MeshCore/src/helpers/esp32/BLELogInterface.h

#pragma once

#include <Arduino.h>
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

// Nordic UART Service UUIDs (standard, recognised by nRF Connect and bleak)
#define NUS_SERVICE_UUID  "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
#define NUS_TX_UUID       "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"

#define BLE_LOG_ADVERT_RESTART_DELAY_MS  1000

/**
 * Unsecured BLE UART (Nordic UART Service) logger for ESP32 platforms.
 * Implements Print so it can be passed to Dispatcher::setPacketLogStream().
 * Any BLE NUS client (e.g. nRF Connect, a Raspberry Pi running bleak) can
 * connect without pairing and receive the log stream as plain text.
 *
 * Lines are buffered and flushed to BLE on each newline character.
 * Call loop() from the Arduino loop() to handle advertising restart on disconnect.
 */
class BLELogInterface : public Print, BLEServerCallbacks {
  BLEServer*          _server;
  BLECharacteristic*  _tx_char;
  bool                _connected;
  unsigned long       _adv_restart_time;
  char                _line_buf[256];
  int                 _line_len;

  void flushLine() {
    if (_line_len > 0 && _connected) {
      _tx_char->setValue((uint8_t*)_line_buf, _line_len);
      _tx_char->notify();
    }
    _line_len = 0;
  }

  void onConnect(BLEServer* pServer) override {
    _connected = true;
  }

  void onDisconnect(BLEServer* pServer) override {
    _connected = false;
    _line_len = 0;  // discard partial line
    _adv_restart_time = millis() + BLE_LOG_ADVERT_RESTART_DELAY_MS;
  }

public:
  BLELogInterface()
    : _server(nullptr), _tx_char(nullptr),
      _connected(false), _adv_restart_time(0), _line_len(0) {}

  void begin(const char* device_name) {
    BLEDevice::init(device_name);

    _server = BLEDevice::createServer();
    _server->setCallbacks(this);

    BLEService* service = _server->createService(NUS_SERVICE_UUID);
    _tx_char = service->createCharacteristic(NUS_TX_UUID, BLECharacteristic::PROPERTY_NOTIFY);
    _tx_char->addDescriptor(new BLE2902());
    service->start();

    BLEAdvertising* adv = BLEDevice::getAdvertising();
    adv->addServiceUUID(NUS_SERVICE_UUID);
    adv->setScanResponse(true);
    adv->setMinPreferred(0x06);  // helps iOS find and stay connected to the device
    adv->setMinPreferred(0x12);
    BLEDevice::startAdvertising();
  }

  void loop() {
    if (_adv_restart_time && millis() >= _adv_restart_time) {
      if (_server->getConnectedCount() == 0) {
        BLEDevice::startAdvertising();
      }
      _adv_restart_time = 0;
    }
  }

  size_t write(uint8_t c) override {
    if (_line_len < (int)sizeof(_line_buf) - 1) {
      _line_buf[_line_len++] = c;
    }
    if (c == '\n' || _line_len >= (int)sizeof(_line_buf) - 1) {
      flushLine();
    }
    return 1;
  }

  size_t write(const uint8_t* buf, size_t size) override {
    for (size_t i = 0; i < size; i++) write(buf[i]);
    return size;
  }
};