#include <fx/core/stream.h>
#include <fx/ds/datetime.h>
#include <fx/ds/string.h>

/*** PRIVATE DATA *************************************************************/

struct fx_datetime_p {
	unsigned int dt_year, dt_month, dt_day;
	unsigned short dt_hour, dt_min, dt_sec;
	unsigned int dt_msec;

	bool dt_has_date, dt_has_time, dt_localtime;
	unsigned short dt_zone_offset_hour, dt_zone_offset_minute;
	bool dt_zone_offset_negative;
};

/*** PRIVATE FUNCTIONS ********************************************************/

static bool is_leap_year(const struct fx_datetime_p *dt)
{
	if ((dt->dt_year % 400) == 0) {
		return true;
	}

	if ((dt->dt_year % 4) == 0 && (dt->dt_year % 100) != 0) {
		return true;
	}

	return false;
}

static bool is_year_valid(const struct fx_datetime_p *dt)
{
	return dt->dt_year >= 0;
}

static bool is_month_valid(const struct fx_datetime_p *dt)
{
	return dt->dt_month >= 1 && dt->dt_month <= 12;
}

static bool is_day_valid(const struct fx_datetime_p *dt)
{
	if (dt->dt_day < 1) {
		return false;
	}

	switch (dt->dt_month) {
	case 2:
		return dt->dt_day <= (is_leap_year(dt) ? 29 : 28);
	case 4:
	case 6:
	case 9:
	case 11:
		return dt->dt_day <= 30;
	case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12:
		return dt->dt_day <= 31;
	default:
		return false;
	}
}

static bool is_time_valid(const struct fx_datetime_p *dt)
{
	if (!(dt->dt_hour >= 0 && dt->dt_hour <= 23)) {
		return false;
	}

	if (!(dt->dt_min >= 0 && dt->dt_min <= 59)) {
		return false;
	}

	if (!(dt->dt_sec >= 0 && dt->dt_sec <= 60)) {
		return false;
	}

	return true;
}

static bool is_zone_valid(const struct fx_datetime_p *dt)
{
	if (!(dt->dt_zone_offset_hour >= 0 && dt->dt_zone_offset_hour <= 23)) {
		return false;
	}

	if (!(dt->dt_zone_offset_minute >= 0 && dt->dt_zone_offset_minute <= 59)) {
		return false;
	}

	return true;
}

static bool validate(const struct fx_datetime_p *dt)
{
	if (dt->dt_has_date) {
		if (!is_year_valid(dt)) {
			return false;
		}

		if (!is_month_valid(dt)) {
			return false;
		}

		if (!is_day_valid(dt)) {
			return false;
		}
	}

	if (dt->dt_has_time) {
		if (!is_time_valid(dt)) {
			return false;
		}

		if (!is_zone_valid(dt)) {
			return false;
		}
	}

	return true;
}

static fx_datetime *parse_rfc3339(const char *s)
{
	fx_datetime *d = fx_datetime_create();
	if (!d) {
		return NULL;
	}

	struct fx_datetime_p *dt = fx_object_get_private(d, FX_TYPE_DATETIME);

	size_t len = strlen(s);

	size_t i = 0, c = 0;

	bool has_date = false, has_time = false;
	dt->dt_localtime = true;

	if (len >= 10 && s[4] == '-' && s[7] == '-') {
		has_date = true;
	}

	if (len >= 8 && s[2] == ':' && s[5] == ':') {
		has_time = true;
	}

	if (len >= 19 && s[4] == '-' && s[7] == '-'
	    && (s[10] == 'T' || s[10] == 't' || s[10] == ' ') && s[13] == ':'
	    && s[16] == ':') {
		has_date = true;
		has_time = true;
	}

	if (!has_date && !has_time) {
		goto fail;
	}

	if (has_date) {
		for (c = 0; c < 4; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_year *= 10;
			dt->dt_year += (s[i] - '0');
		}

		if (s[i++] != '-') {
			goto fail;
		}

		for (c = 0; c < 2; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_month *= 10;
			dt->dt_month += (s[i] - '0');
		}

		if (s[i++] != '-' || dt->dt_month > 12) {
			goto fail;
		}

		for (c = 0; c < 2; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_day *= 10;
			dt->dt_day += (s[i] - '0');
		}

		if (dt->dt_day > 31) {
			goto fail;
		}
	}

	if ((s[i] == 'T' || s[i] == 't' || s[i] == ' ') && !has_time) {
		goto fail;
	}

	if (has_date && has_time) {
		if (s[i] != 'T' && s[i] != 't' && s[i] != ' ') {
			goto fail;
		}

