#include <DHT.h>

// ======================================================
// PIN CONFIGURATION
// ======================================================

#define DHTPIN 2
#define DHTTYPE DHT11

#define MQ2_PIN A0
#define LDR_PIN A1
#define RELAY_PIN 7

// ======================================================
// SENSOR SETUP
// ======================================================

DHT dht(DHTPIN, DHTTYPE);

// ======================================================
// THRESHOLD VALUES
// ======================================================

int gasThreshold = 400;
int lightThreshold = 300;
float tempThreshold = 30.0;

// ======================================================
// SETUP FUNCTION
// ======================================================

void setup() {

  Serial.begin(9600);

  // Relay setup
  pinMode(RELAY_PIN, OUTPUT);

  // Relay OFF initially
  digitalWrite(RELAY_PIN, HIGH);

  // Start DHT sensor
  dht.begin();

  Serial.println("==================================");
  Serial.println(" SMART MONITORING SYSTEM STARTED ");
  Serial.println("==================================");
}

// ======================================================
// MAIN LOOP
// ======================================================

void loop() {

  // -----------------------------
  // READ DHT11 SENSOR
  // -----------------------------

  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

  // Check sensor reading
  if (isnan(temperature) || isnan(humidity)) {

    Serial.println("DHT11 Sensor Reading Failed!");
    delay(2000);
    return;
  }

  // -----------------------------
  // READ ANALOG SENSORS
  // -----------------------------

  int gasValue = analogRead(MQ2_PIN);
  int lightValue = analogRead(LDR_PIN);

  // -----------------------------
  // DISPLAY SENSOR VALUES
  // -----------------------------

  Serial.println("\n========== SENSOR DATA ==========");

  Serial.print("Temperature : ");
  Serial.print(temperature);
  Serial.println(" °C");

  Serial.print("Humidity    : ");
  Serial.print(humidity);
  Serial.println(" %");

  Serial.print("Gas Value   : ");
  Serial.println(gasValue);

  Serial.print("Light Value : ");
  Serial.println(lightValue);

  // =====================================================
  // GAS LEAKAGE DETECTION
  // =====================================================

  if (gasValue > gasThreshold) {

    Serial.println("WARNING: GAS LEAKAGE DETECTED!");
    Serial.println("Relay Activated -> Device OFF");

    // Relay ON (Active LOW)
    digitalWrite(RELAY_PIN, LOW);
  }
  else {

    // Relay OFF
    digitalWrite(RELAY_PIN, HIGH);
  }

  // =====================================================
  // TEMPERATURE MONITORING
  // =====================================================

  if (temperature > tempThreshold) {

    Serial.println("HIGH TEMPERATURE DETECTED!");
  }
  else {

    Serial.println("Temperature Normal");
  }

  // =====================================================
  // LIGHT MONITORING
  // =====================================================

  if (lightValue < lightThreshold) {

    Serial.println("Dark Environment -> Light Needed");
  }
  else {

    Serial.println("Bright Environment");
  }

  Serial.println("=================================\n");

  // Wait before next reading
  delay(2000);
}