Client.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE NumericUnderscores #-}
{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeApplications #-}

-- |
-- Module      : Simplex.Messaging.Client
-- Copyright   : (c) simplex.chat
-- License     : AGPL-3
--
-- Maintainer  : chat@simplex.chat
-- Stability   : experimental
-- Portability : non-portable
--
-- This module provides a functional client API for SMP protocol.
--
-- See https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md
module Simplex.Messaging.Client
  ( -- * Connect (disconnect) client to (from) SMP server
    TransportSession,
    ProtocolClient (thParams, sessionTs),
    SMPClient,
    ProxiedRelay (..),
    getProtocolClient,
    closeProtocolClient,
    protocolClientServer,
    protocolClientServer',
    transportHost',
    transportSession',

    -- * SMP protocol command functions
    createSMPQueue,
    subscribeSMPQueue,
    subscribeSMPQueues,
    streamSubscribeSMPQueues,
    getSMPMessage,
    subscribeSMPQueueNotifications,
    subscribeSMPQueuesNtfs,
    secureSMPQueue,
    secureSndSMPQueue,
    proxySecureSndSMPQueue,
    enableSMPQueueNotifications,
    disableSMPQueueNotifications,
    enableSMPQueuesNtfs,
    disableSMPQueuesNtfs,
    sendSMPMessage,
    ackSMPMessage,
    suspendSMPQueue,
    deleteSMPQueue,
    deleteSMPQueues,
    connectSMPProxiedRelay,
    proxySMPMessage,
    forwardSMPTransmission,
    getSMPQueueInfo,
    sendProtocolCommand,
    sendProtocolCommands,

    -- * Supporting types and client configuration
    ProtocolClientError (..),
    SMPClientError,
    ProxyClientError (..),
    Response (..),
    unexpectedResponse,
    ProtocolClientConfig (..),
    NetworkConfig (..),
    TransportSessionMode (..),
    HostMode (..),
    SocksMode (..),
    SMPProxyMode (..),
    SMPProxyFallback (..),
    defaultClientConfig,
    defaultSMPClientConfig,
    defaultNetworkConfig,
    transportClientConfig,
    clientSocksCredentials,
    chooseTransportHost,
    temporaryClientError,
    smpProxyError,
    textToHostMode,
    ServerTransmissionBatch,
    ServerTransmission (..),
    ClientCommand,

    -- * For testing
    PCTransmission,
    mkTransmission,
    authTransmission,
    smpClientStub,

    -- * For debugging
    TBQueueInfo (..),
    getTBQueueInfo,
    getProtocolClientQueuesInfo,
  )
where

import Control.Applicative ((<|>))
import Control.Concurrent (ThreadId, forkFinally, forkIO, killThread, mkWeakThreadId)
import Control.Concurrent.Async
import Control.Concurrent.STM
import Control.Exception
import Control.Logger.Simple
import Control.Monad
import Control.Monad.Except
import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Except
import Crypto.Random (ChaChaDRG)
import qualified Data.Aeson.TH as J
import qualified Data.Attoparsec.ByteString.Char8 as A
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B
import qualified Data.ByteString.Base64 as B64
import Data.Functor (($>))
import Data.Int (Int64)
import Data.List (find)
import Data.List.NonEmpty (NonEmpty (..))
import qualified Data.List.NonEmpty as L
import Data.Maybe (catMaybes, fromMaybe)
import Data.Text (Text)
import qualified Data.Text as T
import Data.Time.Clock (UTCTime (..), diffUTCTime, getCurrentTime)
import qualified Data.X509 as X
import qualified Data.X509.Validation as XV
import Network.Socket (ServiceName)
import Network.Socks5 (SocksCredentials (..))
import Numeric.Natural
import qualified Simplex.Messaging.Crypto as C
import Simplex.Messaging.Encoding
import Simplex.Messaging.Encoding.String
import Simplex.Messaging.Parsers (defaultJSON, dropPrefix, enumJSON, sumTypeJSON)
import Simplex.Messaging.Protocol
import Simplex.Messaging.Server.QueueStore.QueueInfo
import Simplex.Messaging.TMap (TMap)
import qualified Simplex.Messaging.TMap as TM
import Simplex.Messaging.Transport
import Simplex.Messaging.Transport.Client (SocksAuth (..), SocksProxyWithAuth (..), TransportClientConfig (..), TransportHost (..), defaultSMPPort, defaultTcpConnectTimeout, runTransportClient)
import Simplex.Messaging.Transport.KeepAlive
import Simplex.Messaging.Util (bshow, diffToMicroseconds, ifM, liftEitherWith, raceAny_, threadDelay', tryWriteTBQueue, tshow, whenM)
import Simplex.Messaging.Version
import System.Mem.Weak (Weak, deRefWeak)
import System.Timeout (timeout)

-- | 'SMPClient' is a handle used to send commands to a specific SMP server.
--
-- Use 'getSMPClient' to connect to an SMP server and create a client handle.
data ProtocolClient v err msg = ProtocolClient
  { action :: Maybe (Weak ThreadId),
    thParams :: THandleParams v 'TClient,
    sessionTs :: UTCTime,
    client_ :: PClient v err msg
  }

data PClient v err msg = PClient
  { connected :: TVar Bool,
    transportSession :: TransportSession msg,
    transportHost :: TransportHost,
    tcpConnectTimeout :: Int,
    tcpTimeout :: Int,
    sendPings :: TVar Bool,
    lastReceived :: TVar UTCTime,
    timeoutErrorCount :: TVar Int,
    clientCorrId :: TVar ChaChaDRG,
    sentCommands :: TMap CorrId (Request err msg),
    sndQ :: TBQueue (Maybe (Request err msg), ByteString),
    rcvQ :: TBQueue (NonEmpty (SignedTransmission err msg)),
    msgQ :: Maybe (TBQueue (ServerTransmissionBatch v err msg))
  }

smpClientStub :: TVar ChaChaDRG -> ByteString -> VersionSMP -> Maybe (THandleAuth 'TClient) -> IO SMPClient
smpClientStub g sessionId thVersion thAuth = do
  let ts = UTCTime (read "2024-03-31") 0
  connected <- newTVarIO False
  clientCorrId <- atomically $ C.newRandomDRG g
  sentCommands <- TM.emptyIO
  sendPings <- newTVarIO False
  lastReceived <- newTVarIO ts
  timeoutErrorCount <- newTVarIO 0
  sndQ <- newTBQueueIO 100
  rcvQ <- newTBQueueIO 100
  return
    ProtocolClient
      { action = Nothing,
        thParams =
          THandleParams
            { sessionId,
              thVersion,
              thServerVRange = supportedServerSMPRelayVRange,
              thAuth,
              blockSize = smpBlockSize,
              implySessId = thVersion >= authCmdsSMPVersion,
              encryptBlock = Nothing,
              batch = True
            },
        sessionTs = ts,
        client_ =
          PClient
            { connected,
              transportSession = (1, "smp://LcJUMfVhwD8yxjAiSaDzzGF3-kLG4Uh0Fl_ZIjrRwjI=@localhost:5001", Nothing),
              transportHost = "localhost",
              tcpConnectTimeout = 20_000_000,
              tcpTimeout = 15_000_000,
              sendPings,
              lastReceived,
              timeoutErrorCount,
              clientCorrId,
              sentCommands,
              sndQ,
              rcvQ,
              msgQ = Nothing
            }
      }

type SMPClient = ProtocolClient SMPVersion ErrorType BrokerMsg

-- | Type for client command data
type ClientCommand msg = (Maybe C.APrivateAuthKey, EntityId, ProtoCommand msg)

