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

LiquidCrystal_I2C lcd(0x27, 16, 2);

// -------- DHT --------
#define DHTPIN 4
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// -------- SENSOR PINS --------
#define PM25_PIN 34
#define WIND_PIN 35
#define CO_PIN   32
#define O3_PIN   33

// -------- LED --------
#define GREEN_LED 25
#define YELLOW_LED 26
#define RED_LED 27

// -------- 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);
}

float AQI_CO(float co) {
  if (co <= 1) return calcAQI(co, 0, 1, 0, 50);
  if (co <= 2) return calcAQI(co, 1, 2, 50, 100);
  return calcAQI(co, 2, 10, 100, 200);
}

float AQI_O3(float o3) {
  if (o3 <= 50) return calcAQI(o3, 0, 50, 0, 50);
  if (o3 <= 100) return calcAQI(o3, 50, 100, 50, 100);
  return calcAQI(o3, 100, 200, 100, 200);
}

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

  lcd.init();
  lcd.backlight();
  dht.begin();

  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
}

void loop() {

  // -------- RAW VALUES --------
  float pm25 = map(analogRead(PM25_PIN), 0, 4095, 0, 300);
  float wind = map(analogRead(WIND_PIN), 0, 4095, 0, 5);
  float co   = map(analogRead(CO_PIN),   0, 4095, 0, 3);
  float o3   = map(analogRead(O3_PIN),   0, 4095, 0, 200);

  float temp = dht.readTemperature();
  float hum  = dht.readHumidity();

  if (isnan(temp) || isnan(hum)) {
    Serial.println("DHT Error");
    return;
  }

  // -------- DELHI LOGIC --------

  // Temperature effects
  o3 *= (1 + 0.01 * (temp - 25));
  pm25 *= (1 - 0.005 * (temp - 25));

  // Humidity effects
  if (hum < 30) pm25 *= 1.2;
  if (hum > 70) pm25 *= 1.15;

  // Wind effects
  pm25 *= (1 - 0.08 * wind);
  if (wind > 3.5) pm25 *= 1.2;

  // CO stagnation
  if (wind < 1.5) co *= 1.2;

  // Rain washout
  if (hum > 90) pm25 *= 0.7;

  // PM10 approx
  float PM10 = pm25 * 1.5;

  // -------- AQI --------
  float aqi_pm25 = AQI_PM25(pm25);
  float aqi_co   = AQI_CO(co);
  float aqi_o3   = AQI_O3(o3);

  float AQI = max(aqi_pm25, max(aqi_co, aqi_o3));

  // -------- 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 --------
  Serial.print("PM2.5: "); Serial.print(pm25);
  Serial.print(" | CO: "); Serial.print(co);
  Serial.print(" | O3: "); Serial.print(o3);
  Serial.print(" | Temp: "); Serial.print(temp);
  Serial.print(" | Hum: "); Serial.print(hum);
  Serial.print(" | Wind: "); Serial.print(wind);
  Serial.print(" | AQI: "); Serial.println(AQI);

  delay(500);
}