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

LiquidCrystal_I2C lcd(0x27, 20, 4);

const uint8_t PIN_BTN_UP   = PA0;
const uint8_t PIN_BTN_DOWN = PA1;
const uint8_t PIN_LED      = PA5;

volatile int counter = 0;

struct ButtonState {
  bool stableLevel;
  bool lastReading;          
  uint32_t lastChangeMs;     
  bool pressedEvent;         
};

ButtonState btnUp, btnDown;

const uint32_t DEBOUNCE_MS = 30;

uint32_t lastLedToggleMs = 0;
bool ledState = false;

uint32_t lastLcdUpdateMs = 0;
const uint32_t LCD_UPDATE_MS = 150;

static void initButton(ButtonState &b, bool initialLevel) {
  b.stableLevel = initialLevel;
  b.lastReading = initialLevel;
  b.lastChangeMs = millis();
  b.pressedEvent = false;
}

static bool updateButton(ButtonState &b, bool reading, uint32_t nowMs) {
  b.pressedEvent = false;

  if (reading != b.lastReading) {
    b.lastReading = reading;
    b.lastChangeMs = nowMs;
  }

  if ((nowMs - b.lastChangeMs) >= DEBOUNCE_MS) {
    if (b.stableLevel != reading) {
      bool prev = b.stableLevel;
      b.stableLevel = reading;

      if (prev == HIGH && b.stableLevel == LOW) {
        b.pressedEvent = true;
      }
    }
  }
  return b.pressedEvent;
}

static float calcFrequencyHz(int cnt) {
  float f = 0.5f + 0.2f * (float)abs(cnt);
  if (f > 10.0f) f = 10.0f;
  return f;
}

static uint32_t calcHalfPeriodMs(float freqHz) {
  float periodMs = 1000.0f / freqHz;
  float halfMs = periodMs / 2.0f;
  if (halfMs < 20.0f) halfMs = 20.0f;
  return (uint32_t)(halfMs + 0.5f);
}

void setup() {
  pinMode(PIN_BTN_UP, INPUT_PULLUP);
  pinMode(PIN_BTN_DOWN, INPUT_PULLUP);
  pinMode(PIN_LED, OUTPUT);
  digitalWrite(PIN_LED, LOW);

  Wire.begin();

  lcd.init();
  lcd.backlight();

  initButton(btnUp, digitalRead(PIN_BTN_UP));
  initButton(btnDown, digitalRead(PIN_BTN_DOWN));

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Counter + Buttons");
  lcd.setCursor(0, 1);
  lcd.print("Nucleo C031C6");
  delay(600);
  lcd.clear();
}

void loop() {
  uint32_t now = millis();

  bool upPressed = updateButton(btnUp, digitalRead(PIN_BTN_UP), now);
  bool downPressed = updateButton(btnDown, digitalRead(PIN_BTN_DOWN), now);

  if (upPressed)   counter++;
  if (downPressed) counter--;

  float freq = calcFrequencyHz(counter);
  uint32_t halfPeriodMs = calcHalfPeriodMs(freq);

  if (now - lastLedToggleMs >= halfPeriodMs) {
    lastLedToggleMs = now;
    ledState = !ledState;
    digitalWrite(PIN_LED, ledState ? HIGH : LOW);
  }

  if (now - lastLcdUpdateMs >= LCD_UPDATE_MS) {
    lastLcdUpdateMs = now;

    lcd.setCursor(0, 0);
    lcd.print("Counter: ");
    lcd.setCursor(9, 0);
    lcd.print("          ");
    lcd.setCursor(9, 0);
    lcd.print(counter);

    lcd.setCursor(0, 1);
    lcd.print("BTN1(UP):   ");
    lcd.setCursor(10, 1);
    lcd.print(btnUp.stableLevel == LOW ? "PRESSED " : "RELEASED");

    lcd.setCursor(0, 2);
    lcd.print("BTN2(DN):   ");
    lcd.setCursor(10, 2);
    lcd.print(btnDown.stableLevel == LOW ? "PRESSED " : "RELEASED");

    lcd.setCursor(0, 3);
    lcd.print("LED freq: ");
    lcd.setCursor(10, 3);
    lcd.print("          ");
    lcd.setCursor(10, 3);
    lcd.print(freq, 2);
    lcd.print(" Hz");
  }
}