-- | Type synonym for transmission from SPM servers.
-- Batch response is presented as a single `ServerTransmissionBatch` tuple.
type ServerTransmissionBatch v err msg = (TransportSession msg, Version v, SessionId, NonEmpty (EntityId, ServerTransmission err msg))

data ServerTransmission err msg
  = STEvent (Either (ProtocolClientError err) msg)
  | STResponse (ProtoCommand msg) (Either (ProtocolClientError err) msg)
  | STUnexpectedError (ProtocolClientError err)

data HostMode
  = -- | prefer (or require) onion hosts when connecting via SOCKS proxy
    HMOnionViaSocks
  | -- | prefer (or require) onion hosts
    HMOnion
  | -- | prefer (or require) public hosts
    HMPublic
  deriving (Eq, Show)

textToHostMode :: Text -> Either String HostMode
textToHostMode = \case
  "public" -> Right HMPublic
  "onion" -> Right HMOnionViaSocks
  s -> Left $ T.unpack $ "Invalid host_mode: " <> s

data SocksMode
  = -- | always use SOCKS proxy when enabled
    SMAlways
  | -- | use SOCKS proxy only for .onion hosts when no public host is available
    -- This mode is used in SMP proxy and in notifications server to minimize SOCKS proxy usage.
    SMOnion
  deriving (Eq, Show)

instance StrEncoding SocksMode where
  strEncode = \case
    SMAlways -> "always"
    SMOnion -> "onion"
  strP =
    A.takeTill (== ' ') >>= \case
      "always" -> pure SMAlways
      "onion" -> pure SMOnion
      _ -> fail "Invalid Socks mode"

-- | network configuration for the client
data NetworkConfig = NetworkConfig
  { -- | use SOCKS5 proxy
    socksProxy :: Maybe SocksProxyWithAuth,
    -- | when to use SOCKS proxy
    socksMode :: SocksMode,
    -- | determines critera which host is chosen from the list
    hostMode :: HostMode,
    -- | if above criteria is not met, if the below setting is True return error, otherwise use the first host
    requiredHostMode :: Bool,
    -- | transport sessions are created per user or per entity
    sessionMode :: TransportSessionMode,
    -- | SMP proxy mode
    smpProxyMode :: SMPProxyMode,
    -- | Fallback to direct connection when destination SMP relay does not support SMP proxy protocol extensions
    smpProxyFallback :: SMPProxyFallback,
    -- | use web port 443 for SMP protocol
    smpWebPort :: Bool,
    -- | timeout for the initial client TCP/TLS connection (microseconds)
    tcpConnectTimeout :: Int,
    -- | timeout of protocol commands (microseconds)
    tcpTimeout :: Int,
    -- | additional timeout per kilobyte (1024 bytes) to be sent
    tcpTimeoutPerKb :: Int64,
    -- | break response timeouts into groups, so later responses get later deadlines
    rcvConcurrency :: Int,
    -- | TCP keep-alive options, Nothing to skip enabling keep-alive
    tcpKeepAlive :: Maybe KeepAliveOpts,
    -- | period for SMP ping commands (microseconds, 0 to disable)
    smpPingInterval :: Int64,
    -- | the count of timeout errors after which SMP client terminates (and will be reconnected), 0 to disable
    smpPingCount :: Int,
    logTLSErrors :: Bool
  }
  deriving (Eq, Show)

data TransportSessionMode = TSMUser | TSMSession | TSMServer | TSMEntity
  deriving (Eq, Show)

-- SMP proxy mode for sending messages
data SMPProxyMode
  = SPMAlways
  | SPMUnknown -- use with unknown relays
  | SPMUnprotected -- use with unknown relays when IP address is not protected (i.e., when neither SOCKS proxy nor .onion address is used)
  | SPMNever
  deriving (Eq, Show)

data SMPProxyFallback
  = SPFAllow -- connect directly when chosen proxy or destination relay do not support proxy protocol.
  | SPFAllowProtected -- connect directly only when IP address is protected (SOCKS proxy or .onion address is used).
  | SPFProhibit -- prohibit direct connection to destination relay.
  deriving (Eq, Show)

instance StrEncoding SMPProxyMode where
  strEncode = \case
    SPMAlways -> "always"
    SPMUnknown -> "unknown"
    SPMUnprotected -> "unprotected"
    SPMNever -> "never"
  strP =
    A.takeTill (== ' ') >>= \case
      "always" -> pure SPMAlways
      "unknown" -> pure SPMUnknown
      "unprotected" -> pure SPMUnprotected
      "never" -> pure SPMNever
      _ -> fail "Invalid SMP proxy mode"

instance StrEncoding SMPProxyFallback where
  strEncode = \case
    SPFAllow -> "yes"
    SPFAllowProtected -> "protected"
    SPFProhibit -> "no"
  strP =
    A.takeTill (== ' ') >>= \case
      "yes" -> pure SPFAllow
      "protected" -> pure SPFAllowProtected
      "no" -> pure SPFProhibit
      _ -> fail "Invalid SMP proxy fallback mode"

defaultNetworkConfig :: NetworkConfig
defaultNetworkConfig =
  NetworkConfig
    { socksProxy = Nothing,
      socksMode = SMAlways,
      hostMode = HMOnionViaSocks,
      requiredHostMode = False,
      sessionMode = TSMSession,
      smpProxyMode = SPMNever,
      smpProxyFallback = SPFAllow,
      smpWebPort = False,
      tcpConnectTimeout = defaultTcpConnectTimeout,
      tcpTimeout = 15_000_000,
      tcpTimeoutPerKb = 5_000,
      rcvConcurrency = 8,
      tcpKeepAlive = Just defaultKeepAliveOpts,
      smpPingInterval = 600_000_000, -- 10min
      smpPingCount = 3,
      logTLSErrors = False
    }

transportClientConfig :: NetworkConfig -> TransportHost -> Bool -> TransportClientConfig
transportClientConfig NetworkConfig {socksProxy, socksMode, tcpConnectTimeout, tcpKeepAlive, logTLSErrors} host useSNI =
  TransportClientConfig {socksProxy = useSocksProxy socksMode, tcpConnectTimeout, tcpKeepAlive, logTLSErrors, clientCredentials = Nothing, alpn = Nothing, useSNI}
  where
    socksProxy' = (\(SocksProxyWithAuth _ proxy) -> proxy) <$> socksProxy
    useSocksProxy SMAlways = socksProxy'
    useSocksProxy SMOnion = case host of
      THOnionHost _ -> socksProxy'
      _ -> Nothing

clientSocksCredentials :: ProtocolTypeI (ProtoType msg) => NetworkConfig -> UTCTime -> TransportSession msg -> Maybe SocksCredentials
clientSocksCredentials NetworkConfig {socksProxy, sessionMode} proxySessTs (userId, srv, entityId_) = case socksProxy of
  Just (SocksProxyWithAuth auth _) -> case auth of
    SocksAuthUsername {username, password} -> Just $ SocksCredentials username password
    SocksAuthNull -> Nothing
    SocksIsolateByAuth -> Just $ SocksCredentials sessionUsername ""
  Nothing -> Nothing
  where
    sessionUsername =
      B64.encode $ C.sha256Hash $
        bshow userId <> case sessionMode of
          TSMUser -> ""
          TSMSession -> ":" <> bshow proxySessTs
          TSMServer -> ":" <> bshow proxySessTs <> "@" <> strEncode srv
          TSMEntity -> ":" <> bshow proxySessTs <> "@" <> strEncode srv <> maybe "" ("/" <>) entityId_

