{-# OPTIONS_GHC -Wno-name-shadowing #-}

-- | The client
module Calamity.Client.Client (
    react,
    runBotIO,
    runBotIO',
    stopBot,
    sendPresence,
    events,
    fire,
    waitUntil,
    waitUntilM,
    CalamityEvent (Dispatch, ShutDown),
    customEvt,
) where

import Calamity.Cache.Eff
import Calamity.Client.ShardManager
import Calamity.Client.Types
import Calamity.Gateway.DispatchEvents
import Calamity.Gateway.Intents
import Calamity.Gateway.Types
import Calamity.HTTP.Internal.Ratelimit
import Calamity.Internal.ConstructorName
import Calamity.Internal.RunIntoIO
import qualified Calamity.Internal.SnowflakeMap as SM
import Calamity.Internal.UnixTimestamp
import Calamity.Internal.Updateable
import Calamity.Internal.Utils
import Calamity.Metrics.Eff
import Calamity.Types.LogEff
import Calamity.Types.Model.Channel
import Calamity.Types.Model.Guild
import Calamity.Types.Model.Presence (Presence (..))
import Calamity.Types.Model.User
import qualified Calamity.Types.Model.Voice as V
import Calamity.Types.Snowflake
import Calamity.Types.Token
import Control.Concurrent.Chan.Unagi
import Control.Concurrent.MVar
import Control.Concurrent.STM
import Control.Exception (SomeException)
import Control.Lens hiding ((<.>))
import Control.Monad
import Data.Default.Class
import Data.Dynamic
import Data.Foldable
import Data.Generics.Product.Subtype
import Data.IORef
import Data.Maybe
import Data.Proxy
import qualified Data.Text as S
import Data.Time.Clock.POSIX
import qualified Df1
import qualified Di.Core as DC
import qualified DiPolysemy as Di
import qualified Polysemy as P
import qualified Polysemy.Async as P
import qualified Polysemy.AtomicState as P
import qualified Polysemy.Error as P
import qualified Polysemy.Fail as P
import qualified Polysemy.Reader as P
import qualified Polysemy.Resource as P
import PyF
import TextShow (TextShow (showt))

timeA :: P.Member (P.Embed IO) r => P.Sem r a -> P.Sem r (Double, a)
timeA m = do
    start <- P.embed getPOSIXTime
    res <- m
    end <- P.embed getPOSIXTime
    let duration = fromRational . toRational $ end - start
    pure (duration, res)

newClient :: Token -> Maybe (DC.Di Df1.Level Df1.Path Df1.Message) -> IO Client
newClient token initialDi = do
    shards' <- newTVarIO []
    numShards' <- newEmptyMVar
    rlState' <- newRateLimitState
    (inc, outc) <- newChan
    ehidCounter <- newIORef 0

    pure $
        Client
            shards'
            numShards'
            token
            rlState'
            inc
            outc
            ehidCounter
            initialDi

-- | Create a bot, run your setup action, and then loop until the bot closes.
runBotIO ::
    forall r a.
    (P.Members '[P.Embed IO, P.Final IO, CacheEff, MetricEff, LogEff] r, Typeable (SetupEff r)) =>
    Token ->
    -- | The intents the bot should use
    Intents ->
    P.Sem (SetupEff r) a ->
    P.Sem r (Maybe StartupError)
runBotIO token intents = runBotIO' token intents Nothing

resetDi :: BotC r => P.Sem r a -> P.Sem r a
resetDi m = do
    initialDi <- P.asks (^. #initialDi)
    Di.local (flip fromMaybe initialDi) m

{- | Create a bot, run your setup action, and then loop until the bot closes.

 This version allows you to specify the initial status, and intents.
-}
runBotIO' ::
    forall r a.
    (P.Members '[P.Embed IO, P.Final IO, CacheEff, MetricEff, LogEff] r, Typeable (SetupEff r)) =>
    Token ->
    -- | The intents the bot should use
    Intents ->
    -- | The initial status to send to the gateway
    Maybe StatusUpdateData ->
    P.Sem (SetupEff r) a ->
    P.Sem r (Maybe StartupError)
runBotIO' token intents status setup = do
    initialDi <- Di.fetch
    client <- P.embed $ newClient token initialDi
    handlers <- P.embed $ newTVarIO def
    P.asyncToIOFinal . P.runAtomicStateTVar handlers . P.runReader client . Di.push "calamity" $ do
        void $ Di.push "calamity-setup" setup
        r <- shardBot status intents
        case r of
            Left e -> pure (Just e)
            Right _ -> do
                Di.push "calamity-loop" clientLoop
                Di.push "calamity-stop" finishUp
                pure Nothing

{- | Register an event handler, returning an action that removes the event handler from the bot.

