
propagate base sub = sub `merge` (pickglobals base)
  where
    pickglobals dom = fromMaybe def (siftsubmap (siftsubmap taketlsa) dom)
    siftsubmap f dom =
      let
        sdmap = fromMaybe empty (domSubmap dom)
        sdmap' = foldrWithKey (\k x -> addifjust k (f x)) empty sdmap
        addifjust k mdom acc = case mdom of
          Nothing  -> acc
          Just dom -> insert k dom acc -- dups are impossible here
      in
        if null sdmap' then Nothing else Just $ def { domSubmap = Just sdmap'}
    taketlsa dom = case domTlsa dom of
      Nothing   -> Nothing
      Just tlsa -> case filter (\x -> tlsIncSubdoms x) tlsa of
        []    -> Nothing
        tlsa' -> Just $ def { domTlsa = Just tlsa' }

-- | Presence of some elements require removal of some others
normalizeDom :: NmcDom -> NmcDom
normalizeDom dom = foldr id dom [ translateNormalizer
                                , nsNormalizer
                                ]
  where
    nsNormalizer dom = case domNs dom of
      Nothing  -> dom
      Just ns  -> def { domNs = domNs dom, domEmail = domEmail dom }
    translateNormalizer dom = case domTranslate dom of
      Nothing  -> dom
      Just tr  -> dom { domSubmap = Nothing }

-- | Merge imports and Selfs and follow the maps tree to get dom
descendNmcDom ::
  (String -> IO (Either String ByteString)) -- ^ query operation action
  -> [String]                               -- ^ subdomain chain
  -> NmcDom                                 -- ^ base domain
  -> IO (Either String NmcDom)              -- ^ fully processed result
descendNmcDom queryOp subdom base = do
  base' <- mergeIncl queryOp 10 base
  case subdom of
    []   -> return $ fmap normalizeDom base'
    d:ds ->
      case base' of
        Left err     -> return base'
        Right base'' ->
          case domSubmap base'' of
            Nothing  -> return $ Right def
            Just map ->
              case lookup d map of
                Nothing  -> return $ Right def
                Just sub -> descendNmcDom queryOp ds $ propagate base'' sub

-- | Initial NmcDom populated with "import" only, suitable for "descend"
seedNmcDom ::
  String        -- ^ domain key (without namespace prefix)
  -> NmcDom     -- ^ resulting seed domain
seedNmcDom dn = def { domImport = Just (["d/" ++ dn])}