postgresql-query-2.3.0: src/Database/PostgreSQL/Query/TH/Common.hs

module Database.PostgreSQL.Query.TH.Common
  ( cName
  , cArgs
  , cFieldNames
  , lookupVNameErr
  ) where

import Prelude

import Language.Haskell.TH

-- | Return constructor name
cName :: (Monad m) => Con -> m Name
cName (NormalC n _) = return n
cName (RecC n _) = return n
cName _ = error "Constructor must be simple"

-- | Return count of constructor fields
cArgs :: (Monad m) => Con -> m Int
cArgs (NormalC _ n) = return $ length n
cArgs (RecC _ n) = return $ length n
cArgs _ = error "Constructor must be simple"

-- | Get field names from record constructor
cFieldNames :: Con -> [Name]
cFieldNames (RecC _ vst) = map (\(a, _, _) -> a) vst
cFieldNames _ = error "Constructor must be a record (product type with field names)"


lookupVNameErr :: String -> Q Name
lookupVNameErr name =
    lookupValueName name >>=
    maybe (error $ "could not find identifier: " ++ name)
          return