{-# LANGUAGE CPP #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE InstanceSigs #-} {-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE UndecidableInstances #-} #if !MIN_VERSION_base(4,8,0) {-# LANGUAGE OverlappingInstances #-} #endif -- | This module provides 'client' which can automatically generate -- querying functions for each endpoint just from the type representing your -- API. module Servant.Client ( client , HasClient(..) , ServantError(..) , module Servant.Common.BaseUrl ) where #if !MIN_VERSION_base(4,8,0) import Control.Applicative ((<$>)) #endif import Control.Monad import Control.Monad.Trans.Either 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 (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.Common.BaseUrl 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 Book -- POST /books -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getAllBooks :: EitherT String IO [Book] -- > postNewBook :: Book -> EitherT String IO Book -- > (getAllBooks :<|> postNewBook) = client myApi host -- > where host = BaseUrl Http "localhost" 8080 client :: HasClient layout => Proxy layout -> BaseUrl -> Client layout client p baseurl = clientWithRoute p defReq baseurl -- | 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 -> BaseUrl -> Client layout {-type Client layout = 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 :: EitherT String IO [Book] -- > postNewBook :: Book -> EitherT String IO Book -- > (getAllBooks :<|> postNewBook) = client myApi host -- > where host = BaseUrl Http "localhost" 8080 instance (HasClient a, HasClient b) => HasClient (a :<|> b) where type Client (a :<|> b) = Client a :<|> Client b clientWithRoute Proxy req baseurl = clientWithRoute (Proxy :: Proxy a) req baseurl :<|> clientWithRoute (Proxy :: Proxy b) req baseurl -- | 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 'ToText' instance for your type. -- -- Example: -- -- > type MyApi = "books" :> Capture "isbn" Text :> Get '[JSON] Book -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBook :: Text -> EitherT String IO Book -- > getBook = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- then you can just use "getBook" to query that endpoint instance (KnownSymbol capture, ToText a, HasClient sublayout) => HasClient (Capture capture a :> sublayout) where type Client (Capture capture a :> sublayout) = a -> Client sublayout clientWithRoute Proxy req baseurl val = clientWithRoute (Proxy :: Proxy sublayout) (appendToPath p req) baseurl where p = unpack (toText val) -- | If you have a 'Delete' endpoint in your API, the client -- side querying function that is created when calling 'client' -- will just require an argument that specifies the scheme, host -- and port to send the request to. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPABLE #-} #endif -- See https://downloads.haskell.org/~ghc/7.8.2/docs/html/users_guide/type-class-extensions.html#undecidable-instances (MimeUnrender ct a, cts' ~ (ct ': cts)) => HasClient (Delete cts' a) where type Client (Delete cts' a) = EitherT ServantError IO a clientWithRoute Proxy req baseurl = snd <$> performRequestCT (Proxy :: Proxy ct) H.methodDelete req [200, 202] baseurl -- | If you have a 'Delete xs ()' endpoint, the client expects a 204 No Content -- HTTP header. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif HasClient (Delete cts ()) where type Client (Delete cts ()) = EitherT ServantError IO () clientWithRoute Proxy req baseurl = void $ performRequestNoBody H.methodDelete req [204] baseurl -- | If you have a 'Delete xs (Headers ls x)' endpoint, the client expects the -- corresponding headers. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif -- See https://downloads.haskell.org/~ghc/7.8.2/docs/html/users_guide/type-class-extensions.html#undecidable-instances ( MimeUnrender ct a, BuildHeadersTo ls, cts' ~ (ct ': cts) ) => HasClient (Delete cts' (Headers ls a)) where type Client (Delete cts' (Headers ls a)) = EitherT ServantError IO (Headers ls a) clientWithRoute Proxy req baseurl = do (hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) H.methodDelete req [200, 202] baseurl return $ Headers { getResponse = resp , getHeadersHList = buildHeadersTo hdrs } -- | If you have a 'Get' endpoint in your API, the client -- side querying function that is created when calling 'client' -- will just require an argument that specifies the scheme, host -- and port to send the request to. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPABLE #-} #endif (MimeUnrender ct result) => HasClient (Get (ct ': cts) result) where type Client (Get (ct ': cts) result) = EitherT ServantError IO result clientWithRoute Proxy req baseurl = snd <$> performRequestCT (Proxy :: Proxy ct) H.methodGet req [200, 203] baseurl -- | If you have a 'Get xs ()' endpoint, the client expects a 204 No Content -- HTTP status. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif HasClient (Get (ct ': cts) ()) where type Client (Get (ct ': cts) ()) = EitherT ServantError IO () clientWithRoute Proxy req baseurl = performRequestNoBody H.methodGet req [204] baseurl -- | If you have a 'Get xs (Headers ls x)' endpoint, the client expects the -- corresponding headers. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif ( MimeUnrender ct a, BuildHeadersTo ls ) => HasClient (Get (ct ': cts) (Headers ls a)) where type Client (Get (ct ': cts) (Headers ls a)) = EitherT ServantError IO (Headers ls a) clientWithRoute Proxy req baseurl = do (hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) H.methodGet req [200, 203, 204] baseurl return $ Headers { getResponse = resp , 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 'ToText' instance. -- -- Example: -- -- > newtype Referer = Referer { referrer :: Text } -- > deriving (Eq, Show, Generic, FromText, ToText) -- > -- > -- GET /view-my-referer -- > type MyApi = "view-my-referer" :> Header "Referer" Referer :> Get '[JSON] Referer -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > viewReferer :: Maybe Referer -> EitherT String IO Book -- > viewReferer = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- then you can just use "viewRefer" to query that endpoint -- > -- specifying Nothing or e.g Just "http://haskell.org/" as arguments instance (KnownSymbol sym, ToText a, HasClient sublayout) => HasClient (Header sym a :> sublayout) where type Client (Header sym a :> sublayout) = Maybe a -> Client sublayout clientWithRoute Proxy req baseurl mval = clientWithRoute (Proxy :: Proxy sublayout) (maybe req (\value -> Servant.Common.Req.addHeader hname value req) mval ) baseurl where hname = symbolVal (Proxy :: Proxy sym) -- | If you have a 'Post' endpoint in your API, the client -- side querying function that is created when calling 'client' -- will just require an argument that specifies the scheme, host -- and port to send the request to. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPABLE #-} #endif (MimeUnrender ct a) => HasClient (Post (ct ': cts) a) where type Client (Post (ct ': cts) a) = EitherT ServantError IO a clientWithRoute Proxy req baseurl = snd <$> performRequestCT (Proxy :: Proxy ct) H.methodPost req [200,201] baseurl -- | If you have a 'Post xs ()' endpoint, the client expects a 204 No Content -- HTTP header. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif HasClient (Post (ct ': cts) ()) where type Client (Post (ct ': cts) ()) = EitherT ServantError IO () clientWithRoute Proxy req baseurl = void $ performRequestNoBody H.methodPost req [204] baseurl -- | If you have a 'Post xs (Headers ls x)' endpoint, the client expects the -- corresponding headers. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif ( MimeUnrender ct a, BuildHeadersTo ls ) => HasClient (Post (ct ': cts) (Headers ls a)) where type Client (Post (ct ': cts) (Headers ls a)) = EitherT ServantError IO (Headers ls a) clientWithRoute Proxy req baseurl = do (hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) H.methodPost req [200, 201] baseurl return $ Headers { getResponse = resp , getHeadersHList = buildHeadersTo hdrs } -- | If you have a 'Put' endpoint in your API, the client -- side querying function that is created when calling 'client' -- will just require an argument that specifies the scheme, host -- and port to send the request to. