@startuml
skinparam shadowing false
title Tasks and data flow

rectangle "relay loop (one per server)" as loop {
  card "public socket\nrecv_from" as recv
  card "filter\n(commands, query rate)" as filter
}

rectangle "server state (Mutex, one per server)" as shared {
  card "sessions:\nHashMap<client, Session>" as map
  card "bans\n(bans-<port>.json)" as bans
}

rectangle "registry (Mutex)" as registry {
  card "servers by public port,\ntheir key's hash\n(servers.json)" as servers
}

rectangle "session task (one per client)" as st {
  card "mpsc Receiver\n(queue: 64)" as rx
  card "upstream socket\n(connected to ET)" as up
}

rectangle "heartbeat task (one per server)" as hb {
  card "interval 5 min" as tick
  card "probe socket" as probe
}

rectangle "control API task (axum)" as ctl {
  card "PUT/GET/DELETE /server" as pairing
  card "GET /sessions\nGET/PUT/DELETE /bans" as routes
}

recv --> filter
filter --> bans : banned?
filter --> map : lookup client
map --> rx : try_send(packet)\n(full: drop)
rx --> up : send
up --> recv : recv, then public.send_to(client)
tick --> probe : getinfo
tick --> recv : heartbeat via public socket
routes --> map : list ports,\ndrop a banned IP's sessions
routes --> bans : set / lift
routes --> servers : key -> server
pairing --> servers : register / leave
servers --> loop : start / stop\n(with its heartbeat)
@enduml