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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE NoImplicitPrelude #-}
-- Integer-based identifier.
module Biz.Id
( Id (..),
mk,
untag,
)
where
import Alpha
import Data.Aeson (FromJSON (..), ToJSON (..))
import Data.Binary (Binary)
import Data.Data (Data)
newtype Id entity = Id Int
deriving (Eq, Ord, Show, Generic, Typeable, Data)
mk :: proxy entity -> Int -> Id entity
mk _ = Id
untag :: Id entity -> Int
untag (Id i) = i
instance Hashable (Id entity)
instance Binary (Id entity)
instance Enum (Id entity) where
toEnum n = mk (Proxy :: Proxy entity) n
fromEnum = untag
instance NFData (Id entity) where
rnf (Id s) = rnf s
instance FromJSON (Id entity) where
parseJSON = fmap Id <. parseJSON
instance ToJSON (Id entity) where
toJSON = toJSON <. untag
-- this is just provided to satisfy Monoid, no reason to actually use it
instance Semigroup (Id entity) where
a <> b = mk (Proxy :: Proxy entity) <| untag a + untag b
instance Monoid (Id entity) where
mempty = mk (Proxy :: Proxy entity) 0
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