servant/servant-client/src/Servant/Client.hs
2016-04-05 17:51:25 +08:00

446 lines
16 KiB
Haskell

{-# LANGUAGE CPP #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE InstanceSigs #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
#include "overlapping-compat.h"
-- | This module provides 'client' which can automatically generate
-- querying functions for each endpoint just from the type representing your
-- API.
module Servant.Client
( AuthClientData
, AuthenticateReq(..)
, client
, HasClient(..)
, ClientM
, mkAuthenticateReq
, ServantError(..)
, module Servant.Common.BaseUrl
) where
#if !MIN_VERSION_base(4,8,0)
import Control.Applicative ((<$>))
#endif
import Data.ByteString.Lazy (ByteString)
import Data.List
import Data.Proxy
import Data.String.Conversions
import Data.Text (unpack)
import GHC.TypeLits
import Network.HTTP.Client (Manager, Response)
import Network.HTTP.Media
import qualified Network.HTTP.Types as H
import qualified Network.HTTP.Types.Header as HTTP
import Servant.API
import Servant.Client.Experimental.Auth
import Servant.Common.BaseUrl
import Servant.Common.BasicAuth
import Servant.Common.Req
-- * Accessing APIs as a Client
-- | 'client' allows you to produce operations to query an API from a client.
--
-- > type MyApi = "books" :> Get '[JSON] [Book] -- GET /books
-- > :<|> "books" :> ReqBody '[JSON] Book :> Post '[JSON] Book -- POST /books
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getAllBooks :: Manager -> BaseUrl -> ClientM [Book]
-- > postNewBook :: Book -> Manager -> BaseUrl -> ClientM Book
-- > (getAllBooks :<|> postNewBook) = client myApi
client :: HasClient layout => Proxy layout -> Client layout
client p = clientWithRoute p defReq
-- | This class lets us define how each API combinator
-- influences the creation of an HTTP request. It's mostly
-- an internal class, you can just use 'client'.
class HasClient layout where
type Client layout :: *
clientWithRoute :: Proxy layout -> Req -> Client layout
-- | A client querying function for @a ':<|>' b@ will actually hand you
-- one function for querying @a@ and another one for querying @b@,
-- stitching them together with ':<|>', which really is just like a pair.
--
-- > type MyApi = "books" :> Get '[JSON] [Book] -- GET /books
-- > :<|> "books" :> ReqBody '[JSON] Book :> Post Book -- POST /books
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getAllBooks :: Manager -> BaseUrl -> ClientM [Book]
-- > postNewBook :: Book -> Manager -> BaseUrl -> ClientM Book
-- > (getAllBooks :<|> postNewBook) = client myApi
instance (HasClient a, HasClient b) => HasClient (a :<|> b) where
type Client (a :<|> b) = Client a :<|> Client b
clientWithRoute Proxy req =
clientWithRoute (Proxy :: Proxy a) req :<|>
clientWithRoute (Proxy :: Proxy b) req
-- | If you use a 'Capture' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional argument of the type specified by your 'Capture'.
-- That function will take care of inserting a textual representation
-- of this value at the right place in the request path.
--
-- You can control how values for this type are turned into
-- text by specifying a 'ToHttpApiData' instance for your type.