 Refer to 'EventType' for what events you can register, and 'EHType' for the
 parameters the event handlers they receive.

 You'll probably want @TypeApplications@ and need @DataKinds@ enabled to
 specify the type of @s@.

 ==== Examples

 Reacting to every message:

 @
 'react' @\''MessageCreateEvt' '$' \msg -> 'print' '$' "Got message: " '<>' 'show' msg
 @

 Reacting to a custom event:

 @
 data MyCustomEvt = MyCustomEvt 'Data.Text.Text' 'Message'

 'react' @(\''CustomEvt' MyCustomEvt) $ \\(MyCustomEvt s m) ->
    'void' $ 'Calamity.Types.Tellable.tell' @'Data.Text.Text' m ("Somebody told me to tell you about: " '<>' s)
 @

 ==== Notes

 This function is pretty bad for giving nasty type errors,
 since if something doesn't match then 'EHType' might not get substituted,
 which will result in errors about parameter counts mismatching.
-}
react ::
    forall (s :: EventType) r.
    (BotC r, ReactConstraints s) =>
    (EHType s -> (P.Sem r) ()) ->
    P.Sem r (P.Sem r ())
react handler = do
    handler' <- bindSemToIO handler
    ehidC <- P.asks (^. #ehidCounter)
    id' <- P.embed $ atomicModifyIORef ehidC (\i -> (i + 1, i))
    let handlers = makeEventHandlers (Proxy @s) id' (const () <.> handler')
    P.atomicModify (handlers <>)
    pure $ removeHandler @s id'

removeHandler :: forall (s :: EventType) r. (BotC r, RemoveEventHandler s) => Integer -> P.Sem r ()
removeHandler id' = P.atomicModify (removeEventHandler (Proxy @s) id')

{- | Fire an event that the bot will then handle.

 ==== Examples

 Firing an event named \"my-event\":

 @
 'fire' '$' 'customEvt' @"my-event" ("aha" :: 'Data.Text.Text', msg)
 @
-}
fire :: BotC r => CalamityEvent -> P.Sem r ()
fire e = do
    inc <- P.asks (^. #eventsIn)
    P.embed $ writeChan inc e

{- | Build a Custom CalamityEvent

 The type of @a@ must match up with the event handler you want to receive it.

 ==== Examples

 @
 'customEvt' (MyCustomEvent "lol")
 @
-}
customEvt :: forall a. Typeable a => a -> CalamityEvent
customEvt = Custom

-- | Get a copy of the event stream.
events :: BotC r => P.Sem r (OutChan CalamityEvent)
events = do
    inc <- P.asks (^. #eventsIn)
    P.embed $ dupChan inc

{- | Wait until an event satisfying a condition happens, then returns it's
 parameters.

 The check function for this command is pure unlike 'waitUntilM'

 This is what it would look like with @s ~ \''MessageCreateEvt'@:

 @
 'waitUntil' :: ('Message' -> 'Bool') -> 'P.Sem' r 'Message'
 @

 And for @s ~ \''MessageUpdateEvt'@:

 @
 'waitUntil' :: (('Message', 'Message') -> 'Bool') -> 'P.Sem' r ('Message', 'Message')
 @

 ==== Examples

 Waiting for a message containing the text \"hi\":

 @
 f = do msg \<\- 'waitUntil' @\''MessageCreateEvt' (\\m -> 'Data.Text.Lazy.isInfixOf' "hi" $ m ^. #content)
        print $ msg ^. #content
 @
-}
waitUntil ::
    forall (s :: EventType) r.
    (BotC r, ReactConstraints s) =>
    (EHType s -> Bool) ->
    P.Sem r (EHType s)
waitUntil f = P.resourceToIOFinal $ do
    result <- P.embed newEmptyMVar
    P.bracket
        (P.raise $ react @s (checker result))
        P.raise
        (const . P.embed $ takeMVar result)
  where
    checker :: MVar (EHType s) -> EHType s -> P.Sem r ()
    checker result args = do
        when (f args) $ do
            P.embed $ putMVar result args

