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

#define DHTPIN 15
#define DHTTYPE DHT22

#define MQ2_PIN 34
#define BUZZER 25
#define LED_RED 26
#define LED_GREEN 27

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

int gasThreshold = 2000;
float tempThreshold = 40;

// Lọc nhiễu MQ2
#define SAMPLE_SIZE 10
int gasSamples[SAMPLE_SIZE];
int sampleIndex = 0;

bool fireState = false;
bool gasAlert = false;

unsigned long previousMillis = 0;
unsigned long interval = 1000;

int readGasFiltered() {
  gasSamples[sampleIndex] = analogRead(MQ2_PIN);
  sampleIndex = (sampleIndex + 1) % SAMPLE_SIZE;

  int sum = 0;
  for(int i = 0; i < SAMPLE_SIZE; i++) {
    sum += gasSamples[i];
  }
  return sum / SAMPLE_SIZE;
}

void setup() {
  Serial.begin(115200);

  pinMode(BUZZER, OUTPUT);
  pinMode(LED_RED, OUTPUT);
  pinMode(LED_GREEN, OUTPUT);

  digitalWrite(LED_GREEN, HIGH);

  dht.begin();

  lcd.init();
  lcd.backlight();

  lcd.setCursor(0,0);
  lcd.print("Fire System");
  delay(2000);
  lcd.clear();

  // Khởi tạo mảng lọc
  for(int i = 0; i < SAMPLE_SIZE; i++) {
    gasSamples[i] = 0;
  }
}

void loop() {

  unsigned long currentMillis = millis();

  if(currentMillis - previousMillis >= interval){
    previousMillis = currentMillis;

    int gasValue = readGasFiltered();
    float temp = dht.readTemperature();

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

    Serial.print("Temp: ");
    Serial.println(temp);

    // ===== LOGIC =====

    // Cảnh báo gas
    if(gasValue > gasThreshold){
      gasAlert = true;
    } else {
      gasAlert = false;
    }

    // Cảnh báo cháy
    if(gasValue > gasThreshold && temp > tempThreshold){
      fireState = true;
    } else {
      fireState = false;
    }

    // ===== HIỂN THỊ =====
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("T:");
    lcd.print(temp);
    lcd.print(" G:");
    lcd.print(gasValue);

    // ===== XỬ LÝ =====

    if(fireState){
      lcd.setCursor(0,1);
      lcd.print("!!! FIRE !!!");

      digitalWrite(LED_GREEN, LOW);

      digitalWrite(LED_RED, HIGH);
      tone(BUZZER, 1000);

    }
    else if(gasAlert){
      lcd.setCursor(0,1);
      lcd.print("Gas Warning!");

      digitalWrite(LED_GREEN, LOW);

      digitalWrite(LED_RED, HIGH);
      noTone(BUZZER); // chỉ cảnh báo nhẹ

    }
    else{
      lcd.setCursor(0,1);
      lcd.print("System Normal");

      digitalWrite(LED_GREEN, HIGH);
      digitalWrite(LED_RED, LOW);
      noTone(BUZZER);
    }
  }

  // Nhấp nháy LED khi cháy (không dùng delay)
  if(fireState){
    static unsigned long blinkMillis = 0;
    static bool ledState = false;

    if(millis() - blinkMillis >= 300){
      blinkMillis = millis();
      ledState = !ledState;
      digitalWrite(LED_RED, ledState);
    }
  }
}