--
-- Example:
--
-- > type MyApi = "books" :> Capture "isbn" Text :> Get '[JSON] Book
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getBook :: Text -> Manager -> BaseUrl -> ClientM Book
-- > getBook = client myApi
-- > -- then you can just use "getBook" to query that endpoint
instance (KnownSymbol capture, ToHttpApiData a, HasClient sublayout)
=> HasClient (Capture capture a :> sublayout) where
type Client (Capture capture a :> sublayout) =
a -> Client sublayout
clientWithRoute Proxy req val =
clientWithRoute (Proxy :: Proxy sublayout)
(appendToPath p req)
where p = unpack (toUrlPiece val)
instance OVERLAPPABLE_
-- Note [Non-Empty Content Types]
(MimeUnrender ct a, ReflectMethod method, cts' ~ (ct ': cts)
) => HasClient (Verb method status cts' a) where
type Client (Verb method status cts' a) = Manager -> BaseUrl -> ClientM a
clientWithRoute Proxy req manager baseurl =
snd <$> performRequestCT (Proxy :: Proxy ct) method req manager baseurl
where method = reflectMethod (Proxy :: Proxy method)
instance OVERLAPPING_
(ReflectMethod method) => HasClient (Verb method status cts NoContent) where
type Client (Verb method status cts NoContent)
= Manager -> BaseUrl -> ClientM NoContent
clientWithRoute Proxy req manager baseurl =
performRequestNoBody method req manager baseurl >> return NoContent
where method = reflectMethod (Proxy :: Proxy method)
instance OVERLAPPING_
-- Note [Non-Empty Content Types]
( MimeUnrender ct a, BuildHeadersTo ls, ReflectMethod method, cts' ~ (ct ': cts)
) => HasClient (Verb method status cts' (Headers ls a)) where
type Client (Verb method status cts' (Headers ls a))
= Manager -> BaseUrl -> ClientM (Headers ls a)
clientWithRoute Proxy req manager baseurl = do
let method = reflectMethod (Proxy :: Proxy method)
(hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) method req manager baseurl
return $ Headers { getResponse = resp
, getHeadersHList = buildHeadersTo hdrs
}
instance OVERLAPPING_
( BuildHeadersTo ls, ReflectMethod method
) => HasClient (Verb method status cts (Headers ls NoContent)) where
type Client (Verb method status cts (Headers ls NoContent))
= Manager -> BaseUrl -> ClientM (Headers ls NoContent)
clientWithRoute Proxy req manager baseurl = do
let method = reflectMethod (Proxy :: Proxy method)
hdrs <- performRequestNoBody method req manager baseurl
return $ Headers { getResponse = NoContent
, getHeadersHList = buildHeadersTo hdrs
}
-- | If you use a 'Header' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional argument of the type specified by your 'Header',
-- wrapped in Maybe.
--
-- That function will take care of encoding this argument as Text
-- in the request headers.
--
-- All you need is for your type to have a 'ToHttpApiData' instance.
--
-- Example:
--
-- > newtype Referer = Referer { referrer :: Text }
-- > deriving (Eq, Show, Generic, ToHttpApiData)
-- >
-- > -- GET /view-my-referer
-- > type MyApi = "view-my-referer" :> Header "Referer" Referer :> Get '[JSON] Referer
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > viewReferer :: Maybe Referer -> Manager -> BaseUrl -> ClientM Book
-- > viewReferer = client myApi
-- > -- then you can just use "viewRefer" to query that endpoint
-- > -- specifying Nothing or e.g Just "http://haskell.org/" as arguments
instance (KnownSymbol sym, ToHttpApiData a, HasClient sublayout)
=> HasClient (Header sym a :> sublayout) where
type Client (Header sym a :> sublayout) =
Maybe a -> Client sublayout
clientWithRoute Proxy req mval =
clientWithRoute (Proxy :: Proxy sublayout)
(maybe req
(\value -> Servant.Common.Req.addHeader hname value req)
mval
)
where hname = symbolVal (Proxy :: Proxy sym)
-- | Using a 'HttpVersion' combinator in your API doesn't affect the client
-- functions.
instance HasClient sublayout
=> HasClient (HttpVersion :> sublayout) where
type Client (HttpVersion :> sublayout) =
Client sublayout
clientWithRoute Proxy =
clientWithRoute (Proxy :: Proxy sublayout)
-- | If you use a 'QueryParam' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional argument of the type specified by your 'QueryParam',
-- enclosed in Maybe.
--
-- If you give Nothing, nothing will be added to the query string.