{- | Wait until an event satisfying a condition happens, then returns it's
 parameters

 This is what it would look like with @s ~ \''MessageCreateEvt'@:

 @
 'waitUntilM' :: ('Message' -> 'P.Sem' r 'Bool') -> 'P.Sem' r 'Message'
 @

 And for @s ~ \''MessageUpdateEvt'@:

 @
 'waitUntilM' :: (('Message', 'Message') -> 'P.Sem' r 'Bool') -> 'P.Sem' r ('Message', 'Message')
 @

 ==== Examples

 Waiting for a message containing the text \"hi\":

 @
 f = do msg \<\- 'waitUntilM' @\''MessageCreateEvt' (\\m -> ('debug' $ "got message: " <> 'showt' msg) >> ('pure' $ 'Data.Text.Lazy.isInfixOf' "hi" $ m ^. #content))
        print $ msg ^. #content
 @
-}
waitUntilM ::
    forall (s :: EventType) r.
    (BotC r, ReactConstraints s) =>
    (EHType s -> P.Sem r Bool) ->
    P.Sem r (EHType s)
waitUntilM f = P.resourceToIOFinal $ do
    result <- P.embed newEmptyMVar
    P.bracket
        (P.raise $ react @s (checker result))
        P.raise
        (const . P.embed $ takeMVar result)
  where
    checker :: MVar (EHType s) -> EHType s -> P.Sem r ()
    checker result args = do
        res <- f args
        when res $ do
            P.embed $ putMVar result args

-- | Set the bot's presence on all shards.
sendPresence :: BotC r => StatusUpdateData -> P.Sem r ()
sendPresence s = do
    shards <- P.asks (^. #shards) >>= P.embed . readTVarIO
    for_ shards $ \(inc, _) ->
        P.embed $ writeChan inc (SendPresence s)

-- | Initiate shutting down the bot.
stopBot :: BotC r => P.Sem r ()
stopBot = do
    debug "stopping bot"
    inc <- P.asks (^. #eventsIn)
    P.embed $ writeChan inc ShutDown

finishUp :: BotC r => P.Sem r ()
finishUp = do
    debug "finishing up"
    shards <- P.asks (^. #shards) >>= P.embed . readTVarIO
    for_ shards $ \(inc, _) ->
        P.embed $ writeChan inc ShutDownShard
    for_ shards $ \(_, shardThread) -> P.await shardThread
    debug "bot has stopped"

{- | main loop of the client, handles fetching the next event, processing the
 event and invoking it's handler functions
-}
clientLoop :: BotC r => P.Sem r ()
clientLoop = do
    outc <- P.asks (^. #eventsOut)
    whileMFinalIO $ do
        !evt' <- P.embed $ readChan outc
        case evt' of
            Dispatch !sid !evt -> handleEvent sid evt >> pure True
            Custom d -> handleCustomEvent d >> pure True
            ShutDown -> pure False
    debug "leaving client loop"

handleCustomEvent :: forall a r. (Typeable a, BotC r) => a -> P.Sem r ()
handleCustomEvent d = do
    eventHandlers <- P.atomicGet

    let handlers = getCustomEventHandlers @a eventHandlers

    for_ handlers (\h -> P.async . P.embed $ h d)

catchAllLogging :: BotC r => P.Sem r () -> P.Sem r ()
catchAllLogging m = do
    r <- P.errorToIOFinal . P.fromExceptionSem @SomeException $ P.raise m
    case r of
        Right _ -> pure ()
        Left e -> debug [fmt|got exception: {e:s}|]

handleEvent :: BotC r => Int -> DispatchData -> P.Sem r ()
handleEvent shardID data' = do
    debug "handling an event"
    eventHandlers <- P.atomicGet
    actions <- P.runFail $ do
        evtCounter <- registerCounter "events_received" [("type", S.pack $ ctorName data'), ("shard", showt shardID)]
        void $ addCounter 1 evtCounter
        cacheUpdateHisto <- registerHistogram "cache_update" mempty [10, 20 .. 100]
        (time, res) <- timeA $ resetDi $ handleEvent' eventHandlers data'
        void $ observeHistogram time cacheUpdateHisto
        pure res

