#include <ds3231/ds3231.hpp>
#include <libavr/libavr.hpp>

using namespace avr::literals;

// One source for the tiny85 (open-drain software I2C on the USI pins) and
// the mega328P (TWI hardware). On first power-up the clock is seeded and
// alarm 1 armed; then the LED mirrors the seconds parity - a stuck LED
// means bus errors.
using dev = avr::device<{.clock = 8_MHz}>;
using bus = dev::i2c<{.frequency = 100_kHz}>;
using rtc = ds3231::device<bus>;
using led = dev::output<avr::pb3>;

int main()
{
	avr::init<bus, led>();

	if (auto stopped = rtc::oscillator_stopped(); stopped.value_or(false)) {
		// A failed seed leaves the LED dark before the loop ever runs - the
		// same signal a stuck bus gives it below.
		const bool seeded = rtc::write_clock({{2026, 1, 1}, {12, 0, 0}}) &&
		                    rtc::set_alarm1({}, ds3231::alarm1_rate::once_per_second) &&
		                    rtc::clear_oscillator_stopped();
		led::write(seeded);
	}

	while (true) {
		if (auto now = rtc::read_clock(); now.has_value()) {
			led::write(now->second % 2 == 0);
		}
		if (auto fired = rtc::alarm1_fired(); fired.value_or(false) && !rtc::clear_alarm1()) {
			led::clear(); // a clear that failed holds the LED dark, like any bus error
		}
		dev::delay<100_ms>();
	}
}