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

// Wi-Fi credentials
const char* ssid = "husam";
const char* password = "18002859";

// MQTT broker
const char* mqtt_server = "broker.hivemq.com";
const char* topic = "sensor/data";

// DHT22 settings
#define DHTPIN 33      // DHT22 pin
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// MQ-135 settings
#define MQ135_PIN 34  // MQ-135 pin
// Calibration values (from the datasheet curve)
#define RZERO 76.63   // Clean air resistance ratio

// Dust sensor settings
#define DUST_PIN 36   // DSM501A pin

WiFiClient espClient;
PubSubClient client(espClient);

/**
 * This function sets up the WiFi connection.
 * It initializes the serial communication, prints the SSID of the WiFi network,
 * connects to the WiFi network, and waits until the connection is established.
 * Then it prints the IP address of the ESP32.
 */
void setup_wifi() {
  // Delay for 10 milliseconds to allow the serial communication to stabilize
  delay(10);

  // Initialize the serial communication with a baud rate of 921600
  Serial.begin(921600);

  // Print a new line character to separate the previous output
  Serial.println();

  // Print the message "Connecting to " followed by the SSID of the WiFi network
  Serial.print("Connecting to ");
  Serial.println(ssid);

  // Connect to the WiFi network using the provided SSID and password
  WiFi.begin("Wokwi-GUEST");

  // Wait until the connection is established
  while (WiFi.status() != WL_CONNECTED) {
    // Delay for 500 milliseconds before checking the connection status again
    delay(500);
    // Print a dot character to show the progress of the connection attempt
    Serial.print(".");
  }

  // Print a new line character to separate the previous output
  Serial.println("");

  // Print the message "WiFi connected" to indicate that the connection is established
  Serial.println("WiFi connected");

  // Print the message "IP address: " followed by the IP address of the ESP32
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
}

/**
 * This function attempts to reconnect to the MQTT broker until it succeeds or
 * until the user cancels the operation.
 *
 * The function loops until the client is connected, trying to connect each time
 * by calling `client.connect("ESP32Client")`. If the connection is successful,
 * it prints the message "connected". If the connection fails, it prints the
 * message "failed, rc=XXX try again in 5 seconds", where XXX is the error code
 * returned by `client.state()`. After each failed attempt it waits for 5
 * seconds before trying again.
 *
 * The function is called in the `loop()` function to attempt to reconnect the
 * client if it is not connected.
 */
void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP32Client")) {
      Serial.println("connected");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

/**
 * This function is called once when the ESP32 starts up.
 * It sets up the serial communication at a baud rate of 115200,
 * sets up the WiFi connection, sets up the MQTT client, and
 * initializes the DHT22 sensor.
 */
void setup() {
  // Initialize the serial communication at a baud rate of 115200
  Serial.begin(921600);

  // Set up the WiFi connection
  setup_wifi();

  // Set up the MQTT client to connect to the specified server on port 1883
  client.setServer(mqtt_server, 1883);

  // Initialize the DHT22 sensor
  dht.begin();
}

void loop() {
  // Check if the MQTT client is not connected
  if (!client.connected()) {
    // Attempt to reconnect to the MQTT broker
    reconnect();
  }

  // Keep the MQTT client connected by calling its loop function
  client.loop();

  // Read temperature and humidity from the DHT22 sensor
  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

// Read gas concentration from the MQ-135 sensor
  int mq135_raw = analogRead(MQ135_PIN);
  float r0 = RZERO; // Calibrate with clean air
  float rs = ((1023.0 * 5.0 / mq135_raw) - 1.0) * 10000.0;
  float ratio = rs / r0;
  float ppm = pow(10, ((log10(ratio) - 0.45) / -0.37)); // Derived from the datasheet curve

  // Read dust concentration from the DSM501A sensor
  int dust_value = pulseIn(DUST_PIN, LOW);
  float concentration = 0.001915 * dust_value + 0.09522; // Example calibration

  // Create a JSON payload with the sensor data
  String payload = "{\"temperature\":";
  payload += temperature;
  payload += ",\"humidity\":";
  payload += humidity;
  payload += ",\"gas\":";
  payload += ppm;
  payload += ",\"dust\":";
  payload += concentration;
  payload += "}";

  // Print the JSON payload to the serial monitor
  Serial.print("Publishing payload: ");
  // Print the payload to the serial monitor
  Serial.println(payload.c_str());
  // Publish the payload to the MQTT topic
  client.publish(topic, payload.c_str());

  // Delay for 10 seconds before publishing the next data set
  delay(10000); // Publish data every 10 seconds
}