/* 
 * Lab Trial Test 2
 * Name: Nas
 * Room: 06-03-0004
 * Date: 18/7/2025
 * Requirements:
 * 1. Blink the red LED every 2 seconds.
 * 2. When the MQTT topic /<your_student_id>/y_led receives an "on" payload, turn on yellow LED.
 * 3. When the same topic receives an "off" payload, turn off the yellow LED.
 * 4. Every 2 seconds, publish potentiometer's raw value to MQTT topic <your_student_id>/pot/raw
 */

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

unsigned long previousMillis = 0;  
int interval = 2000;
int state = LOW;

const char* ssid = "Wokwi-GUEST";
const char* password = "";
const char* hostname = "broker.hivemq.com";
const int   portnum = 1883;

WiFiClient espClient;
PubSubClient client(espClient);
const char* espClientName = "<a_Uniqud_ID>";

void setup_wifi() {
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("Given IP by the router to ESP32 is ");
  Serial.println(WiFi.localIP());
}

void connectMQTT() {
  while(!client.connected()) {
    Serial.println("Connecting to MQTT ...");
    if (client.connect(espClientName)) {
      Serial.println("Connected");
      MQTTSubscribe();
    }
    else {
      Serial.print("Failed with state ");
      Serial.print(client.state() );
      delay(2000);
    }
  }
}

void callback(const char *topic, byte *payload, unsigned int length) {
  String message;
  Serial.print("Message received in topic: ");
  Serial.print(topic);
  Serial.print(" length is: ");
  Serial.println(length);

  Serial.print("Data received from broker: ");
  for (int i=0; i<length; i++) {
    Serial.print((char)payload[i]);
    message += (char)payload[i];
  }
  Serial.println();

  if (String(topic) == "_____") {          // TODO 1
    if (message == "____") {               // TODO 2a
      ____________;                        // TODO 2b
    }
    else if (message == "____") {          // TODO 3a
      ____________;                        // TODO 3b
    }
  }
}

void MQTTSubscribe() {
  client.subscribe("__________________");  // TODO 4
}

void setup_MQTT() {
  client.setServer(hostname, portnum);
  client.setCallback(callback);
}

void setup() {
  Serial.begin(115200);

  pinMode(___, OUTPUT);                    // TODO 5a
  pinMode(___, OUTPUT);                    // TODO 5b
  pinMode(___, INPUT);                     // TODO 6

  setup_wifi();
  setup_MQTT();
}

void loop() {
  if (!client.connected()) {
    connectMQTT();
  }
  client.loop();

  unsigned long currentMillis = millis(); 
  if (currentMillis-previousMillis >= interval) { 
    previousMillis = currentMillis; 
    if (state == LOW) {
      state = ____;                        // TODO 7a
      digitalWrite(____, ____);            // TODO 7b
    }
    else {
      state = ____;                        // TODO 8a
      digitalWrite(____, ____);            // TODO 8b
    }

    int val = analogRead(___);             // TODO 9
    char str[6];
    sprintf(str, "%d", val);
    client.publish("____________", str);   // TODO 10
  }
}