{-# OPTIONS_GHC -Wwarn #-}

module Vere.Pier
  ( booted, resumed, pier, runPersist, runCompute, generateBootSeq
  ) where

import UrbitPrelude

import Arvo
import System.Random
import Vere.Pier.Types

import System.Posix.Files (ownerModes, setFileMode)
import Vere.Ames          (ames)
import Vere.Behn          (behn)
import Vere.Clay          (clay)
import Vere.Http.Client   (client)
import Vere.Http.Server   (serv)
import Vere.Log           (EventLog)
import Vere.Serf          (Serf, SerfState(..), doJob, sStderr)

import RIO.Directory

import qualified System.Console.Terminal.Size as TSize
import qualified System.Entropy               as Ent
import qualified Urbit.Time                   as Time
import qualified Vere.Log                     as Log
import qualified Vere.Serf                    as Serf
import qualified Vere.Term                    as Term
import qualified Vere.Term.API                as Term
import qualified Vere.Term.Demux              as Term


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

_ioDrivers = [] :: [IODriver]

setupPierDirectory :: FilePath -> RIO e ()
setupPierDirectory shipPath = do
   for_ ["put", "get", "log", "chk"] $ \seg -> do
       let pax = shipPath <> "/.urb/" <> seg
       createDirectoryIfMissing True pax
       io $ setFileMode pax ownerModes


-- Load pill into boot sequence. -----------------------------------------------

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

generateBootSeq :: Ship -> Pill -> RIO e 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 = [ EvBlip $ BlipEvArvo $ ArvoEvWhom ()     ship
                  , EvBlip $ BlipEvArvo $ ArvoEvWack ()     ent
                  , EvBlip $ BlipEvTerm $ TermEvBoot (1,()) (Fake (who ident))
                  ]


-- Write a batch of jobs into the event log ------------------------------------

writeJobs :: EventLog -> Vector Job -> RIO e ()
writeJobs log !jobs = do
    expect <- Log.nextEv log
    events <- fmap fromList $ traverse fromJob (zip [expect..] $ toList jobs)
    Log.appendEvents log events
  where
    fromJob :: (EventId, Job) -> RIO e ByteString
    fromJob (expectedId, job) = do
        unless (expectedId == jobId job) $
            error $ show ("bad job id!", expectedId, jobId job)
        pure $ jamBS $ jobPayload job

    jobPayload :: Job -> Noun
    jobPayload (RunNok (LifeCyc _ m n)) = toNoun (m, n)
    jobPayload (DoWork (Work _ m d o))  = toNoun (m, d, o)


-- Boot a new ship. ------------------------------------------------------------

booted :: HasLogFunc e
       => FilePath -> FilePath -> Serf.Flags -> Ship
       -> RAcquire e (Serf e, EventLog, SerfState)
booted pillPath pierPath flags ship = do
  rio $ logTrace "LOADING PILL"

  pill <- io (loadFile pillPath >>= either throwIO pure)

  rio $ logTrace "PILL LOADED"

  seq@(BootSeq ident x y) <- rio $ generateBootSeq ship pill

  rio $ logTrace "BootSeq Computed"

  liftRIO (setupPierDirectory pierPath)

  rio $ logTrace "Directory Setup"

  log  <- Log.new (pierPath <> "/.urb/log") ident

  rio $ logTrace "Event Log Initialized"

  serf <- Serf.run (Serf.Config pierPath flags)

  rio $ logTrace "Serf Started"

  rio $ do
      (events, serfSt) <- Serf.bootFromSeq serf seq
      logTrace "Boot Sequence completed"
      Serf.snapshot serf serfSt
      logTrace "Snapshot taken"
      writeJobs log (fromList events)
      logTrace "Events written"
      pure (serf, log, serfSt)


-- Resume an existing ship. ----------------------------------------------------

resumed :: HasLogFunc e
        => FilePath -> Serf.Flags
        -> RAcquire e (Serf e, EventLog, SerfState)
resumed top flags = do
    log    <- Log.existing (top <> "/.urb/log")
    serf   <- Serf.run (Serf.Config top flags)
    serfSt <- rio $ Serf.replay serf log

    rio $ Serf.snapshot serf serfSt

    pure (serf, log, serfSt)


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

acquireWorker :: RIO e () -> RAcquire e (Async ())
acquireWorker act = mkRAcquire start stop
  where
    stop t = cancel t >> void (waitCatch t)
    start = async act

pier :: ∀e. HasLogFunc e
     => FilePath
     -> Maybe Port
     -> (Serf e, EventLog, SerfState)
     -> RAcquire e ()
pier pierPath mPort (serf, log, ss) = do
    computeQ  <- newTQueueIO
    persistQ  <- newTQueueIO
    executeQ  <- newTQueueIO
    saveM     <- newEmptyTMVarIO
    shutdownM <- newEmptyTMVarIO

    let shutdownEvent = putTMVar shutdownM ()

    inst <- io (KingId . UV . fromIntegral <$> randomIO @Word16)

