#pragma GCC push_options
#pragma GCC optimize ("O1")

// I2C
#include <Wire.h>
// RTC
#include <DS3231.h>
// Use 74HC164 shift registers

// Init DS3231 RTC
DS3231 rtc;
bool h12;
bool hPM;

int btnHr = 10;
int btnMin = 9;
int btnTemp = 8;
int regData = 5;
int regClk = 6;

void setup() {
	// Buttons
	for(int i = 8; i < 11; i++)
		pinMode(i,INPUT);
	// Shift register
	for(int i = 5; i < 7; i++)
		pinMode(i,OUTPUT);
	// RTC
	Wire.begin();
	rtc.setClockMode(false); // 24 hour

	// Check RTC for problems
	if(!rtc.oscillatorCheck()) {
		// RTC NOT OK, set values to known ones
		rtc.setMinute(0);
		rtc.setHour(12);
	}
}

byte minute, hour, previousMinute, previousHour, needsUpdate, previousTemp, decTemp;
const uint8_t seg[] = {
	//    gfedcba
	0b0111111, // 0
	0b0000110, // 1
	0b1011011, // 2
	0b1001111, // 3
	0b1100110, // 4
	0b1101101, // 5
	0b1111101, // 6
	0b0000111, // 7
	0b1111111, // 8
	0b1101111, // 9
	0b1100011, // degree
	0b0111001, // C
	0b1000000  // -
};

void loop() {
	// Get time from RTC
	minute = rtc.getMinute();
	hour = rtc.getHour(h12, hPM);

	// Avoid refreshing if possible since we have no latch
	if(previousMinute != minute || previousHour != hour || needsUpdate != 0) {
		previousMinute = minute;
		previousHour = hour;
		needsUpdate = 0;
		shiftOut(regData, regClk, MSBFIRST, seg[minute%10]);
		shiftOut(regData, regClk, MSBFIRST, seg[minute/10]);
		shiftOut(regData, regClk, MSBFIRST, seg[hour%10]);
		shiftOut(regData, regClk, MSBFIRST, seg[hour/10]);
	} else {delay(10);}
	// Hour up
	if(digitalRead(10)) {
		if(rtc.getHour(h12, hPM) == 23) {
			rtc.setHour(0);
		} else {
			rtc.setHour(rtc.getHour(h12, hPM) + 1);
		}
		while(digitalRead(10));
	}

	// Minute up, set seconds to 0
	if(digitalRead(9)) {
		if(rtc.getMinute() == 59) {
			rtc.setMinute(0);
		}
		rtc.setSecond(0);
		rtc.setMinute(rtc.getMinute() + 1);
		while(digitalRead(9));
	}

	if(digitalRead(8)) { needsUpdate = 1; }
	// Show temperature reading from RTC
	while(digitalRead(8)) {
		decTemp = (int)rtc.getTemperature();
		if(previousTemp != decTemp || needsUpdate != 0) {
			previousTemp = decTemp;
			needsUpdate = 0;
			if(decTemp > -9999) {
				// OK
				shiftOut(regData, regClk, MSBFIRST, seg[11]);
				shiftOut(regData, regClk, MSBFIRST, seg[10]);
				shiftOut(regData, regClk, MSBFIRST, seg[decTemp%10]);
				shiftOut(regData, regClk, MSBFIRST, seg[decTemp/10]);
			} else {
				shiftOut(regData, regClk, MSBFIRST, seg[11]);
				shiftOut(regData, regClk, MSBFIRST, seg[10]);
				shiftOut(regData, regClk, MSBFIRST, seg[12]);
				shiftOut(regData, regClk, MSBFIRST, seg[12]);
			}
		} else {delay(10);}
		if(!digitalRead(8)) { needsUpdate = 1; break; }
	}
}

#pragma GCC pop_options