#include "datetime.h"

#include "blue/core/stream.h"
#include "blue/object/string.h"

#include <blue/object/datetime.h>

static void datetime_to_string(const struct b_object *obj, struct b_stream *out);

static struct b_object_type string_type = {
	.t_name = "corelib::string",
	.t_flags = B_OBJECT_FUNDAMENTAL,
	.t_id = B_OBJECT_TYPE_DATETIME,
	.t_instance_size = sizeof(struct b_datetime),
	.t_to_string = datetime_to_string,
};

struct b_datetime *b_datetime_create(void)
{
	return (struct b_datetime *)b_object_type_instantiate(&string_type);
}

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

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

static bool is_day_valid(const struct b_datetime *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 b_datetime *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 b_datetime *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 b_datetime *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;
}

struct b_datetime *parse_rfc3339(const char *s)
{
	struct b_datetime *dt = b_datetime_create();
	if (!dt) {
		return NULL;
	}

	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 dt;
fail:
	b_datetime_release(dt);
	return NULL;
}

struct b_datetime *b_datetime_parse(enum b_datetime_format format, const char *s)
{
	struct b_datetime *dt = NULL;

	switch (format) {
	case B_DATETIME_FORMAT_RFC3339:
		dt = parse_rfc3339(s);
		break;
	default:
		return NULL;
	}

	if (!dt) {
		return NULL;
	}

	if (!validate(dt)) {
		b_datetime_release(dt);
		return NULL;
	}

	return dt;
}

enum b_status encode_rfc3339(const struct b_datetime *dt, struct b_stream *out)
{
	if (dt->dt_has_date) {
		b_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) {
		b_stream_write_char(out, 'T');
	}

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

		if (dt->dt_msec > 0) {
			b_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) {
				b_stream_write_char(out, 'Z');
			} else {
				b_stream_write_fmt(
					out, NULL, "%c%02ld:%02ld",
					dt->dt_zone_offset_negative ? '-' : '+',
					dt->dt_zone_offset_hour,
					dt->dt_zone_offset_minute);
			}
		}
	}

	return B_SUCCESS;
}

void b_datetime_to_string(
	const b_datetime *dt, b_datetime_format format, struct b_string *dest)
{
	struct b_stream *out;
	b_string_open_stream(dest, &out);

	switch (format) {
	case B_DATETIME_FORMAT_RFC3339:
		encode_rfc3339(dt, out);
		break;
	default:
		break;
	}

	b_stream_close(out);
}

bool b_datetime_is_localtime(const b_datetime *dt)
{
	return dt->dt_localtime;
}

bool b_datetime_has_date(const b_datetime *dt)
{
	return dt->dt_has_date;
}

bool b_datetime_has_time(const b_datetime *dt)
{
	return dt->dt_has_time;
}

long b_datetime_year(const b_datetime *dt)
{
	return dt->dt_year;
}

long b_datetime_month(const b_datetime *dt)
{
	return dt->dt_month;
}

long b_datetime_day(const b_datetime *dt)
{
	return dt->dt_day;
}

long b_datetime_hour(const b_datetime *dt)
{
	return dt->dt_hour;
}

long b_datetime_minute(const b_datetime *dt)
{
	return dt->dt_min;
}

long b_datetime_second(const b_datetime *dt)
{
	return dt->dt_sec;
}

long b_datetime_subsecond(const b_datetime *dt)
{
	return dt->dt_msec;
}

bool b_datetime_zone_offset_is_negative(const b_datetime *dt)
{
	return dt->dt_zone_offset_negative;
}

long b_datetime_zone_offset_hour(const b_datetime *dt)
{
	return dt->dt_zone_offset_hour;
}

long b_datetime_zone_offset_minute(const b_datetime *dt)
{
	return dt->dt_zone_offset_minute;
}

static void datetime_to_string(const struct b_object *obj, struct b_stream *out)
{
	struct b_datetime *dt = B_DATETIME(obj);

	if (dt->dt_has_date) {
		b_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) {
		b_stream_write_char(out, ' ');
	}

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

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

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