#define TRIG_PIN 2
#define ECHO_PIN 18

#define LED_MERAH 27
#define LED_KUNING 26
#define LED_HIJAU 25
#define BUZZER 33

float jarak = 100;        // jarak awal (air kosong)
float tinggiAir = 0;
const float tinggiMaks = 20;

void setup() {
  Serial.begin(9600);

  pinMode(LED_MERAH, OUTPUT);
  pinMode(LED_KUNING, OUTPUT);
  pinMode(LED_HIJAU, OUTPUT);
  pinMode(BUZZER, OUTPUT);
}

void loop() {

  // = SIMULASI AIR NAIK =
  jarak -= 1;                 // air naik 1 cm
  if (jarak < 0) jarak = 0;   // batas bawah

  tinggiAir = tinggiMaks - jarak;

  Serial.print("Jarak: ");
  Serial.print(jarak);
  Serial.print(" cm | Tinggi Air: ");
  Serial.print(tinggiAir);
  Serial.println(" cm");

  // = LOGIKA PERINGATAN =
  if (tinggiAir >= 15) {
    digitalWrite(LED_MERAH, HIGH);
    digitalWrite(LED_KUNING, LOW);
    digitalWrite(LED_HIJAU, LOW);
    digitalWrite(BUZZER, HIGH);
  }
  else if (tinggiAir >= 8) {
    digitalWrite(LED_MERAH, LOW);
    digitalWrite(LED_KUNING, HIGH);
    digitalWrite(LED_HIJAU, LOW);
    digitalWrite(BUZZER, LOW);
  }
  else {
    digitalWrite(LED_MERAH, LOW);
    digitalWrite(LED_KUNING, LOW);
    digitalWrite(LED_HIJAU, HIGH);
    digitalWrite(BUZZER, LOW);
  }

  delay(1000); // 1 detik
}