servant/servant/src/Servant/API/Alternative.hs

{-# LANGUAGE CPP                #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveFoldable     #-}
{-# LANGUAGE DeriveFunctor      #-}
{-# LANGUAGE DeriveTraversable  #-}
{-# LANGUAGE TypeOperators      #-}
{-# OPTIONS_HADDOCK not-home    #-}
module Servant.API.Alternative ((:<|>)(..)) where

import           Data.Semigroup
                 (Semigroup (..))
import           Data.Typeable
                 (Typeable)
import           Prelude ()
import           Prelude.Compat

-- | Union of two APIs, first takes precedence in case of overlap.
--
-- Example:
--
-- >>> :{
--type MyApi = "books" :> Get '[JSON] [Book] -- GET /books
--        :<|> "books" :> ReqBody '[JSON] Book :> Post '[JSON] () -- POST /books
-- :}
data a :<|> b = a :<|> b
    deriving (Typeable, Eq, Show, Functor, Traversable, Foldable, Bounded)
infixr 3 :<|>

instance (Semigroup a, Semigroup b) => Semigroup (a :<|> b) where
    (a :<|> b) <> (a' :<|> b') = (a <> a') :<|> (b <> b')

instance (Monoid a, Monoid b) => Monoid (a :<|> b) where
    mempty = mempty :<|> mempty
    (a :<|> b) `mappend` (a' :<|> b') = (a `mappend` a') :<|> (b `mappend` b')

-- $setup
-- >>> import Servant.API
-- >>> import Data.Aeson
-- >>> import Data.Text
-- >>> data Book
-- >>> instance ToJSON Book where { toJSON = undefined }