    (sz, local) <- Term.localClient

    (waitExternalTerm, termServPort) <- Term.termServer

    (demux, muxed) <- atomically $ do
        res <- Term.mkDemux
        Term.addDemux local res
        pure (res, Term.useDemux res)

    rio $ logInfo $ display $
        "Terminal Server running on port: " <> tshow termServPort

    let listenLoop = do
            ok <- atomically $ do
                waitExternalTerm >>= \case
                    Nothing  -> pure False
                    Just ext -> Term.addDemux ext demux >> pure True
            when ok listenLoop

    acquireWorker listenLoop

    swapMVar (sStderr serf) (atomically . Term.trace muxed)

    let ship = who (Log.identity log)

    let (bootEvents, startDrivers) =
            drivers pierPath inst ship mPort
                (writeTQueue computeQ)
                shutdownEvent
                (sz, muxed)

    io $ atomically $ for_ bootEvents (writeTQueue computeQ)

    tExe  <- startDrivers >>= router (readTQueue executeQ)
    tDisk <- runPersist log persistQ (writeTQueue executeQ)
    tCpu  <- runCompute serf ss
               (readTQueue computeQ)
               (takeTMVar saveM)
               (takeTMVar shutdownM)
               (Term.spin muxed)
               (Term.stopSpin muxed)
               (writeTQueue persistQ)

    tSaveSignal <- saveSignalThread saveM

    -- Wait for something to die.

    let ded = asum [ death "effect thread" tExe
                   , death "persist thread" tDisk
                   , death "compute thread" tCpu
                   ]

    atomically ded >>= \case
      Left (txt, exn) -> logError $ displayShow ("Somthing died", txt, exn)
      Right tag       -> logError $ displayShow ("something simply exited", tag)

death :: Text -> Async () -> STM (Either (Text, SomeException) Text)
death tag tid = do
  waitCatchSTM tid <&> \case
    Left exn -> Left (tag, exn)
    Right () -> Right tag

saveSignalThread :: TMVar () -> RAcquire e (Async ())
saveSignalThread tm = mkRAcquire start cancel
  where
    start = async $ forever $ do
      threadDelay (120 * 1000000) -- 120 seconds
      atomically $ putTMVar tm ()

-- Start All Drivers -----------------------------------------------------------

data Drivers e = Drivers
    { dAmes       :: EffCb e AmesEf
    , dBehn       :: EffCb e BehnEf
    , dHttpClient :: EffCb e HttpClientEf
    , dHttpServer :: EffCb e HttpServerEf
    , dNewt       :: EffCb e NewtEf
    , dSync       :: EffCb e SyncEf
    , dTerm       :: EffCb e TermEf
    }

drivers :: HasLogFunc e
        => FilePath -> KingId -> Ship -> Maybe Port -> (Ev -> STM ()) -> STM()
        -> (TSize.Window Word, Term.Client)
        -> ([Ev], RAcquire e (Drivers e))
drivers pierPath inst who mPort plan shutdownSTM termSys =
    (initialEvents, runDrivers)
  where
    (behnBorn, runBehn) = behn inst plan
    (amesBorn, runAmes) = ames inst who mPort plan
    (httpBorn, runHttp) = serv pierPath inst plan
    (clayBorn, runClay) = clay pierPath inst plan
    (irisBorn, runIris) = client inst plan
    (termBorn, runTerm) = Term.term termSys shutdownSTM pierPath inst plan
    initialEvents       = mconcat [behnBorn, clayBorn, amesBorn, httpBorn,
                                   termBorn, irisBorn]
    runDrivers          = do
        dNewt       <- liftAcquire $ runAmes
        dBehn       <- liftAcquire $ runBehn
        dAmes       <- pure $ const $ pure ()
        dHttpClient <- runIris
        dHttpServer <- runHttp
        dSync       <- runClay
        dTerm       <- runTerm
        pure (Drivers{..})


-- Route Effects to Drivers ----------------------------------------------------

router :: HasLogFunc e => STM FX -> Drivers e -> RAcquire e (Async ())
router waitFx Drivers{..} =
    mkRAcquire start cancel
  where
    start = async $ forever $ do
        fx <- atomically waitFx
        for_ fx $ \ef -> do
            logEffect ef
            case ef of
              GoodParse (EfVega _ _)               -> error "TODO"
              GoodParse (EfExit _ _)               -> error "TODO"
              GoodParse (EfVane (VEAmes ef))       -> dAmes ef
              GoodParse (EfVane (VEBehn ef))       -> dBehn ef
              GoodParse (EfVane (VEBoat ef))       -> dSync ef
              GoodParse (EfVane (VEClay ef))       -> dSync ef
              GoodParse (EfVane (VEHttpClient ef)) -> dHttpClient ef
              GoodParse (EfVane (VEHttpServer ef)) -> dHttpServer ef
              GoodParse (EfVane (VENewt ef))       -> dNewt ef
              GoodParse (EfVane (VESync ef))       -> dSync ef
              GoodParse (EfVane (VETerm ef))       -> dTerm ef
              FailParse n                          -> logError
                                                    $ display
                                                    $ pack @Text (ppShow n)


