{-# LANGUAGE DataKinds             #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE LambdaCase            #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE RankNTypes            #-}
{-# LANGUAGE ScopedTypeVariables   #-}

module Hasura.Server.Auth
  ( getUserInfo
  , AuthMode(..)
  , AccessKey (..)
  , Webhook (..)
  -- JWT related
  , RawJWT
  , JWTConfig (..)
  , JWTCtx (..)
  , JWKSet (..)
  , processJwt
  , updateJwkRef
  , jwkRefreshCtrl
  ) where

import           Control.Exception      (try)
import           Control.Lens
import           Data.Aeson
import           Data.CaseInsensitive   (CI (..), original)

import qualified Data.ByteString.Lazy   as BL
import qualified Data.HashMap.Strict    as M
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           Hasura.Prelude
import           Hasura.RQL.Types
import           Hasura.Server.Auth.JWT
import           Hasura.Server.Logging
import           Hasura.Server.Utils

import qualified Hasura.Logging         as L


newtype AccessKey
  = AccessKey { getAccessKey :: T.Text }
  deriving (Show, Eq)

newtype Webhook
  = Webhook { getWebhook :: T.Text }
  deriving (Show, Eq)

data AuthMode
  = AMNoAuth
  | AMAccessKey !AccessKey
  | AMAccessKeyAndHook !AccessKey !Webhook
  | AMAccessKeyAndJWT !AccessKey !JWTCtx
  deriving (Show, Eq)


mkUserInfoFromResp
  :: (MonadIO m, MonadError QErr m)
  => WebHookLogger
  -> T.Text
  -> N.Status
  -> BL.ByteString
  -> m UserInfo
mkUserInfoFromResp logger url 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
      let headers = M.fromList [(T.toLower k, v) | (k, v) <- M.toList rawHeaders]
      case M.lookup userRoleHeader headers of
        Nothing -> do
          logError
          throw500 "missing x-hasura-role key in webhook response"
        Just v  -> do
          logWebHookResp L.LevelInfo Nothing
          return $ UserInfo (RoleName v) headers

    logError =
      logWebHookResp L.LevelError $ Just respBody

    logWebHookResp logLevel mResp =
      liftIO $ logger $ WebHookLog logLevel (Just statusCode)
        url Nothing $ fmap (bsToTxt . BL.toStrict) mResp

userInfoFromWebhook
  :: (MonadIO m, MonadError QErr m)
  => WebHookLogger
  -> H.Manager
  -> Webhook
  -> [N.Header]
  -> m UserInfo
userInfoFromWebhook logger manager hook reqHeaders = do
  let options =
        Wreq.defaults
        & Wreq.headers .~ filteredHeaders
        & Wreq.checkResponse ?~ (\_ _ -> return ())
        & Wreq.manager .~ Right manager

      urlT = getWebhook hook
  res <- liftIO $ try $ Wreq.getWith options $ T.unpack urlT
  resp <- either logAndThrow return res
  let status = resp ^. Wreq.responseStatus
      respBody = resp ^. Wreq.responseBody

  mkUserInfoFromResp logger urlT status respBody
  where
    logAndThrow err = do
      let urlT = getWebhook hook
      liftIO $ logger $ WebHookLog L.LevelError Nothing urlT (Just err) Nothing
      throw500 "Internal Server Error"

    filteredHeaders = flip filter reqHeaders $ \(n, _) ->
      n `notElem` [ "Content-Length", "Content-MD5", "User-Agent", "Host"
                  , "Origin", "Referer" , "Accept", "Accept-Encoding"
                  , "Accept-Language", "Accept-Datetime"
                  , "Cache-Control", "Connection", "DNT"
                  ]


getUserInfo
  :: (MonadIO m, MonadError QErr m)
  => WebHookLogger
  -> H.Manager
  -> [N.Header]
  -> AuthMode
  -> m UserInfo
getUserInfo logger manager rawHeaders = \case

  AMNoAuth -> return userInfoFromHeaders

  AMAccessKey accKey ->
    case getHeader accessKeyHeader of
      Just givenAccKey -> userInfoWhenAccessKey accKey givenAccKey
      Nothing -> throw401 $ accessKeyHeader <> " required, but not found"

  AMAccessKeyAndHook accKey hook ->
    whenAccessKeyAbsent accKey (userInfoFromWebhook logger manager hook rawHeaders)

  AMAccessKeyAndJWT accKey jwtSecret ->
    whenAccessKeyAbsent accKey (processJwt jwtSecret rawHeaders)

  where
    -- when access key is absent, run the action to retrieve UserInfo, otherwise
    -- accesskey override
    whenAccessKeyAbsent ak action =
      maybe action (userInfoWhenAccessKey ak) $ getHeader accessKeyHeader

    headers =
      M.fromList $ filter (T.isPrefixOf "x-hasura-" . fst) $
      flip map rawHeaders $
      \(hdrName, hdrVal) ->
        (T.toLower $ bsToTxt $ original hdrName, bsToTxt hdrVal)

    getHeader h = M.lookup h headers

    userInfoFromHeaders =
      case M.lookup userRoleHeader headers of
        Just v  -> UserInfo (RoleName v) headers
        Nothing -> adminUserInfo

    userInfoWhenAccessKey key reqKey = do
      when (reqKey /= getAccessKey key) $ throw401 $ "invalid " <> accessKeyHeader
      return userInfoFromHeaders