-- | protocol client configuration.
data ProtocolClientConfig v = ProtocolClientConfig
  { -- | size of TBQueue to use for server commands and responses
    qSize :: Natural,
    -- | default server port if port is not specified in ProtocolServer
    defaultTransport :: (ServiceName, ATransport),
    -- | network configuration
    networkConfig :: NetworkConfig,
    clientALPN :: Maybe [ALPN],
    -- | client-server protocol version range
    serverVRange :: VersionRange v,
    -- | agree shared session secret (used in SMP proxy for additional encryption layer)
    agreeSecret :: Bool,
    -- | Whether connecting client is a proxy server. See comment in ClientHandshake
    proxyServer :: Bool,
    -- | send SNI to server, False for SMP
    useSNI :: Bool
  }

-- | Default protocol client configuration.
defaultClientConfig :: Maybe [ALPN] -> Bool -> VersionRange v -> ProtocolClientConfig v
defaultClientConfig clientALPN useSNI serverVRange =
  ProtocolClientConfig
    { qSize = 64,
      defaultTransport = ("443", transport @TLS),
      networkConfig = defaultNetworkConfig,
      clientALPN,
      serverVRange,
      agreeSecret = False,
      proxyServer = False,
      useSNI
    }
{-# INLINE defaultClientConfig #-}

defaultSMPClientConfig :: ProtocolClientConfig SMPVersion
defaultSMPClientConfig =
  (defaultClientConfig (Just supportedSMPHandshakes) False supportedClientSMPRelayVRange)
    { defaultTransport = (show defaultSMPPort, transport @TLS),
      agreeSecret = True
    }
{-# INLINE defaultSMPClientConfig #-}

data Request err msg = Request
  { corrId :: CorrId,
    entityId :: EntityId,
    command :: ProtoCommand msg,
    pending :: TVar Bool,
    responseVar :: TMVar (Either (ProtocolClientError err) msg)
  }

data Response err msg = Response
  { entityId :: EntityId,
    response :: Either (ProtocolClientError err) msg
  }

chooseTransportHost :: NetworkConfig -> NonEmpty TransportHost -> Either (ProtocolClientError err) TransportHost
chooseTransportHost NetworkConfig {socksProxy, hostMode, requiredHostMode} hosts =
  firstOrError $ case hostMode of
    HMOnionViaSocks -> maybe publicHost (const onionHost) socksProxy
    HMOnion -> onionHost
    HMPublic -> publicHost
  where
    firstOrError
      | requiredHostMode = maybe (Left PCEIncompatibleHost) Right
      | otherwise = Right . fromMaybe (L.head hosts)
    isOnionHost = \case THOnionHost _ -> True; _ -> False
    onionHost = find isOnionHost hosts
    publicHost = find (not . isOnionHost) hosts

protocolClientServer :: ProtocolTypeI (ProtoType msg) => ProtocolClient v err msg -> String
protocolClientServer = B.unpack . strEncode . protocolClientServer'
{-# INLINE protocolClientServer #-}

protocolClientServer' :: ProtocolClient v err msg -> ProtoServer msg
protocolClientServer' = snd3 . transportSession . client_
  where
    snd3 (_, s, _) = s
{-# INLINE protocolClientServer' #-}

transportHost' :: ProtocolClient v err msg -> TransportHost
transportHost' = transportHost . client_
{-# INLINE transportHost' #-}

transportSession' :: ProtocolClient v err msg -> TransportSession msg
transportSession' = transportSession . client_
{-# INLINE transportSession' #-}

type UserId = Int64

-- | Transport session key - includes entity ID if `sessionMode = TSMEntity`.
-- Please note that for SMP connection ID is used as entity ID, not queue ID.
type TransportSession msg = (UserId, ProtoServer msg, Maybe ByteString)

-- | Connects to 'ProtocolServer' using passed client configuration
-- and queue for messages and notifications.
--
-- A single queue can be used for multiple 'SMPClient' instances,
-- as 'SMPServerTransmission' includes server information.
getProtocolClient :: forall v err msg. Protocol v err msg => TVar ChaChaDRG -> TransportSession msg -> ProtocolClientConfig v -> Maybe (TBQueue (ServerTransmissionBatch v err msg)) -> UTCTime -> (ProtocolClient v err msg -> IO ()) -> IO (Either (ProtocolClientError err) (ProtocolClient v err msg))
getProtocolClient g transportSession@(_, srv, _) cfg@ProtocolClientConfig {qSize, networkConfig, clientALPN, serverVRange, agreeSecret, proxyServer, useSNI} msgQ proxySessTs disconnected = do
  case chooseTransportHost networkConfig (host srv) of
    Right useHost ->
      (getCurrentTime >>= mkProtocolClient useHost >>= runClient useTransport useHost)
        `catch` \(e :: IOException) -> pure . Left $ PCEIOError e
    Left e -> pure $ Left e
  where
    NetworkConfig {smpWebPort, tcpConnectTimeout, tcpTimeout, smpPingInterval} = networkConfig
    mkProtocolClient :: TransportHost -> UTCTime -> IO (PClient v err msg)
    mkProtocolClient transportHost ts = do
      connected <- newTVarIO False
      sendPings <- newTVarIO False
      lastReceived <- newTVarIO ts
      timeoutErrorCount <- newTVarIO 0
      clientCorrId <- atomically $ C.newRandomDRG g
      sentCommands <- TM.emptyIO
      sndQ <- newTBQueueIO qSize
      rcvQ <- newTBQueueIO qSize
      return
        PClient
          { connected,
            transportSession,
            transportHost,
            tcpConnectTimeout,
            tcpTimeout,
            sendPings,
            lastReceived,
            timeoutErrorCount,
            clientCorrId,
            sentCommands,
            sndQ,
            rcvQ,
            msgQ
          }

    runClient :: (ServiceName, ATransport) -> TransportHost -> PClient v err msg -> IO (Either (ProtocolClientError err) (ProtocolClient v err msg))
    runClient (port', ATransport t) useHost c = do
      cVar <- newEmptyTMVarIO
      let tcConfig = (transportClientConfig networkConfig useHost useSNI) {alpn = clientALPN}
          socksCreds = clientSocksCredentials networkConfig proxySessTs transportSession
      tId <-
        runTransportClient tcConfig socksCreds useHost port' (Just $ keyHash srv) (client t c cVar)
          `forkFinally` \_ -> void (atomically . tryPutTMVar cVar $ Left PCENetworkError)
      c_ <- tcpConnectTimeout `timeout` atomically (takeTMVar cVar)
      case c_ of
        Just (Right c') -> mkWeakThreadId tId >>= \tId' -> pure $ Right c' {action = Just tId'}
        Just (Left e) -> pure $ Left e
        Nothing -> killThread tId $> Left PCENetworkError

    useTransport :: (ServiceName, ATransport)
    useTransport = case port srv of
      "" -> case protocolTypeI @(ProtoType msg) of
        SPSMP | smpWebPort -> ("443", transport @TLS)
        _ -> defaultTransport cfg
      p -> (p, transport @TLS)

    client :: forall c. Transport c => TProxy c -> PClient v err msg -> TMVar (Either (ProtocolClientError err) (ProtocolClient v err msg)) -> c -> IO ()
    client _ c cVar h = do
      ks <- if agreeSecret then Just <$> atomically (C.generateKeyPair g) else pure Nothing
      runExceptT (protocolClientHandshake @v @err @msg h ks (keyHash srv) serverVRange proxyServer) >>= \case
        Left e -> atomically . putTMVar cVar . Left $ PCETransportError e
        Right th@THandle {params} -> do
          sessionTs <- getCurrentTime
          let c' = ProtocolClient {action = Nothing, client_ = c, thParams = params, sessionTs}
          atomically $ writeTVar (lastReceived c) sessionTs
          atomically $ do
            writeTVar (connected c) True
            putTMVar cVar $ Right c'
          raceAny_ ([send c' th, process c', receive c' th] <> [monitor c' | smpPingInterval > 0])
            `finally` disconnected c'

