/**************************************************************
 *
 * For this example, you need to install PubSubClient library:
 *   https://github.com/knolleary/pubsubclient/releases/latest
 *
 * TinyGSM Getting Started guide:
 *   http://tiny.cc/tiny-gsm-readme
 *
 **************************************************************
 * Use Mosquitto client tools to work with MQTT
 *   Ubuntu/Linux: sudo apt-get install mosquitto-clients
 *   Windows:      https://mosquitto.org/download/
 *
 * Subscribe for messages:
 *   mosquitto_sub -h test.mosquitto.org -t GsmClientTest/init -t GsmClientTest/ledStatus -q 1
 * Toggle led:
 *   mosquitto_pub -h test.mosquitto.org -t GsmClientTest/led -q 1 -m "toggle"
 *
 * You can use Node-RED for wiring together MQTT-enabled devices
 *   https://nodered.org/
 * Also, take a look at these additional Node-RED modules:
 *   node-red-contrib-blynk-websockets
 *   node-red-dashboard
 *
 **************************************************************/

#include <TinyGsmClient.h>
#include <PubSubClient.h>

// Your GPRS credentials
// Leave empty, if missing user or pass
char apn[]  = "YourAPN";
char user[] = "";
char pass[] = "";

// Use Hardware Serial on Mega, Leonardo, Micro
#define GsmSerial Serial1

// or Software Serial on Uno, Nano
//#include <SoftwareSerial.h>
//SoftwareSerial GsmSerial(2, 3); // RX, TX

TinyGsmClient gsm(GsmSerial);
PubSubClient mqtt(gsm);

const char* broker = "test.mosquitto.org";

const char* topicLed = "GsmClientTest/led";
const char* topicInit = "GsmClientTest/init";
const char* topicLedStatus = "GsmClientTest/ledStatus";

#define LED_PIN 13
int ledStatus = LOW;

long lastReconnectAttempt = 0;

void setup() {
  pinMode(LED_PIN, OUTPUT);

  // Set console baud rate
  Serial.begin(115200);
  delay(10);

  // Set GSM module baud rate
  GsmSerial.begin(115200);
  delay(3000);

  // Restart takes quite some time
  // You can skip it in many cases
  Serial.println("Restarting modem...");
  gsm.restart();

  Serial.print("Connecting to ");
  Serial.print(apn);
  if (!gsm.networkConnect(apn, user, pass)) {
    Serial.println(" failed");
    while (true);
  }
  Serial.println(" OK");

  // MQTT Broker setup
  mqtt.setServer(broker, 1883);
  mqtt.setCallback(mqttCallback);
}

boolean mqttConnect() {
  Serial.print("Connecting to ");
  Serial.print(broker);
  if (!mqtt.connect("GsmClientTest")) {
    Serial.println(" failed");
    return false;
  }
  Serial.println(" OK");
  mqtt.publish(topicInit, "GsmClientTest started");
  mqtt.subscribe(topicLed);
  return mqtt.connected();
}

void loop() {

  if (mqtt.connected()) {
    mqtt.loop();
  } else {
    // Reconnect every 10 seconds
    unsigned long t = millis();
    if (t - lastReconnectAttempt > 10000L) {
      lastReconnectAttempt = t;
      if (mqttConnect()) {
        lastReconnectAttempt = 0;
      }
    }
  }

}

void mqttCallback(char* topic, byte* payload, unsigned int len) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("]: ");
  Serial.write(payload, len);
  Serial.println();

  // Only proceed if incoming message's topic matches
  if (String(topic) == topicLed) {
    ledStatus = !ledStatus;
    digitalWrite(LED_PIN, ledStatus);
    mqtt.publish(topicLedStatus, ledStatus ? "1" : "0");
  }
}