{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE RecordWildCards #-}

module Main where

import Control.Concurrent.Extended qualified as C
import Control.Exception
import Control.Monad.Trans.Managed (ManagedT (..), lowerManagedT)
import Data.ByteString.Char8 qualified as BC
import Data.Environment qualified as Env
import Data.Int (Int64)
import Data.Kind (Type)
import Data.Text.Conversions (convertText)
import Data.Time.Clock (getCurrentTime)
import Data.Time.Clock.POSIX (getPOSIXTime)
import Database.PG.Query qualified as Q
import GHC.TypeLits (Symbol)
import Hasura.App
import Hasura.GC qualified as GC
import Hasura.Logging (Hasura, LogLevel (..), defaultEnabledEngineLogTypes)
import Hasura.Prelude
import Hasura.RQL.DDL.Schema
import Hasura.RQL.Types
import Hasura.Server.Init
import Hasura.Server.Metrics (ServerMetricsSpec, createServerMetrics)
import Hasura.Server.Migrate (downgradeCatalog)
import Hasura.Server.Version
import System.Exit qualified as Sys
import System.Metrics qualified as EKG
import System.Posix.Signals qualified as Signals

main :: IO ()
main = do
  tryExit $ do
    args <- parseArgs
    env <- Env.getEnvironment
    runApp env args
  where
    tryExit io =
      try io >>= \case
        Left (ExitException _code msg) -> BC.putStrLn msg >> Sys.exitFailure
        Right r -> return r

runApp :: Env.Environment -> HGEOptions Hasura -> IO ()
runApp env (HGEOptionsG rci metadataDbUrl hgeCmd) = do
  initTime <- liftIO getCurrentTime
  globalCtx@GlobalCtx {..} <- initGlobalCtx env metadataDbUrl rci
  let (maybeDefaultPgConnInfo, maybeRetries) = _gcDefaultPostgresConnInfo

  case hgeCmd of
    HCServe serveOptions -> do
      (ekgStore, serverMetrics) <- liftIO $ do
        store <- EKG.newStore @AppMetricsSpec
        void $ EKG.register (EKG.subset GcSubset store) EKG.registerGcMetrics

        let getTimeMs :: IO Int64
            getTimeMs = (round . (* 1000)) `fmap` getPOSIXTime
        void $ EKG.register store $ EKG.registerCounter ServerTimestampMs () getTimeMs

        serverMetrics <-
          liftIO $ createServerMetrics $ EKG.subset ServerSubset store

        pure (EKG.subset EKG.emptyOf store, serverMetrics)

      -- It'd be nice if we didn't have to call runManagedT twice here, but
      -- there is a data dependency problem since the call to runPGMetadataStorageApp
      -- below depends on serveCtx.
      runManagedT (initialiseServeCtx env globalCtx serveOptions) $ \serveCtx -> do
        -- Catches the SIGTERM signal and initiates a graceful shutdown.
        -- Graceful shutdown for regular HTTP requests is already implemented in
        -- Warp, and is triggered by invoking the 'closeSocket' callback.
        -- We only catch the SIGTERM signal once, that is, if the user hits CTRL-C
        -- once again, we terminate the process immediately.

        -- The function is written in this style to avoid the shutdown
        -- handler retaining a reference to the entire serveCtx (see #344)
        -- If you modify this code then you should check the core to see
        -- that serveCtx is not retained.
        _ <- case serveCtx of
          ServeCtx {_scShutdownLatch} ->
            liftIO $ do
              void $ Signals.installHandler Signals.sigTERM (Signals.CatchOnce (shutdownGracefully _scShutdownLatch)) Nothing
              void $ Signals.installHandler Signals.sigINT (Signals.CatchOnce (shutdownGracefully _scShutdownLatch)) Nothing

        let Loggers _ logger pgLogger = _scLoggers serveCtx

        _idleGCThread <-
          C.forkImmortal "ourIdleGC" logger $
            GC.ourIdleGC logger (seconds 0.3) (seconds 10) (seconds 60)

        flip runPGMetadataStorageAppT (_scMetadataDbPool serveCtx, pgLogger) . lowerManagedT $ do
          runHGEServer (const $ pure ()) env serveOptions serveCtx initTime Nothing serverMetrics ekgStore
    HCExport -> do
      res <- runTxWithMinimalPool _gcMetadataDbConnInfo fetchMetadataFromCatalog
      either (printErrJExit MetadataExportError) printJSON res
    HCClean -> do
      res <- runTxWithMinimalPool _gcMetadataDbConnInfo dropHdbCatalogSchema
      let cleanSuccessMsg = "successfully cleaned graphql-engine related data"
      either (printErrJExit MetadataCleanError) (const $ liftIO $ putStrLn cleanSuccessMsg) res
    HCDowngrade opts -> do
      let defaultSourceConfig =
            maybeDefaultPgConnInfo <&> \(dbUrlConf, _) ->
              let pgSourceConnInfo =
                    PostgresSourceConnInfo
                      dbUrlConf
                      (Just setPostgresPoolSettings {_ppsRetries = maybeRetries <|> Just 1})
                      False
                      Q.ReadCommitted
                      Nothing
               in PostgresConnConfiguration pgSourceConnInfo Nothing
      res <- runTxWithMinimalPool _gcMetadataDbConnInfo $ downgradeCatalog defaultSourceConfig opts initTime
      either (printErrJExit DowngradeProcessError) (liftIO . print) res
    HCVersion -> liftIO $ putStrLn $ "Hasura GraphQL Engine: " ++ convertText currentVersion
  where
    runTxWithMinimalPool connInfo tx = lowerManagedT $ do
      minimalPool <- mkMinimalPool connInfo
      liftIO $ runExceptT $ Q.runTx minimalPool (Q.ReadCommitted, Nothing) tx

    mkMinimalPool connInfo = do
      pgLogger <- _lsPgLogger <$> mkLoggers defaultEnabledEngineLogTypes LevelInfo
      let connParams = Q.defaultConnParams {Q.cpConns = 1}
      liftIO $ Q.initPGPool connInfo connParams pgLogger

-- | A specification of all EKG metrics tracked in `runApp`.
data
  AppMetricsSpec ::
    Symbol -> -- Metric name
    EKG.MetricType -> -- Metric type, e.g. Counter, Gauge
    Type -> -- Tag structure
    Type
  where
  ServerSubset ::
    ServerMetricsSpec name metricType tags ->
    AppMetricsSpec name metricType tags
  GcSubset ::
    EKG.GcMetrics name metricType tags ->
    AppMetricsSpec name metricType tags
  ServerTimestampMs ::
    AppMetricsSpec "ekg.server_timestamp_ms" 'EKG.CounterType ()