/*
 * This file is part of INAV.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Alternatively, the contents of this file may be used under the terms
 * of the GNU General Public License Version 3, as described below:
 *
 * This file is free software: you may copy, redistribute and/or modify
 * it under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see http://www.gnu.org/licenses/.
 *
 * @author Alberto Garcia Hierro <alberto@garciahierro.com>
 */

#include <stdint.h>

#include "common/maths.h"
#include "common/printf.h"
#include "common/time.h"

#include "pg/pg_ids.h"

#include "drivers/time.h"

#ifdef USE_RTC_TIME

#define UNIX_REFERENCE_YEAR 1970
#define MILLIS_PER_SECOND 1000

// rtcTime_t when the system was started.
// Calculated in rtcSet().
static rtcTime_t started = 0;

static const uint16_t days[4][12] =
{
    {   0,  31,     60,     91,     121,    152,    182,    213,    244,    274,    305,    335},
    { 366,  397,    425,    456,    486,    517,    547,    578,    609,    639,    670,    700},
    { 731,  762,    790,    821,    851,    882,    912,    943,    974,    1004,   1035,   1065},
    {1096,  1127,   1155,   1186,   1216,   1247,   1277,   1308,   1339,   1369,   1400,   1430},
};

PG_REGISTER_WITH_RESET_TEMPLATE(timeConfig_t, timeConfig, PG_TIME_CONFIG, 0);

PG_RESET_TEMPLATE(timeConfig_t, timeConfig,
    .tz_offsetMinutes = 0,
);

static rtcTime_t dateTimeToRtcTime(dateTime_t *dt)
{
    unsigned int second = dt->seconds;  // 0-59
    unsigned int minute = dt->minutes;  // 0-59
    unsigned int hour = dt->hours;      // 0-23
    unsigned int day = dt->day - 1;     // 0-30
    unsigned int month = dt->month - 1; // 0-11
    unsigned int year = dt->year - UNIX_REFERENCE_YEAR; // 0-99
    int32_t unixTime = (((year / 4 * (365 * 4 + 1) + days[year % 4][month] + day) * 24 + hour) * 60 + minute) * 60 + second;
    return rtcTimeMake(unixTime, dt->millis);
}

static void rtcTimeToDateTime(dateTime_t *dt, rtcTime_t t)
{
    int32_t unixTime = t / MILLIS_PER_SECOND;
    dt->seconds = unixTime % 60;
    unixTime /= 60;
    dt->minutes = unixTime % 60;
    unixTime /= 60;
    dt->hours = unixTime % 24;
    unixTime /= 24;

    unsigned int years = unixTime / (365 * 4 + 1) * 4;
    unixTime %= 365 * 4 + 1;

    unsigned int year;
    for (year = 3; year > 0; year--) {
        if (unixTime >= days[year][0]) {
            break;
        }
    }

    unsigned int month;
    for (month = 11; month > 0; month--) {
        if (unixTime >= days[year][month]) {
            break;
        }
    }

    dt->year = years + year + UNIX_REFERENCE_YEAR;
    dt->month = month + 1;
    dt->day = unixTime - days[year][month] + 1;
    dt->millis = t % MILLIS_PER_SECOND;
}

static void rtcGetDefaultDateTime(dateTime_t *dateTime)
{
    dateTime->year = 0;
    dateTime->month = 1;
    dateTime->day = 1;
    dateTime->hours = 0;
    dateTime->minutes = 0;
    dateTime->seconds = 0;
    dateTime->millis = 0;
}

static bool rtcIsDateTimeValid(dateTime_t *dateTime)
{
    return (dateTime->year >= UNIX_REFERENCE_YEAR) &&
           (dateTime->month >= 1 && dateTime->month <= 12) &&
           (dateTime->day >= 1 && dateTime->day <= 31) &&
           (dateTime->hours <= 23) &&
           (dateTime->minutes <= 59) &&
           (dateTime->seconds <= 59) &&
           (dateTime->millis <= 999);
}

static void dateTimeWithOffset(dateTime_t *dateTimeOffset, dateTime_t *dateTimeInitial, int16_t minutes)
{
    rtcTime_t initialTime = dateTimeToRtcTime(dateTimeInitial);
    rtcTime_t offsetTime = rtcTimeMake(rtcTimeGetSeconds(&initialTime) + minutes * 60, rtcTimeGetMillis(&initialTime));
    rtcTimeToDateTime(dateTimeOffset, offsetTime);
}

static bool dateTimeFormat(char *buf, dateTime_t *dateTime, int16_t offsetMinutes, bool shortVersion)
{
    dateTime_t local;

    int tz_hours = 0;
    int tz_minutes = 0;
    bool retVal = true;

