/*  Prac Test 2 (DEEC1)
* Name: [WEE XIN ING]
* Room: [06-03-04]
* Date: 25-July-2025
*/

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

unsigned long previousMillis = 0;  
int interval = 2000;
int redLedState = 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 = "<1657276R>";

// State variables for voltage limit handling
bool voltageExceeded85 = false;
bool voltageDroppedBelow83 = false;

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();

  // Handle MQTT messages for yellow LED control
  if (String(topic) == "1657276R/LED") { // TODO 1a: check for received topic

    // TODO 1b: Turn on/off the yellow LED based on payload
  if (message == "High") {
    digitalWrite(18, HIGH);
    }
    else if (message == "Low") {
      digitalWrite(18, LOW);
    }
  }
}

void MQTTSubscribe() {
  client.subscribe("1657276R/LED"); // TODO 2a: Subscribe topic
}

void setup_MQTT() {
  client.setServer(hostname, portnum);      // TODO 2b: Setup MQTT broker and port
  client.setCallback(callback);             // TODO 2c: Setup callback
}

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

  // Pin configuration
  pinMode(18, OUTPUT); // Yellow LED
  pinMode(19, OUTPUT); // Red LED
  pinMode(36, INPUT);  // Potentiometer (VP)

  // Initialize WiFi and MQTT
  setup_wifi();
  setup_MQTT();
}

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

  // Perform all actions every 2 seconds
  unsigned long currentMillis =  millis();         // TODO 3a: Get current milliseconds
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMilli;               // TODO 3b: Update previousMillis
    
    if (redLedState == LOW) {
      redLedState = HIGH;
      digitalWrite(19, HIGH); // Turn on red LED
    } else {
      redLedState = LOW;
      digitalWrite(19, LOW);  // Turn off red LED
    }

    int adcValue = analogRead(36);
    float voltage = (adcValue / 4095) * val;       // TODO 4a: Convert ADC value to voltage

    char voltageStr[10];
    dtostrf(voltage, 1, 2, voltageStr); // Convert float to string with 2 decimal places
    client.publish("1657276R/VAL", voltageStr);    // TODO 4b: Publish the voltage

    float maxVoltage = 5.0; // Maximum voltage (5V)
    float threshold85 = 0.85 * maxVoltage; // 85% of maximum voltage
    float threshold83 = 0.83 * maxVoltage; // 83% of maximum voltage

    if (voltage > threshold85 && !voltageExceeded85) {
      client.publish("1657276R/VAL/LIMIT", "App");  // TODO 5a: limit violation alarm
      voltageExceeded85 = true;
      voltageDroppedBelow83 = false; // Reset the drop state
    } else if (voltage < threshold83 && !voltageDroppedBelow83) {
      client.publish("1657276R/VAL/LIMIT", "Dis);  // TODO 5b: limit violation alarm
      voltageDroppedBelow83 = true;
      voltageExceeded85 = false; // Reset the exceed state
    }
  }
}