@startuml Bluetooth Thread Model

box "nimble_host task\n(NimBLE internal, 4 KB stack)" #LightBlue
    participant "gap_event_handler\n(esp32_ble.cpp)" as GAP
    participant "ble_gatt\ncallbacks" as GATT
    participant "bt_event_bridge\n(Bluetooth.cpp)" as Bridge
    participant "hidHostGapCb\n& discovery\n(BluetoothHidHost.cpp)" as HID
end box

box "main_dispatcher task\n(Tactility main task)" #LightGreen
    participant "settings I/O\n& peer updates" as Dispatch
end box

box "App tasks" #LightYellow
    participant "BtManage\nBtPeerSettings" as Apps
end box

box "esp_timer task" #LightGray
    participant "advRestart\nmidiKeepalive\nhidEncRetry" as Timers
end box

box "LVGL task\n(GuiService)" #MistyRose
    participant "hidHostKeyboard\nReadCb / mouseReadCb" as LVGL
end box

GAP -> Bridge : ble_publish_event() →\nBtEventCallback (bt_event_bridge)
Bridge -> Dispatch : getMainDispatcher().dispatch()\n(settings::load/save, autoConnect)
Dispatch -> Apps : publishEventCpp → PubSub callbacks
GATT -> GAP : GATT access within\nnimble_host task
HID -> Dispatch : getMainDispatcher().dispatch()\n(indev cleanup, ProfileStateChanged)
Timers -> GAP : advRestartCallback\n(calls ble_start_advertising)
LVGL -> HID : lv_indev read callbacks\n(LVGL tick)

note over GAP, GATT
  NO file I/O on NimBLE host task —
  stringstream blows the 4 KB stack
end note

note over GAP, Bridge
  Driver fires BtEvent via callback array.
  Bridge (Tactility layer) translates to
  C++ PubSub<BtEvent> and dispatches I/O.
end note

@enduml