		i++;
	}

	if (has_time) {
		for (c = 0; c < 2; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_hour *= 10;
			dt->dt_hour += (s[i] - '0');
		}

		if (s[i++] != ':') {
			goto fail;
		}

		for (c = 0; c < 2; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_min *= 10;
			dt->dt_min += (s[i] - '0');
		}

		if (s[i++] != ':') {
			goto fail;
		}

		for (c = 0; c < 2; c++, i++) {
			if (!isdigit(s[i])) {
				goto fail;
			}

			dt->dt_sec *= 10;
			dt->dt_sec += (s[i] - '0');
		}

		if (s[i] == '.') {
			i++;
			for (c = 0; s[i]; c++, i++) {
				if (!isdigit(s[i])) {
					break;
				}

				dt->dt_msec *= 10;
				dt->dt_msec += (s[i] - '0');
			}

			if (c == 0) {
				goto fail;
			}
		}

		if (s[i] == '+' || s[i] == '-') {
			dt->dt_localtime = false;
			dt->dt_zone_offset_negative = s[i] == '-';
			i++;

			for (c = 0; c < 2; c++, i++) {
				if (!isdigit(s[i])) {
					goto fail;
				}

				dt->dt_zone_offset_hour *= 10;
				dt->dt_zone_offset_hour += (s[i] - '0');
			}

			if (s[i++] != ':') {
				goto fail;
			}

			for (c = 0; c < 2; c++, i++) {
				if (!isdigit(s[i])) {
					goto fail;
				}

				dt->dt_zone_offset_minute *= 10;
				dt->dt_zone_offset_minute += (s[i] - '0');
			}
		} else if (s[i] == 'Z' || s[i] == 'z') {
			dt->dt_localtime = false;
			i++;
		}
	}

	if (s[i] != 0) {
		goto fail;
	}

	dt->dt_has_date = has_date;
	dt->dt_has_time = has_time;
	return d;
fail:
	fx_datetime_unref(d);
	return NULL;
}

static enum fx_status encode_rfc3339(const struct fx_datetime_p *dt, fx_stream *out)
{
	if (dt->dt_has_date) {
		fx_stream_write_fmt(
			out, NULL, "%04ld-%02ld-%02ld", dt->dt_year,
			dt->dt_month, dt->dt_day);
	}

	if (dt->dt_has_date && dt->dt_has_time) {
		fx_stream_write_char(out, 'T');
	}

	if (dt->dt_has_time) {
		fx_stream_write_fmt(
			out, NULL, "%02ld:%02ld:%02ld", dt->dt_hour, dt->dt_min,
			dt->dt_sec);

		if (dt->dt_msec > 0) {
			fx_stream_write_fmt(out, NULL, ".%04ld", dt->dt_msec);
		}

		if (!dt->dt_localtime) {
			if (dt->dt_zone_offset_hour == 0
			    && dt->dt_zone_offset_minute == 0) {
				fx_stream_write_char(out, 'Z');
			} else {
				fx_stream_write_fmt(
					out, NULL, "%c%02ld:%02ld",
					dt->dt_zone_offset_negative ? '-' : '+',
					dt->dt_zone_offset_hour,
					dt->dt_zone_offset_minute);
			}
		}
	}

	return FX_SUCCESS;
}

static void datetime_to_string(
	const struct fx_datetime_p *dt, fx_datetime_format format, fx_stream *dest)
{
	switch (format) {
	case FX_DATETIME_FORMAT_RFC3339:
		encode_rfc3339(dt, dest);
		break;
	default:
		break;
	}
}

static bool datetime_is_localtime(const struct fx_datetime_p *dt)
{
	return dt->dt_localtime;
}

static bool datetime_has_date(const struct fx_datetime_p *dt)
{
	return dt->dt_has_date;
}

static bool datetime_has_time(const struct fx_datetime_p *dt)
{
	return dt->dt_has_time;
}

static long datetime_year(const struct fx_datetime_p *dt)
{
	return dt->dt_year;
}

static long datetime_month(const struct fx_datetime_p *dt)
{
	return dt->dt_month;
}

static long datetime_day(const struct fx_datetime_p *dt)
{
	return dt->dt_day;
}

static long datetime_hour(const struct fx_datetime_p *dt)
{
	return dt->dt_hour;
}

static long datetime_minute(const struct fx_datetime_p *dt)
{
	return dt->dt_min;
}

static long datetime_second(const struct fx_datetime_p *dt)
{
	return dt->dt_sec;
}

static long datetime_subsecond(const struct fx_datetime_p *dt)
{
	return dt->dt_msec;
}

static bool datetime_zone_offset_is_negative(const struct fx_datetime_p *dt)
{
	return dt->dt_zone_offset_negative;
}

static long datetime_zone_offset_hour(const struct fx_datetime_p *dt)
{
	return dt->dt_zone_offset_hour;
}

static long datetime_zone_offset_minute(const struct fx_datetime_p *dt)
{
	return dt->dt_zone_offset_minute;
}