    eventHandleHisto <- registerHistogram "event_handle" mempty [10, 20 .. 100]

    case actions of
        Right actions -> for_ actions $ \action -> P.async $ do
            (time, _) <- timeA . catchAllLogging $ P.embed action
            void $ observeHistogram time eventHandleHisto
        -- pattern match failures are usually stuff like events for uncached guilds, etc
        Left err -> debug [fmt|Failed handling actions for event: {err:s}|]

handleEvent' ::
    BotC r =>
    EventHandlers ->
    DispatchData ->
    P.Sem (P.Fail ': r) [IO ()]
handleEvent' eh evt@(Ready rd@ReadyData{}) = do
    updateCache evt
    pure $ map ($ rd) (getEventHandlers @ 'ReadyEvt eh)
handleEvent' _ Resumed = pure []
handleEvent' eh evt@(ChannelCreate (DMChannel' chan)) = do
    updateCache evt
    Just newChan <- DMChannel' <<$>> getDM (getID chan)
    pure $ map ($ newChan) (getEventHandlers @ 'ChannelCreateEvt eh)
handleEvent' eh evt@(ChannelCreate (GuildChannel' chan)) = do
    updateCache evt
    Just guild <- getGuild (getID chan)
    Just newChan <- pure $ GuildChannel' <$> guild ^. #channels . at (getID chan)
    pure $ map ($ newChan) (getEventHandlers @ 'ChannelCreateEvt eh)
handleEvent' eh evt@(ChannelUpdate (DMChannel' chan)) = do
    Just oldChan <- DMChannel' <<$>> getDM (getID chan)
    updateCache evt
    Just newChan <- DMChannel' <<$>> getDM (getID chan)
    pure $ map ($ (oldChan, newChan)) (getEventHandlers @ 'ChannelUpdateEvt eh)
handleEvent' eh evt@(ChannelUpdate (GuildChannel' chan)) = do
    Just oldGuild <- getGuild (getID chan)
    Just oldChan <- pure $ GuildChannel' <$> oldGuild ^. #channels . at (getID chan)
    updateCache evt
    Just newGuild <- getGuild (getID chan)
    Just newChan <- pure $ GuildChannel' <$> newGuild ^. #channels . at (getID chan)
    pure $ map ($ (oldChan, newChan)) (getEventHandlers @ 'ChannelUpdateEvt eh)
handleEvent' eh evt@(ChannelDelete (GuildChannel' chan)) = do
    Just oldGuild <- getGuild (getID chan)
    Just oldChan <- pure $ GuildChannel' <$> oldGuild ^. #channels . at (getID chan)
    updateCache evt
    pure $ map ($ oldChan) (getEventHandlers @ 'ChannelDeleteEvt eh)
handleEvent' eh evt@(ChannelDelete (DMChannel' chan)) = do
    Just oldChan <- DMChannel' <<$>> getDM (getID chan)
    updateCache evt
    pure $ map ($ oldChan) (getEventHandlers @ 'ChannelDeleteEvt eh)

-- handleEvent' eh evt@(ChannelPinsUpdate ChannelPinsUpdateData { channelID, lastPinTimestamp }) = do
--   chan <- (GuildChannel' <$> os ^? #channels . at (coerceSnowflake channelID) . _Just)
--     <|> (DMChannel' <$> os ^? #dms . at (coerceSnowflake channelID) . _Just)
--   pure $ map (\f -> f chan lastPinTimestamp) (getEventHandlers @"channelpinsupdate" eh)

handleEvent' eh evt@(GuildCreate guild) = do
    isNew <- not <$> isUnavailableGuild (getID guild)
    updateCache evt
    Just guild <- getGuild (getID guild)
    pure $
        map
            ($ (guild, (if isNew then GuildCreateNew else GuildCreateAvailable)))
            (getEventHandlers @ 'GuildCreateEvt eh)
handleEvent' eh evt@(GuildUpdate guild) = do
    Just oldGuild <- getGuild (getID guild)
    updateCache evt
    Just newGuild <- getGuild (getID guild)
    pure $ map ($ (oldGuild, newGuild)) (getEventHandlers @ 'GuildUpdateEvt eh)

