{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE RankNTypes #-}
module Yesod.Auth.OpenId
    ( authOpenId
    , forwardUrl
    , claimedKey
    , opLocalKey
    , credsIdentClaimed
    , IdentifierType (..)
    ) where

import Yesod.Auth
import qualified Web.Authenticate.OpenId as OpenId

import Yesod.Form
import Yesod.Core
import Text.Cassius (cassius)
import Data.Text (Text, isPrefixOf)
import qualified Yesod.Auth.Message as Msg
import Control.Exception.Lifted (SomeException, try)
import Data.Maybe (fromMaybe)

forwardUrl :: AuthRoute
forwardUrl = PluginR "openid" ["forward"]

data IdentifierType = Claimed | OPLocal

authOpenId :: YesodAuth m
           => IdentifierType
           -> [(Text, Text)] -- ^ extension fields
           -> AuthPlugin m
authOpenId idType extensionFields =
    AuthPlugin "openid" dispatch login
  where
    complete = PluginR "openid" ["complete"]
    name = "openid_identifier"
    login tm = do
        ident <- newIdent
        -- FIXME this is a hack to get GHC 7.6's type checker to allow the
        -- code, but it shouldn't be necessary
        let y :: a -> [(Text, Text)] -> Text
            y = undefined
        toWidget (\x -> [cassius|##{ident}
    background: #fff url(http://www.myopenid.com/static/openid-icon-small.gif) no-repeat scroll 0pt 50%;
    padding-left: 18px;
|] $ x `asTypeOf` y)
        [whamlet|
$newline never
<form method="get" action="@{tm forwardUrl}">
    <input type="hidden" name="openid_identifier" value="https://www.google.com/accounts/o8/id">
    <button .openid-google>_{Msg.LoginGoogle}
<form method="get" action="@{tm forwardUrl}">
    <input type="hidden" name="openid_identifier" value="http://me.yahoo.com">
    <button .openid-yahoo>_{Msg.LoginYahoo}
<form method="get" action="@{tm forwardUrl}">
    <label for="#{ident}">OpenID: #
    <input id="#{ident}" type="text" name="#{name}" value="http://">
    <input type="submit" value="_{Msg.LoginOpenID}">
|]
    dispatch "GET" ["forward"] = do
        roid <- lift $ runInputGet $ iopt textField name
        case roid of
            Just oid -> do
                render <- getUrlRender
                let complete' = render complete
                master <- lift getYesod
                eres <- lift $ try $ OpenId.getForwardUrl oid complete' Nothing extensionFields (authHttpManager master)
                case eres of
                    Left err -> do
                        setMessage $ toHtml $ show (err :: SomeException)
                        redirect LoginR
                    Right x -> redirect x
            Nothing -> do
                lift $ setMessageI Msg.NoOpenID
                redirect LoginR
    dispatch "GET" ["complete", ""] = dispatch "GET" ["complete"] -- compatibility issues
    dispatch "GET" ["complete"] = do
        rr <- getRequest
        completeHelper idType $ reqGetParams rr
    dispatch "POST" ["complete", ""] = dispatch "POST" ["complete"] -- compatibility issues
    dispatch "POST" ["complete"] = do
        (posts, _) <- runRequestBody
        completeHelper idType posts
    dispatch _ _ = notFound

completeHelper :: IdentifierType -> [(Text, Text)] -> AuthHandler master ()
completeHelper idType gets' = do
        master <- lift getYesod
        eres <- try $ OpenId.authenticateClaimed gets' (authHttpManager master)
        let onFailure err = do
            setMessage $ toHtml $ show (err :: SomeException)
            redirect LoginR
        let onSuccess oir = do
                let claimed =
                        case OpenId.oirClaimed oir of
                            Nothing -> id
                            Just (OpenId.Identifier i') -> ((claimedKey, i'):)
                    oplocal =
                        case OpenId.oirOpLocal oir of
                            OpenId.Identifier i' -> ((opLocalKey, i'):)
                    gets'' = oplocal $ claimed $ filter (\(k, _) -> not $ "__" `isPrefixOf` k) gets'
                    i = OpenId.identifier $
                            case idType of
                                OPLocal -> OpenId.oirOpLocal oir
                                Claimed -> fromMaybe (OpenId.oirOpLocal oir) $ OpenId.oirClaimed oir
                lift $ setCreds True $ Creds "openid" i gets''
        either onFailure onSuccess eres

-- | The main identifier provided by the OpenID authentication plugin is the
-- \"OP-local identifier\". There is also sometimes a \"claimed\" identifier
-- available.
--
-- In the 'credsExtra' field of the 'Creds' datatype, you can lookup this key
-- to find the claimed identifier, if available.
--
-- > let finalID = fromMaybe (credsIdent creds)
-- >             $ lookup claimedKey (credsExtra creds)
--
-- Since 1.0.2
claimedKey :: Text
claimedKey = "__CLAIMED"

opLocalKey :: Text
opLocalKey = "__OPLOCAL"

-- | A helper function which will get the claimed identifier, if available, falling back to the OP local identifier.
--
-- See 'claimedKey'.
--
-- Since 1.0.2
credsIdentClaimed :: Creds m -> Text

-- Prevent other backends from overloading the __CLAIMED value, which could
-- possibly open us to security holes.
credsIdentClaimed c | credsPlugin c /= "openid" = credsIdent c

credsIdentClaimed c = fromMaybe (credsIdent c)
                    $ lookup claimedKey (credsExtra c)