#define LED_PIN LED_BUILTIN
#define BUTTON_PIN PC13

const int debDelay = 50;

bool ledState = false;
bool lastBtnState = HIGH;

//===== t-2
#define PWM_PERIOD 20
#define MAX_DUTY_CYCLE 1000
#define STEP_SIZE 50
#define UPDATE_INTERVAL 200

bool increaseBrightness;
uint8_t buttonState;
uint16_t currentDutyCycle;
uint32_t lastUpdateTime;


void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);

  //===== t-2
  increaseBrightness = true;
  currentDutyCycle = 0;
  lastUpdateTime = 0;
}

void heartbeatBlink(int interval) {
  digitalWrite(LED_PIN, HIGH);
  delay(interval);

  digitalWrite(LED_PIN, LOW);
  delay(interval);
}

void lightOnBtnPress() {
  bool btnState =  digitalRead(BUTTON_PIN);

  if (btnState == LOW) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
  }
}

void toggleDebounce() {
  bool btnState =  digitalRead(BUTTON_PIN);

  if (lastBtnState == HIGH && btnState == LOW) {
    delay(debDelay);

    btnState =  digitalRead(BUTTON_PIN);

    if (btnState == LOW) {
      ledState = !ledState;

      digitalWrite(LED_PIN, ledState);
    }
  }

  lastBtnState = btnState;
}

void PWM(uint16_t dutyCycle) {
  uint16_t onTime = (dutyCycle * PWM_PERIOD) / MAX_DUTY_CYCLE;
  uint16_t offTIme = PWM_PERIOD - onTime;

  if (onTime > 0) {
    digitalWrite(LED_PIN, HIGH);
    delay(onTime);
  }

  if (offTIme > 0) {
    digitalWrite(LED_PIN, HIGH);
    delay(onTime);
  }
}

void dimming() {
  buttonState =  digitalRead(BUTTON_PIN);

  // update brightness every 200 ms
  if (buttonState == LOW && (millis() - lastUpdateTime >= UPDATE_INTERVAL )) {
    lastUpdateTime = millis();
    log(lastUpdateTime);

    // chnage dir
    if (currentDutyCycle >= MAX_DUTY_CYCLE) {
      increaseBrightness = false;
    } else if (currentDutyCycle <= 0 ) {
      increaseBrightness = true;
    }

    // update brightness
    if (increaseBrightness) {
      currentDutyCycle += STEP_SIZE;
    } else {
      currentDutyCycle -= STEP_SIZE;
    }
  }

  PWM(currentDutyCycle);
}

void loop() {

  // t-1-a
  // heartbeatBlink(500);

  // t-1-b
  // lightOnBtnPress();

  // t-1-c
  // toggleDebounce();

  // t-2
  dimming();
}