-- Compute Thread --------------------------------------------------------------

data ComputeRequest
    = CREvent Ev
    | CRSave ()
    | CRShutdown ()
  deriving (Eq, Show)

logEvent :: HasLogFunc e => Ev -> RIO e ()
logEvent ev =
    logDebug $ display $ "[EVENT]\n" <> pretty
  where
    pretty :: Text
    pretty = pack $ unlines $ fmap ("\t" <>) $ lines $ ppShow ev

logEffect :: HasLogFunc e => Lenient Ef -> RIO e ()
logEffect ef =
    logDebug $ display $ "[EFFECT]\n" <> pretty ef
  where
    pretty :: Lenient Ef -> Text
    pretty = \case
       GoodParse e -> pack $ unlines $ fmap ("\t" <>) $ lines $ ppShow e
       FailParse n -> pack $ unlines $ fmap ("\t" <>) $ lines $ ppShow n

runCompute :: ∀e. HasLogFunc e
           => Serf e
           -> SerfState
           -> STM Ev
           -> STM ()
           -> STM ()
           -> (Maybe Text -> STM ())
           -> STM ()
           -> ((Job, FX) -> STM ())
           -> RAcquire e (Async ())
runCompute serf ss getEvent getSaveSignal getShutdownSignal
           showSpinner hideSpinner putResult =
    mkRAcquire (async (go ss)) cancel
  where
    go :: SerfState -> RIO e ()
    go ss = do
        cr  <- atomically $
          CRShutdown <$> getShutdownSignal <|>
          CRSave     <$> getSaveSignal     <|>
          CREvent    <$> getEvent
        case cr of
          CREvent ev -> do
            logEvent ev
            wen <- io Time.now
            eId <- pure (ssNextEv ss)
            mug <- pure (ssLastMug ss)

            atomically $ showSpinner (getSpinnerNameForEvent ev)
            (job', ss', fx) <- doJob serf $ DoWork $ Work eId mug wen ev
            atomically $ hideSpinner
            atomically (putResult (job', fx))
            go ss'
          CRSave () -> do
            logDebug $ "Taking periodic snapshot"
            Serf.snapshot serf ss
            go ss
          CRShutdown () -> do
            -- When shutting down, we first request a snapshot, and then we
            -- just exit this recursive processing, which will cause the serf
            -- to exit from its RAcquire.
            logDebug $ "Shutting down compute system..."
            Serf.snapshot serf ss
            pure ()


-- Persist Thread --------------------------------------------------------------

data PersistExn = BadEventId EventId EventId
  deriving Show

instance Exception PersistExn where
  displayException (BadEventId expected got) =
    unlines [ "Out-of-order event id send to persist thread."
            , "\tExpected " <> show expected <> " but got " <> show got
            ]

runPersist :: EventLog
           -> TQueue (Job, FX)
           -> (FX -> STM ())
           -> RAcquire e (Async ())
runPersist log inpQ out =
    mkRAcquire runThread cancelWait
  where
    cancelWait :: Async () -> RIO e ()
    cancelWait tid = cancel tid >> wait tid

    runThread :: RIO e (Async ())
    runThread = asyncBound $ forever $ do
        writs  <- atomically getBatchFromQueue
        events <- validateJobsAndGetBytes (toNullable writs)
        Log.appendEvents log events
        atomically $ for_ writs $ \(_,fx) -> out fx

    validateJobsAndGetBytes :: [(Job, FX)] -> RIO e (Vector ByteString)
    validateJobsAndGetBytes writs = do
        expect <- Log.nextEv log
        fmap fromList
            $ for (zip [expect..] writs)
            $ \(expectedId, (j, fx)) -> do
                unless (expectedId == jobId j) $
                    throwIO (BadEventId expectedId (jobId j))
                case j of
                  RunNok _ ->
                      error "This shouldn't happen here!"
                  DoWork (Work eId mug wen ev) ->
                      pure $ jamBS $ toNoun (mug, wen, ev)

    getBatchFromQueue :: STM (NonNull [(Job, FX)])
    getBatchFromQueue =
        readTQueue inpQ >>= go . singleton
      where
        go acc =
          tryReadTQueue inpQ >>= \case
            Nothing   -> pure (reverse acc)
            Just item -> go (item <| acc)