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

// ================== PIN DEFINITIONS ==================
#define DHTPIN      13
#define DHTTYPE     DHT22

#define TRIG_PIN    12    // Ultrasonic Trigger
#define ECHO_PIN    14     // Ultrasonic Echo
#define RELAY_PIN   19     // Relay
#define BUZZER_PIN  27     // Buzzer
#define LDR_PIN     15     // LDR

// ================== THRESHOLDS ==================
#define TEMP_HIGH   30.0
#define TEMP_LOW    25.0
#define HUM_LOW     50.0
#define HUM_HIGH    60.0
#define DIST_MAX    20.0     // Buzzer if distance > 20 cm
#define LUX_THRESHOLD 100

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

// Function to make different beeps
void beep(int times, int delayTime = 150) {
  for(int i = 0; i < times; i++) {
    digitalWrite(BUZZER_PIN, HIGH);
    delay(delayTime);
    digitalWrite(BUZZER_PIN, LOW);
    delay(delayTime);
  }
}

float getLux() {
  int raw = analogRead(LDR_PIN);
  float voltage = raw * (3.3 / 4095.0);
  if (voltage < 0.1) return 0;
  
  float ldrResistance = (10.0 * (3.3 - voltage)) / voltage;
  float lux = 100000.0 / (ldrResistance * 10.0);
  return lux;
}

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

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  digitalWrite(RELAY_PIN, HIGH);   // Relay OFF
  digitalWrite(BUZZER_PIN, LOW);

  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.print("Distance Updated");
  lcd.setCursor(0,1);
  lcd.print("Ready...");
  delay(2000);
  lcd.clear();
}

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // Read Ultrasonic Distance
  digitalWrite(TRIG_PIN, LOW); delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  float distance = pulseIn(ECHO_PIN, HIGH) * 0.034 / 2.0;

  float lux = getLux();

  if (isnan(h) || isnan(t)) {
    lcd.clear();
    lcd.print("DHT22 Error!");
    delay(1000);
    return;
  }

  // ================== LCD DISPLAY ==================
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("T:");
  lcd.print(t,1);
  lcd.print(" H:");
  lcd.print(h,1);
  lcd.print("%");

  lcd.setCursor(0,1);
  lcd.print("D:");
  lcd.print(distance,0);
  lcd.print("cm L:");
  lcd.print(lux,0);

  Serial.printf("Temp: %.1f°C | Hum: %.1f%% | Dist: %.0fcm | Lux: %.0f\n", t, h, distance, lux);

  // ================== BUZZER CONDITIONS ==================

  // Temperature too hot or too cold
  if (t > TEMP_HIGH || t < TEMP_LOW) {
    Serial.print("→ Buzzer: Temp out of range (");
    Serial.print(t,1);
    Serial.println("°C)");
    beep(1, 250);                    // Single long beep for temperature
  }

  // Humidity too low or too high
  else if (h < HUM_LOW || h > HUM_HIGH) {
    Serial.print("→ Buzzer: Humidity out of range (");
    Serial.print(h,1);
    Serial.println("%)");
    beep(2, 150);                    // Double beep for humidity
  }

  // ================== DISTANCE CONDITION (Updated) ==================
  else if (distance > DIST_MAX) {
    Serial.print("→ Buzzer: Distance > 20cm (");
    Serial.print(distance,0);
    Serial.println(" cm)");
    beep(3, 100);                    // Triple short beep for distance
  }

  // If none of the above conditions are true → Buzzer OFF
  else {
    digitalWrite(BUZZER_PIN, LOW);
  }

  // ================== RELAY (LDR) ==================
  if (lux < LUX_THRESHOLD) {
    digitalWrite(RELAY_PIN, LOW);     // Relay ON when dark
    Serial.println("→ Relay ON: Low Light (Lux < 100)");
  } else {
    digitalWrite(RELAY_PIN, HIGH);    // Relay OFF
  }

  delay(1000);
}