#include <avr/eeprom.h>
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/sleep.h>

#include <stdint.h>

#define VALUE_MIN -99999
#define VALUE_MAX 999999

#define PIN_BTN_DEC PINB3
#define PIN_BTN_INC PINB4

#define BTN_FLAG_DEC 0x02
#define BTN_FLAG_INC 0x01

#define DISPLAY_SIZE 6

// Time(ms) to wait before sleep
#define DISPLAY_DELAY	1000

// Time(ms) to assume long button press
#define LONG_PRESS		500

// Event queue macros
#define MAX_EVENT_COUNT 64
#define PTR_INC(x) ((x) = events + ((((x) - events) + 1) % MAX_EVENT_COUNT))

uint8_t events[MAX_EVENT_COUNT];
uint8_t event_count  = 0;
uint8_t *event_read  = events;
uint8_t *event_write = events;

int32_t counter_value = 0;
uint8_t btn_flag = 0;
volatile uint32_t ms = 0;
uint8_t display_buffer[DISPLAY_SIZE];

// Shift way (P is DP)
// GFAB 1->6
// PCDE 6->1
// Therefore - EDCPBAFG
#define DP 0b00010000
uint8_t seg_table[11] =
{
	//EDCPBAFG
	0b11101110, // 0
	0b00101000, // 1
	0b11001101, // 2
	0b01101101, // 3
	0b00101011, // 4
	0b01100111, // 5
	0b11100111, // 6
	0b00101100, // 7
	0b11101111, // 8
	0b01101111, // 9
	0b00000001  // -
};

enum event_e
{
	EVENT_NONE,
	EVENT_DEC_DOWN,
	EVENT_DEC_UP,
	EVENT_INC_DOWN,
	EVENT_INC_UP
};

// ms counter
ISR(TIM0_COMPA_vect)
{
	cli();
	ms += 8;
	sei();
}

// Button interrupt
ISR(PCINT0_vect)
{
	uint8_t new_btn_flag = 0;
	uint8_t event = EVENT_NONE;

	cli();
	if (0 == (PINB & (1 << PIN_BTN_DEC)))
	{
		new_btn_flag |= BTN_FLAG_DEC;
	}

	if (0 == (PINB & (1 << PIN_BTN_INC)))
	{
		new_btn_flag |= BTN_FLAG_INC;
	}

	if ((new_btn_flag & BTN_FLAG_DEC) != (btn_flag & BTN_FLAG_DEC))
	{
		// Press
		if (new_btn_flag & BTN_FLAG_DEC)
		{
			event = EVENT_DEC_DOWN;
		}
		// Unpress
		else
		{
			event = EVENT_DEC_UP;
		}

		// Actually put the event in the queue
		if (event_count < MAX_EVENT_COUNT)
		{
			*event_write = event;
			++event_count;
			PTR_INC(event_write);
		}
	}

	if ((new_btn_flag & BTN_FLAG_INC) != (btn_flag & BTN_FLAG_INC))
	{
		// Press
		if (new_btn_flag & BTN_FLAG_INC)
		{
			event = EVENT_INC_DOWN;
		}
		// Unpress
		else
		{
			event = EVENT_INC_UP;
		}

		// Actually put the event in the queue
		if (event_count < MAX_EVENT_COUNT)
		{
			*event_write = event;
			++event_count;
			PTR_INC(event_write);
		}
	}

	btn_flag = new_btn_flag;
	sei();
}

void hard_init()
{
	// Output Store, Data, Clock
	DDRB = (1 << DDB0) | (1 << DDB1) | (1 << DDB2);

	// Pull-up Buttons
	PORTB = (1 << PORTB3) | (1 << PORTB4);

	// Sleep mode - Power down
	MCUCR = (1 << SM1);

	// Disable power to Timer1, USI, ADC
	PRR = (1 << PRTIM1) | (1 << PRUSI) | (1 << PRADC);

	// Enable button interrupts
	PCMSK = (1 << PCINT3) | (1 << PCINT4);
	GIMSK = (1 << PCIE);

	// CTC Mode
	TCCR0A = (1 << WGM01);

	// 64 Prescaler
	TCCR0B = (1 << CS01) | (1 << CS00);

	// Interrupt every 8 ms
	OCR0A = 125;

	// 1 000 000 / 64 = 15625 (Hz)
	// 15625 / 125 = 125 (Hz)
	// 1000 / 125 = 8 (ms)

	// Enable Timer interrupt
	TIMSK = (1 << OCIE0A);

	sei();
}

void display_send_bit(uint8_t bit)
{
	if (0 != bit)
	{
		PORTB |= (1 << PORTB1);
	}
	else
	{
		PORTB &= ~(1 << PORTB1);
	}

