#include <Arduino.h>

#define FLOW_POT_PIN 34
#define TRIG_PIN 5
#define ECHO_PIN 18
#define LED_PIN 2

const float TANK_AREA_M2 = 0.5;
const float ADC_MAX = 4095.0;
const float VREF = 3.3;
const float MAX_FLOW_LPM = 30.0;

unsigned long lastMillis = 0;
float accumulatedVolumeL = 0.0;

void setup() {
  Serial.begin(115200);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
  lastMillis = millis();
}

float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  unsigned long duration = pulseIn(ECHO_PIN, HIGH, 30000UL);
  if (duration == 0) return -1.0;
  return (duration * 0.0343) / 2.0;
}

float readFlowLPerMin() {
  int raw = analogRead(FLOW_POT_PIN);
  float v = (raw / ADC_MAX) * VREF;
  return (v / VREF) * MAX_FLOW_LPM;
}

void loop() {
  unsigned long now = millis();
  float dt = (now - lastMillis) / 1000.0;
  if (dt <= 0) dt = 0.001;
  lastMillis = now;

  float flowLpm = readFlowLPerMin();
  float flowLps = flowLpm / 60.0;
  accumulatedVolumeL += flowLps * dt;

  float distCM = readDistanceCM();
  float heightM = 0.0, tankVolumeL = 0.0;
  if (distCM > 0) {
    float sensorToBottomM = 2.00;
    float distM = distCM / 100.0;
    heightM = sensorToBottomM - distM;
    if (heightM < 0) heightM = 0;
    tankVolumeL = heightM * TANK_AREA_M2 * 1000.0;
  }

  bool lowVolume = (tankVolumeL > 0) ? (tankVolumeL < 20.0) : false;
  digitalWrite(LED_PIN, lowVolume ? HIGH : LOW);

  Serial.print("Flow (L/min): "); Serial.print(flowLpm, 2);
  Serial.print(" | Volume Total (L): "); Serial.print(accumulatedVolumeL, 2);
  Serial.print(" | Tinggi Air (m): "); Serial.print(heightM, 3);
  Serial.print(" | Volume Tangki (L): "); Serial.println(tankVolumeL, 2);

  delay(500);
}