--
-- If you give a non-'Nothing' value, this function will take care
-- of inserting a textual representation of this value in the query string.
--
-- You can control how values for your type are turned into
-- text by specifying a 'ToHttpApiData' instance for your type.
--
-- Example:
--
-- > type MyApi = "books" :> QueryParam "author" Text :> Get '[JSON] [Book]
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getBooksBy :: Maybe Text -> Manager -> BaseUrl -> ClientM [Book]
-- > getBooksBy = client myApi
-- > -- then you can just use "getBooksBy" to query that endpoint.
-- > -- 'getBooksBy Nothing' for all books
-- > -- 'getBooksBy (Just "Isaac Asimov")' to get all books by Isaac Asimov
instance (KnownSymbol sym, ToHttpApiData a, HasClient sublayout)
=> HasClient (QueryParam sym a :> sublayout) where
type Client (QueryParam sym a :> sublayout) =
Maybe a -> Client sublayout
-- if mparam = Nothing, we don't add it to the query string
clientWithRoute Proxy req mparam =
clientWithRoute (Proxy :: Proxy sublayout)
(maybe req
(flip (appendToQueryString pname) req . Just)
mparamText
)
where pname = cs pname'
pname' = symbolVal (Proxy :: Proxy sym)
mparamText = fmap toQueryParam mparam
-- | If you use a 'QueryParams' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional argument, a list of values of the type specified
-- by your 'QueryParams'.
--
-- If you give an empty list, nothing will be added to the query string.
--
-- Otherwise, this function will take care
-- of inserting a textual representation of your values in the query string,
-- under the same query string parameter name.
--
-- You can control how values for your type are turned into
-- text by specifying a 'ToHttpApiData' instance for your type.
--
-- Example:
--
-- > type MyApi = "books" :> QueryParams "authors" Text :> Get '[JSON] [Book]
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getBooksBy :: [Text] -> Manager -> BaseUrl -> ClientM [Book]
-- > getBooksBy = client myApi
-- > -- then you can just use "getBooksBy" to query that endpoint.
-- > -- 'getBooksBy []' for all books
-- > -- 'getBooksBy ["Isaac Asimov", "Robert A. Heinlein"]'
-- > -- to get all books by Asimov and Heinlein
instance (KnownSymbol sym, ToHttpApiData a, HasClient sublayout)
=> HasClient (QueryParams sym a :> sublayout) where
type Client (QueryParams sym a :> sublayout) =
[a] -> Client sublayout
clientWithRoute Proxy req paramlist =
clientWithRoute (Proxy :: Proxy sublayout)
(foldl' (\ req' -> maybe req' (flip (appendToQueryString pname) req' . Just))
req
paramlist'
)
where pname = cs pname'
pname' = symbolVal (Proxy :: Proxy sym)
paramlist' = map (Just . toQueryParam) paramlist
-- | If you use a 'QueryFlag' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional 'Bool' argument.
--
-- If you give 'False', nothing will be added to the query string.
--
-- Otherwise, this function will insert a value-less query string
-- parameter under the name associated to your 'QueryFlag'.
--
-- Example:
--
-- > type MyApi = "books" :> QueryFlag "published" :> Get '[JSON] [Book]
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > getBooks :: Bool -> Manager -> BaseUrl -> ClientM [Book]
-- > getBooks = client myApi
-- > -- then you can just use "getBooks" to query that endpoint.