/*** PUBLIC FUNCTIONS *********************************************************/

fx_datetime *fx_datetime_parse(enum fx_datetime_format format, const char *s)
{
	fx_datetime *dt = NULL;

	switch (format) {
	case FX_DATETIME_FORMAT_RFC3339:
		dt = parse_rfc3339(s);
		break;
	default:
		return NULL;
	}

	if (!dt) {
		return NULL;
	}

	struct fx_datetime_p *p = fx_object_get_private(dt, FX_TYPE_DATETIME);

	if (!validate(p)) {
		fx_datetime_unref(dt);
		return NULL;
	}

	return dt;
}

void fx_datetime_to_string(
	const fx_datetime *dt, fx_datetime_format format, fx_stream *dest)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_DATETIME, datetime_to_string, dt, format, dest);
}

bool fx_datetime_is_localtime(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_is_localtime, dt);
}

bool fx_datetime_has_date(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_has_date, dt);
}

bool fx_datetime_has_time(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_has_time, dt);
}

long fx_datetime_year(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_year, dt);
}

long fx_datetime_month(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_month, dt);
}

long fx_datetime_day(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_day, dt);
}

long fx_datetime_hour(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_hour, dt);
}

long fx_datetime_minute(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_minute, dt);
}

long fx_datetime_second(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_second, dt);
}

long fx_datetime_subsecond(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_subsecond, dt);
}

bool fx_datetime_zone_offset_is_negative(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_TYPE_DATETIME, datetime_zone_offset_is_negative, dt);
}

long fx_datetime_zone_offset_hour(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_zone_offset_hour, dt);
}

long fx_datetime_zone_offset_minute(const fx_datetime *dt)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_DATETIME, datetime_zone_offset_minute, dt);
}

/*** VIRTUAL FUNCTIONS ********************************************************/

static void datetime_init(fx_object *obj, void *priv)
{
	struct fx_datetime_p *dt = priv;
}

static void datetime_fini(fx_object *obj, void *priv)
{
	struct fx_datetime_p *dt = priv;
}

static void _datetime_to_string(const fx_object *obj, fx_stream *out)
{
	struct fx_datetime_p *dt = fx_object_get_private(obj, FX_TYPE_DATETIME);

	if (dt->dt_has_date) {
		fx_stream_write_fmt(
			out, NULL, "%04ld-%02ld-%02ld", dt->dt_year,
			dt->dt_month, dt->dt_day);
	}

	if (dt->dt_has_date && dt->dt_has_time) {
		fx_stream_write_char(out, ' ');
	}

	if (dt->dt_has_time) {
		fx_stream_write_fmt(
			out, NULL, "%02ld:%02ld:%02ld", dt->dt_hour, dt->dt_min,
			dt->dt_sec);

		if (dt->dt_msec > 0) {
			fx_stream_write_fmt(out, NULL, ".%04ld", dt->dt_msec);
		}

		if (!dt->dt_localtime) {
			fx_stream_write_fmt(
				out, NULL, " %c%02ld:%02ld",
				dt->dt_zone_offset_negative ? '-' : '+',
				dt->dt_zone_offset_hour,
				dt->dt_zone_offset_minute);
		}
	}
}

/*** CLASS DEFINITION *********************************************************/

FX_TYPE_CLASS_DEFINITION_BEGIN(fx_datetime)
	FX_TYPE_CLASS_INTERFACE_BEGIN(fx_object, FX_TYPE_OBJECT)
		FX_INTERFACE_ENTRY(to_string) = _datetime_to_string;
	FX_TYPE_CLASS_INTERFACE_END(fx_object, FX_TYPE_OBJECT)
FX_TYPE_CLASS_DEFINITION_END(fx_datetime)

FX_TYPE_DEFINITION_BEGIN(fx_datetime)
	FX_TYPE_ID(0x06a6030b, 0x1e3c, 0x4be2, 0xbd23, 0xf34f4a8e68be);
	FX_TYPE_CLASS(fx_datetime_class);
	FX_TYPE_INSTANCE_PRIVATE(struct fx_datetime_p);
	FX_TYPE_INSTANCE_INIT(datetime_init);
	FX_TYPE_INSTANCE_FINI(datetime_fini);
FX_TYPE_DEFINITION_END(fx_datetime)