Add WordPress.com as an auth provider

Documentation at https://developer.wordpress.com/docs/wpcc/

example/Main.hs

@@ -46,6 +46,7 @@ import Yesod.Auth.OAuth2.Nylas
 import Yesod.Auth.OAuth2.Salesforce
 import Yesod.Auth.OAuth2.Slack
 import Yesod.Auth.OAuth2.Spotify
+import Yesod.Auth.OAuth2.WordPressDotCom
 import Yesod.Auth.OAuth2.Upcase
 
 data App = App
@@ -145,6 +146,7 @@ mkFoundation = do
         , loadPlugin oauth2Salesforce "SALES_FORCE"
         , loadPlugin oauth2Slack "SLACK"
         , loadPlugin (oauth2Spotify []) "SPOTIFY"
+        , loadPlugin oauth2WordPressDotCom "WORDPRESS_DOT_COM"
         , loadPlugin oauth2Upcase "UPCASE"
         ]
 

src/Yesod/Auth/OAuth2/WordPressDotCom.hs

@@ -0,0 +1,44 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Yesod.Auth.OAuth2.WordPressDotCom where
+
+import qualified Data.Text as T
+import Yesod.Auth.OAuth2.Prelude
+
+pluginName :: Text
+pluginName = "WordPress.com"
+
+newtype WpUser = WpUser Int
+
+instance FromJSON WpUser where
+    parseJSON = withObject "WpUser" $ \o -> WpUser
+        <$> o .: "ID"
+
+oauth2WordPressDotCom
+    :: ( YesodAuth m )
+    => Text -- client ID
+    -> Text -- client secret
+    -> AuthPlugin m
+oauth2WordPressDotCom clientId clientSecret =
+    authOAuth2 pluginName oauth2 $ \manager token -> do
+        (WpUser userId, userResponse) <-
+            authGetProfile pluginName manager token
+                "https://public-api.wordpress.com/rest/v1/me/"
+
+        pure Creds
+            { credsPlugin = pluginName
+            , credsIdent = T.pack $ show userId
+            , credsExtra = setExtra token userResponse
+            }
+
+  where
+    oauth2 = OAuth2
+        { oauthClientId = clientId
+        , oauthClientSecret = clientSecret
+        , oauthOAuthorizeEndpoint =
+            "https://public-api.wordpress.com/oauth2/authorize"
+                `withQuery` [ scopeParam "," [ "auth" ] ]
+        , oauthAccessTokenEndpoint =
+            "https://public-api.wordpress.com/oauth2/token"
+        , oauthCallback = Nothing
+        }