/*
   Exercise 9 - MQTT Publisher
   ESP32 + Potentiometer
*/

#include <WiFi.h>
#include <PubSubClient.h>

// ------------------- WiFi -------------------
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// ------------------- MQTT -------------------
const char* mqtt_server = "broker.hivemq.com";
const int mqtt_port = 1883;

const char* topic_temperature = "vit/iot/temp";
const char* topic_status = "vit/iot/status";

// ------------------- Pins -------------------
#define POT_PIN 34
#define LED_PIN 23

// ------------------- Variables -------------------
WiFiClient espClient;
PubSubClient client(espClient);

unsigned long lastMsg = 0;
const long interval = 5000;   // publish every 5 seconds
int msgCount = 0;
float temperature = 0;

// ------------------- Setup -------------------
void setup() {
  Serial.begin(115200);

  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  Serial.println("EXERCISE 9 - MQTT PUBLISHER");
  Serial.println("Connecting to WiFi...");

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("\nWiFi Connected ✓");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  client.setServer(mqtt_server, mqtt_port);
}

// ------------------- Reconnect Function -------------------
void reconnect() {
  while (!client.connected()) {
    Serial.print("Connecting to MQTT...");

    String clientId = "ESP32_Publisher_";
    clientId += String(random(0xffff), HEX);

    if (client.connect(clientId.c_str())) {
      Serial.println(" Connected ✓");
      Serial.println("Client ID: " + clientId);

      // Publish online status
      client.publish(topic_status, "{\"status\":\"online\",\"device\":\"publisher\"}");
    } else {
      Serial.print(" Failed, rc=");
      Serial.print(client.state());
      Serial.println(" Retrying in 5 seconds...");
      delay(5000);
    }
  }
}

// ------------------- Main Loop -------------------
void loop() {

  if (!client.connected()) {
    reconnect();
  }

  client.loop();

  unsigned long now = millis();

  if (now - lastMsg > interval) {
    lastMsg = now;

    // Read potentiometer
    int potValue = analogRead(POT_PIN);

    // Convert to temperature (0–50°C)
    temperature = map(potValue, 0, 4095, 0, 500) / 10.0;

    msgCount++;

    // Create JSON payload
    String payload = "{";
    payload += "\"temp\":" + String(temperature, 1) + ",";
    payload += "\"count\":" + String(msgCount) + ",";
    payload += "\"time\":" + String(millis());
    payload += "}";

    Serial.println("\n--- PUBLISHING ---");
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");

    Serial.print("Payload: ");
    Serial.println(payload);

    // Publish
    if (client.publish(topic_temperature, payload.c_str())) {
      Serial.println("Publish Successful ✓");

      // Blink LED
      digitalWrite(LED_PIN, HIGH);
      delay(200);
      digitalWrite(LED_PIN, LOW);

    } else {
      Serial.println("Publish Failed ✗");
    }
  }
}