-- NOTE: Guild will be deleted in the new cache if unavailable was false
handleEvent' eh evt@(GuildDelete UnavailableGuild{id, unavailable}) = do
    Just oldGuild <- getGuild id
    updateCache evt
    pure $
        map
            ($ (oldGuild, (if unavailable then GuildDeleteUnavailable else GuildDeleteRemoved)))
            (getEventHandlers @ 'GuildDeleteEvt eh)
handleEvent' eh evt@(GuildBanAdd BanData{guildID, user}) = do
    Just guild <- getGuild guildID
    updateCache evt
    pure $ map ($ (guild, user)) (getEventHandlers @ 'GuildBanAddEvt eh)
handleEvent' eh evt@(GuildBanRemove BanData{guildID, user}) = do
    Just guild <- getGuild guildID
    updateCache evt
    pure $ map ($ (guild, user)) (getEventHandlers @ 'GuildBanRemoveEvt eh)

-- NOTE: we fire this event using the guild data with old emojis
handleEvent' eh evt@(GuildEmojisUpdate GuildEmojisUpdateData{guildID, emojis}) = do
    Just guild <- getGuild guildID
    updateCache evt
    pure $ map ($ (guild, emojis)) (getEventHandlers @ 'GuildEmojisUpdateEvt eh)
handleEvent' eh evt@(GuildIntegrationsUpdate GuildIntegrationsUpdateData{guildID}) = do
    updateCache evt
    Just guild <- getGuild guildID
    pure $ map ($ guild) (getEventHandlers @ 'GuildIntegrationsUpdateEvt eh)
handleEvent' eh evt@(GuildMemberAdd member) = do
    updateCache evt
    Just guild <- getGuild (getID member)
    Just member <- pure $ guild ^. #members . at (getID member)
    pure $ map ($ member) (getEventHandlers @ 'GuildMemberAddEvt eh)
handleEvent' eh evt@(GuildMemberRemove GuildMemberRemoveData{user, guildID}) = do
    Just guild <- getGuild guildID
    Just member <- pure $ guild ^. #members . at (getID user)
    updateCache evt
    pure $ map ($ member) (getEventHandlers @ 'GuildMemberRemoveEvt eh)
handleEvent' eh evt@(GuildMemberUpdate GuildMemberUpdateData{user, guildID}) = do
    Just oldGuild <- getGuild guildID
    Just oldMember <- pure $ oldGuild ^. #members . at (getID user)
    updateCache evt
    Just newGuild <- getGuild guildID
    Just newMember <- pure $ newGuild ^. #members . at (getID user)
    pure $ map ($ (oldMember, newMember)) (getEventHandlers @ 'GuildMemberUpdateEvt eh)
handleEvent' eh evt@(GuildMembersChunk GuildMembersChunkData{members, guildID}) = do
    updateCache evt
    Just guild <- getGuild guildID
    let memberIDs = map (getID @Member) members
    let members' = catMaybes $ map (\mid -> guild ^. #members . at mid) memberIDs
    pure $ map ($ (guild, members')) (getEventHandlers @ 'GuildMembersChunkEvt eh)
handleEvent' eh evt@(GuildRoleCreate GuildRoleData{guildID, role}) = do
    updateCache evt
    Just guild <- getGuild guildID
    Just role' <- pure $ guild ^. #roles . at (getID role)
    pure $ map ($ (guild, role')) (getEventHandlers @ 'GuildRoleCreateEvt eh)
handleEvent' eh evt@(GuildRoleUpdate GuildRoleData{guildID, role}) = do
    Just oldGuild <- getGuild guildID
    Just oldRole <- pure $ oldGuild ^. #roles . at (getID role)
    updateCache evt
    Just newGuild <- getGuild guildID
