module Hasura.Server.Auth.WebHook
  ( AuthHookType(..)
  , AuthHookG (..)
  , AuthHook
  , userInfoFromAuthHook
  , type ReqsText
  ) where

import           Control.Exception.Lifted               (try)
import           Control.Lens
import           Control.Monad.Trans.Control            (MonadBaseControl)
import           Control.Monad.Trans.Maybe
import           Data.Aeson
import           Data.Time.Clock                        (UTCTime, addUTCTime, getCurrentTime)
import           Hasura.Server.Version                  (HasVersion)

import qualified Data.Aeson                             as J
import qualified Data.ByteString.Lazy                   as BL
import qualified Data.HashMap.Strict                    as Map
import qualified Data.Text                              as T
import qualified Network.HTTP.Client                    as H
import qualified Network.HTTP.Types                     as N
import qualified Network.Wreq                           as Wreq

import           Data.Parser.CacheControl
import           Data.Parser.Expires
import qualified Hasura.GraphQL.Transport.HTTP.Protocol as GH
import           Hasura.HTTP
import           Hasura.Logging
import           Hasura.Prelude
import           Hasura.RQL.Types
import           Hasura.Server.Logging
import           Hasura.Server.Utils
import           Hasura.Session
import qualified Hasura.Tracing                         as Tracing

data AuthHookType
  = AHTGet
  | AHTPost
  deriving (Eq)

instance Show AuthHookType where
  show AHTGet  = "GET"
  show AHTPost = "POST"


data AuthHookG a b
  = AuthHookG
  { ahUrl  :: !a
  , ahType :: !b
  } deriving (Show, Eq)

type AuthHook = AuthHookG Text AuthHookType

hookMethod :: AuthHook -> N.StdMethod
hookMethod authHook = case ahType authHook of
  AHTGet  -> N.GET
  AHTPost -> N.POST

type ReqsText = GH.GQLBatchedReqs GH.GQLQueryText

-- | Makes an authentication request to the given AuthHook and returns
--   UserInfo parsed from the response, plus an expiration time if one
--   was returned. Optionally passes a batch of raw GraphQL requests
--   for finer-grained auth. (#2666)
userInfoFromAuthHook
  :: forall m
   . (HasVersion, MonadIO m, MonadBaseControl IO m, MonadError QErr m, Tracing.MonadTrace m)
  => Logger Hasura
  -> H.Manager
  -> AuthHook
  -> [N.Header]
  -> Maybe ReqsText
  -> m (UserInfo, Maybe UTCTime)
userInfoFromAuthHook logger manager hook reqHeaders reqs = do
  resp <- (`onLeft` logAndThrow) =<< try performHTTPRequest
  let status   = resp ^. Wreq.responseStatus
      respBody = resp ^. Wreq.responseBody
  mkUserInfoFromResp logger (ahUrl hook) (hookMethod hook) status respBody
  where
    performHTTPRequest :: m (Wreq.Response BL.ByteString)
    performHTTPRequest =  do
      let url = T.unpack $ ahUrl hook
      req <- liftIO $ H.parseRequest url
      Tracing.tracedHttpRequest req \req' -> liftIO do
        case ahType hook of
          AHTGet  -> do
            let isCommonHeader  = (`elem` commonClientHeadersIgnored)
                filteredHeaders = filter (not . isCommonHeader . fst) reqHeaders
            H.httpLbs (req' { H.requestHeaders = addDefaultHeaders filteredHeaders }) manager
          AHTPost -> do
            let contentType = ("Content-Type", "application/json")
                headersPayload = J.toJSON $ Map.fromList $ hdrsToText reqHeaders
            H.httpLbs (req' { H.method         = "POST"
                           , H.requestHeaders = addDefaultHeaders [contentType]
                           , H.requestBody    = H.RequestBodyLBS . J.encode $ object ["headers" J..= headersPayload,
                                                                                     "request" J..= reqs]
                           }) manager

    logAndThrow :: H.HttpException -> m a
    logAndThrow err = do
      unLogger logger $
        WebHookLog LevelError Nothing (ahUrl hook) (hookMethod hook)
        (Just $ HttpException err) Nothing Nothing
      throw500 "webhook authentication request failed"


mkUserInfoFromResp
  :: (MonadIO m, MonadError QErr m)
  => Logger Hasura
  -> Text
  -> N.StdMethod
  -> N.Status
  -> BL.ByteString
  -> m (UserInfo, Maybe UTCTime)
mkUserInfoFromResp (Logger logger) url method statusCode respBody
  | statusCode == N.status200 =
    case eitherDecode respBody of
      Left e -> do
        logError
        throw500 $ "Invalid response from authorization hook: " <> T.pack e
      Right rawHeaders -> getUserInfoFromHdrs rawHeaders

  | statusCode == N.status401 = do
    logError
    throw401 "Authentication hook unauthorized this request"

  | otherwise = do
    logError
    throw500 "Invalid response from authorization hook"
  where
    getUserInfoFromHdrs rawHeaders = do
      userInfo <- mkUserInfo URBFromSessionVariables UAdminSecretNotSent $
                  mkSessionVariablesText rawHeaders
      logWebHookResp LevelInfo Nothing Nothing
      expiration <- runMaybeT $ timeFromCacheControl rawHeaders <|> timeFromExpires rawHeaders
      pure (userInfo, expiration)

    logWebHookResp :: MonadIO m => LogLevel -> Maybe BL.ByteString -> Maybe Text -> m ()
    logWebHookResp logLevel mResp message =
      logger $ WebHookLog logLevel (Just statusCode)
        url method Nothing (bsToTxt . BL.toStrict <$> mResp) message
    logWarn message = logWebHookResp LevelWarn (Just respBody) (Just message)
    logError = logWebHookResp LevelError (Just respBody) Nothing

    timeFromCacheControl headers = do
      header <- afold $ Map.lookup "Cache-Control" headers
      duration <- parseMaxAge header `onLeft` \err -> logWarn (T.pack err) *> empty
      addUTCTime (fromInteger duration) <$> liftIO getCurrentTime
    timeFromExpires headers = do
      header <- afold $ Map.lookup "Expires" headers
      parseExpirationTime header `onLeft` \err -> logWarn (T.pack err) *> empty