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPABLE #-} #endif (MimeUnrender ct a) => HasClient (Put (ct ': cts) a) where type Client (Put (ct ': cts) a) = EitherT ServantError IO a clientWithRoute Proxy req baseurl = snd <$> performRequestCT (Proxy :: Proxy ct) H.methodPut req [200,201] baseurl -- | If you have a 'Put xs ()' endpoint, the client expects a 204 No Content -- HTTP header. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif HasClient (Put (ct ': cts) ()) where type Client (Put (ct ': cts) ()) = EitherT ServantError IO () clientWithRoute Proxy req baseurl = void $ performRequestNoBody H.methodPut req [204] baseurl -- | If you have a 'Put xs (Headers ls x)' endpoint, the client expects the -- corresponding headers. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif ( MimeUnrender ct a, BuildHeadersTo ls ) => HasClient (Put (ct ': cts) (Headers ls a)) where type Client (Put (ct ': cts) (Headers ls a)) = EitherT ServantError IO (Headers ls a) clientWithRoute Proxy req baseurl = do (hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) H.methodPut req [200, 201] baseurl return $ Headers { getResponse = resp , getHeadersHList = buildHeadersTo hdrs } -- | If you have a 'Patch' endpoint in your API, the client -- side querying function that is created when calling 'client' -- will just require an argument that specifies the scheme, host -- and port to send the request to. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPABLE #-} #endif (MimeUnrender ct a) => HasClient (Patch (ct ': cts) a) where type Client (Patch (ct ': cts) a) = EitherT ServantError IO a clientWithRoute Proxy req baseurl = snd <$> performRequestCT (Proxy :: Proxy ct) H.methodPatch req [200,201] baseurl -- | If you have a 'Patch xs ()' endpoint, the client expects a 204 No Content -- HTTP header. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif HasClient (Patch (ct ': cts) ()) where type Client (Patch (ct ': cts) ()) = EitherT ServantError IO () clientWithRoute Proxy req baseurl = void $ performRequestNoBody H.methodPatch req [204] baseurl -- | If you have a 'Patch xs (Headers ls x)' endpoint, the client expects the -- corresponding headers. instance #if MIN_VERSION_base(4,8,0) {-# OVERLAPPING #-} #endif ( MimeUnrender ct a, BuildHeadersTo ls ) => HasClient (Patch (ct ': cts) (Headers ls a)) where type Client (Patch (ct ': cts) (Headers ls a)) = EitherT ServantError IO (Headers ls a) clientWithRoute Proxy req baseurl = do (hdrs, resp) <- performRequestCT (Proxy :: Proxy ct) H.methodPatch req [200, 201, 204] baseurl return $ Headers { getResponse = resp , getHeadersHList = buildHeadersTo hdrs } -- | 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 'ToText' instance for your type. -- -- Example: -- -- > type MyApi = "books" :> QueryParam "author" Text :> Get '[JSON] [Book] -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBooksBy :: Maybe Text -> EitherT String IO [Book] -- > getBooksBy = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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, ToText 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 baseurl mparam = clientWithRoute (Proxy :: Proxy sublayout) (maybe req (flip (appendToQueryString pname) req . Just) mparamText ) baseurl where pname = cs pname' pname' = symbolVal (Proxy :: Proxy sym) mparamText = fmap toText 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 'ToText' instance for your type. -- -- Example: -- -- > type MyApi = "books" :> QueryParams "authors" Text :> Get '[JSON] [Book] -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBooksBy :: [Text] -> EitherT String IO [Book] -- > getBooksBy = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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, ToText a, HasClient sublayout) => HasClient (QueryParams sym a :> sublayout) where type Client (QueryParams sym a :> sublayout) = [a] -> Client sublayout clientWithRoute Proxy req baseurl paramlist = clientWithRoute (Proxy :: Proxy sublayout) (foldl' (\ req' -> maybe req' (flip (appendToQueryString pname) req' . Just)) req paramlist' ) baseurl where pname = cs pname' pname' = symbolVal (Proxy :: Proxy sym) paramlist' = map (Just . toText) 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 -> EitherT String IO [Book] -- > getBooks = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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 baseurl flag = clientWithRoute (Proxy :: Proxy sublayout) (if flag then appendToQueryString paramname Nothing req else req ) baseurl where paramname = cs $ symbolVal (Proxy :: Proxy sym) -- | If you use a 'MatrixParam' in one of your endpoints in your API, -- the corresponding querying function will automatically take -- an additional argument of the type specified by your 'MatrixParam', -- 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 'ToText' instance for your type. -- -- Example: -- -- > type MyApi = "books" :> MatrixParam "author" Text :> Get '[JSON] [Book] -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBooksBy :: Maybe Text -> EitherT String IO [Book] -- > getBooksBy = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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, ToText a, HasClient sublayout) => HasClient (MatrixParam sym a :> sublayout) where type Client (MatrixParam sym a :> sublayout) = Maybe a -> Client sublayout -- if mparam = Nothing, we don't add it to the query string clientWithRoute Proxy req baseurl mparam = clientWithRoute (Proxy :: Proxy sublayout) (maybe req (flip (appendToMatrixParams pname . Just) req) mparamText ) baseurl where pname = symbolVal (Proxy :: Proxy sym) mparamText = fmap (cs . toText) mparam -- | If you use a 'MatrixParams' 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 -- 'MatrixParams'. -- -- 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 path segment string, under the -- same matrix string parameter name. -- -- You can control how values for your type are turned into text by -- specifying a 'ToText' instance for your type. -- -- Example: -- -- > type MyApi = "books" :> MatrixParams "authors" Text :> Get '[JSON] [Book] -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBooksBy :: [Text] -> EitherT String IO [Book] -- > getBooksBy = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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, ToText a, HasClient sublayout) => HasClient (MatrixParams sym a :> sublayout) where type Client (MatrixParams sym a :> sublayout) = [a] -> Client sublayout clientWithRoute Proxy req baseurl paramlist = clientWithRoute (Proxy :: Proxy sublayout) (foldl' (\ req' value -> maybe req' (flip (appendToMatrixParams pname) req' . Just . cs) value) req paramlist' ) baseurl where pname = cs pname' pname' = symbolVal (Proxy :: Proxy sym) paramlist' = map (Just . toText) paramlist -- | If you use a 'MatrixFlag' 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 path segment. -- -- Otherwise, this function will insert a value-less matrix parameter -- under the name associated to your 'MatrixFlag'. -- -- Example: -- -- > type MyApi = "books" :> MatrixFlag "published" :> Get '[JSON] [Book] -- > -- > myApi :: Proxy MyApi -- > myApi = Proxy -- > -- > getBooks :: Bool -> EitherT String IO [Book] -- > getBooks = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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 (MatrixFlag sym :> sublayout) where type Client (MatrixFlag sym :> sublayout) = Bool -> Client sublayout clientWithRoute Proxy req baseurl flag = clientWithRoute (Proxy :: Proxy sublayout) (if flag then appendToMatrixParams paramname Nothing req else req ) baseurl 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 -> EitherT ServantError IO (Int, ByteString, MediaType, [HTTP.Header], Response ByteString) clientWithRoute :: Proxy Raw -> Req -> BaseUrl -> Client Raw clientWithRoute Proxy req baseurl httpMethod = do performRequest httpMethod req (const True) baseurl -- | 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 -> EitherT String IO Book -- > addBook = client myApi host -- > where host = BaseUrl Http "localhost" 8080 -- > -- 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 baseurl body = clientWithRoute (Proxy :: Proxy sublayout) (let ctProxy = Proxy :: Proxy ct in setRQBody (mimeRender ctProxy body) (contentType ctProxy) req ) baseurl -- | 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 baseurl = clientWithRoute (Proxy :: Proxy sublayout) (appendToPath p req) baseurl where p = symbolVal (Proxy :: Proxy path)