    Just newRole <- pure $ newGuild ^. #roles . at (getID role)
    pure $ map ($ (newGuild, oldRole, newRole)) (getEventHandlers @ 'GuildRoleUpdateEvt eh)
handleEvent' eh evt@(GuildRoleDelete GuildRoleDeleteData{guildID, roleID}) = do
    Just guild <- getGuild guildID
    Just role <- pure $ guild ^. #roles . at roleID
    updateCache evt
    pure $ map ($ (guild, role)) (getEventHandlers @ 'GuildRoleDeleteEvt eh)
handleEvent' eh (InviteCreate d) = do
    pure $ map ($ d) (getEventHandlers @ 'InviteCreateEvt eh)
handleEvent' eh (InviteDelete d) = do
    pure $ map ($ d) (getEventHandlers @ 'InviteDeleteEvt eh)
handleEvent' eh evt@(MessageCreate msg _) = do
    updateCache evt
    pure $ map ($ msg) (getEventHandlers @ 'MessageCreateEvt eh)
handleEvent' eh evt@(MessageUpdate msg) = do
    oldMsg <- getMessage (getID msg)
    updateCache evt
    newMsg <- getMessage (getID msg)
    let rawActions = map ($ msg) (getEventHandlers @ 'RawMessageUpdateEvt eh)
    let actions = case (oldMsg, newMsg) of
            (Just oldMsg', Just newMsg') ->
                map ($ (oldMsg', newMsg')) (getEventHandlers @ 'MessageUpdateEvt eh)
            _ -> []
    pure $ rawActions <> actions
handleEvent' eh evt@(MessageDelete MessageDeleteData{id}) = do
    oldMsg <- getMessage id
    updateCache evt
    let rawActions = map ($ id) (getEventHandlers @ 'RawMessageDeleteEvt eh)
    let actions = case oldMsg of
            Just oldMsg' ->
                map ($ oldMsg') (getEventHandlers @ 'MessageDeleteEvt eh)
            _ -> []
    pure $ rawActions <> actions
handleEvent' eh evt@(MessageDeleteBulk MessageDeleteBulkData{ids}) = do
    messages <- catMaybes <$> traverse getMessage ids
    updateCache evt
    let rawActions = map ($ ids) (getEventHandlers @ 'RawMessageDeleteBulkEvt eh)
    let actions = map ($ messages) (getEventHandlers @ 'MessageDeleteBulkEvt eh)
    pure $ rawActions <> actions
handleEvent' eh evt@(MessageReactionAdd reaction) = do
    updateCache evt
    msg <- getMessage (getID reaction)
    user <- getUser (getID reaction)
    chan <- case reaction ^. #guildID of
        Just _ -> do
            chan <- getGuildChannel (coerceSnowflake $ getID @Channel reaction)
            pure (GuildChannel' <$> chan)
        Nothing -> do
            chan <- getDM (coerceSnowflake $ getID @Channel reaction)
            pure (DMChannel' <$> chan)
    let rawActions = map ($ reaction) (getEventHandlers @ 'RawMessageReactionAddEvt eh)
    let actions = case (msg, user, chan) of
            (Just msg', Just user', Just chan') ->
                map ($ (msg', user', chan', reaction ^. #emoji)) (getEventHandlers @ 'MessageReactionAddEvt eh)
            _ -> []
    pure $ rawActions <> actions
handleEvent' eh evt@(MessageReactionRemove reaction) = do
    msg <- getMessage (getID reaction)
    updateCache evt
    user <- getUser (getID reaction)
    chan <- case reaction ^. #guildID of
        Just _ -> do
            chan <- getGuildChannel (coerceSnowflake $ getID @Channel reaction)
