#include <HX711.h>
#include <Wire.h>
#include <U8x8lib.h>

#define DT 2
#define SCK 3
#define TRIG 9
#define ECHO 10

U8X8_SSD1306_128X64_NONAME_HW_I2C display(U8X8_PIN_NONE);

HX711 scale;

// ===== TIMER REALTIME =====
unsigned long previousMillis = 0;
const long interval = 2000; // 2 detik

// ===== STRUCT =====
struct DataSiswa {
  float berat;
  float tinggi;
  float bmi;
  String statusGizi;
};

// ===== FIFO =====
DataSiswa antreanFIFO[10];
int head = 0;
int tail = 0;
int totalAntrean = 0;

// ====================
// BACA BERAT
// ====================
float bacaBerat() {
  float berat = scale.get_units(10);
  berat = berat / 420.0;
  if (berat < 0) berat = 0;
  return berat * 2.0;
}

// ====================
// BACA TINGGI
// ====================
float bacaTinggi() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  long durasi = pulseIn(ECHO, HIGH);
  float jarak = durasi * 0.034 / 2.0;
  return jarak;
}

// ====================
// HITUNG STATUS BMI
// ====================
String hitungStatusGizi(float berat, float tinggi) {
  if (tinggi <= 0) return "Error";

  float t = tinggi / 100.0;
  float bmi = berat / (t * t);

  if (bmi < 18.5) return "Kurus";
  if (bmi < 25) return "Gizi Baik";
  return "Obesitas";
}

// ====================
// REALTIME PROCESS
// ====================
void prosesRealtime() {

  float berat = bacaBerat();
  float tinggi = bacaTinggi();

  float bmi = 0;
  if (tinggi > 0) {
    float t = tinggi / 100.0;
    bmi = berat / (t * t);
  }

  String status = hitungStatusGizi(berat, tinggi);

  DataSiswa data;
  data.berat = berat;
  data.tinggi = tinggi;
  data.bmi = bmi;
  data.statusGizi = status;

  // ===== MASUK FIFO =====
  antreanFIFO[tail] = data;
  tail = (tail + 1) % 10;

  if (totalAntrean < 10) totalAntrean++;

  // ===== KELUAR FIFO (REALTIME) =====
  DataSiswa out = antreanFIFO[head];
  head = (head + 1) % 10;
  totalAntrean--;

  // ===== SERIAL OUTPUT (RAPI) =====
  Serial.println("============================");
  Serial.println("===== HASIL PENGUKURAN =====");

  Serial.print("Berat  : ");
  Serial.print(out.berat, 1);
  Serial.println(" kg");

  Serial.print("Tinggi : ");
  Serial.print((int)out.tinggi);
  Serial.println(" cm");

  Serial.print("BMI    : ");
  Serial.println(out.bmi, 1);

  Serial.print("Status : ");
  Serial.println(out.statusGizi);

  Serial.println("============================");

  // ===== OLED (SUDAH DIPERBAIKI) =====
  display.clearDisplay();

  display.drawString(0,0,"REALTIME BMI");

  display.drawString(0,2,("Berat  : " + String(out.berat,1) + " kg").c_str());
  display.drawString(0,3,("Tinggi : " + String((int)out.tinggi) + " cm").c_str());
  display.drawString(0,4,("BMI    : " + String(out.bmi,1)).c_str());
  display.drawString(0,5,("Status : " + out.statusGizi).c_str());
}

// ====================
// SETUP
// ====================
void setup() {
  Serial.begin(9600);

  display.begin();
  display.setFont(u8x8_font_chroma48medium8_r);
  display.clearDisplay();
  display.drawString(0,1,"SYSTEM ONLINE");

  scale.begin(DT, SCK);
  scale.set_scale();
  scale.tare();

  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
}

// ====================
// LOOP REALTIME
// ====================
void loop() {
  if (millis() - previousMillis >= interval) {
    previousMillis = millis();
    prosesRealtime();
  }
}