    // Apply offset if necessary
    if (offsetMinutes != 0) {
        tz_hours = offsetMinutes / 60;
        tz_minutes = ABS(offsetMinutes % 60);
        dateTimeWithOffset(&local, dateTime, offsetMinutes);
        dateTime = &local;
    }

    if (!rtcIsDateTimeValid(dateTime)) {
        rtcGetDefaultDateTime(&local);
        dateTime = &local;
        retVal = false;
    }

    if (shortVersion) {
        tfp_sprintf(buf, "%04u-%02u-%02u %02u:%02u:%02u",
            dateTime->year, dateTime->month, dateTime->day,
            dateTime->hours, dateTime->minutes, dateTime->seconds);
    } else {
        // Changes to this format might require updates in
        // dateTimeSplitFormatted()
        // Datetime is in ISO_8601 format, https://en.wikipedia.org/wiki/ISO_8601
        tfp_sprintf(buf, "%04u-%02u-%02uT%02u:%02u:%02u.%03u%c%02d:%02d",
            dateTime->year, dateTime->month, dateTime->day,
            dateTime->hours, dateTime->minutes, dateTime->seconds, dateTime->millis,
            tz_hours >= 0 ? '+' : '-', ABS(tz_hours), tz_minutes);
    }

    return retVal;
}

rtcTime_t rtcTimeMake(int32_t secs, uint16_t millis)
{
    return ((rtcTime_t)secs) * MILLIS_PER_SECOND + millis;
}

int32_t rtcTimeGetSeconds(rtcTime_t *t)
{
    return *t / MILLIS_PER_SECOND;
}

uint16_t rtcTimeGetMillis(rtcTime_t *t)
{
    return *t % MILLIS_PER_SECOND;
}

bool dateTimeFormatUTC(char *buf, dateTime_t *dt)
{
    return dateTimeFormat(buf, dt, 0, false);
}

bool dateTimeFormatLocal(char *buf, dateTime_t *dt)
{
    return dateTimeFormat(buf, dt, timeConfig()->tz_offsetMinutes, false);
}

bool dateTimeFormatLocalShort(char *buf, dateTime_t *dt)
{
    return dateTimeFormat(buf, dt, timeConfig()->tz_offsetMinutes, true);
}

void dateTimeUTCToLocal(dateTime_t *utcDateTime, dateTime_t *localDateTime)
{
    dateTimeWithOffset(localDateTime, utcDateTime, timeConfig()->tz_offsetMinutes);
}

bool dateTimeSplitFormatted(char *formatted, char **date, char **time)
{
    // Just look for the T and replace it with a zero
    // XXX: Keep in sync with dateTimeFormat()
    for (char *p = formatted; *p; p++) {
        if (*p == 'T') {
            *date = formatted;
            *time = (p+1);
            *p = '\0';
            return true;
        }
    }
    return false;
}

bool rtcHasTime(void)
{
    return started != 0;
}

bool rtcGet(rtcTime_t *t)
{
    if (!rtcHasTime()) {
        return false;
    }
    *t = started + millis();
    return true;
}

bool rtcSet(rtcTime_t *t)
{
    started = *t - millis();
    return true;
}

bool rtcGetDateTime(dateTime_t *dt)
{
    rtcTime_t t;
    if (rtcGet(&t)) {
        rtcTimeToDateTime(dt, t);
        return true;
    }
    // No time stored, fill dt with 0000-01-01T00:00:00.000
    rtcGetDefaultDateTime(dt);
    return false;
}

bool rtcSetDateTime(dateTime_t *dt)
{
    rtcTime_t t = dateTimeToRtcTime(dt);
    return rtcSet(&t);
}

#endif