461 lines
17 KiB
Haskell
461 lines
17 KiB
Haskell
{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE InstanceSigs #-}
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{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE TypeOperators #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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-- | This module provides 'client' which can automatically generate
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-- querying functions for each endpoint just from the type representing your
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-- API.
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module Servant.Client
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( client
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, HasClient(..)
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, ServantError(..)
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, module Servant.Common.BaseUrl
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) where
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import Control.Monad
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import Control.Monad.Trans.Either
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import Data.ByteString.Lazy (ByteString)
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import Data.List
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import Data.Proxy
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import Data.String.Conversions
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import Data.Text (unpack)
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import GHC.TypeLits
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import Network.HTTP.Client (Response)
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import Network.HTTP.Media
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import qualified Network.HTTP.Types as H
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import Servant.API
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import Servant.API.ContentTypes
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import Servant.Common.BaseUrl
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import Servant.Common.Req
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-- * Accessing APIs as a Client
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-- | 'client' allows you to produce operations to query an API from a client.
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--
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-- > type MyApi = "books" :> Get [Book] -- GET /books
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-- > :<|> "books" :> ReqBody Book :> Post Book -- POST /books
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getAllBooks :: BaseUrl -> EitherT String IO [Book]
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-- > postNewBook :: Book -> BaseUrl -> EitherT String IO Book
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-- > (getAllBooks :<|> postNewBook) = client myApi
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client :: HasClient layout => Proxy layout -> Client layout
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client p = clientWithRoute p defReq
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-- | This class lets us define how each API combinator
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-- influences the creation of an HTTP request. It's mostly
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-- an internal class, you can just use 'client'.
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class HasClient layout where
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type Client layout :: *
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clientWithRoute :: Proxy layout -> Req -> Client layout
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-- | A client querying function for @a ':<|>' b@ will actually hand you
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-- one function for querying @a@ and another one for querying @b@,
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-- stitching them together with ':<|>', which really is just like a pair.
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--
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-- > type MyApi = "books" :> Get [Book] -- GET /books
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-- > :<|> "books" :> ReqBody Book :> Post Book -- POST /books
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getAllBooks :: BaseUrl -> EitherT String IO [Book]
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-- > postNewBook :: Book -> BaseUrl -> EitherT String IO Book
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-- > (getAllBooks :<|> postNewBook) = client myApi
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instance (HasClient a, HasClient b) => HasClient (a :<|> b) where
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type Client (a :<|> b) = Client a :<|> Client b
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clientWithRoute Proxy req =
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clientWithRoute (Proxy :: Proxy a) req :<|>
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clientWithRoute (Proxy :: Proxy b) req
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-- | If you use a 'Capture' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument of the type specified by your 'Capture'.
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-- That function will take care of inserting a textual representation
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-- of this value at the right place in the request path.
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--
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-- You can control how values for this type are turned into
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-- text by specifying a 'ToText' instance for your type.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> Capture "isbn" Text :> Get Book
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBook :: Text -> BaseUrl -> EitherT String IO Book
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-- > getBook = client myApi
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-- > -- then you can just use "getBook" to query that endpoint
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instance (KnownSymbol capture, ToText a, HasClient sublayout)
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=> HasClient (Capture capture a :> sublayout) where
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type Client (Capture capture a :> sublayout) =
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a -> Client sublayout
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clientWithRoute Proxy req val =
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clientWithRoute (Proxy :: Proxy sublayout) $
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appendToPath p req
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where p = unpack (toText val)
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-- | If you have a 'Delete' endpoint in your API, the client
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-- side querying function that is created when calling 'client'
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-- will just require an argument that specifies the scheme, host
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-- and port to send the request to.
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instance HasClient Delete where
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type Client Delete = BaseUrl -> EitherT ServantError IO ()
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clientWithRoute Proxy req host =
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void $ performRequest H.methodDelete req (`elem` [200, 202, 204]) host
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-- | If you have a 'Get' endpoint in your API, the client
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-- side querying function that is created when calling 'client'
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-- will just require an argument that specifies the scheme, host
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-- and port to send the request to.
