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

LiquidCrystal_I2C lcd(0x27, 16, 2);

#define ENCODER_CLK 18
#define ENCODER_DT  19

volatile int pulseCount   = 0;
float flowRate            = 0.0;
float totalLiters         = 0.0;
unsigned long lastCalc    = 0;
unsigned long lastDisplay = 0;

void IRAM_ATTR onPulse() {
  pulseCount++;
}

void setup() {
  Serial.begin(115200);
  Serial.println("Starting...");

  Wire.begin(21, 22);
  delay(500); // ✅ Give I2C time to settle

  // ✅ Try both common Wokwi I2C addresses
  lcd = LiquidCrystal_I2C(0x27, 16, 2);
  lcd.init();
  lcd.backlight();
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("WINDMILL  FLOW");
  lcd.setCursor(0, 1);
  lcd.print("  CALCULATOR  ");
  delay(2000);
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("  ESD PROJECT ");
  lcd.setCursor(0, 1);
  lcd.print(" Spin the knob");
  delay(2000);
  lcd.clear();

  pinMode(ENCODER_CLK, INPUT_PULLUP);
  pinMode(ENCODER_DT,  INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(ENCODER_CLK), onPulse, FALLING);

  lastCalc    = millis();
  lastDisplay = millis();
  Serial.println("Ready!");
}

void loop() {
  unsigned long now = millis();

  // Calculate flow every 1 second
  if (now - lastCalc >= 1000) {
    noInterrupts();
    int p      = pulseCount;
    pulseCount = 0;
    interrupts();

    flowRate     = p / 7.5;          // L/min
    totalLiters += flowRate / 60.0;  // L
    lastCalc     = now;

    Serial.print("Flow: ");
    Serial.print(flowRate, 2);
    Serial.print(" L/min | Total: ");
    Serial.print(totalLiters, 3);
    Serial.println(" L");
  }

  // Update LCD every 600ms
  if (now - lastDisplay >= 600) {
    lastDisplay = now;

    lcd.setCursor(0, 0);
    lcd.print("Flow:");
    if (flowRate < 10) lcd.print(" ");
    lcd.print(flowRate, 1);
    lcd.print(" L/min ");

    lcd.setCursor(0, 1);
    lcd.print("Tot: ");
    lcd.print(totalLiters, 3);
    lcd.print(" L    ");
  }
}