    send :: Transport c => ProtocolClient v err msg -> THandle v c 'TClient -> IO ()
    send ProtocolClient {client_ = PClient {sndQ}} h = forever $ atomically (readTBQueue sndQ) >>= sendPending
      where
        sendPending (r, s) = case r of
          Nothing -> void $ tPutLog h s
          Just Request {pending, responseVar} ->
            whenM (readTVarIO pending) $ tPutLog h s >>= either responseErr pure
            where
              responseErr = atomically . putTMVar responseVar . Left . PCETransportError

    receive :: Transport c => ProtocolClient v err msg -> THandle v c 'TClient -> IO ()
    receive ProtocolClient {client_ = PClient {rcvQ, lastReceived, timeoutErrorCount}} h = forever $ do
      tGet h >>= atomically . writeTBQueue rcvQ
      getCurrentTime >>= atomically . writeTVar lastReceived
      atomically $ writeTVar timeoutErrorCount 0

    monitor :: ProtocolClient v err msg -> IO ()
    monitor c@ProtocolClient {client_ = PClient {sendPings, lastReceived, timeoutErrorCount}} = loop smpPingInterval
      where
        loop :: Int64 -> IO ()
        loop delay = do
          threadDelay' delay
          diff <- diffUTCTime <$> getCurrentTime <*> readTVarIO lastReceived
          let idle = diffToMicroseconds diff
              remaining = smpPingInterval - idle
          if remaining > 1_000_000 -- delay pings only for significant time
            then loop remaining
            else do
              whenM (readTVarIO sendPings) $ void . runExceptT $ sendProtocolCommand c Nothing NoEntity (protocolPing @v @err @msg)
              -- sendProtocolCommand/getResponse updates counter for each command
              cnt <- readTVarIO timeoutErrorCount
              -- drop client when maxCnt of commands have timed out in sequence, but only after some time has passed after last received response
              when (maxCnt == 0 || cnt < maxCnt || diff < recoverWindow) $ loop smpPingInterval
        recoverWindow = 15 * 60 -- seconds
        maxCnt = smpPingCount networkConfig

    process :: ProtocolClient v err msg -> IO ()
    process c = forever $ atomically (readTBQueue $ rcvQ $ client_ c) >>= processMsgs c

    processMsgs :: ProtocolClient v err msg -> NonEmpty (SignedTransmission err msg) -> IO ()
    processMsgs c ts = do
      ts' <- catMaybes <$> mapM (processMsg c) (L.toList ts)
      forM_ msgQ $ \q ->
        mapM_ (atomically . writeTBQueue q . serverTransmission c) (L.nonEmpty ts')

    processMsg :: ProtocolClient v err msg -> SignedTransmission err msg -> IO (Maybe (EntityId, ServerTransmission err msg))
    processMsg ProtocolClient {client_ = PClient {sentCommands}} (_, _, (corrId, entId, respOrErr))
      | B.null $ bs corrId = sendMsg $ STEvent clientResp
      | otherwise =
          TM.lookupIO corrId sentCommands >>= \case
            Nothing -> sendMsg $ STUnexpectedError unexpected
            Just Request {entityId, command, pending, responseVar} -> do
              wasPending <-
                atomically $ do
                  TM.delete corrId sentCommands
                  ifM
                    (swapTVar pending False)
                    (True <$ tryPutTMVar responseVar (if entityId == entId then clientResp else Left unexpected))
                    (pure False)
              if wasPending
                then pure Nothing
                else sendMsg $ if entityId == entId then STResponse command clientResp else STUnexpectedError unexpected
      where
        unexpected = unexpectedResponse respOrErr
        clientResp = case respOrErr of
          Left e -> Left $ PCEResponseError e
          Right r -> case protocolError r of
            Just e -> Left $ PCEProtocolError e
            _ -> Right r
        sendMsg :: ServerTransmission err msg -> IO (Maybe (EntityId, ServerTransmission err msg))
        sendMsg t = case msgQ of
          Just _ -> pure $ Just (entId, t)
          Nothing ->
            Nothing <$ case clientResp of
              Left e -> logError $ "SMP client error: " <> tshow e
              Right _ -> logWarn "SMP client unprocessed event"

unexpectedResponse :: Show r => r -> ProtocolClientError err
unexpectedResponse = PCEUnexpectedResponse . B.pack . take 32 . show

-- | Disconnects client from the server and terminates client threads.
closeProtocolClient :: ProtocolClient v err msg -> IO ()
closeProtocolClient = mapM_ (deRefWeak >=> mapM_ killThread) . action
{-# INLINE closeProtocolClient #-}

-- | SMP client error type.
data ProtocolClientError err
  = -- | Correctly parsed SMP server ERR response.
    -- This error is forwarded to the agent client as `ERR SMP err`.
    PCEProtocolError err
  | -- | Invalid server response that failed to parse.
    -- Forwarded to the agent client as `ERR BROKER RESPONSE`.
    PCEResponseError err
  | -- | Different response from what is expected to a certain SMP command,
    -- e.g. server should respond `IDS` or `ERR` to `NEW` command,
    -- other responses would result in this error.
    -- Forwarded to the agent client as `ERR BROKER UNEXPECTED`.
    PCEUnexpectedResponse ByteString
  | -- | Used for TCP connection and command response timeouts.
    -- Forwarded to the agent client as `ERR BROKER TIMEOUT`.
    PCEResponseTimeout
  | -- | Failure to establish TCP connection.
    -- Forwarded to the agent client as `ERR BROKER NETWORK`.
    PCENetworkError
  | -- | No host compatible with network configuration
    PCEIncompatibleHost
  | -- | TCP transport handshake or some other transport error.
    -- Forwarded to the agent client as `ERR BROKER TRANSPORT e`.
    PCETransportError TransportError
  | -- | Error when cryptographically "signing" the command or when initializing crypto_box.
    PCECryptoError C.CryptoError
  | -- | IO Error
    PCEIOError IOException
  deriving (Eq, Show, Exception)

type SMPClientError = ProtocolClientError ErrorType

temporaryClientError :: ProtocolClientError err -> Bool
temporaryClientError = \case
  PCENetworkError -> True
  PCEResponseTimeout -> True
  PCEIOError _ -> True
  _ -> False
{-# INLINE temporaryClientError #-}

-- converts error of client running on proxy to the error sent to client connected to proxy
smpProxyError :: SMPClientError -> ErrorType
smpProxyError = \case
  PCEProtocolError e -> PROXY $ PROTOCOL e
  PCEResponseError e -> PROXY $ BROKER $ RESPONSE $ B.unpack $ strEncode e
  PCEUnexpectedResponse e -> PROXY $ BROKER $ UNEXPECTED $ B.unpack e
  PCEResponseTimeout -> PROXY $ BROKER TIMEOUT
  PCENetworkError -> PROXY $ BROKER NETWORK
  PCEIncompatibleHost -> PROXY $ BROKER HOST
  PCETransportError t -> PROXY $ BROKER $ TRANSPORT t
  PCECryptoError _ -> CRYPTO
  PCEIOError _ -> INTERNAL

-- | Create a new SMP queue.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#create-queue-command
createSMPQueue ::
  SMPClient ->
  C.AAuthKeyPair -> -- SMP v6 - signature key pair, SMP v7 - DH key pair
  RcvPublicDhKey ->
  Maybe BasicAuth ->
  SubscriptionMode ->
  Bool ->
  ExceptT SMPClientError IO QueueIdsKeys
createSMPQueue c (rKey, rpKey) dhKey auth subMode sndSecure =
  sendSMPCommand c (Just rpKey) NoEntity (NEW rKey dhKey auth subMode sndSecure) >>= \case
    IDS qik -> pure qik
    r -> throwE $ unexpectedResponse r

