userid-0.1.2.2: Data/UserId.hs

{-# LANGUAGE DeriveDataTypeable, DeriveGeneric, GeneralizedNewtypeDeriving, TemplateHaskell #-}
{- | This module provides a `UserId` type plus some useful instances for web development. -}
module Data.UserId where

import Control.Applicative ((<$>))
import Control.Lens        ((?=), (.=), (^.), (.~), makeLenses, view, set)
import Data.Aeson          (FromJSON(..), ToJSON(..), Result(..), fromJSON)
import Data.Data           (Data)
import Data.SafeCopy       (SafeCopy, base, deriveSafeCopy)
import Data.Typeable       (Typeable)
import GHC.Generics        (Generic)
import Text.Boomerang.TH   (makeBoomerangs)
import Web.Routes          (PathInfo(..))
import Web.Routes.TH       (derivePathInfo)

-- | a 'UserId' uniquely identifies a user.
newtype UserId = UserId { _unUserId :: Integer }
    deriving (Eq, Ord, Enum, Read, Show, Data, Typeable, Generic)
deriveSafeCopy 1 'base ''UserId
makeLenses ''UserId
makeBoomerangs ''UserId

instance ToJSON   UserId where toJSON (UserId i) = toJSON i
instance FromJSON UserId where parseJSON v = UserId <$> parseJSON v

instance PathInfo UserId where
    toPathSegments (UserId i) = toPathSegments i
    fromPathSegments = UserId <$> fromPathSegments

-- | get the next `UserId`
succUserId :: UserId -> UserId
succUserId (UserId i) = UserId (succ i)