            pure (GuildChannel' <$> chan)
        Nothing -> do
            chan <- getDM (coerceSnowflake $ getID @Channel reaction)
            pure (DMChannel' <$> chan)
    let rawActions = map ($ reaction) (getEventHandlers @ 'RawMessageReactionRemoveEvt eh)
    let actions = case (msg, user, chan) of
            (Just msg', Just user', Just chan') ->
                map ($ (msg', user', chan', reaction ^. #emoji)) (getEventHandlers @ 'MessageReactionRemoveEvt eh)
            _ -> []
    pure $ rawActions <> actions
handleEvent' eh evt@(MessageReactionRemoveAll MessageReactionRemoveAllData{messageID}) = do
    msg <- getMessage messageID
    updateCache evt
    let rawActions = map ($ messageID) (getEventHandlers @ 'RawMessageReactionRemoveAllEvt eh)
    let actions = case msg of
            Just msg' ->
                map ($ msg') (getEventHandlers @ 'MessageReactionRemoveAllEvt eh)
            _ -> []
    pure $ rawActions <> actions
handleEvent' eh evt@(PresenceUpdate PresenceUpdateData{userID, presence = Presence{guildID}}) = do
    Just oldGuild <- getGuild guildID
    Just oldMember <- pure $ oldGuild ^. #members . at (coerceSnowflake userID)
    updateCache evt
    Just newGuild <- getGuild guildID
    Just newMember <- pure $ newGuild ^. #members . at (coerceSnowflake userID)
    let oldUser :: User = upcast oldMember
        newUser :: User = upcast newMember
        userUpdates =
            if oldUser /= newUser
                then map ($ (oldUser, newUser)) (getEventHandlers @ 'UserUpdateEvt eh)
                else mempty
    pure $ userUpdates <> map ($ (oldMember, newMember)) (getEventHandlers @ 'GuildMemberUpdateEvt eh)
handleEvent' eh (TypingStart TypingStartData{channelID, guildID, userID, timestamp = UnixTimestamp timestamp}) =
    case guildID of
        Just gid -> do
            Just guild <- getGuild gid
            Just chan <- pure $ GuildChannel' <$> guild ^. #channels . at (coerceSnowflake channelID)
            pure $ map ($ (chan, userID, timestamp)) (getEventHandlers @ 'TypingStartEvt eh)
        Nothing -> do
            Just chan <- DMChannel' <<$>> getDM (coerceSnowflake channelID)
            pure $ map ($ (chan, userID, timestamp)) (getEventHandlers @ 'TypingStartEvt eh)
handleEvent' eh evt@(UserUpdate _) = do
    Just oldUser <- getBotUser
    updateCache evt
    Just newUser <- getBotUser
    pure $ map ($ (oldUser, newUser)) (getEventHandlers @ 'UserUpdateEvt eh)
handleEvent' eh evt@(VoiceStateUpdate newVoiceState@V.VoiceState{guildID = Just guildID}) = do
    oldVoiceState <- ((find ((== V.sessionID newVoiceState) . V.sessionID) . voiceStates) =<<) <$> getGuild guildID
    updateCache evt
    pure $ map ($ (oldVoiceState, newVoiceState)) (getEventHandlers @ 'VoiceStateUpdateEvt eh)
handleEvent' eh evt@(InteractionCreate interaction) = do
    updateCache evt
    pure $ map ($ interaction) (getEventHandlers @ 'InteractionEvt eh)
handleEvent' _ e = fail $ "Unhandled event: " <> show e