-- > -- 'getBooksBy False' for all books
-- > -- 'getBooksBy True' to only get _already published_ books
instance (KnownSymbol sym, HasClient sublayout)
=> HasClient (QueryFlag sym :> sublayout) where
type Client (QueryFlag sym :> sublayout) =
Bool -> Client sublayout
clientWithRoute Proxy req flag =
clientWithRoute (Proxy :: Proxy sublayout)
(if flag
then appendToQueryString paramname Nothing req
else req
)
where paramname = cs $ symbolVal (Proxy :: Proxy sym)
-- | Pick a 'Method' and specify where the server you want to query is. You get
-- back the full `Response`.
instance HasClient Raw where
type Client Raw
= H.Method -> Manager -> BaseUrl -> ClientM (Int, ByteString, MediaType, [HTTP.Header], Response ByteString)
clientWithRoute :: Proxy Raw -> Req -> Client Raw
clientWithRoute Proxy req httpMethod = do
performRequest httpMethod req
-- | If you use a 'ReqBody' in one of your endpoints in your API,
-- the corresponding querying function will automatically take
-- an additional argument of the type specified by your 'ReqBody'.
-- That function will take care of encoding this argument as JSON and
-- of using it as the request body.
--
-- All you need is for your type to have a 'ToJSON' instance.
--
-- Example:
--
-- > type MyApi = "books" :> ReqBody '[JSON] Book :> Post '[JSON] Book
-- >
-- > myApi :: Proxy MyApi
-- > myApi = Proxy
-- >
-- > addBook :: Book -> Manager -> BaseUrl -> ClientM Book
-- > addBook = client myApi
-- > -- then you can just use "addBook" to query that endpoint
instance (MimeRender ct a, HasClient sublayout)
=> HasClient (ReqBody (ct ': cts) a :> sublayout) where
type Client (ReqBody (ct ': cts) a :> sublayout) =
a -> Client sublayout
clientWithRoute Proxy req body =
clientWithRoute (Proxy :: Proxy sublayout)
(let ctProxy = Proxy :: Proxy ct
in setRQBody (mimeRender ctProxy body)
(contentType ctProxy)
req
)
-- | Make the querying function append @path@ to the request path.
instance (KnownSymbol path, HasClient sublayout) => HasClient (path :> sublayout) where
type Client (path :> sublayout) = Client sublayout
clientWithRoute Proxy req =
clientWithRoute (Proxy :: Proxy sublayout)
(appendToPath p req)
where p = symbolVal (Proxy :: Proxy path)
instance HasClient api => HasClient (Vault :> api) where
type Client (Vault :> api) = Client api
clientWithRoute Proxy req =
clientWithRoute (Proxy :: Proxy api) req
instance HasClient api => HasClient (RemoteHost :> api) where
type Client (RemoteHost :> api) = Client api
clientWithRoute Proxy req =
clientWithRoute (Proxy :: Proxy api) req
instance HasClient api => HasClient (IsSecure :> api) where
type Client (IsSecure :> api) = Client api
clientWithRoute Proxy req =
clientWithRoute (Proxy :: Proxy api) req
instance HasClient subapi =>
HasClient (WithNamedContext name context subapi) where
type Client (WithNamedContext name context subapi) = Client subapi
clientWithRoute Proxy = clientWithRoute (Proxy :: Proxy subapi)
instance ( HasClient api
) => HasClient (AuthProtect tag :> api) where
type Client (AuthProtect tag :> api)
= AuthenticateReq (AuthProtect tag) -> Client api
clientWithRoute Proxy req (AuthenticateReq (val,func)) =
clientWithRoute (Proxy :: Proxy api) (func val req)
-- * Basic Authentication
instance HasClient api => HasClient (BasicAuth realm usr :> api) where
type Client (BasicAuth realm usr :> api) = BasicAuthData -> Client api
clientWithRoute Proxy req val =
clientWithRoute (Proxy :: Proxy api) (basicAuthReq val req)
{- Note [Non-Empty Content Types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Rather than have
instance (..., cts' ~ (ct ': cts)) => ... cts' ...
It may seem to make more sense to have:
instance (...) => ... (ct ': cts) ...
But this means that if another instance exists that does *not* require
non-empty lists, but is otherwise more specific, no instance will be overall
more specific. This in turn generally means adding yet another instance (one
for empty and one for non-empty lists).
-}