#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/exti.h>
#include <libopencm3/stm32/rtc.h>

#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/pwr.h>

#include <rtc.h>

static int reset = 0;

static uint8_t u8_to_bcd(uint8_t val)
{
	uint32_t quot = (uint32_t)val / 10;
	uint32_t rem = val - quot * 10;

	return (quot << 4) | rem;
}

static inline uint32_t rtc_to_sec(uint32_t rtc)
{
	uint32_t sec;

	sec = (rtc & 0xf) + ((rtc >> 4) & 0xf) * 10;
	sec += (((rtc >> 8) & 0xf) + ((rtc >> 12) & 0xf) * 10) * 60;
	sec += (((rtc >> 16) & 0xf) + ((rtc >> 20) & 0xf) * 10) * 3600;

	return sec;
}

static inline uint32_t sec_to_rtc(uint32_t sec)
{
	uint32_t rtc;
	uint8_t hour;
	uint8_t min;

	sec %= SECS_PER_DAY;

	hour = sec / 3600;
	rtc = u8_to_bcd(hour) << 16;

	sec -= hour * 3600;
	min = sec / 60;
	rtc |= u8_to_bcd(min) << 8;

	sec -= min * 60;
	rtc |= u8_to_bcd(sec);

	return rtc;
}

static void rtc_enable_alarm_interrupt(void)
{
	exti_enable_request(EXTI17);
	exti_set_trigger(EXTI17, EXTI_TRIGGER_RISING);

	nvic_enable_irq(NVIC_RTC_IRQ);
	nvic_set_priority(NVIC_RTC_IRQ, 1);

	RTC_CR |= RTC_CR_ALRAIE;
}

static void rtc_disable_alarm_interrupt(void)
{
	exti_disable_request(EXTI17);

	nvic_disable_irq(NVIC_RTC_IRQ);

	RTC_CR &= ~RTC_CR_ALRAIE;
}

void rtc_isr(void)
{
	uint32_t alarm_sec;

	gpio_toggle(GPIOC, GPIO8);

	pwr_disable_backup_domain_write_protect();
	rtc_unlock();

	/* Disable the alarm. */
	RTC_CR &= ~RTC_CR_ALRAE;
	RTC_ISR &= ~RTC_ISR_ALRAF;
	exti_reset_request(EXTI17);

	if (!reset) {
		reset = 1;
		gpio_set(GPIOA, GPIO1);

		/* Set the alarm time. */
		alarm_sec = rtc_to_sec(RTC_TR);
		(volatile void)RTC_DR;
		RTC_ALRMAR = sec_to_rtc(alarm_sec + 5) | 0xc0000000;

		/* Enable the alarm. */
		RTC_CR |= RTC_CR_ALRAE;
	} else {
		reset = 0;
		gpio_clear(GPIOA, GPIO1);
		alarm_disable();
	}

	rtc_lock();
	pwr_enable_backup_domain_write_protect();
}

int alarm_enable(uint32_t timeout)
{
	uint32_t alarm_sec;

	pwr_disable_backup_domain_write_protect();
	rtc_unlock();

	/* Set the alarm time. */
	alarm_sec = rtc_to_sec(RTC_TR);
	(volatile void)RTC_DR;
	RTC_ALRMAR = sec_to_rtc(alarm_sec + timeout) | 0xc0000000;

	RTC_CR |= RTC_CR_ALRAE;
	rtc_enable_alarm_interrupt();

	rtc_lock();
	pwr_enable_backup_domain_write_protect();

	return 0;
}

int alarm_disable(void)
{
	gpio_set(GPIOC, GPIO8);

	pwr_disable_backup_domain_write_protect();
	rtc_unlock();

	RTC_CR &= ~RTC_CR_ALRAE;
	rtc_disable_alarm_interrupt();

	rtc_lock();
	pwr_enable_backup_domain_write_protect();

	return 0;
}