#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>

// Pin definitions
#define DHTPIN D2
#define DHTTYPE DHT22
#define MQ2_PIN A1
#define PIR_PIN D5
#define TRIG_PIN D3
#define ECHO_PIN D4
#define RED_LED D6
#define GREEN_LED D7
#define BLUE_LED D8

LiquidCrystal_I2C lcd(0x27, 16, 2);
DHT dht(DHTPIN, DHTTYPE);

// RGB LED control
void setRGB(uint8_t r, uint8_t g, uint8_t b) {
  analogWrite(RED_LED, r);
  analogWrite(GREEN_LED, g);
  analogWrite(BLUE_LED, b);
}

void setup() {
  pinMode(MQ2_PIN, INPUT);
  pinMode(PIR_PIN, INPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(BLUE_LED, OUTPUT);

  dht.begin();
  lcd.begin(16, 2);
  lcd.backlight();
}

void loop() {
  // Sensor readings
  int temp = (int)dht.readTemperature();
  int humid = (int)dht.readHumidity();
  int gas = analogRead(MQ2_PIN);
  bool motion = digitalRead(PIR_PIN);

  // Distance calculation
  digitalWrite(TRIG_PIN, LOW); delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH, 30000);
  int dist = (duration > 0) ? (duration / 58) : -1;

  // Display
  lcd.setCursor(0, 0);
  lcd.print(F("T:")); lcd.print(temp); lcd.print(F("C "));
  lcd.print(F("H:")); lcd.print(humid); lcd.print(F("%"));

  lcd.setCursor(0, 1);
  lcd.print(F("G:")); lcd.print(gas);
  lcd.print(F(" M:")); lcd.print(motion ? F("Y") : F("N"));

  // Alert condition
  bool alert = (gas > 400 || temp > 35 || motion || (dist >= 0 && dist < 10));
  setRGB(alert ? 255 : 0, alert ? 0 : 255, 0);

  delay(1000);
}