-- | Subscribe to the SMP queue.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#subscribe-to-queue
subscribeSMPQueue :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> ExceptT SMPClientError IO ()
subscribeSMPQueue c rpKey rId = do
  liftIO $ enablePings c
  sendSMPCommand c (Just rpKey) rId SUB >>= \case
    OK -> pure ()
    cmd@MSG {} -> liftIO $ writeSMPMessage c rId cmd
    r -> throwE $ unexpectedResponse r

-- | Subscribe to multiple SMP queues batching commands if supported.
subscribeSMPQueues :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId) -> IO (NonEmpty (Either SMPClientError ()))
subscribeSMPQueues c qs = do
  liftIO $ enablePings c
  sendProtocolCommands c cs >>= mapM (processSUBResponse c)
  where
    cs = L.map (\(rpKey, rId) -> (Just rpKey, rId, Cmd SRecipient SUB)) qs

streamSubscribeSMPQueues :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId) -> ([(RecipientId, Either SMPClientError ())] -> IO ()) -> IO ()
streamSubscribeSMPQueues c qs cb = streamProtocolCommands c cs $ mapM process >=> cb
  where
    cs = L.map (\(rpKey, rId) -> (Just rpKey, rId, Cmd SRecipient SUB)) qs
    process r@(Response rId _) = (rId,) <$> processSUBResponse c r

processSUBResponse :: SMPClient -> Response ErrorType BrokerMsg -> IO (Either SMPClientError ())
processSUBResponse c (Response rId r) = case r of
  Right OK -> pure $ Right ()
  Right cmd@MSG {} -> writeSMPMessage c rId cmd $> Right ()
  Right r' -> pure . Left $ unexpectedResponse r'
  Left e -> pure $ Left e

writeSMPMessage :: SMPClient -> RecipientId -> BrokerMsg -> IO ()
writeSMPMessage c rId msg = atomically $ mapM_ (`writeTBQueue` serverTransmission c [(rId, STEvent (Right msg))]) (msgQ $ client_ c)

serverTransmission :: ProtocolClient v err msg -> NonEmpty (RecipientId, ServerTransmission err msg) -> ServerTransmissionBatch v err msg
serverTransmission ProtocolClient {thParams = THandleParams {thVersion, sessionId}, client_ = PClient {transportSession}} ts =
  (transportSession, thVersion, sessionId, ts)

-- | Get message from SMP queue. The server returns ERR PROHIBITED if a client uses SUB and GET via the same transport connection for the same queue
--
-- https://github.covm/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#receive-a-message-from-the-queue
getSMPMessage :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> ExceptT SMPClientError IO (Maybe RcvMessage)
getSMPMessage c rpKey rId =
  sendSMPCommand c (Just rpKey) rId GET >>= \case
    OK -> pure Nothing
    cmd@(MSG msg) -> liftIO (writeSMPMessage c rId cmd) $> Just msg
    r -> throwE $ unexpectedResponse r

-- | Subscribe to the SMP queue notifications.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#subscribe-to-queue-notifications
subscribeSMPQueueNotifications :: SMPClient -> NtfPrivateAuthKey -> NotifierId -> ExceptT SMPClientError IO ()
subscribeSMPQueueNotifications c npKey nId = do
  liftIO $ enablePings c
  okSMPCommand NSUB c npKey nId
{-# INLINE subscribeSMPQueueNotifications #-}

-- | Subscribe to multiple SMP queues notifications batching commands if supported.
subscribeSMPQueuesNtfs :: SMPClient -> NonEmpty (NtfPrivateAuthKey, NotifierId) -> IO (NonEmpty (Either SMPClientError ()))
subscribeSMPQueuesNtfs c qs = do
  liftIO $ enablePings c
  okSMPCommands NSUB c qs
{-# INLINE subscribeSMPQueuesNtfs #-}

enablePings :: SMPClient -> IO ()
enablePings ProtocolClient {client_ = PClient {sendPings}} = atomically $ writeTVar sendPings True
{-# INLINE enablePings #-}

-- | Secure the SMP queue by adding a sender public key.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#secure-queue-command
secureSMPQueue :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> SndPublicAuthKey -> ExceptT SMPClientError IO ()
secureSMPQueue c rpKey rId senderKey = okSMPCommand (KEY senderKey) c rpKey rId
{-# INLINE secureSMPQueue #-}

-- | Secure the SMP queue via sender queue ID.
secureSndSMPQueue :: SMPClient -> SndPrivateAuthKey -> SenderId -> SndPublicAuthKey -> ExceptT SMPClientError IO ()
secureSndSMPQueue c spKey sId senderKey = okSMPCommand (SKEY senderKey) c spKey sId
{-# INLINE secureSndSMPQueue #-}

proxySecureSndSMPQueue :: SMPClient -> ProxiedRelay -> SndPrivateAuthKey -> SenderId -> SndPublicAuthKey -> ExceptT SMPClientError IO (Either ProxyClientError ())
proxySecureSndSMPQueue c proxiedRelay spKey sId senderKey = proxySMPCommand c proxiedRelay (Just spKey) sId (SKEY senderKey)
{-# INLINE proxySecureSndSMPQueue #-}

-- | Enable notifications for the queue for push notifications server.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#enable-notifications-command
enableSMPQueueNotifications :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> NtfPublicAuthKey -> RcvNtfPublicDhKey -> ExceptT SMPClientError IO (NotifierId, RcvNtfPublicDhKey)
enableSMPQueueNotifications c rpKey rId notifierKey rcvNtfPublicDhKey =
  sendSMPCommand c (Just rpKey) rId (NKEY notifierKey rcvNtfPublicDhKey) >>= \case
    NID nId rcvNtfSrvPublicDhKey -> pure (nId, rcvNtfSrvPublicDhKey)
    r -> throwE $ unexpectedResponse r

-- | Enable notifications for the multiple queues for push notifications server.
enableSMPQueuesNtfs :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId, NtfPublicAuthKey, RcvNtfPublicDhKey) -> IO (NonEmpty (Either SMPClientError (NotifierId, RcvNtfPublicDhKey)))
enableSMPQueuesNtfs c qs = L.map process <$> sendProtocolCommands c cs
  where
    cs = L.map (\(rpKey, rId, notifierKey, rcvNtfPublicDhKey) -> (Just rpKey, rId, Cmd SRecipient $ NKEY notifierKey rcvNtfPublicDhKey)) qs
    process (Response _ r) = case r of
      Right (NID nId rcvNtfSrvPublicDhKey) -> Right (nId, rcvNtfSrvPublicDhKey)
      Right r' -> Left $ unexpectedResponse r'
      Left e -> Left e

-- | Disable notifications for the queue for push notifications server.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#disable-notifications-command
disableSMPQueueNotifications :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> ExceptT SMPClientError IO ()
disableSMPQueueNotifications = okSMPCommand NDEL
{-# INLINE disableSMPQueueNotifications #-}

-- | Disable notifications for multiple queues for push notifications server.
disableSMPQueuesNtfs :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId) -> IO (NonEmpty (Either SMPClientError ()))
disableSMPQueuesNtfs = okSMPCommands NDEL
{-# INLINE disableSMPQueuesNtfs #-}

