/*
 * Copyright (C) 2012 Andy Spencer <andy753421@gmail.com>
 *
 * This program is free software: you can redistribute it 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 program 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/>.
 */

/* Time Keeping Bugs Abound! */

#define _POSIX_C_SOURCE 200112L

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "util.h"
#include "conf.h"
#include "date.h"

/* Global data */
date_t  NOW;
date_t  SEL;

/* Initialize */
void date_init(void)
{
	/* Sync current time */
	NOW = get_date(0);

	/* Sync selection */
	SEL.year  = NOW.year;
	SEL.month = NOW.month;
	SEL.day   = NOW.day;
}

void date_config(const char *group, const char *name, const char *key, const char *value)
{
	if (match(group, "date") && match(key, "timezone") && value)
		setenv("TZ", get_string(value), 1);
}

void date_sync(void)
{
	NOW = get_date(0);
}

/* Time functions */
int is_leap_year(year_t year)
{
	return (year % 400 == 0) ? 1 :
	       (year % 100 == 0) ? 0 :
	       (year % 4   == 0) ? 1 : 0;
}

int days_in_year(year_t year)
{
	return 365 + is_leap_year(year);
}

int days_in_month(year_t year, month_t month)
{
	static int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
	int days = mdays[month];
	if (month == FEB)
		days += is_leap_year(year);
	return days;
}

int weeks_in_month(year_t year, month_t month)
{
	int start = start_of_month(year, month);
	int days  = days_in_month(year, month);
	return ((start + days)-1) / 7 + 1;
}

wday_t day_of_week(year_t year, month_t month, day_t day)
{
	static int tmp[] = {0, 3, 2, 5, 0, 3,
		            5, 1, 4, 6, 2, 4};
	if (month < MAR)
		year--;
	int start = year + year / 4
		         - year / 100
		         + year / 400
		         + tmp[month];
	return (start + day + 1) % 7;
}

wday_t start_of_month(year_t year, month_t month)
{
	return day_of_week(year, month, 0);
}

void add_days(year_t *year, month_t *month, day_t *day, int days)
{
	date_t date = {
		.year  = *year,
		.month = *month,
		.day   = *day,
		.hour  = 12
	};
	stamp_t stamp = get_stamp(date);
	date_t  then  = get_date(stamp + days*24*60*60);
	*year  = then.year;
	*month = then.month;
	*day   = then.day;
}

void add_months(year_t *year, month_t *month, int months)
{
	int total = *year*12 + *month + months;
	*year  = total / 12;
	*month = total % 12;
}

/* Date functions */
date_t get_date(stamp_t stamp)
{
	time_t t = stamp ? stamp : time(NULL);
	struct tm *tm = localtime(&t);
	date_t date = {
		.year  = tm->tm_year+1900,
		.month = tm->tm_mon,
		.day   = tm->tm_mday-1,
		.hour  = tm->tm_hour,
		.min   = tm->tm_min,
		.sec   = tm->tm_sec,
	};
	return date;
}

stamp_t get_stamp(date_t date)
{
	struct tm tm = {
		.tm_year = date.year-1900,
		.tm_mon  = date.month,
		.tm_mday = date.day+1,
		.tm_hour = date.hour,
		.tm_min  = date.min,
		.tm_sec  = date.sec,
	};
	time_t t = mktime(&tm);
	return (stamp_t)t;
}

int get_mins(date_t *start, date_t *end)
{
	return (get_stamp(*end)-get_stamp(*start))/60;
}

int get_secs(date_t *start, date_t *end)
{
	return (get_stamp(*end)-get_stamp(*start));
}

int compare(date_t *a, date_t *b)
{
	int rval = a->year  < b->year  ? -1 : a->year  > b->year  ? 1 :
	           a->month < b->month ? -1 : a->month > b->month ? 1 :
	           a->day   < b->day   ? -1 : a->day   > b->day   ? 1 :
	           a->hour  < b->hour  ? -1 : a->hour  > b->hour  ? 1 :
	           a->min   < b->min   ? -1 : a->min   > b->min   ? 1 : 0;
	return rval;
}

int same_day(date_t *a, date_t *b)
{
	return a->year  == b->year  &&
	       a->month == b->month &&
	       a->day   == b->day;
}

int before(date_t *start, int year, int month, int day, int hour, int min)
{
	return compare(start, &(date_t){year, month, day, hour, min}) < 0;
}

int all_day(date_t *start, date_t *end)
{
	date_t test = *start;
	add_days(&test.year, &test.month, &test.day, 1);
	return compare(&test, end) <= 0;
}

int no_date(date_t *date)
{
	return date->year == 0;
}

/* Debug functions */
const char *month_to_str(month_t month)
{
	static const char *map[] =
		{ "Jan", "Feb", "Mar", "Apr", "May", "Jun",
		  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", };
	return map[month%12];
}
const char *month_to_string(month_t month)
{
	static const char *map[] =
		{ "January",   "February", "March",    "April",
		  "May",       "June",     "July",     "August",
		  "September", "October",  "November", "December" };
	return map[month%12];
}

const char *day_to_st(wday_t day)
{
	static const char *map[] =
		{ "Su","Mo", "Tu", "We", "Th", "Fr", "Sa" };
	return map[day%7];
}
const char *day_to_str(wday_t day)
{
	static const char *map[] =
		{ "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
	return map[day%7];
}
const char *day_to_string(wday_t day)
{
	static const char *map[] =
		{ "Sunday",   "Monday", "Tuesday", "Wednesday",
		  "Thursday", "Friday", "Saturday" };
	return map[day%7];
}

/* Test functions */
void date_test(void)
{
	setenv("TZ", "US/Central", 1);

	time_t  timet = time(NULL);
	date_t  date  = get_date(timet);
	stamp_t stamp = get_stamp(date);

	printf("Time\n");
	printf("  time  %ld\n",  timet);
	printf("  stamp %lld\n", stamp);
	printf("  date  %04d-%02d-%02d %02d:%02d %02ds\n",
			date.year, date.month, date.day,
			date.hour, date.min,   date.sec);

	printf("Info\n");
	printf("  Year   Month       Start   Weeks   Days\n");
	for (int y = 2012; y <= 2012; y++)
	for (int m = JAN;  m <= DEC;  m++) {
		printf("  %-5d",  y);
		printf("  %-10s", month_to_string(m));
		printf("  %-6s",  day_to_str(start_of_month(y,m)));
		printf("  %-6d",  weeks_in_month(y,m));
		printf("  %-2d",  days_in_month(y,m));
		printf("\n");
	}
}