Google.hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
-- |
--
-- OAuth2 plugin for http://www.google.com
--
-- * Authenticates against Google
-- * Uses Google user id as credentials identifier
--
-- If you were previously relying on email as the creds identifier, you can
-- still do that (and more) by overriding it in the creds returned by the plugin
-- with any value read out of the new @userResponse@ key in @'credsExtra'@.
--
-- For example:
--
-- > data User = User { userEmail :: Text }
-- >
-- > instance FromJSON User where -- you know...
-- >
-- > authenticate creds = do
-- >     -- 'getUserResponseJSON' provided by "Yesod.Auth.OAuth" module
-- >     let Right email = userEmail <$> getUserResponseJSON creds
-- >         updatedCreds = creds { credsIdent = email }
-- >
-- >     -- continue normally with updatedCreds
--
module Yesod.Auth.OAuth2.Google
  ( oauth2Google
  , oauth2GoogleWidget
  , oauth2GoogleScoped
  , oauth2GoogleScopedWidget
  ) where

import Yesod.Auth.OAuth2.Prelude
import Yesod.Core (WidgetFor, whamlet)

newtype User = User Text

instance FromJSON User where
  parseJSON =
    withObject "User" $ \o -> User
      -- Required for data backwards-compatibility
                                   <$> (("google-uid:" <>) <$> o .: "sub")

pluginName :: Text
pluginName = "google"

defaultScopes :: [Text]
defaultScopes = ["openid", "email"]

oauth2Google :: YesodAuth m => Text -> Text -> AuthPlugin m
oauth2Google = oauth2GoogleScoped defaultScopes

oauth2GoogleWidget
  :: YesodAuth m => WidgetFor m () -> Text -> Text -> AuthPlugin m
oauth2GoogleWidget widget = oauth2GoogleScopedWidget widget defaultScopes

oauth2GoogleScoped :: YesodAuth m => [Text] -> Text -> Text -> AuthPlugin m
oauth2GoogleScoped =
  oauth2GoogleScopedWidget [whamlet|Login via #{pluginName}|]

oauth2GoogleScopedWidget
  :: YesodAuth m => WidgetFor m () -> [Text] -> Text -> Text -> AuthPlugin m
oauth2GoogleScopedWidget widget scopes clientId clientSecret =
  authOAuth2Widget widget pluginName oauth2 $ \manager token -> do
    (User userId, userResponse) <- authGetProfile
      pluginName
      manager
      token
      "https://www.googleapis.com/oauth2/v3/userinfo"

    pure Creds { credsPlugin = pluginName
               , credsIdent  = userId
               , credsExtra  = setExtra token userResponse
               }
 where
  oauth2 = OAuth2
    { oauth2ClientId          = clientId
    , oauth2ClientSecret      = Just clientSecret
    , oauth2AuthorizeEndpoint = "https://accounts.google.com/o/oauth2/auth"
                                  `withQuery` [scopeParam " " scopes]
    , oauth2TokenEndpoint     = "https://www.googleapis.com/oauth2/v3/token"
    , oauth2RedirectUri       = Nothing
    }