-- | Send SMP message.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#send-message
sendSMPMessage :: SMPClient -> Maybe SndPrivateAuthKey -> SenderId -> MsgFlags -> MsgBody -> ExceptT SMPClientError IO ()
sendSMPMessage c spKey sId flags msg =
  sendSMPCommand c spKey sId (SEND flags msg) >>= \case
    OK -> pure ()
    r -> throwE $ unexpectedResponse r

proxySMPMessage :: SMPClient -> ProxiedRelay -> Maybe SndPrivateAuthKey -> SenderId -> MsgFlags -> MsgBody -> ExceptT SMPClientError IO (Either ProxyClientError ())
proxySMPMessage c proxiedRelay spKey sId flags msg = proxySMPCommand c proxiedRelay spKey sId (SEND flags msg)

-- | Acknowledge message delivery (server deletes the message).
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#acknowledge-message-delivery
ackSMPMessage :: SMPClient -> RcvPrivateAuthKey -> QueueId -> MsgId -> ExceptT SMPClientError IO ()
ackSMPMessage c rpKey rId msgId =
  sendSMPCommand c (Just rpKey) rId (ACK msgId) >>= \case
    OK -> return ()
    cmd@MSG {} -> liftIO $ writeSMPMessage c rId cmd
    r -> throwE $ unexpectedResponse r

-- | Irreversibly suspend SMP queue.
-- The existing messages from the queue will still be delivered.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#suspend-queue
suspendSMPQueue :: SMPClient -> RcvPrivateAuthKey -> QueueId -> ExceptT SMPClientError IO ()
suspendSMPQueue = okSMPCommand OFF
{-# INLINE suspendSMPQueue #-}

-- | Irreversibly delete SMP queue and all messages in it.
--
-- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#delete-queue
deleteSMPQueue :: SMPClient -> RcvPrivateAuthKey -> RecipientId -> ExceptT SMPClientError IO ()
deleteSMPQueue = okSMPCommand DEL
{-# INLINE deleteSMPQueue #-}

-- | Delete multiple SMP queues batching commands if supported.
deleteSMPQueues :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId) -> IO (NonEmpty (Either SMPClientError ()))
deleteSMPQueues = okSMPCommands DEL
{-# INLINE deleteSMPQueues #-}

-- send PRXY :: SMPServer -> Maybe BasicAuth -> Command Sender
-- receives PKEY :: SessionId -> X.CertificateChain -> X.SignedExact X.PubKey -> BrokerMsg
connectSMPProxiedRelay :: SMPClient -> SMPServer -> Maybe BasicAuth -> ExceptT SMPClientError IO ProxiedRelay
connectSMPProxiedRelay c@ProtocolClient {client_ = PClient {tcpConnectTimeout, tcpTimeout}} relayServ@ProtocolServer {keyHash = C.KeyHash kh} proxyAuth
  | thVersion (thParams c) >= sendingProxySMPVersion =
      sendProtocolCommand_ c Nothing tOut Nothing NoEntity (Cmd SProxiedClient (PRXY relayServ proxyAuth)) >>= \case
        PKEY sId vr (chain, key) ->
          case supportedClientSMPRelayVRange `compatibleVersion` vr of
            Nothing -> throwE $ transportErr TEVersion
            Just (Compatible v) -> liftEitherWith (const $ transportErr $ TEHandshake IDENTITY) $ ProxiedRelay sId v proxyAuth <$> validateRelay chain key
        r -> throwE $ unexpectedResponse r
  | otherwise = throwE $ PCETransportError TEVersion
  where
    tOut = Just $ tcpConnectTimeout + tcpTimeout
    transportErr = PCEProtocolError . PROXY . BROKER . TRANSPORT
    validateRelay :: X.CertificateChain -> X.SignedExact X.PubKey -> Either String C.PublicKeyX25519
    validateRelay (X.CertificateChain cert) exact = do
      serverKey <- case cert of
        [leaf, ca]
          | XV.Fingerprint kh == XV.getFingerprint ca X.HashSHA256 ->
              C.x509ToPublic (X.certPubKey . X.signedObject $ X.getSigned leaf, []) >>= C.pubKey
        _ -> throwError "bad certificate"
      pubKey <- C.verifyX509 serverKey exact
      C.x509ToPublic (pubKey, []) >>= C.pubKey

data ProxiedRelay = ProxiedRelay
  { prSessionId :: SessionId,
    prVersion :: VersionSMP,
    prBasicAuth :: Maybe BasicAuth, -- auth is included here to allow reconnecting via the same proxy after NO_SESSION error
    prServerKey :: C.PublicKeyX25519
  }

data ProxyClientError
  = -- | protocol error response from proxy
    ProxyProtocolError {protocolErr :: ErrorType}
  | -- | unexpexted response
    ProxyUnexpectedResponse {responseStr :: String}
  | -- | error between proxy and server
    ProxyResponseError {responseErr :: ErrorType}
  deriving (Eq, Show, Exception)

instance StrEncoding ProxyClientError where
  strEncode = \case
    ProxyProtocolError e -> "PROTOCOL " <> strEncode e
    ProxyUnexpectedResponse s -> "UNEXPECTED " <> B.pack s
    ProxyResponseError e -> "SYNTAX " <> strEncode e
  strP =
    A.takeTill (== ' ') >>= \case
      "PROTOCOL" -> ProxyProtocolError <$> _strP
      "UNEXPECTED" -> ProxyUnexpectedResponse . B.unpack <$> (A.space *> A.takeByteString)
      "SYNTAX" -> ProxyResponseError <$> _strP
      _ -> fail "bad ProxyClientError"

-- consider how to process slow responses - is it handled somehow locally or delegated to the caller
-- this method is used in the client
-- sends PFWD :: C.PublicKeyX25519 -> EncTransmission -> Command Sender
-- receives PRES :: EncResponse -> BrokerMsg -- proxy to client

-- When client sends message via proxy, there may be one successful scenario and 9 error scenarios
-- as shown below (WTF stands for unexpected response, ??? for response that failed to parse).
--    client        proxy   relay   proxy        client
-- 0) PFWD(SEND) -> RFWD -> RRES -> PRES(OK)  -> ok
-- 1) PFWD(SEND) -> RFWD -> RRES -> PRES(ERR) -> PCEProtocolError - business logic error for client
-- 2) PFWD(SEND) -> RFWD -> RRES -> PRES(WTF) -> PCEUnexpectedReponse - relay/client protocol logic error
-- 3) PFWD(SEND) -> RFWD -> RRES -> PRES(???) -> PCEResponseError - relay/client syntax error
-- 4) PFWD(SEND) -> RFWD -> ERR ->  ERR PROXY PROTOCOL -> ProxyProtocolError - proxy/relay business logic error
-- 5) PFWD(SEND) -> RFWD -> WTF ->  ERR PROXY $ BROKER (UNEXPECTED s) -> ProxyProtocolError - proxy/relay protocol logic
-- 6) PFWD(SEND) -> RFWD -> ??? ->  ERR PROXY $ BROKER (RESPONSE s) -> ProxyProtocolError - - proxy/relay syntax
-- 7) PFWD(SEND) -> ERR  -> ProxyProtocolError - client/proxy business logic
-- 8) PFWD(SEND) -> WTF  -> ProxyUnexpectedResponse - client/proxy protocol logic
-- 9) PFWD(SEND) -> ???  -> ProxyResponseError - client/proxy syntax
--
-- We report as proxySMPCommand error (ExceptT error) the errors of two kinds:
-- - protocol errors from the destination relay wrapped in PRES - to simplify processing of AUTH and QUOTA errors, in this case proxy is "transparent" for such errors (PCEProtocolError, PCEUnexpectedResponse, PCEResponseError)
-- - other response/transport/connection errors from the client connected to proxy itself
-- Other errors are reported in the function result as `Either ProxiedRelayError ()`, including
-- - protocol  errors from the client connected to proxy in ProxyClientError (PCEProtocolError, PCEUnexpectedResponse, PCEResponseError)
-- - other errors from the client running on proxy and connected to relay in PREProxiedRelayError