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instance (MimeUnrender ct result) => HasClient (Get (ct ': cts) result) where
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type Client (Get (ct ': cts) result) = BaseUrl -> EitherT ServantError IO result
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clientWithRoute Proxy req host =
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performRequestCT (Proxy :: Proxy ct) H.methodGet req [200, 203] host
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-- | If you use a 'Header' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument of the type specified by your 'Header',
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-- wrapped in Maybe.
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--
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-- That function will take care of encoding this argument as Text
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-- in the request headers.
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--
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-- All you need is for your type to have a 'ToText' instance.
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--
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-- Example:
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--
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-- > newtype Referer = Referer Text
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-- > deriving (Eq, Show, FromText, ToText)
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-- >
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-- > -- GET /view-my-referer
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-- > type MyApi = "view-my-referer" :> Header "Referer" Referer :> Get Referer
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > viewReferer :: Maybe Referer -> BaseUrl -> EitherT String IO Book
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-- > viewReferer = client myApi
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-- > -- then you can just use "viewRefer" to query that endpoint
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-- > -- specifying Nothing or Just "http://haskell.org/" as arguments
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instance (KnownSymbol sym, ToText a, HasClient sublayout)
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=> HasClient (Header sym a :> sublayout) where
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type Client (Header sym a :> sublayout) =
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Maybe a -> Client sublayout
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clientWithRoute Proxy req mval =
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clientWithRoute (Proxy :: Proxy sublayout) $
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maybe req (\value -> addHeader hname value req) mval
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where hname = symbolVal (Proxy :: Proxy sym)
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-- | If you have a 'Post' endpoint in your API, the client
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-- side querying function that is created when calling 'client'
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-- will just require an argument that specifies the scheme, host
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-- and port to send the request to.
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instance (MimeUnrender ct a) => HasClient (Post (ct ': cts) a) where
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type Client (Post (ct ': cts) a) = BaseUrl -> EitherT ServantError IO a
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clientWithRoute Proxy req uri =
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performRequestCT (Proxy :: Proxy ct) H.methodPost req [200,201] uri
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-- | If you have a 'Put' endpoint in your API, the client
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-- side querying function that is created when calling 'client'
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-- will just require an argument that specifies the scheme, host
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-- and port to send the request to.
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instance (MimeUnrender ct a) => HasClient (Put (ct ': cts) a) where
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type Client (Put (ct ': cts) a) = BaseUrl -> EitherT ServantError IO a
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clientWithRoute Proxy req host =
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performRequestCT (Proxy :: Proxy ct) H.methodPut req [200,201] host
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-- | If you use a 'QueryParam' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument of the type specified by your 'QueryParam',
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-- enclosed in Maybe.
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--
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-- If you give Nothing, nothing will be added to the query string.
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--
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-- If you give a non-'Nothing' value, this function will take care
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-- of inserting a textual representation of this value in the query string.
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--
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-- You can control how values for your type are turned into
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-- text by specifying a 'ToText' instance for your type.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> QueryParam "author" Text :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooksBy :: Maybe Text -> BaseUrl -> EitherT String IO [Book]
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-- > getBooksBy = client myApi
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-- > -- then you can just use "getBooksBy" to query that endpoint.
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-- > -- 'getBooksBy Nothing' for all books
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-- > -- 'getBooksBy (Just "Isaac Asimov")' to get all books by Isaac Asimov
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instance (KnownSymbol sym, ToText a, HasClient sublayout)
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=> HasClient (QueryParam sym a :> sublayout) where
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type Client (QueryParam sym a :> sublayout) =
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Maybe a -> Client sublayout
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-- if mparam = Nothing, we don't add it to the query string
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clientWithRoute Proxy req mparam =
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clientWithRoute (Proxy :: Proxy sublayout) $
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maybe req (flip (appendToQueryString pname) req . Just) mparamText
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where pname = cs pname'
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pname' = symbolVal (Proxy :: Proxy sym)
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mparamText = fmap toText mparam
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-- | If you use a 'QueryParams' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument, a list of values of the type specified
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-- by your 'QueryParams'.
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--
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-- If you give an empty list, nothing will be added to the query string.
