module LaunchDarkly.Server.Network.Polling (pollingThread) where

import           GHC.Generics                            (Generic)
import           Data.Text                               (Text)
import qualified Data.Text as                            T
import           Network.HTTP.Client                     (Manager, Request(..), Response(..), httpLbs)
import           Data.Generics.Product                   (getField)
import           Control.Monad                           (forever)
import           Control.Concurrent                      (threadDelay)
import           Data.Aeson                              (eitherDecode, FromJSON(..))
import           Control.Monad.Logger                    (MonadLogger, logInfo, logError)
import           Control.Monad.IO.Class                  (MonadIO, liftIO)
import           Control.Monad.Catch                     (MonadMask, MonadThrow)
import           Network.HTTP.Types.Status               (ok200)

import           LaunchDarkly.Server.Network.Common      (checkAuthorization, tryHTTP, handleUnauthorized)
import           LaunchDarkly.Server.Features            (Flag, Segment)
import           LaunchDarkly.AesonCompat                (KeyMap)


import GHC.Natural (Natural)
import LaunchDarkly.Server.DataSource.Internal (DataSourceUpdates(..))
import LaunchDarkly.Server.Config.ClientContext
import LaunchDarkly.Server.Client.Internal (Status(..))
import LaunchDarkly.Server.Config.HttpConfiguration (HttpConfiguration(..), prepareRequest)

data PollingResponse = PollingResponse
    { flags    :: !(KeyMap Flag)
    , segments :: !(KeyMap Segment)
    } deriving (Generic, FromJSON, Show)

processPoll :: (MonadIO m, MonadLogger m, MonadMask m, MonadThrow m) => Manager -> DataSourceUpdates -> Request -> m ()
processPoll manager dataSourceUpdates request = liftIO (tryHTTP $ httpLbs request manager) >>= \case
    (Left err)       -> $(logError) (T.pack $ show err)
    (Right response) -> checkAuthorization response >> if responseStatus response /= ok200
        then $(logError) "unexpected polling status code"
        else case (eitherDecode (responseBody response) :: Either String PollingResponse) of
            (Left err)   -> $(logError) (T.pack $ show err)
            (Right body) -> do
                status <- liftIO $ dataSourceUpdatesInit dataSourceUpdates (getField @"flags" body) (getField @"segments" body)
                case status of
                  Right () -> liftIO $ dataSourceUpdatesSetStatus dataSourceUpdates Initialized
                  Left err ->
                    $(logError) $ T.append "store failed put: " err


pollingThread :: (MonadIO m, MonadLogger m, MonadMask m) => Text -> Natural -> ClientContext -> DataSourceUpdates -> m ()
pollingThread baseURI pollingIntervalSeconds clientContext dataSourceUpdates = do
    let pollingMicroseconds = fromIntegral pollingIntervalSeconds * 1000000
    req <- liftIO $ prepareRequest (httpConfiguration clientContext) (T.unpack baseURI ++ "/sdk/latest-all") 
    handleUnauthorized dataSourceUpdates $ forever $ do
        $(logInfo) "starting poll"
        processPoll (tlsManager $ httpConfiguration clientContext) dataSourceUpdates req
        $(logInfo) "finished poll"
        liftIO $ threadDelay pollingMicroseconds