updateCache :: P.Members '[CacheEff, P.Fail] r => DispatchData -> P.Sem r ()
updateCache (Ready ReadyData{user, guilds}) = do
    setBotUser user
    for_ (map getID guilds) setUnavailableGuild
updateCache Resumed = pure ()
updateCache (ChannelCreate (DMChannel' chan)) =
    setDM chan
updateCache (ChannelCreate (GuildChannel' chan)) =
    updateGuild (getID chan) (#channels %~ SM.insert chan)
updateCache (ChannelUpdate (DMChannel' chan)) =
    updateDM (getID chan) (update chan)
updateCache (ChannelUpdate (GuildChannel' chan)) =
    updateGuild (getID chan) (#channels . ix (getID chan) %~ update chan)
updateCache (ChannelDelete (DMChannel' chan)) =
    delDM (getID chan)
updateCache (ChannelDelete (GuildChannel' chan)) =
    updateGuild (getID chan) (#channels %~ sans (getID chan))
updateCache (GuildCreate guild) = do
    isNew <- isUnavailableGuild (getID guild)
    when isNew $ delUnavailableGuild (getID guild)
    setGuild guild
    for_ (SM.fromList (guild ^.. #members . traverse . super)) setUser
updateCache (GuildUpdate guild) =
    updateGuild (getID guild) (update guild)
updateCache (GuildDelete UnavailableGuild{id, unavailable}) =
    if unavailable
        then setUnavailableGuild id
        else delGuild id
updateCache (GuildEmojisUpdate GuildEmojisUpdateData{guildID, emojis}) =
    updateGuild guildID (#emojis .~ SM.fromList emojis)
updateCache (GuildMemberAdd member) = do
    setUser (member ^. super)
    updateGuild (getID member) (#members . at (getID member) ?~ member)
updateCache (GuildMemberRemove GuildMemberRemoveData{guildID, user}) =
    updateGuild guildID (#members %~ sans (getID user))
updateCache (GuildMemberUpdate GuildMemberUpdateData{guildID, roles = AesonVector roles, user, nick}) = do
    setUser user
    updateGuild guildID (#members . ix (getID user) %~ (#roles .~ roles) . (#nick .~ nick))
updateCache (GuildMembersChunk GuildMembersChunkData{members}) =
    traverse_ (updateCache . GuildMemberAdd) members
updateCache (GuildRoleCreate GuildRoleData{guildID, role}) =
    updateGuild guildID (#roles %~ SM.insert role)
updateCache (GuildRoleUpdate GuildRoleData{guildID, role}) =
    updateGuild guildID (#roles %~ SM.insert role)
updateCache (GuildRoleDelete GuildRoleDeleteData{guildID, roleID}) =
    updateGuild guildID (#roles %~ sans roleID)
updateCache (MessageCreate !msg !user) = do
    setMessage msg
    for_ user setUser
updateCache (MessageUpdate msg) =
    updateMessage (getID msg) (update msg)
updateCache (MessageDelete MessageDeleteData{id}) = delMessage id
updateCache (MessageDeleteBulk MessageDeleteBulkData{ids}) =
    for_ ids delMessage
updateCache (MessageReactionAdd reaction) = do
    isMe <- (\u -> Just (getID @User reaction) == (getID @User <$> u)) <$> getBotUser
    updateMessage
        (getID reaction)
        ( \m ->
            case m ^. #reactions & filter ((== (reaction ^. #emoji)) . (^. #emoji)) of
                [] -> m & #reactions <>~ [Reaction 1 isMe (reaction ^. #emoji)]
                _ ->
                    m & #reactions . traverse . filtered ((== (reaction ^. #emoji)) . (^. #emoji))
                        %~ (#count +~ 1) . (#me ||~ isMe)
        )
updateCache (MessageReactionRemove reaction) = do
    isMe <- (\u -> Just (getID @User reaction) == (getID @User <$> u)) <$> getBotUser
    updateMessage
        (getID reaction)
        ( \m ->
            m
                & #reactions . traverse . filtered ((== (reaction ^. #emoji)) . (^. #emoji))
                    %~ (#count -~ 1) . (#me &&~ not isMe)
                & #reactions %~ filter (\r -> r ^. #count /= 0)
        )
updateCache (MessageReactionRemoveAll MessageReactionRemoveAllData{messageID}) =
    updateMessage messageID (#reactions .~ mempty)
updateCache (PresenceUpdate PresenceUpdateData{userID, presence}) =
    updateGuild (getID presence) (#presences . at userID ?~ presence)
updateCache (UserUpdate user) = setBotUser user
-- we don't handle group channels currently
updateCache (ChannelCreate (GroupChannel' _)) = pure ()
updateCache (ChannelUpdate (GroupChannel' _)) = pure ()
updateCache (ChannelDelete (GroupChannel' _)) = pure ()
-- these don't modify state
updateCache (GuildBanAdd _) = pure ()
updateCache (GuildBanRemove _) = pure ()
updateCache (GuildIntegrationsUpdate _) = pure ()
updateCache (TypingStart _) = pure ()
updateCache (ChannelPinsUpdate _) = pure ()
updateCache (WebhooksUpdate _) = pure ()
updateCache (InviteCreate _) = pure ()
updateCache (InviteDelete _) = pure ()
updateCache (VoiceStateUpdate voiceState@V.VoiceState{guildID = Just guildID}) =
    updateGuild guildID (#voiceStates %~ updateVoiceStates)
  where
    updateVoiceStates [] = [voiceState]
    updateVoiceStates (x : xs)
        | V.sessionID x == V.sessionID voiceState = voiceState : xs
        | otherwise = x : updateVoiceStates xs

-- we don't handle voice server update and direct voice connections currently
updateCache (VoiceStateUpdate V.VoiceState{guildID = Nothing}) = pure ()
updateCache (VoiceServerUpdate _) = pure ()
-- we don't update the cache from interactions
-- TODO: should we?
updateCache (InteractionCreate _) = pure ()