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--
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-- Otherwise, this function will take care
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-- of inserting a textual representation of your values in the query string,
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-- under the same query string parameter name.
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--
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-- You can control how values for your type are turned into
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-- text by specifying a 'ToText' instance for your type.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> QueryParams "authors" Text :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooksBy :: [Text] -> BaseUrl -> EitherT String IO [Book]
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-- > getBooksBy = client myApi
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-- > -- then you can just use "getBooksBy" to query that endpoint.
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-- > -- 'getBooksBy []' for all books
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-- > -- 'getBooksBy ["Isaac Asimov", "Robert A. Heinlein"]'
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-- > -- to get all books by Asimov and Heinlein
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instance (KnownSymbol sym, ToText a, HasClient sublayout)
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=> HasClient (QueryParams sym a :> sublayout) where
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type Client (QueryParams sym a :> sublayout) =
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[a] -> Client sublayout
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clientWithRoute Proxy req paramlist =
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clientWithRoute (Proxy :: Proxy sublayout) $
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foldl' (\ req' -> maybe req' (flip (appendToQueryString pname) req' . Just)) req paramlist'
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where pname = cs pname'
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pname' = symbolVal (Proxy :: Proxy sym)
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paramlist' = map (Just . toText) paramlist
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-- | If you use a 'QueryFlag' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional 'Bool' argument.
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--
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-- If you give 'False', nothing will be added to the query string.
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--
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-- Otherwise, this function will insert a value-less query string
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-- parameter under the name associated to your 'QueryFlag'.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> QueryFlag "published" :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooks :: Bool -> BaseUrl -> EitherT String IO [Book]
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-- > getBooks = client myApi
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-- > -- then you can just use "getBooks" to query that endpoint.
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-- > -- 'getBooksBy False' for all books
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-- > -- 'getBooksBy True' to only get _already published_ books
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instance (KnownSymbol sym, HasClient sublayout)
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=> HasClient (QueryFlag sym :> sublayout) where
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type Client (QueryFlag sym :> sublayout) =
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Bool -> Client sublayout
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clientWithRoute Proxy req flag =
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clientWithRoute (Proxy :: Proxy sublayout) $
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if flag
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then appendToQueryString paramname Nothing req
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else req
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where paramname = cs $ symbolVal (Proxy :: Proxy sym)
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-- | If you use a 'MatrixParam' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument of the type specified by your 'MatrixParam',
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-- enclosed in Maybe.
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--
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-- If you give Nothing, nothing will be added to the query string.
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--
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-- If you give a non-'Nothing' value, this function will take care
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-- of inserting a textual representation of this value in the query string.
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--
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-- You can control how values for your type are turned into
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-- text by specifying a 'ToText' instance for your type.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> MatrixParam "author" Text :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooksBy :: Maybe Text -> BaseUrl -> EitherT String IO [Book]
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-- > getBooksBy = client myApi
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-- > -- then you can just use "getBooksBy" to query that endpoint.
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-- > -- 'getBooksBy Nothing' for all books
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-- > -- 'getBooksBy (Just "Isaac Asimov")' to get all books by Isaac Asimov
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instance (KnownSymbol sym, ToText a, HasClient sublayout)
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=> HasClient (MatrixParam sym a :> sublayout) where
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type Client (MatrixParam sym a :> sublayout) =
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Maybe a -> Client sublayout
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-- if mparam = Nothing, we don't add it to the query string
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clientWithRoute Proxy req mparam =
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clientWithRoute (Proxy :: Proxy sublayout) $
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maybe req (flip (appendToMatrixParams pname . Just) req) mparamText
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where pname = symbolVal (Proxy :: Proxy sym)
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mparamText = fmap (cs . toText) mparam
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-- | If you use a 'MatrixParams' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take an
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-- additional argument, a list of values of the type specified by your
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-- 'MatrixParams'.
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--
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-- If you give an empty list, nothing will be added to the query string.
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--
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-- Otherwise, this function will take care of inserting a textual
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-- representation of your values in the path segment string, under the
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-- same matrix string parameter name.