-- This function proxies Sender commands that return OK or ERR
proxySMPCommand ::
  SMPClient ->
  -- proxy session from PKEY
  ProxiedRelay ->
  -- message to deliver
  Maybe SndPrivateAuthKey ->
  SenderId ->
  Command 'Sender ->
  ExceptT SMPClientError IO (Either ProxyClientError ())
proxySMPCommand c@ProtocolClient {thParams = proxyThParams, client_ = PClient {clientCorrId = g, tcpTimeout}} (ProxiedRelay sessionId v _ serverKey) spKey sId command = do
  -- prepare params
  let serverThAuth = (\ta -> ta {serverPeerPubKey = serverKey}) <$> thAuth proxyThParams
      serverThParams = smpTHParamsSetVersion v proxyThParams {sessionId, thAuth = serverThAuth}
  (cmdPubKey, cmdPrivKey) <- liftIO . atomically $ C.generateKeyPair @'C.X25519 g
  let cmdSecret = C.dh' serverKey cmdPrivKey
  nonce@(C.CbNonce corrId) <- liftIO . atomically $ C.randomCbNonce g
  -- encode
  let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth serverThParams (CorrId corrId, sId, Cmd SSender command)
  auth <- liftEitherWith PCETransportError $ authTransmission serverThAuth spKey nonce tForAuth
  b <- case batchTransmissions (batch serverThParams) (blockSize serverThParams) [Right (auth, tToSend)] of
    [] -> throwE $ PCETransportError TELargeMsg
    TBError e _ : _ -> throwE $ PCETransportError e
    TBTransmission s _ : _ -> pure s
    TBTransmissions s _ _ : _ -> pure s
  et <- liftEitherWith PCECryptoError $ EncTransmission <$> C.cbEncrypt cmdSecret nonce b paddedProxiedTLength
  -- proxy interaction errors are wrapped
  let tOut = Just $ 2 * tcpTimeout
  tryE (sendProtocolCommand_ c (Just nonce) tOut Nothing (EntityId sessionId) (Cmd SProxiedClient (PFWD v cmdPubKey et))) >>= \case
    Right r -> case r of
      PRES (EncResponse er) -> do
        -- server interaction errors are thrown directly
        t' <- liftEitherWith PCECryptoError $ C.cbDecrypt cmdSecret (C.reverseNonce nonce) er
        case tParse serverThParams t' of
          t'' :| [] -> case tDecodeParseValidate serverThParams t'' of
            (_auth, _signed, (_c, _e, cmd)) -> case cmd of
              Right OK -> pure $ Right ()
              Right (ERR e) -> throwE $ PCEProtocolError e -- this is the error from the destination relay
              Right r' -> throwE $ unexpectedResponse r'
              Left e -> throwE $ PCEResponseError e
          _ -> throwE $ PCETransportError TEBadBlock
      ERR e -> pure . Left $ ProxyProtocolError e -- this will not happen, this error is returned via Left
      _ -> pure . Left $ ProxyUnexpectedResponse $ take 32 $ show r
    Left e -> case e of
      PCEProtocolError e' -> pure . Left $ ProxyProtocolError e'
      PCEUnexpectedResponse e' -> pure . Left $ ProxyUnexpectedResponse $ B.unpack e'
      PCEResponseError e' -> pure . Left $ ProxyResponseError e'
      _ -> throwE e

-- this method is used in the proxy
-- sends RFWD :: EncFwdTransmission -> Command Sender
-- receives RRES :: EncFwdResponse -> BrokerMsg
-- proxy should send PRES to the client with EncResponse
forwardSMPTransmission :: SMPClient -> CorrId -> VersionSMP -> C.PublicKeyX25519 -> EncTransmission -> ExceptT SMPClientError IO EncResponse
forwardSMPTransmission c@ProtocolClient {thParams, client_ = PClient {clientCorrId = g}} fwdCorrId fwdVersion fwdKey fwdTransmission = do
  -- prepare params
  sessSecret <- case thAuth thParams of
    Nothing -> throwE $ PCETransportError TENoServerAuth
    Just THAuthClient {sessSecret} -> maybe (throwE $ PCETransportError TENoServerAuth) pure sessSecret
  nonce <- liftIO . atomically $ C.randomCbNonce g
  -- wrap
  let fwdT = FwdTransmission {fwdCorrId, fwdVersion, fwdKey, fwdTransmission}
      eft = EncFwdTransmission $ C.cbEncryptNoPad sessSecret nonce (smpEncode fwdT)
  -- send
  sendProtocolCommand_ c (Just nonce) Nothing Nothing NoEntity (Cmd SSender (RFWD eft)) >>= \case
    RRES (EncFwdResponse efr) -> do
      -- unwrap
      r' <- liftEitherWith PCECryptoError $ C.cbDecryptNoPad sessSecret (C.reverseNonce nonce) efr
      FwdResponse {fwdCorrId = _, fwdResponse} <- liftEitherWith (const $ PCEResponseError BLOCK) $ smpDecode r'
      pure fwdResponse
    r -> throwE $ unexpectedResponse r

getSMPQueueInfo :: SMPClient -> C.APrivateAuthKey -> QueueId -> ExceptT SMPClientError IO QueueInfo
getSMPQueueInfo c pKey qId =
  sendSMPCommand c (Just pKey) qId QUE >>= \case
    INFO info -> pure info
    r -> throwE $ unexpectedResponse r

okSMPCommand :: PartyI p => Command p -> SMPClient -> C.APrivateAuthKey -> QueueId -> ExceptT SMPClientError IO ()
okSMPCommand cmd c pKey qId =
  sendSMPCommand c (Just pKey) qId cmd >>= \case
    OK -> return ()
    r -> throwE $ unexpectedResponse r

okSMPCommands :: PartyI p => Command p -> SMPClient -> NonEmpty (C.APrivateAuthKey, QueueId) -> IO (NonEmpty (Either SMPClientError ()))
okSMPCommands cmd c qs = L.map process <$> sendProtocolCommands c cs
  where
    aCmd = Cmd sParty cmd
    cs = L.map (\(pKey, qId) -> (Just pKey, qId, aCmd)) qs
    process (Response _ r) = case r of
      Right OK -> Right ()
      Right r' -> Left $ unexpectedResponse r'
      Left e -> Left e

-- | Send SMP command
sendSMPCommand :: PartyI p => SMPClient -> Maybe C.APrivateAuthKey -> QueueId -> Command p -> ExceptT SMPClientError IO BrokerMsg
sendSMPCommand c pKey qId cmd = sendProtocolCommand c pKey qId (Cmd sParty cmd)
{-# INLINE sendSMPCommand #-}

type PCTransmission err msg = (Either TransportError SentRawTransmission, Request err msg)

