/*
 * Auxiliary functions to handle date/time along with lwIP sntp implementation.
 *
 * Jesus Alonso (doragasu)
 */

#include <sys/reent.h>
#include <sys/types.h>
#include <sys/errno.h>
#include <stdio.h>
#include <espressif/esp_common.h>
#include <esp/timer.h>
#include <esp/rtc_regs.h>
#include <sntp.h>

#define TIMER_COUNT			RTC.COUNTER

// daylight settings
// Base calculated with value obtained from NTP server (64 bits)
#define sntp_base	(*((uint64_t*)RTC.SCRATCH))
// Timer value when base was obtained
#define tim_ref 	(RTC.SCRATCH[2])
// Calibration value
#define cal 		(RTC.SCRATCH[3])

// Timezone related data.
static struct timezone stz;

// Implemented in sntp.c
void sntp_init(void);

// Sets time zone.
// NOTE: Settings do not take effect until SNTP time is updated.
void sntp_set_timezone(const struct timezone *tz) {
	if (tz) {
		stz = *tz;
	} else {
		stz.tz_minuteswest = 0;
		stz.tz_dsttime = 0;
	}
}

// Initialization
void sntp_initialize(const struct timezone *tz) {
	if (tz) {
		stz = *tz;
	} else {
		stz.tz_minuteswest = 0;
		stz.tz_dsttime = 0;
	}
	sntp_base = 0;
	// To avoid div by 0 exceptions if requesting time before SNTP config
	cal = 1;
	tim_ref = TIMER_COUNT;
	sntp_init();
}

// Check if a timer wrap has occurred. Compensate sntp_base reference
// if affirmative.
// TODO: think about multitasking and race conditions
static inline void sntp_check_timer_wrap(uint32_t current_value) {
	if (current_value < tim_ref) {
		// Timer wrap has occurred, compensate by subtracting 2^32 to ref.
		sntp_base -= 1LLU<<32;
		// DEBUG
		printf("\nTIMER WRAPPED!\n");
	}
}

// Return secs. If us is not a null pointer, fill it with usecs
inline time_t sntp_get_rtc_time(int32_t *us) {
	time_t secs;
	uint32_t tim;
	uint64_t base;

	tim = TIMER_COUNT;
	// Check for timer wrap
	sntp_check_timer_wrap(tim);
	base = sntp_base + tim - tim_ref;
	secs = base * cal / (1000000U<<12);
	if (us) {
		*us = base * cal % (1000000U<<12);
	}
	return secs;
}

// Syscall implementation. doesn't seem to use tzp.
int _gettimeofday_r(struct _reent *r, struct timeval *tp, void *tzp) {
	(void)r;
	// Syscall defined by xtensa newlib defines tzp as void*
	// So it looks like it is not used. Also check tp is not NULL
	if (tzp || !tp) return EINVAL;

	tp->tv_sec = sntp_get_rtc_time((int32_t*)&tp->tv_usec);
	return 0;
}

// Update RTC timer. Called by SNTP module each time it receives an update.
void sntp_update_rtc(time_t t, uint32_t us) {
	// Apply daylight and timezone correction
	t += (stz.tz_minuteswest + stz.tz_dsttime * 60) * 60;
	// DEBUG: Compute and print drift
	int64_t sntp_current = sntp_base + TIMER_COUNT - tim_ref;
	int64_t sntp_correct = (((uint64_t)us + (uint64_t)t * 1000000U)<<12) / cal;
	printf("\nRTC Adjust: drift = %lld ticks, cal = %d\n", (time_t)(sntp_correct - sntp_current), (uint32_t)cal);

	tim_ref = TIMER_COUNT;
	cal = sdk_system_rtc_clock_cali_proc();

	sntp_base = (((uint64_t)us + (uint64_t)t * 1000000U)<<12) / cal;
}