Utils.hs

module Database.Bolt.Extras.Utils
  (
    dummyId
  , union
  , currentLoc
  ) where

import           Data.List           (nub)
import qualified Data.Map.Strict     as M (union)
import           Database.Bolt       (Node (..))
import           Language.Haskell.TH (Exp (..), Lit (..), Loc (..), Q, location)
import           Text.Printf         (printf)


-- | 'dummyId' is used to load 'Node' and 'URelationship' into database,
-- because id from database is not known for such moment.
--
dummyId :: Int
dummyId = -1

-- | 'Node's can be merged. 'union' is useful when you have to store in one node
-- several labels and props from different classes.
--
union :: Node -> Node -> Node
(Node _ labels1 props1) `union` (Node _ labels2 props2) = Node dummyId
                                                               (nub $ labels1 ++ labels2)
                                                               (props1 `M.union` props2)

-- | 'currentLoc' shows module name and line where this expression is used.
--
currentLoc :: Q Exp
currentLoc = do
  loc <- location
  pure $ LitE $ StringL $ printf "%s:%d: " (loc_module loc) (fst $ loc_start loc)