#define F_CPU 10000000UL

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

inline uint8_t BIT(uint8_t n)
{
    return (1 << n);
}

namespace LCD1602
{
    inline void RS_0(void) {PORTD &= ~BIT(0);}
    inline void RS_1(void) {PORTD |= BIT(0);}
    inline void RW_0(void) {PORTD &= ~BIT(1);}
    inline void RW_1(void) {PORTD |= BIT(1);}
    inline void E_0(void) {PORTD &= ~BIT(2);}
    inline void E_1(void) {PORTD |= BIT(2);}
    inline void SetData(uint8_t data) {PORTA = data;}
    inline void BeginRead(void) {DDRA = 0x00;}
    inline void EndRead(void) {DDRA = 0xff;}

    void BusyWait(void)
    {
        BeginRead();
        RS_0();
        RW_1();
        E_1();
        while (PINA & 0x80);
        E_0();
        EndRead();
    }

    void WriteCmd(uint8_t cmd)
    {
        BusyWait();
        SetData(cmd);
        RS_0();
        RW_0();
        _delay_ms(1);
        E_1();
        _delay_ms(1);
        E_0();
    }

    void WriteData(uint8_t data)
    {
        BusyWait();
        SetData(data);
        RS_1();
        RW_0();
        _delay_ms(1);
        E_1();
        _delay_ms(1);
        E_0();
    }

    void WriteString(const char *s)
    {
        while (*s)
            WriteData(*s++);
    }

    void Init(void)
    {
        DDRA = 0xff;
        DDRD = 0x7f;
        PORTD |= BIT(7);
        _delay_ms(15);
        WriteCmd(0x38);
        _delay_ms(5);
        WriteCmd(0x38);
        _delay_ms(5);
        WriteCmd(0x38);
        WriteCmd(0x01);
        WriteCmd(0x0c);
    }
}

void display(uint16_t i)
{
    LCD1602::WriteCmd(0xc0);
    LCD1602::WriteData('0' + i % 1000 / 100);
    LCD1602::WriteData('0' + i % 100 / 10);
    LCD1602::WriteData('0' + i % 10);
}

int main(void)
{
    uint16_t i = 0;
    LCD1602::Init();
    LCD1602::WriteString("Hello World!");
    display(i);
    while (1)
    {
        if ((PIND & BIT(7)) == 0)
        {
            _delay_ms(1);
            if ((PIND & BIT(7)) == 0)
            {
                i++;
                display(i);
                if (i >= 1000)
                    i = 0;
                while ((PIND & BIT(7)) == 0)
                    _delay_ms(10);
                _delay_ms(200);
            }
        }
    }
}