-- | Send multiple commands with batching and collect responses
sendProtocolCommands :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> NonEmpty (ClientCommand msg) -> IO (NonEmpty (Response err msg))
sendProtocolCommands c@ProtocolClient {thParams = THandleParams {batch, blockSize}} cs = do
  bs <- batchTransmissions' batch blockSize <$> mapM (mkTransmission c) cs
  validate . concat =<< mapM (sendBatch c) bs
  where
    validate :: [Response err msg] -> IO (NonEmpty (Response err msg))
    validate rs
      | diff == 0 = pure $ L.fromList rs
      | diff > 0 = do
          putStrLn "send error: fewer responses than expected"
          pure $ L.fromList $ rs <> replicate diff (Response NoEntity $ Left $ PCETransportError TEBadBlock)
      | otherwise = do
          putStrLn "send error: more responses than expected"
          pure $ L.fromList $ take (L.length cs) rs
      where
        diff = L.length cs - length rs

streamProtocolCommands :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> NonEmpty (ClientCommand msg) -> ([Response err msg] -> IO ()) -> IO ()
streamProtocolCommands c@ProtocolClient {thParams = THandleParams {batch, blockSize}} cs cb = do
  bs <- batchTransmissions' batch blockSize <$> mapM (mkTransmission c) cs
  mapM_ (cb <=< sendBatch c) bs

sendBatch :: ProtocolClient v err msg -> TransportBatch (Request err msg) -> IO [Response err msg]
sendBatch c@ProtocolClient {client_ = PClient {sndQ}} b = do
  case b of
    TBError e Request {entityId} -> do
      putStrLn "send error: large message"
      pure [Response entityId $ Left $ PCETransportError e]
    TBTransmissions s n rs
      | n > 0 -> do
          nonBlockingWriteTBQueue sndQ (Nothing, s) -- do not expire batched responses
          mapConcurrently (getResponse c Nothing) rs
      | otherwise -> pure []
    TBTransmission s r -> do
      nonBlockingWriteTBQueue sndQ (Nothing, s)
      (: []) <$> getResponse c Nothing r

-- | Send Protocol command
sendProtocolCommand :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.APrivateAuthKey -> EntityId -> ProtoCommand msg -> ExceptT (ProtocolClientError err) IO msg
sendProtocolCommand c = sendProtocolCommand_ c Nothing Nothing

-- Currently there is coupling - batch commands do not expire, and individually sent commands do.
-- This is to reflect the fact that we send subscriptions only as batches, and also because we do not track a separate timeout for the whole batch, so it is not obvious when should we expire it.
-- We could expire a batch of deletes, for example, either when the first response expires or when the last one does.
-- But a better solution is to process delayed delete responses.
sendProtocolCommand_ :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.CbNonce -> Maybe Int -> Maybe C.APrivateAuthKey -> EntityId -> ProtoCommand msg -> ExceptT (ProtocolClientError err) IO msg
sendProtocolCommand_ c@ProtocolClient {client_ = PClient {sndQ}, thParams = THandleParams {batch, blockSize}} nonce_ tOut pKey entId cmd =
  ExceptT $ uncurry sendRecv =<< mkTransmission_ c nonce_ (pKey, entId, cmd)
  where
    -- two separate "atomically" needed to avoid blocking
    sendRecv :: Either TransportError SentRawTransmission -> Request err msg -> IO (Either (ProtocolClientError err) msg)
    sendRecv t_ r = case t_ of
      Left e -> pure . Left $ PCETransportError e
      Right t
        | B.length s > blockSize - 2 -> pure . Left $ PCETransportError TELargeMsg
        | otherwise -> do
            nonBlockingWriteTBQueue sndQ (Just r, s)
            response <$> getResponse c tOut r
        where
          s
            | batch = tEncodeBatch1 t
            | otherwise = tEncode t

nonBlockingWriteTBQueue :: TBQueue a -> a -> IO ()
nonBlockingWriteTBQueue q x = do
  sent <- atomically $ tryWriteTBQueue q x
  unless sent $ void $ forkIO $ atomically $ writeTBQueue q x

getResponse :: ProtocolClient v err msg -> Maybe Int -> Request err msg -> IO (Response err msg)
getResponse ProtocolClient {client_ = PClient {tcpTimeout, timeoutErrorCount}} tOut Request {entityId, pending, responseVar} = do
  r <- fromMaybe tcpTimeout tOut `timeout` atomically (takeTMVar responseVar)
  response <- atomically $ do
    writeTVar pending False
    -- Try to read response again in case it arrived after timeout expired
    -- but before `pending` was set to False above.
    -- See `processMsg`.
    ((r <|>) <$> tryTakeTMVar responseVar) >>= \case
      Just r' -> writeTVar timeoutErrorCount 0 $> r'
      Nothing -> modifyTVar' timeoutErrorCount (+ 1) $> Left PCEResponseTimeout
  pure Response {entityId, response}

mkTransmission :: Protocol v err msg => ProtocolClient v err msg -> ClientCommand msg -> IO (PCTransmission err msg)
mkTransmission c = mkTransmission_ c Nothing

mkTransmission_ :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.CbNonce -> ClientCommand msg -> IO (PCTransmission err msg)
mkTransmission_ ProtocolClient {thParams, client_ = PClient {clientCorrId, sentCommands}} nonce_ (pKey_, entityId, command) = do
  nonce@(C.CbNonce corrId) <- maybe (atomically $ C.randomCbNonce clientCorrId) pure nonce_
  let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (CorrId corrId, entityId, command)
      auth = authTransmission (thAuth thParams) pKey_ nonce tForAuth
  r <- mkRequest (CorrId corrId)
  pure ((,tToSend) <$> auth, r)
  where
    mkRequest :: CorrId -> IO (Request err msg)
    mkRequest corrId = do
      pending <- newTVarIO True
      responseVar <- newEmptyTMVarIO
      let r =
            Request
              { corrId,
                entityId,
                command,
                pending,
                responseVar
              }
      atomically $ TM.insert corrId r sentCommands
      pure r

authTransmission :: Maybe (THandleAuth 'TClient) -> Maybe C.APrivateAuthKey -> C.CbNonce -> ByteString -> Either TransportError (Maybe TransmissionAuth)
authTransmission thAuth pKey_ nonce t = traverse authenticate pKey_
  where
    authenticate :: C.APrivateAuthKey -> Either TransportError TransmissionAuth
    authenticate (C.APrivateAuthKey a pk) = case a of
      C.SX25519 -> case thAuth of
        Just THAuthClient {serverPeerPubKey = k} -> Right $ TAAuthenticator $ C.cbAuthenticate k pk nonce t
        Nothing -> Left TENoServerAuth
      C.SEd25519 -> sign pk
      C.SEd448 -> sign pk
    sign :: forall a. (C.AlgorithmI a, C.SignatureAlgorithm a) => C.PrivateKey a -> Either TransportError TransmissionAuth
    sign pk = Right $ TASignature $ C.ASignature (C.sAlgorithm @a) (C.sign' pk t)

data TBQueueInfo = TBQueueInfo
  { qLength :: Int,
    qFull :: Bool
  }
  deriving (Show)

getTBQueueInfo :: TBQueue a -> STM TBQueueInfo
getTBQueueInfo q = do
  qLength <- fromIntegral <$> lengthTBQueue q
  qFull <- isFullTBQueue q
  pure TBQueueInfo {qLength, qFull}

getProtocolClientQueuesInfo :: ProtocolClient v err msg -> IO (TBQueueInfo, TBQueueInfo)
getProtocolClientQueuesInfo ProtocolClient {client_ = PClient {sndQ, rcvQ}} = do
  sndQInfo <- atomically $ getTBQueueInfo sndQ
  rcvQInfo <- atomically $ getTBQueueInfo rcvQ
  pure (sndQInfo, rcvQInfo)

$(J.deriveJSON (enumJSON $ dropPrefix "HM") ''HostMode)

$(J.deriveJSON (enumJSON $ dropPrefix "SM") ''SocksMode)

$(J.deriveJSON (enumJSON $ dropPrefix "TSM") ''TransportSessionMode)

$(J.deriveJSON (enumJSON $ dropPrefix "SPM") ''SMPProxyMode)

$(J.deriveJSON (enumJSON $ dropPrefix "SPF") ''SMPProxyFallback)

$(J.deriveJSON defaultJSON ''NetworkConfig)

$(J.deriveJSON (sumTypeJSON $ dropPrefix "Proxy") ''ProxyClientError)

$(J.deriveJSON defaultJSON ''TBQueueInfo)