#include <WiFi.h>
#include <HTTPClient.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// -------- WiFi --------
const char* ssid = "Wokwi-GUEST";
const char* password = "";
String apiKey = "KKFB3R1UY0BY13S7";
const char* server = "http://api.thingspeak.com/update";

// -------- LCD --------
LiquidCrystal_I2C lcd(0x27, 16, 2);

// -------- Pins --------
#define GREEN_LED 25
#define YELLOW_LED 26
#define RED_LED 27
#define BUTTON_PIN 13

// -------- AQI --------
float calcAQI(float Cp, float Clow, float Chigh, float Ilow, float Ihigh) {
  return ((Ihigh - Ilow) / (Chigh - Clow)) * (Cp - Clow) + Ilow;
}

float AQI_PM25(float pm) {
  if (pm <= 30) return calcAQI(pm, 0, 30, 0, 50);
  if (pm <= 60) return calcAQI(pm, 30, 60, 50, 100);
  if (pm <= 90) return calcAQI(pm, 60, 90, 100, 200);
  if (pm <= 120) return calcAQI(pm, 90, 120, 200, 300);
  if (pm <= 250) return calcAQI(pm, 120, 250, 300, 400);
  return calcAQI(pm, 250, 350, 400, 500);
}

// -------- VARIABLES --------
float pm25 = 150;
float CO = 1.0;
float O3 = 90;
float temp = 25;
float hum = 60;
float wind = 2.0;

// inertia buffers
float pm25_mem = 150;
float CO_mem = 1.0;
float O3_mem = 90;

// mitigation
bool mitigation = false;
unsigned long mitigationStart = 0;
const int mitigationDuration = 60;

bool lastButton = HIGH;

// -------- SETUP --------
void setup() {
  Serial.begin(115200);

  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);

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

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) delay(300);
}

// -------- LOOP --------
void loop() {

  unsigned long t = millis() / 1000;
  bool isNight = (t % 7200 < 3600);

  // -------- BUTTON --------
  bool currentButton = digitalRead(BUTTON_PIN);
  if (lastButton == HIGH && currentButton == LOW) {
    mitigation = true;
    mitigationStart = millis() / 1000;
  }
  lastButton = currentButton;

  // -------- DAY/NIGHT BASELINES --------
  float base_pm25 = isNight ? 170 : 110;
  float base_CO   = isNight ? 1.4 : 0.8;
  float base_O3   = isNight ? 60  : 120;
  float base_temp = isNight ? 18  : 32;
  float base_hum  = isNight ? 75  : 50;
  float base_wind = isNight ? 1.2 : 3.0;

  // -------- SLOW DRIFT --------
  pm25 += (base_pm25 - pm25) * 0.003;
  CO   += (base_CO   - CO)   * 0.003;
  O3   += (base_O3   - O3)   * 0.003;
  temp += (base_temp - temp) * 0.002;
  hum  += (base_hum  - hum)  * 0.002;
  wind += (base_wind - wind) * 0.002;

  // -------- SMALL FLUCTUATIONS --------
  pm25 += random(-5, 6);   // gives ±5 variation
  CO   += random(-2, 3) * 0.05;
  O3   += random(-5, 6);
  temp += random(-2, 3) * 0.2;
  hum  += random(-3, 4);
  wind += random(-2, 3) * 0.1;

  // -------- MITIGATION --------
  if (mitigation) {
    unsigned long now = millis() / 1000;

    if (now - mitigationStart >= mitigationDuration) {
      mitigation = false;
    } else {
      pm25 += (100 - pm25) * 0.02;
      CO   += (0.7 - CO) * 0.02;
      O3   += (80 - O3) * 0.02;
      wind += (3.5 - wind) * 0.02;
    }
  }

  // -------- INERTIA --------
  pm25_mem = pm25_mem * 0.9 + pm25 * 0.1;
  CO_mem   = CO_mem   * 0.9 + CO   * 0.1;
  O3_mem   = O3_mem   * 0.9 + O3   * 0.1;

  pm25 = pm25_mem;
  CO   = CO_mem;
  O3   = O3_mem;

  // -------- LIMITS --------
  pm25 = constrain(pm25, 50, 300);
  CO   = constrain(CO, 0.5, 2.5);
  O3   = constrain(O3, 40, 200);
  temp = constrain(temp, 10, 40);
  hum  = constrain(hum, 20, 95);
  wind = constrain(wind, 0.5, 5);

  float PM10 = pm25 * 1.4;
  float AQI = AQI_PM25(pm25);

  // -------- ALERT --------
  int alert = 0;
  String text = "NORMAL";

  if (AQI > 200) {
    alert = 2;
    text = "HOTSPOT";
  } else if (AQI > 100) {
    alert = 1;
    text = "WARNING";
  }

  digitalWrite(GREEN_LED, alert == 0);
  digitalWrite(YELLOW_LED, alert == 1);
  digitalWrite(RED_LED, alert == 2);

  // -------- LCD --------
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("AQI:");
  lcd.print((int)AQI);

  lcd.setCursor(0, 1);
  lcd.print(text);

  // -------- SERIAL (IMPORTANT FOR YOU) --------
  Serial.print(isNight ? "NIGHT | " : "DAY | ");
  Serial.print("AQI: "); Serial.print(AQI);
  Serial.print(" | PM2.5: "); Serial.print(pm25);
  Serial.print(" | CO: "); Serial.print(CO);
  Serial.print(" | O3: "); Serial.print(O3);
  Serial.print(" | T: "); Serial.print(temp);
  Serial.print(" | H: "); Serial.print(hum);
  Serial.print(" | W: "); Serial.println(wind);

  // -------- THINGSPEAK --------
  static unsigned long lastUpload = 0;

  if (WiFi.status() == WL_CONNECTED && millis() - lastUpload > 15000) {

    lastUpload = millis();

    HTTPClient http;

    String url = server;
    url += "?api_key=" + apiKey;
    url += "&field1=" + String(pm25);
    url += "&field2=" + String(CO);
    url += "&field3=" + String(O3);
    url += "&field4=" + String(temp);
    url += "&field5=" + String(AQI);
    url += "&field6=" + String(hum);
    url += "&field7=" + String(wind);
    url += "&field8=" + String(alert);

    http.begin(url);
    http.GET();
    http.end();
  }

  delay(1000);
}