// Include WiFi library for ESP32 WiFi functions
#include <WiFi.h>

// Include ThingSpeak library to send data to cloud
#include <ThingSpeak.h>

// Include DHT sensor library
#include "DHTesp.h"

// WiFi credentials (Wokwi default WiFi)
char ssid[] = "Wokwi-GUEST";   // WiFi network name
char pass[] = "";             // WiFi password (empty for Wokwi)

// Create a WiFi client object
WiFiClient client;

// ThingSpeak channel number
unsigned long myChannelNumber = 2581126;

// ThingSpeak Write API Key
const char * myWriteAPIKey = "ARI56ZCIQ06EBI6H";

// Create DHT sensor object
DHTesp dhtSensor;

// Structure to store temperature and humidity values
TempAndHumidity data;

// Define DHT sensor pin
const int DHT_PIN = 15;

// Define Ultrasonic sensor pins
const int TRIG_PIN = 2;
const int ECHO_PIN = 4;

// Variables to store ultrasonic pulse duration and distance
long duration, distance;

// Variable to store HTTP status code from ThingSpeak
int statusCode;

void setup() {

  // Start serial communication for debugging
  Serial.begin(115200);

  // Set ESP32 WiFi mode as Station
  WiFi.mode(WIFI_STA);

  // Initialize ThingSpeak with WiFi client
  ThingSpeak.begin(client);

  // Initialize DHT22 sensor on specified pin
  dhtSensor.setup(DHT_PIN, DHTesp::DHT22);

  // Set TRIG pin as OUTPUT
  pinMode(TRIG_PIN, OUTPUT);

  // Set ECHO pin as INPUT
  pinMode(ECHO_PIN, INPUT);
}

void loop() {

  // Ensure WiFi connection is active
  connectToCloud();

  // Read sensor values
  computeData();

  // Upload data to ThingSpeak
  writeData();

  // Delay before next cycle
  delay(1000);
}

// Function to connect ESP32 to WiFi
void connectToCloud(){

  // Check if WiFi is not connected
  if(WiFi.status() != WL_CONNECTED) {

    Serial.print("Attempting to connect");

    // Keep trying until connected
    while(WiFi.status() != WL_CONNECTED) {

      // Start WiFi connection
      WiFi.begin(ssid, pass);

      // Print dots while waiting
      for(int i=0;i<5;i++) {
        Serial.print(".....");
        delay(1000);
      }
    }

    // Print confirmation message
    Serial.println("\nConnected.");
  }
}

// Function to read DHT and Ultrasonic sensor data
void computeData(){

  // Measure distance using ultrasonic sensor
  distance = getDistanceInCentimeters();

  // Read temperature and humidity from DHT sensor
  data = dhtSensor.getTempAndHumidity();

  // Display sensor values on Serial Monitor
  Serial.println("-----------");
  Serial.println("Humidity: " + String(data.humidity));
  Serial.println("Temperature: " + String(data.temperature));
  Serial.println("Distance: " + String(distance));
  Serial.println("-----------");
}

// Function to upload data to ThingSpeak
void writeData()
{
  // Set Field 1 with humidity value
  ThingSpeak.setField(1, data.humidity);

  // Set Field 2 with temperature value
  ThingSpeak.setField(2, data.temperature);

  // Set Field 3 with distance value
  ThingSpeak.setField(3, distance);

  // Send data to ThingSpeak
  statusCode = ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);

  // Check if data upload is successful
  if(statusCode == 200)
    Serial.println(" \n Channel Update Successful");
  else
    Serial.println("Problem Writing data. HTTP error code :" + String(statusCode));

  // Delay to avoid rapid uploads
  delay(1500);
}

// Function to calculate distance using Ultrasonic sensor
long getDistanceInCentimeters() {

  // Ensure trigger pin is LOW
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  // Send 10 microsecond HIGH pulse
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Measure pulse duration on ECHO pin
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance using speed of sound
  return (duration * 0.034 / 2);
}