#include <avr/io.h>
#include <avr/delay.h>
#include <stdint.h>
#include <math.h>
#include <avr/interrupt.h>

#define RS 0
#define EN 1
#define D4 4
#define D5 5
#define D6 6
#define D7 7
#define LCD PORTA
#define KL_PORT PORTC

#define CMD  (uint8_t)0
#define DATA (uint8_t)1

#define _nop() asm volatile("nop")

volatile uint16_t now = 0;
volatile int c = 0;
volatile int tryb = 0;


void send(const uint8_t data, const uint8_t type) {
    if (type == 0) {
        LCD &= ~_BV(RS);    // rejestr
    } else if (type == 1) {
        LCD |= _BV(RS);     // dane
    }

    LCD |= _BV(EN);
    LCD = (LCD & 0x0F) | (data & 0xF0);
    LCD &= ~_BV(EN);

    _nop();

    LCD |= _BV(EN);
    LCD = (LCD & 0x0F) | (data << 4);
    LCD &= ~_BV(EN);

    _delay_ms(2);
}

void init() {
    DDRA = 0xFF;
    LCD = 0;

    _delay_ms(20);

    send(0b00000010, CMD);
    send(0b00101000, CMD);
    send(0b00001100, CMD);
    send(0b00000001, CMD);

    _delay_ms(20);
}
void lcd_clear() {
    send(0b00000001, CMD); // clear
}

void string(const uint8_t* data) {
    uint8_t line = 0;
    uint8_t i = 0;
    while (data[i])
    {
        if (i > 15 && line == 0) {
            send(0xC0, CMD);
            line = 1;
        }

        send(data[i], DATA);
        i++;
    }
}
  ISR(TIMER0_OVF_vect){
  if(c == 10){
  	if(tryb == 1) now--;
	if(tryb == 0) now++;
	c = 0;
	}
    TCNT0 = 155;
	c++;

}



void update_time() {
	if(tryb == 2){
	lcd_clear();
	string("twoj czas minął");
	}else{
	if(tryb == 1 &&  now == 0){
		buzz();
		tryb = 2;
	}
    uint8_t hours = (uint8_t)floor(now / (60 * 60));

    uint8_t divisor_for_minutes = (uint8_t)(now % (60 * 60));
    uint8_t minutes = floor(divisor_for_minutes / 60);

    uint8_t divisor_for_seconds = (uint8_t)(divisor_for_minutes % 60);
    uint8_t seconds = (uint8_t)ceil(divisor_for_seconds);


    char buf[32];

    sprintf(buf, "%.2d:%.2d:%.2d", hours, minutes, seconds);

    lcd_clear();
    string(buf);
	}
}
 void buzz(){
 	PORTB = 1;
	_delay_ms(10);
	PORTB = 0;
 }
 void ogarnij_wyswietlacz(){
 	if(tryb!=3){
		update_time();
	}
 }

int main() {

	DDRB = 255;
	PORTB = 0;

	tryb = 0;
    init();

	TCCR0 |=  (1<<CS00) | (1<<CS02);
    TIMSK |= (1<<TOIE0);
 	TCNT0 = 55;
    sei();

	//klawiatura
    DDRC = 0xF0;
	KL_PORT = 0xFF;
	char x,  kl;

    while(1){
	ogarnij_wyswietlacz();


		x = (PINC & 0x0f);
            if(x == 0b00001110)tryb = 1;
            if(x == 0b00001101)tryb = 0;
            if(x == 0b00001011)tryb = 3;
			if(x == 0b00000111)kl = 4;
	}
	return 0;
}