{-# OPTIONS_GHC -Wwarn #-}

module Vere.Pier where

import UrbitPrelude

import Vere.Pier.Types

import qualified System.Entropy as Ent
import qualified Vere.Log       as Log
import qualified Vere.Persist   as Persist
import qualified Vere.Serf      as Serf

import Vere.Serf (EventId, Serf)


--------------------------------------------------------------------------------

ioDrivers = [] :: [IODriver]


--------------------------------------------------------------------------------

genEntropy :: IO Word512
genEntropy = fromIntegral . view (from atomBytes) <$> Ent.getEntropy 64

generateBootSeq :: Ship -> Pill -> IO BootSeq
generateBootSeq ship Pill{..} = do
    ent <- genEntropy
    let ovums = preKern ent <> pKernelOvums <> pUserspaceOvums
    pure $ BootSeq ident pBootFormulas ovums
  where
    ident       = LogIdentity ship True (fromIntegral $ length pBootFormulas)
    preKern ent = [ Ovum (Path ["", "term", "1"]) (Boot $ Fake $ who ident)
                  , Ovum (Path ["", "arvo"])      (Whom ship)
                  , Ovum (Path ["", "arvo"])      (Wack ent)
                  ]


--------------------------------------------------------------------------------

-- This is called to make a freshly booted pier. It assigns an identity to an
-- event log and takes a chill pill.
boot :: FilePath -> FilePath -> Ship -> IO (Serf, EventLog, EventId, Mug)
boot pillPath top ship = do
  let logPath = top <> "/.urb/log"

  pill <- loadFile @Pill pillPath >>= \case
            Left l  -> error (show l)
            Right p -> pure p


  seq@(BootSeq ident _ _) <- generateBootSeq ship pill

  Log.wipeEvents logPath
  log <- Log.open logPath

  Log.writeIdent log ident

  serf   <- Serf.startSerfProcess top
  events <- Serf.bootFromSeq serf seq

  -- traceM "Requesting snapshot"
  -- Serf.sendOrder serf (OSave lastEv)

  -- traceM "Requesting shutdown"
  -- Serf.sendOrder serf (OExit 0)

  Persist.writeEvents log events

  (eId, atom) : _     <- evaluate (reverse events)
  Just (mug, _::Noun) <- evaluate (atom ^? atomBytes . _Cue >>= fromNoun)

  pure (serf, log, eId, mug)

-- snapshot :: Serf -> IO ()
-- snapshot serf = Serf.sendOrder serf (OSave lastEv)

{-
    What we really want to do is write the log identity and then do
    normal startup, but writeIdent requires a full log state
    including input/output queues.
-}
resume :: FilePath -> IO (Serf, EventLog, EventId, Mug)
resume top = do
  log    <- Log.open (top <> "/.urb/log")
  ident  <- Log.readIdent log
  lastEv <- Log.latestEventNumber log
  serf   <- Serf.startSerfProcess top
  (e, m) <- Serf.replay serf ident lastEv (Log.readEvents log)

  pure (serf, log, e, m)


-- Run Pier --------------------------------------------------------------------

{-
/* _pier_work_save(): tell worker to save checkpoint.
*/
static void
_pier_work_save(u3_pier* pir_u)
{
  u3_controller* god_u = pir_u->god_u;
  u3_disk* log_u = pir_u->log_u;
  u3_save* sav_u = pir_u->sav_u;

  c3_assert( god_u->dun_d == sav_u->req_d );
  c3_assert( log_u->com_d >= god_u->dun_d );

  {
    u3_noun mat = u3ke_jam(u3nc(c3__save, u3i_chubs(1, &god_u->dun_d)));
    u3_newt_write(&god_u->inn_u, mat, 0);

    //  XX wait on some report of success before updating?
    //
    sav_u->dun_d = sav_u->req_d;
  }

  //  if we're gracefully shutting down, do so now
  //
  if ( u3_psat_done == pir_u->sat_e ) {
    _pier_exit_done(pir_u);
  }
}
-}



{-
performCommonPierStartup :: Serf.Serf
                         -> TQueue Ovum
                         -> TQueue (Writ [Eff])
                         -> TQueue (Writ [Eff])
                         -> LogState
                         -> IO Pier
performCommonPierStartup serf computeQ persistQ releaseQ logState = do
  for ioDrivers $ \x -> do
    bootMessage <- bornEvent x
    atomically $ writeTQueue computeQ bootMessage

  driverThreads <- for ioDrivers $ \x -> do
    startDriver x (writeTQueue computeQ)

  -- TODO: Don't do a bunch of extra work; we send all events to all drivers
  portingThread <- async $ do
    forever $ do
      r <- atomically (readTQueue releaseQ)
      for_ driverThreads $ \(_, k) ->
        for_ (payload r) $ \eff ->
          k eff

  Serf.workerThread serf (readTQueue computeQ) undefined

  pure (Pier{..})
-}