#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>
#include <BLEBeacon.h>
#define DEVICE_NAME            "ESP32 iBeacon"
#define SERVICE_UUID           "87b99b2c-9080-4d04-8f00-a5d9a3f9a0e7"
#define BEACON_UUID            "87b99b2c-9080-4d04-8f00-a5d9a3f9a0e7"
#define BEACON_UUID_REV        "e7a0f9a3-d9a5-008f-044d8090-2c9bb987"
#define CHARACTERISTIC_UUID    "87b99b2c-9080-4d04-8f00-a5d9a3f9a0e7"
BLEServer *pServer;
BLECharacteristic *pCharacteristic;
bool deviceConnected = false;
uint8_t value = 0;

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
      Serial.println("deviceConnected = true");
    };

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;

      Serial.println("deviceConnected = false");
      // Restart advertising to be visible and connectable again
      BLEAdvertising* pAdvertising;
      pAdvertising = pServer->getAdvertising();
      pAdvertising->start();
      Serial.println("iBeacon advertising restarted");

    }

};

class MyCallbacks: public BLECharacteristicCallbacks {
    void onWrite(BLECharacteristic *pCharacteristic) {

      std::string rxValue = pCharacteristic->getValue();
      if (rxValue.length() > 0) {
        Serial.println("*********");
        Serial.print("Received Value: ");
        for (int i = 0; i < rxValue.length(); i++) {
          Serial.print(rxValue[i]);
        }

        Serial.println();
        Serial.println("*********");

      }

    }

};

void init_service() {
  BLEAdvertising* pAdvertising;
  pAdvertising = pServer->getAdvertising();
  pAdvertising->stop();
  
// Create the BLE Service
  BLEService *pService = pServer->createService(BLEUUID(SERVICE_UUID));

  // Create a BLE Characteristic
  pCharacteristic = pService->createCharacteristic(
                      CHARACTERISTIC_UUID,
                      BLECharacteristic::PROPERTY_READ   |
                      BLECharacteristic::PROPERTY_WRITE  |
                      BLECharacteristic::PROPERTY_NOTIFY
                    );

  pCharacteristic->setCallbacks(new MyCallbacks());
  pCharacteristic->addDescriptor(new BLE2902());
  pAdvertising->addServiceUUID(BLEUUID(SERVICE_UUID));

  // Start the service
  pService->start();
  pAdvertising->start();

}

void init_beacon() {
  BLEAdvertising* pAdvertising;
  pAdvertising = pServer->getAdvertising();
  pAdvertising->stop();

  // iBeacon
  BLEBeacon myBeacon;
  myBeacon.setManufacturerId(0x004C);
  myBeacon.setMajor(1);
  myBeacon.setMinor(3);                                             // ESP32-ID: 1 to n
  myBeacon.setSignalPower(0xc5);
  myBeacon.setProximityUUID(BLEUUID(BEACON_UUID_REV));
  BLEAdvertisementData advertisementData;
  advertisementData.setFlags(0x1A);
  advertisementData.setManufacturerData(myBeacon.getData());
  pAdvertising->setAdvertisementData(advertisementData);
  pAdvertising->start();
}

void setup() {
  Serial.begin(115200);
  Serial.println();
  Serial.println("Initializing...");
  Serial.flush();
  BLEDevice::init(DEVICE_NAME);
  pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());
  init_service();
  init_beacon();
  Serial.println("iBeacon + service defined and advertising!");
}

void loop() {
  if (deviceConnected) {
    Serial.printf("*** NOTIFY: %d ***n", value);
    pCharacteristic->setValue(&value, 1);
    pCharacteristic->notify();
    value++;
  }

  delay(2000);

}