#include <DHTesp.h>
#include <WiFi.h>         // Library for connecting the ESP32 to a Wi-Fi network.
#include <PubSubClient.h> // Publish and subscribe to messages on an MQTT broker.
#include <NTPClient.h>    // Provides access to NTP servers for synchronizing the ESP32's internal clock.
#include <WiFiUdp.h>      // Used by NTPClient for communication with NTP servers.

// Define connection pins
#define DHT_PIN 15
#define BUZZER 12

// Initializing objects related to WiFi, MQTT communication, and time synchronization.
WiFiClient espClient;                 // A WiFiClient object for establishing a connection to the Wi-Fi network.
PubSubClient mqttClient(espClient);   // A PubSubClient object used to interact with the MQTT broker using espClient connection
WiFiUDP ntpUDP;                       // A WiFiUdp object used by NTPClient for communication with NTP servers.
NTPClient timeClient(ntpUDP);         // An NTPClient object for synchronizing the ESP32's clock with an NTP server.

DHTesp dhtSensor;   // A DHTesp object representing the DHT sensor.

// Variable for temperature
char tempAr[6];   // A character array of size 6 to store the temperature reading as a string.

// Variables for scheduling alarm
bool isScheduledON = false;
unsigned long scheduledOnTime;

/********************************************************************************/
/********************************************************************************/

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

  setupWifi();
  setupMqtt();

  dhtSensor.setup(DHT_PIN, DHTesp :: DHT22);   // Initializes the DHT sensor object (dhtSensor).

  timeClient.begin();   //  Initializing the NTP client for communication with NTP servers.
  timeClient.setTimeOffset(5.5 * 3600);   // Adjust the retrieved NTP time to match your local time zone.

  // Sets the buzzer pin as output and sets it to LOW initially.
  pinMode(BUZZER, OUTPUT);
  digitalWrite(BUZZER, LOW);
}

/********************************************************************************/
/********************************************************************************/

void loop() {

  if (!mqttClient.connected()) {   // Checks if the connection to the MQTT broker is lost.
    connectToBroker();             // Reconnects if necessary using connectToBroker().
  }
  mqttClient.loop();   // Keeps the MQTT client connection active and manages message exchange.

  updateTemperature();
  Serial.println(tempAr);
  mqttClient.publish("EE-Arjun-TEMP", tempAr); // Publishes tempAr to the MQTT broker.

  checkSchedule();

  delay(500);
}

/********************************************************************************/

void updateTemperature() {
  TempAndHumidity data = dhtSensor.getTempAndHumidity();
  String(data. temperature, 2).toCharArray(tempAr, 6);
}

/********************************************************************************/

void setupWifi() {
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println("Wokwi-GUEST");
  WiFi.begin("Wokwi-GUEST", "");   // Connects the ESP32 to a WiFi network (SSID, Password).

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

/********************************************************************************/

void setupMqtt() {
  mqttClient.setServer("test.mosquitto.org", 1883);   // Sets the MQTT broker server.
  mqttClient.setCallback(receiveCallback);
  // setCallback function allows you to specify a function that will be called
  // whenever a message is received on a topic the client is subscribed to.
}

/********************************************************************************/

// This function gets called whenever a message is received on a topic the ESP32 is subscribed to.
void receiveCallback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");

  char payloadCharAr[length];
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);      // Prints each byte of the payload data as a character.
    payloadCharAr[i] = (char)payload[i]; // Copies each byte of the payload data into the payloadCharAr character array
  }
  Serial.println();

  // strcmp - String compare
  // If topic and EE-ARJUN-MAIN-ON-OFF matches, strcmp returns 0
  if (strcmp(topic, "EE-ARJUN-MAIN-ON-OFF") == 0) {
    buzzerOn(payloadCharAr[0] == 't');
  } else if (strcmp(topic, "EE-ARJUN-SCH-ON-OFF") == 0) {
    if (payloadCharAr[0] == 'N') {
      isScheduledON = false;
    } else {
      isScheduledON = true;
      scheduledOnTime = atol(payloadCharAr);
    }
  }
}

/********************************************************************************/

void connectToBroker() {
  while (!mqttClient.connected()) {
    Serial.println("Attempting MQTT connection ... ");
    if (mqttClient.connect("ESP32-56465653791")) {   // The connect() method returns true if the connection is successful
      Serial.println("Connected to MQTT broker");
      mqttClient.subscribe("EE-ARJUN-MAIN-ON-OFF");
      mqttClient.subscribe("EE-ARJUN-SCH-ON-OFF");
    } else {
      Serial.print("failed ");
      Serial.println(mqttClient.state());   // To get the connection error code.
      delay(2000);
    }
  }
}

/********************************************************************************/

void buzzerOn(bool on) {
  if (on) {
    tone(BUZZER, 256);
  } else {
    noTone(BUZZER);
  }
}

/********************************************************************************/

unsigned long getTime() {
  timeClient.update();
  return timeClient.getEpochTime();
}

/********************************************************************************/

void checkSchedule() {
  if (isScheduledON) {
    unsigned long currentTime = getTime();
    if (currentTime > scheduledOnTime) {
      buzzerOn(true);
      isScheduledON = false;
      mqttClient. publish("EE-ARJUN-MAIN-ON-OFF-ESP", "1");
      mqttClient. publish("EE-ARJUN-SCH-ESP-ON", "0");
      Serial.println("Scheduled On");
    }
  }
}