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--
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-- You can control how values for your type are turned into text by
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-- specifying a 'ToText' instance for your type.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> MatrixParams "authors" Text :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooksBy :: [Text] -> BaseUrl -> EitherT String IO [Book]
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-- > getBooksBy = client myApi
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-- > -- then you can just use "getBooksBy" to query that endpoint.
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-- > -- 'getBooksBy []' for all books
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-- > -- 'getBooksBy ["Isaac Asimov", "Robert A. Heinlein"]'
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-- > -- to get all books by Asimov and Heinlein
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instance (KnownSymbol sym, ToText a, HasClient sublayout)
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=> HasClient (MatrixParams sym a :> sublayout) where
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type Client (MatrixParams sym a :> sublayout) =
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[a] -> Client sublayout
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clientWithRoute Proxy req paramlist =
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clientWithRoute (Proxy :: Proxy sublayout) $
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foldl' (\ req' value -> maybe req' (flip (appendToMatrixParams pname) req' . Just . cs) value) req paramlist'
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where pname = cs pname'
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pname' = symbolVal (Proxy :: Proxy sym)
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paramlist' = map (Just . toText) paramlist
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-- | If you use a 'MatrixFlag' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take an
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-- additional 'Bool' argument.
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--
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-- If you give 'False', nothing will be added to the path segment.
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--
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-- Otherwise, this function will insert a value-less matrix parameter
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-- under the name associated to your 'MatrixFlag'.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> MatrixFlag "published" :> Get [Book]
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > getBooks :: Bool -> BaseUrl -> EitherT String IO [Book]
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-- > getBooks = client myApi
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-- > -- then you can just use "getBooks" to query that endpoint.
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-- > -- 'getBooksBy False' for all books
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-- > -- 'getBooksBy True' to only get _already published_ books
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instance (KnownSymbol sym, HasClient sublayout)
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=> HasClient (MatrixFlag sym :> sublayout) where
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type Client (MatrixFlag sym :> sublayout) =
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Bool -> Client sublayout
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clientWithRoute Proxy req flag =
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clientWithRoute (Proxy :: Proxy sublayout) $
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if flag
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then appendToMatrixParams paramname Nothing req
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else req
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where paramname = cs $ symbolVal (Proxy :: Proxy sym)
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-- | Pick a 'Method' and specify where the server you want to query is. You get
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-- back the full `Response`.
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instance HasClient Raw where
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type Client Raw = H.Method -> BaseUrl -> EitherT ServantError IO (Int, ByteString, MediaType, Response ByteString)
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clientWithRoute :: Proxy Raw -> Req -> Client Raw
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clientWithRoute Proxy req httpMethod host = do
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performRequest httpMethod req (const True) host
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-- | If you use a 'ReqBody' in one of your endpoints in your API,
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-- the corresponding querying function will automatically take
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-- an additional argument of the type specified by your 'ReqBody'.
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-- That function will take care of encoding this argument as JSON and
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-- of using it as the request body.
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--
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-- All you need is for your type to have a 'ToJSON' instance.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> ReqBody Book :> Post Book
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-- >
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-- > myApi :: Proxy MyApi
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-- > myApi = Proxy
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-- >
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-- > addBook :: Book -> BaseUrl -> EitherT String IO Book
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-- > addBook = client myApi
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-- > -- then you can just use "addBook" to query that endpoint
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instance (MimeRender ct a, HasClient sublayout)
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=> HasClient (ReqBody (ct ': cts) a :> sublayout) where
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type Client (ReqBody (ct ': cts) a :> sublayout) =
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a -> Client sublayout
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clientWithRoute Proxy req body =
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clientWithRoute (Proxy :: Proxy sublayout) $ do
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let ctProxy = Proxy :: Proxy ct
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setRQBody (toByteString ctProxy body) (contentType ctProxy) req
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-- | Make the querying function append @path@ to the request path.
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instance (KnownSymbol path, HasClient sublayout) => HasClient (path :> sublayout) where
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type Client (path :> sublayout) = Client sublayout
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clientWithRoute Proxy req =
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clientWithRoute (Proxy :: Proxy sublayout) $
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appendToPath p req
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where p = symbolVal (Proxy :: Proxy path)
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