#include <WiFi.h>
#include <HTTPClient.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define GAS_PIN 34
#define LED_PIN 14
#define BUZZER_PIN 27

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// Telegram bot info
String BOT_TOKEN = "8388279702:AAGEUp9tiZznlAoI9_tKzdgswPrbB3EAlDA";
String CHAT_ID   = "7835992814";

// WiFi
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// Ngưỡng phát hiện gas
int thresholdValue = 2500;

// Tránh spam telegram
bool alertSent = false;
unsigned long lastAlertTime = 0;

void sendTelegram(String message) {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    String url = "https://api.telegram.org/bot" + BOT_TOKEN +
                 "/sendMessage?chat_id=" + CHAT_ID +
                 "&text=" + message;
    http.begin(url);
    http.GET();
    http.end();
  }
}

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

  pinMode(GAS_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  // WiFi
  WiFi.begin(ssid, password);
  Serial.print("Connecting WiFi...");
  while (WiFi.status() != WL_CONNECTED) {
    delay(300);
    Serial.print(".");
  }
  Serial.println(" Connected!");

  // OLED
  oled.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  oled.clearDisplay();
  oled.setTextSize(2);
  oled.setTextColor(WHITE);
  oled.setCursor(0, 0);
  oled.println("Gas Monitor");
  oled.display();
  delay(1000);
}

void loop() {
  int gasValue = analogRead(GAS_PIN);
  Serial.println(gasValue);

  oled.clearDisplay();
  oled.setCursor(0, 0);
  oled.setTextSize(1);
  oled.print("Gas Value: ");
  oled.println(gasValue);

  // =============================
  //       GAS VƯỢT NGƯỠNG
  // =============================
  if (gasValue > thresholdValue) {
    oled.setTextSize(2);
    oled.setCursor(0, 20);
    oled.println("DANGER!");
    oled.display();

    // LED + Buzzer nhấp nháy
    digitalWrite(LED_PIN, HIGH);
    tone(BUZZER_PIN, 1500);
    delay(200);
    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);

    // Gửi Telegram tránh spam mỗi 10 giây 1 lần
    if (!alertSent || millis() - lastAlertTime > 10000) {
      sendTelegram("⚠️ CẢNH BÁO! Khí gas vượt ngưỡng nguy hiểm!\nGiá trị: " + String(gasValue));
      alertSent = true;
      lastAlertTime = millis();
    }
  } 
  
  // =============================
  //       GAS AN TOÀN
  // =============================
  else {
    oled.setTextSize(2);
    oled.setCursor(0, 20);
    oled.println("SAFE");
    oled.display();

    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);

    alertSent = false;  // reset để nếu lần sau vượt ngưỡng sẽ gửi cảnh báo
  }

  delay(200);
}