Servant Client structure example (for servant-0.8)

ApiClient.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TypeOperators #-}
module ApiClient where

import Data.Aeson
import Data.Proxy

import Network.HTTP.Client (Manager)
import Servant.API
import Servant.Client

type Bar = String
type Foo = String
type FooId = Int

type API
    = "bar" :> Get '[JSON] Bar
 :<|> "foo" :> Capture "foo_id" FooId :>
         ( "a" :> Get '[JSON] Foo
      :<|> "b" :> Get '[JSON] Foo )

data ApiClient = ApiClient
  { getBar :: Manager -> BaseUrl -> ClientM Bar
  , mkFooClient :: FooId -> FooClient
  }

data FooClient = FooClient
  { getFooA :: Manager -> BaseUrl -> ClientM Foo
  , getFooB :: Manager -> BaseUrl -> ClientM Foo
  }

mkClient :: ApiClient
mkClient = ApiClient{..}
  where
    apiClient = client (Proxy :: Proxy API) 
    getBar :<|> fooClient = apiClient

    mkFooClient fooId = FooClient{..}
      where
        getFooA :<|> getFooB = fooClient fooId