#include <Arduino.h>
#include <WiFi.h>
#include <MQTT.h>   // 256dpi MQTT library
 
//////////////// EDIT THESE ////////////////
const char* WIFI_SSID     = "YOUR_SSID";
const char* WIFI_PASSWORD = "YOUR_PASSWORD";
const char* MQTT_HOST     = "test.mosquitto.org";   // or your lab broker
const uint16_t MQTT_PORT  = 1883;
const char* BASE_TOPIC    = "iot/studentname";        // change per student
////////////////////////////////////////////
 
WiFiClient net;
MQTTClient mqtt(1024);  // 1KB message buffer
 
unsigned long lastPub = 0;
 
void connectWiFi() {
  if (WiFi.status() == WL_CONNECTED) return;
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("WiFi connecting");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.printf("\nWiFi OK, IP: %s\n", WiFi.localIP().toString().c_str());
}
 
void messageReceived(String &topic, String &payload) {
  Serial.printf("Message on %s: %s\n", topic.c_str(), payload.c_str());
}
 
void connectMQTT() {
  // Build a real String, then pass c_str()
  String clientId = "esp32-client-" + String((uint32_t)ESP.getEfuseMac(), HEX);
 
  Serial.println("MQTT connecting...");
  while (!mqtt.connect(clientId.c_str())) {
    Serial.print(".");
    delay(1000);
  }
  Serial.println("\nMQTT connected!");
 
  // Optional subscription
  String subTopic = String(BASE_TOPIC) + "/#";
  mqtt.subscribe(subTopic);
  Serial.printf("Subscribed to %s\n", subTopic.c_str());
}
 
void setup() {
  Serial.begin(115200);
  delay(500);
 
  connectWiFi();
 
  mqtt.begin(MQTT_HOST, MQTT_PORT, net);
  mqtt.onMessage(messageReceived);
 
  // Optional: last will so brokers/clients know if we drop
  String willTopic = String(BASE_TOPIC) + "/status";
  mqtt.setWill(willTopic.c_str(), "offline", true, 1);
 
  connectMQTT();
 
  // Publish "online" once connected
  mqtt.publish(willTopic, "online", true, 1);
}
 
void loop() {
  connectWiFi();       // ensure WiFi
  if (!mqtt.connected()) connectMQTT();
  mqtt.loop();         // non-blocking
  delay(10);
 
  // Publish every 5 seconds
  if (millis() - lastPub > 5000) {
    lastPub = millis();
    String topic = String(BASE_TOPIC) + "/heartbeat";
    String payload = String("{\"uptime_ms\":") + millis() + "}";
    bool ok = mqtt.publish(topic, payload);
    Serial.printf("Publish %s => %s (%s)\n",
                  topic.c_str(), payload.c_str(), ok ? "OK" : "FAIL");
  }
}