#include <WiFi.h>
#include <ThingSpeak.h>

#define gasPin 34        // Analog input pin for MQ-2
#define buzzerPin 25     // Buzzer pin
#define RL 10000.0       // 10k Ohms
#define R0 3050.0        // Replace with your own calibrated R0 value

// Wi-Fi
const char* ssid = "Wokwi-GUEST";     // Change as needed
const char* password = "";            // Change as needed

// ThingSpeak
WiFiClient client;
unsigned long channelID = 2869806;     // Your channel ID
const char* writeAPIKey = "6Y3JTFY09CMPEMNC";   // Your Write API key

void setup() {
  Serial.begin(115200);
  pinMode(buzzerPin, OUTPUT);

  WiFi.begin(ssid, password);
  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(1000);
  }
  Serial.println("\nWi-Fi Connected");

  ThingSpeak.begin(client);
}

void loop() {
  int adcValue = analogRead(gasPin);
  float voltage = adcValue * (3.3 / 4095.0);
  float Rs = (3.3 - voltage) * RL / voltage;
  float ratio = Rs / R0;

  // MQ-2 LPG/Smoke PPM calculation (approximation)
  float ppm = 100 * pow(ratio, -2.6);
  digitalWrite(buzzerPin, LOW);
  Serial.print("Gas Concentration: ");
  Serial.print(ppm);
  Serial.println(" ppm");

  // Send ppm data to ThingSpeak Field 3 ✅
  ThingSpeak.setField(3, ppm);

  int statusCode = ThingSpeak.writeFields(channelID, writeAPIKey);
  if (statusCode == 200) {
    Serial.println("ThingSpeak update successful.");
  } else {
    Serial.print("ThingSpeak update failed, Error code: ");
    Serial.println(statusCode);
  }

  // Buzzer alert if ppm exceeds 500 (adjustable)
  if (ppm > 500) {
    digitalWrite(buzzerPin, HIGH);
    delay(1000); // Buzzer ON
    Serial.println("WARNING! High Gas Concentration Detected!");
  } else {
    digitalWrite(buzzerPin, LOW);   // Buzzer OFF
  }

  delay(15000);  // ThingSpeak minimum interval
}