#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdio.h>

void usart_init(uint16_t ubrr) {
    UBRR0H = (ubrr >> 8);
    UBRR0L = ubrr;
    UCSR0B = (1 << RXEN0) | (1 << TXEN0); // Enable receiver & transmitter
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00); // 8-bit data, 1 stop bit
}

void usart_transmit(char data) {
    while (!(UCSR0A & (1 << UDRE0))); // Wait for empty buffer
    UDR0 = data;
}

void usart_print(const char *str) {
    while (*str) {
        usart_transmit(*str++);
    }
}

#define F_CPU 16000000UL  
#define BAUD 115200
#define UBRR_VALUE ((F_CPU / (16UL * BAUD)) - 1)

volatile uint8_t button_count = 0;  

void setup() {
    usart_init(UBRR_VALUE);
    
    DDRD &= ~(1<<PD0);// INT0 is also PD0 and we set the DDR to input
    PORTD |= (1<<PD0);// enable pullup resistor on PD0

    EICRA |= (1<<ISC01); // these two bits set
    EICRA &= ~(1<<ISC00);// INT0 to trigger on a FALLING edge
    EIMSK |= (1<<INT0);

    sei();  // Enable global interrupts
}

ISR(INT0_vect) {
  usart_print("Interrupt Triggered!\n");
  _delay_ms(50); // Software debounce

  if (!(PIND & (1 << PD3))) {  // Confirm button is still pressed
      button_count++;
      char buffer[16];
      sprintf(buffer, "Count: %d\n", button_count);
      usart_print(buffer);
  }
}

int main() {
    setup();

    while (1) {
        usart_print("Hello\n");
        _delay_ms(1000);
    }
}