//ライブラリーは下記のようにインクルードします
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>
#include <M5Stack.h>

BLEServer* pServer = NULL;
BLECharacteristic* pCharacteristic = NULL;
bool deviceConnected = false;
bool oldDeviceConnected = false;
uint8_t value = 0;

//UUID（ユニバーサル固有識別番号）を任意で決め、記述します。
//これはデータを識別するための番号です。
#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

//LEDのピンとその状態を指定します
int ledPin = 21;
int ledState = LOW;

//BLEがデバイスと接続されたとき「true」、そうでないとき「false」を変数「deviceConnected」に格納します
class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
    };

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


//BLEを使う設定やM5Stackの設定を記述します
void setup() {
  Serial.begin(921600);

  M5.begin();
  pinMode(ledPin,OUTPUT);

  // Create the BLE Device
  BLEDevice::init("M5Stack_BLE");

  // Create the BLE Server
  pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

  // Create the BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

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

  // Create a BLE Descriptor
  pCharacteristic->addDescriptor(new BLE2902());

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

  // Start advertising
  pServer->getAdvertising()->start();
  Serial.println("Waiting a client connection to notify...");
}

void loop() {
    // notify changed value
    // BLEがデバイスと接続したときLEDが点灯します
    if (deviceConnected) {
        ledState = HIGH;
        digitalWrite(ledPin,ledState);

        pCharacteristic->setValue(&value, 1);
        pCharacteristic->notify();
        value++;
        delay(10); // bluetooth stack will go into congestion, if too many packets are sent
    }
    // disconnecting
    // BLEがデバイスと接続したときLEDが消灯します
    if (!deviceConnected && oldDeviceConnected) {
        delay(500); // give the bluetooth stack the chance to get things ready
        pServer->startAdvertising(); // restart advertising
        Serial.println("start advertising");
        oldDeviceConnected = deviceConnected;
        ledState = LOW;
        digitalWrite(ledPin,ledState);
    }
    // connecting
    if (deviceConnected && !oldDeviceConnected) {
        // do stuff here on connecting
        oldDeviceConnected = deviceConnected;
    }

    m5.update();
}