#include <WiFi.h>
#include <PubSubClient.h>
#include "DHTesp.h"
#include <math.h>

/* ===== Pins ===== */
#define DHT_PIN 15
#define LED_PIN 13
#define MQ2_PIN 34

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

/* ===== MQTT ===== */
const char* mqttServer = "broker.hivemq.com";
const int mqttPort = 1883;

/* Topics */
const char* TOPIC_LED  = "esp32/devender/led";
const char* TOPIC_TEMP = "esp32/yourname/temperature";
const char* TOPIC_HUM  = "esp32/yourname/humidity";
const char* TOPIC_MQ2  = "esp32/yourname/smoke";

/* ===== MQ2 ===== */
const float Vcc = 3.3;
const float RL = 5.0;
float Ro = 10.0;

/* ===== Objects ===== */
WiFiClient espClient;
PubSubClient client(espClient);
DHTesp dht;

/* ===== MQ2 Helpers ===== */
float getRs(int adc) {
  if (adc == 0) return 0;
  float Vout = (adc / 4095.0) * Vcc;
  return ((Vcc / Vout) - 1.0) * RL;
}

float rsRoToPPM(float ratio) {
  if (ratio <= 0) return 0;
  return 1000.0 * pow(ratio, -2.2);
}

/* ===== MQTT Callback (LED Control) ===== */
void callback(char* topic, byte* payload, unsigned int length) {
  String msg;
  for (unsigned int i = 0; i < length; i++) msg += (char)payload[i];
  msg.toUpperCase();

  if (String(topic) == TOPIC_LED) {
    digitalWrite(LED_PIN, (msg == "ON") ? HIGH : LOW);
  }
}

/* ===== MQTT Reconnect ===== */
void reconnect() {
  while (!client.connected()) {
    String cid = "ESP32-" + String(random(0xffff), HEX);
    if (client.connect(cid.c_str())) {
      client.subscribe(TOPIC_LED);
    } else {
      delay(3000);
    }
  }
}

/* ===== Setup ===== */
void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  dht.setup(DHT_PIN, DHTesp::DHT22);

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) delay(500);

  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback);

  delay(20000); // MQ2 warm-up

  float rsSum = 0;
  for (int i = 0; i < 50; i++) {
    rsSum += getRs(analogRead(MQ2_PIN));
    delay(100);
  }
  Ro = (rsSum / 50.0) / 9.83;
}

/* ===== Loop ===== */
void loop() {
  if (!client.connected()) reconnect();
  client.loop();

  static unsigned long lastSend = 0;
  if (millis() - lastSend > 5000) {
    lastSend = millis();

    /* ---- DHT22 ---- */
    TempAndHumidity d = dht.getTempAndHumidity();
    if (!isnan(d.temperature)) {
      char tempStr[10];
      dtostrf(d.temperature, 4, 2, tempStr);
      client.publish(TOPIC_TEMP, tempStr);
    }

    if (!isnan(d.humidity)) {
      char humStr[10];
      dtostrf(d.humidity, 4, 2, humStr);
      client.publish(TOPIC_HUM, humStr);
    }

    /* ---- MQ2 ---- */
    float ppm = rsRoToPPM(getRs(analogRead(MQ2_PIN)) / Ro);
    char smokeStr[10];
    dtostrf(ppm, 4, 2, smokeStr);
    client.publish(TOPIC_MQ2, smokeStr);
  }
}