	PORTB |= (1 << PORTB2);
	while(!(PINB & (1 << PINB2)));
	PORTB &= ~(1 << PORTB2);
	while(PINB & (1 << PINB2));
}

void display_send_buffer()
{
	uint8_t i;
	uint8_t b;
	uint8_t custom_buffer[DISPLAY_SIZE];

	for (b = 0; b < DISPLAY_SIZE / 2; ++b)
	{
		custom_buffer[b] = ((display_buffer[b * 2] & 0xF0) | ((display_buffer[b * 2 + 1] & 0xF0) >> 4));
	}

	for (b = 0; b < DISPLAY_SIZE / 2; ++b)
	{
		custom_buffer[b + DISPLAY_SIZE / 2] = (((display_buffer[DISPLAY_SIZE - 1 - b * 2] & 0x0F) << 4) | (display_buffer[DISPLAY_SIZE - 1 - b * 2 - 1] & 0x0F));
	}

	for (b = 0; b < DISPLAY_SIZE; ++b)
	{
		for (i = 0; i < 8; ++i)
		{
			display_send_bit(((custom_buffer[b]) >> (7 - i)) & 0x01);
		}
	}
}

void display_show()
{
	PORTB |= (1 << PORTB0);
	while(!(PINB & (1 << PINB0)));
	PORTB &= ~(1 << PORTB0);
	while(PINB & (1 << PINB0));
}

void display_show_value(uint8_t dots)
{
	uint8_t i;
	uint32_t div_val = 1;
	uint32_t counter_copy;
	uint8_t digit;
	uint8_t txt;

	for (i = 0; i < DISPLAY_SIZE; ++i)
	{
		display_buffer[i] = 0;
		div_val *= 10;
	}

	div_val /= 10;

	if (counter_value < 0)
	{
		counter_copy = -counter_value;
		display_buffer[0] = seg_table[10];
	}
	else
	{
		counter_copy = counter_value;
	}

	txt = 0;
	for (i = 0; i < DISPLAY_SIZE; ++i)
	{
		digit = counter_copy / div_val;
		if ((0 != txt) || (0 != digit) || (DISPLAY_SIZE - 1 == i))
		{
			txt = 1;
			display_buffer[i] = seg_table[digit];
		}
		counter_copy %= div_val;
		div_val /= 10;
	}

	if (0 != dots)
	{
		display_buffer[DISPLAY_SIZE - 1] |= DP;
	}

	display_send_buffer();
	display_show();
}

void mem_load()
{
	int32_t value = 0;
	uint8_t curr_byte;
	uint8_t i;

	value = 0;
	for (i = 0; i < 4; ++i)
	{
		curr_byte = eeprom_read_byte((uint8_t *) i);
		value <<= 8;
		value |= curr_byte;
	}
	counter_value = value;
}

void mem_save()
{
	int32_t value = counter_value;
	uint8_t curr_byte;
	uint8_t i;

	for (i = 0; i < 4; ++i)
	{
		curr_byte = (value >> (24 - 8 * i)) & 0xFF;
		eeprom_update_byte((uint8_t *) i, curr_byte);
	}
}

int main()
{
	uint32_t ms_sleep = DISPLAY_DELAY;
	uint32_t dec_ms_long = 0;
	uint32_t inc_ms_long = 0;
	uint8_t event;

	hard_init();
	display_show_value(0);

	while(1)
	{
		while (event_count > 0)
		{
			// Consume Event
			cli();
			event = *event_read;
			PTR_INC(event_read);
			--event_count;
			sei();

			if (event != EVENT_NONE)
			{
				ms_sleep = ms + DISPLAY_DELAY;
			}

			// Process Event
			switch (event)
			{
			case EVENT_DEC_DOWN:
				dec_ms_long = ms + LONG_PRESS;
				break;

			case EVENT_DEC_UP:
				if (0 != dec_ms_long)
				{
					if (counter_value > VALUE_MIN)
					{
						--counter_value;
					}
					dec_ms_long = 0;
				}
				display_show_value(0);
				break;

			case EVENT_INC_DOWN:
				inc_ms_long = ms + LONG_PRESS;
				break;

			case EVENT_INC_UP:
				if (0 != inc_ms_long)
				{
					if (counter_value < VALUE_MAX)
					{
						++counter_value;
					}
					inc_ms_long = 0;
				}
				display_show_value(0);
				break;
			}
		}

		if ((0 != dec_ms_long) && (ms > dec_ms_long))
		{
			mem_load();
			dec_ms_long = 0;
			display_show_value(1);
		}

		if ((0 != inc_ms_long) && (ms > inc_ms_long))
		{
			mem_save();
			inc_ms_long = 0;
			display_show_value(1);
		}

		if (ms >= ms_sleep)
		{
			// Enable sleep
			MCUCR |= (1 << SE);

			// Go to sleep
			sleep_cpu();

			cli();
			ms = 0;
			sei();

			// Disable sleep
			MCUCR &= ~(1 << SE);

			ms_sleep = ms + DISPLAY_DELAY;
		}
	}

	return 0;
}